Strategic surface-modification techniques can tailor the effectiveness of graphene oxide-based lo... more Strategic surface-modification techniques can tailor the effectiveness of graphene oxide-based loose nanofiltration membranes for the retention of emerging contaminants.
Reduction of graphene oxide (GO) has emerged as one of the most feasible and cost-efficient route... more Reduction of graphene oxide (GO) has emerged as one of the most feasible and cost-efficient routes to graphene-based materials. While many approaches reliant on the use of chemicals and/or irradiat...
Hollow fiber membranes were produced from a commercial polyvinylidene fluoride (PVDF) polymer, Ky... more Hollow fiber membranes were produced from a commercial polyvinylidene fluoride (PVDF) polymer, Kynar HSV 900, with a unique sandwich structure consisting of two sponge-like layers connected to the outer and inner skin layers while the middle layer comprises macrovoids. The sponge-like layer allows the membrane to have good mechanical strength even at low skin thickness and favors water vapor transportation during vacuum membrane distillation (VMD). The middle layer with macrovoids helps to significantly reduce the trans-membrane resistance during water vapor transportation from the feed side to the permeate side. Together, these novel structural characteristics are expected to render the PVDF hollow fiber membranes more efficient in terms of vapor flux as well as mechanical integrity. Using the chemistry and process conditions adopted from previous work, we were able to scale up the membrane fabrication from a laboratory scale of 1.5 kg to a manufacturing scale of 50 kg with consist...
During the last two decades, the photocatalytic degradation for the oxidation of volatile organic... more During the last two decades, the photocatalytic degradation for the oxidation of volatile organic compounds (VOC) has gained force since these compounds represents an environmental risk and a public health problem. A particular group of these VOCs: the BTEX (benzene-toluene-ethylbezene-xylene), are often used as a solvent in paints and it is also considerably dangerous on service stations and oil companies. On that way, it is a group of gases that can be present in both environments, indoor and/or outdoor. The fumes which are produced are highly polluting and persistent. To determine the degradation of those gases, a prototype of a packed bed photoreactor with UV lamps and TiO2 (1%p/p) as catalyst was used. The catalyst is supported on polyester granules. Conversion of each contaminant were determined and the mixture as well. The research found conversions between 72% and 99% giving better results for the treatment of the mixture where all conversions achieved were above 94% for a r...
ABSTRACT During the last two decades, the photocatalytic degradation for the oxidation of volatil... more ABSTRACT During the last two decades, the photocatalytic degradation for the oxidation of volatile organic compounds (VOC) has gained force since these compounds represents an environmental risk and a public health problem. A particular group of these VOCs: the BTEX (benzene-toluene-ethylbezene-xylene), are often used as a solvent in paints and it is also considerably dangerous on service stations and oil companies. On that way, it is a group of gases that can be present in both environments, indoor and/or outdoor. The fumes which are produced are highly polluting and persistent. To determine the degradation of those gases, a prototype of a packed bed photoreactor with UV lamps and TiO2 (1%p/p) as catalyst was used. The catalyst is supported on polyester granules. Conversion of each contaminant were determined and the mixture as well. The research found conversions between 72% and 99% giving better results for the treatment of the mixture where all conversions achieved were above 94% for a residence time of 160 min. It was found that an increment in the initial concentration of pollutant can improve the final conversion for components such as ethylbenzene. Finally, kinetic constants were determined for pollutants degradation which ranged between 0.005 and 0.03 min-1
Un estudio fue desarrollado a escala laboratorio de un proceso foto-Fenton con el fin de evaluar ... more Un estudio fue desarrollado a escala laboratorio de un proceso foto-Fenton con el fin de evaluar la factibilidad técnica de un sistema de tratamiento de aguas residuales con colorantes del sector textil. El proceso foto – Fenton fue aplicado como pretratamiento para así obtener un agua compatible con un proceso biológico. Se exploraron diferentes concentraciones Fenton que permitieron aumentar la biotratabilidad (DBO5/DQO) de una solución artificial con colorante y del agua residual real, como también la disminución del color (Abs580). Las soluciones pretratadas con mejores resultados se agregaron a un biorreactor de lodos activados para determinar la tasa específica de consumo de oxígeno (TECO). Los mejores resultados para la solución con colorante fueron obtenidos a concentraciones Fenton de 0.1:10 (Fe (II):H2O2, mM) y una TECO de 14.65(mg/g)/h. Para el agua residual, los resultados fueron con Fenton de 1:10mM y una TECO de 7.81 (mg/g)/h, la cual no estuvo dentro del rango deseado.
An investigation of photo-catalytical degradation to organic pollutants present in waste waters u... more An investigation of photo-catalytical degradation to organic pollutants present in waste waters used in the cleaning of ink in impression cartridges was carried out. In order to accomplish this degradation a titanium dioxide (TiO2-Degussa) supported on activated carbon (TiO2-AC) photo-catalyst was manufactured, so as to allow the organic dissolved species to easily contact the ions and free radicals generated by the oxidizing species exposed to UV light throughout the reactor. The composite particles of TiO2 and activated carbon were prepared using methylene chloride and liquid silicon to generate one dispersion with TiO2 which diffuses into the AC granules for a period of 20 hours at 298K, followed by an hour of thermal treatment at 373K. An advanced catalytic oxidation process was preformed with the aim of determining the photo-catalytic reaction kinetics of the CMYK inks found in the impression cartridges. An accurate kinetic model was developed by measuring the concentration of ...
Water is a vital resource for human survival, so it is the duty of ensuring security of supplies ... more Water is a vital resource for human survival, so it is the duty of ensuring security of supplies in any situation. There have been several studies and found that the savannah of Bogotá has a functional and seismic vulnerability in the event of a natural disaster, in which their systems of water supply fail, leaving a large percentage of affected population. Given the magnitude of the problem, there is an alternative, portable treatment plants that provide the necessary water satisfactorily during the scope of the emergency. For this purpose, we identified the technologies available for water treatment, in order to achieve assess the best con-figuration of such plants to ensure water quality within a limited time.
The generation of membranes has grown in recent years, and that has caused a high business impact... more The generation of membranes has grown in recent years, and that has caused a high business impact. One of the materials used to manufacture membranes are polymers due to properties such as the adoption of different shapes and control over their molecular configurations. There are different methods of separation for the generation of membranes. Polystyrene membranes were performed by extraction and sulfonation. In the method of extraction was varied the percentage by weight of the polymer and solvent, in order to determine the composition and the most suitable solvent for an appropriate pore distribution, while the extractant remained constant. For sulfonation method was used only a percentage by weight of polymer, and by sulfonation reaction sulfonated polystyrene was prepared prior to generating the membrane. After obtaining the membranes, covered with gold, because the samples are not conductive and observed in scanning electron microscopy for characterization and structure determ...
This work describes the preparation of a polymer of acrylic acid (AA) and ethylene glycol (EG) by... more This work describes the preparation of a polymer of acrylic acid (AA) and ethylene glycol (EG) by redox polymerization and the use of the exhausted metal based catalysts (ferric ion) of the process to synthesize zero-valent iron nanoparticles for water remediation applications. The polymerization is done by free radicals in a reaction between a catalyst (FeCl2 or FeSO4) and an initiator (Potassium persulfate). This redox polymerization is the source of the metal ions that are going to be reduced and immobilized simultaneously in the polymer. The creation of a support like polymer hydrogel or membrane pore domain for the immobilization of nanoparticles (NPs) prevents their loss and reduction of active surface. For direct solution-phase (no polymers) synthesis, NPs loss and aggregation occurs, making them unable to recover and possibly increasing the costs in the practice. The novelty of this work is that the nanoparticles are synthesized using the metal catalysts from the polymerizat...
With the synthesis and functionalization of membranes for selective separations, reactivity, and ... more With the synthesis and functionalization of membranes for selective separations, reactivity, and stimuli responsive behavior arises new and advanced opportunities. The integration of bio-based channels is one of these advancements in membrane technologies. By a layer-by-layer (LbL) assembly of polyelectrolytes, outer membrane protein F trimers (OmpF) or "porins" from Escherichia coli with a central pore of ~2 nm diameter at its opening and ~0.7 × 1.1 nm at its constricted region are immobilized within the pores of poly(vinylidene fluoride) microfiltration membranes, as opposed to traditional ruptured lipid bilayer or vesicles processes. These OmpF-membranes demonstrate selective rejections of non-charged organics over ionic solutes, allowing the passage of salts up to 2 times higher than traditional nanofiltration membranes starting with rejections of 84% for 0.4-1.0 kDa organics. The presence of charged groups in OmpF membranes also leads to pH-dependent salt rejection th...
Functionalized polymer materials with ion-exchange groups and the integration of nanostructured m... more Functionalized polymer materials with ion-exchange groups and the integration of nanostructured materials is an emerging area for catalytic and water pollution control applications. The polymerization of materials such as acrylic acid often requires persulfate initiator and a high-temperature start. However, is generally known that metal ions accelerate such polymerizations starting from room temperature. If the metal is properly selected, then it can be used in environmental applications, adding two advantages simultaneously. This article deals with this by polymerizing acrylic acid using iron as an accelerant and subsequently using it for nanoparticle synthesis in hydrogels and PVDF membranes. Characterizations of hydrogels, membranes, and nanoparticles were carried out with different techniques. Nanoparticles sizes of 30–60 nm were synthesized. Permeability and swelling measurements demonstrate an inverse relationship between the hydrogel mesh size (6.30 to 8.34 nm) and the membrane pore size (222 to 110 nm). The quantitative reduction of trichloroethylene/chloride generation by Fe/Pd nanoparticles in hydrogel/membrane platforms was also performed.
Este resumen pretende dar una visión global de los aportes de la Universidad de los Andes en el t... more Este resumen pretende dar una visión global de los aportes de la Universidad de los Andes en el tratamiento de aguas y suelos con la presencia de compuestos de difícil degradación o tiempo de vida media prolongado, tales como fármacos (Ciclofosfamida), lodos aceitosos y derivados de la industria del petróleo (Tolueno, Xileno, Fenol) derivados de la industria textil, química y pesticidas (Bisphenol A, AMBI, Glifosato, Isoproturon y Metobromuron), usando tecnologías ya sea basadas en procesos biológicos (biorremediación y bioadsorción) o de oxidación avanzada (foto-Fenton).
This summary intends to give a global view of the Universidad de los Andes contributions related to the water and soil treatment in the presence of recalcitrant or long half-life aquatic pollutants such as drugs (Cyclophosphamide), oil sludge and petroleum (Toluene, Xylene and Phenol), textile, chemical (Bisphenol A, AMBI) and pesticides (Glyphosate, Isoproturon, and Metobromuron) industry derived products based on biological (bioremediation and bioadsortion) and advanced oxidation (Photo-Fenton) approaches.
Functionalized microfiltration membranes containing iron nanoparticles are a novel platform for o... more Functionalized microfiltration membranes containing iron nanoparticles are a novel platform for organic pollutant degradation reactions and for selective removal of contaminants such as heavy metals, without the drawback of potential nanoparticle loss to the environment. These environmentally friendly and sustainable technology approaches allow various water treatment applications exploit the enhanced water transport through the membrane pores. The present work deals with “green” techniques to create nanocomposite materials based on sponge-like membranes for water remediation containing chlorinated organic compounds. First, hydrophobic hollow fiber microfiltration membranes (HF) of polyvinylidene fluoride were hydrophilized using a water-based chemistry process with polyvinylpyrrolidone and persulfate. HF and flat sheet membrane pores were then functionalized with poly(acrylic acid) hydrogel followed by a double ion exchange sodium/iron and subsequent in situ synthesis of bimetallic Fe/Pd nanoparticles. The nanocomposite membrane modifications were determined by contact angle, surface free energy and infrared spectroscopy. The synthesized nanoparticles were characterized by electronic microscopy, X-ray spectrometry, image analysis and other techniques. Nanoparticle sizes between 193 and 301 nm were obtained for each of the membranes. Depending on the concentration of the dopant (Pd) in the membrane, the catalytic activity (established by trichloroethylene (TCE) reduction) was enhanced up to tenfold compared to other reported results. Chloride produced in reduction was close to the stoichiometric 3/1 (Cl/TCE), indicating absence of reaction intermediates.
Water pollution is a serious concern in all the aspects of society. Most of the pollutants have t... more Water pollution is a serious concern in all the aspects of society. Most of the pollutants have two main origins: organic compounds and heavy metals. One of these contaminants, Trichloroethylene (TCE), has high interest because their persistency in nature and the difficulties related with their treatment and/or elimination. Nano-structured material synthesis or metal capturing using functionalized membranes with polymers that contain ion exchange groups is a promising research field for water pollution, catalytic and mining applications. The polymerization of such materials requires initiation using strong oxidants and heat. However, a redox reaction can take place using metal ions to accelerate it.
This work describes this redox polymerization in order to synthesize a hydrogel of poly (acrylic acid) (PAA) for Polyvinylidene fluoride (PVDF) membrane functionalization using ferrous ions as accelerant and persulfate as initiator. The iron accelerant selected was subsequently used for nanoparticle synthesis and compared with a process of ion exchange and nanoparticle synthesis developed previously by this group. Redox polymerization resulted exothermic with temperatures around 50°C producing ferric ions contributing to the decrease in pH values around 2.0. Iron nanoparticles sizes of 30-60 nm were synthesized. From the use of the ferrous ions in the polymerization of the hydrogel, 9.2 mg Fe /g PAA were produced. This value is lower compared to ion exchange procedure (450 mg Fe/ g PAA) due to the small concentrations used in the polymerization. Since the functionalization of the membranes carry less PAA inside (8.5 to 13.4% wt), the amount of iron in the membranes was lower.
The PAA hydrogel was also characterized by swelling behavior along with the permeability of the PVDF-PAA membranes. The rate of swelling of the cross-linked PAA hydrogel follows a second order swelling kinetics, making the swelling process faster at higher pH values and higher responsive behavior. It was defined an inverse relationship between the hydrogel mesh size (6.30 to 8.34 nm) and the membrane pore size (222 to 110nm). An increase in the mesh size of the hydrogel creates around 93% of decrease in permeability.
Quantitative TCE/chloride generation by Fe/Pd nanoparticles in hydrogel and functionalized membrane were performed in batch process. Iron nanoparticles followed pseudo-first order reaction kinetics with a higher surface-area constant ksa in hydrogel (2.46 L/ (m2h)) than functionalized membrane (0.10 to 0.13 L/ (m2h)) due to a more open area and larger volume of reaction. The produced chloride using bimetallic Fe/Pd nanoparticles in dechlorination experiments is close to the stoichiometric value, indicating negligible production of intermediates.
The project described was supported by Grant Number P42ES007380 from the National Institute of Environmental Health Sciences. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Environmental Health Sciences or the National Institutes of Health.
Strategic surface-modification techniques can tailor the effectiveness of graphene oxide-based lo... more Strategic surface-modification techniques can tailor the effectiveness of graphene oxide-based loose nanofiltration membranes for the retention of emerging contaminants.
Reduction of graphene oxide (GO) has emerged as one of the most feasible and cost-efficient route... more Reduction of graphene oxide (GO) has emerged as one of the most feasible and cost-efficient routes to graphene-based materials. While many approaches reliant on the use of chemicals and/or irradiat...
Hollow fiber membranes were produced from a commercial polyvinylidene fluoride (PVDF) polymer, Ky... more Hollow fiber membranes were produced from a commercial polyvinylidene fluoride (PVDF) polymer, Kynar HSV 900, with a unique sandwich structure consisting of two sponge-like layers connected to the outer and inner skin layers while the middle layer comprises macrovoids. The sponge-like layer allows the membrane to have good mechanical strength even at low skin thickness and favors water vapor transportation during vacuum membrane distillation (VMD). The middle layer with macrovoids helps to significantly reduce the trans-membrane resistance during water vapor transportation from the feed side to the permeate side. Together, these novel structural characteristics are expected to render the PVDF hollow fiber membranes more efficient in terms of vapor flux as well as mechanical integrity. Using the chemistry and process conditions adopted from previous work, we were able to scale up the membrane fabrication from a laboratory scale of 1.5 kg to a manufacturing scale of 50 kg with consist...
During the last two decades, the photocatalytic degradation for the oxidation of volatile organic... more During the last two decades, the photocatalytic degradation for the oxidation of volatile organic compounds (VOC) has gained force since these compounds represents an environmental risk and a public health problem. A particular group of these VOCs: the BTEX (benzene-toluene-ethylbezene-xylene), are often used as a solvent in paints and it is also considerably dangerous on service stations and oil companies. On that way, it is a group of gases that can be present in both environments, indoor and/or outdoor. The fumes which are produced are highly polluting and persistent. To determine the degradation of those gases, a prototype of a packed bed photoreactor with UV lamps and TiO2 (1%p/p) as catalyst was used. The catalyst is supported on polyester granules. Conversion of each contaminant were determined and the mixture as well. The research found conversions between 72% and 99% giving better results for the treatment of the mixture where all conversions achieved were above 94% for a r...
ABSTRACT During the last two decades, the photocatalytic degradation for the oxidation of volatil... more ABSTRACT During the last two decades, the photocatalytic degradation for the oxidation of volatile organic compounds (VOC) has gained force since these compounds represents an environmental risk and a public health problem. A particular group of these VOCs: the BTEX (benzene-toluene-ethylbezene-xylene), are often used as a solvent in paints and it is also considerably dangerous on service stations and oil companies. On that way, it is a group of gases that can be present in both environments, indoor and/or outdoor. The fumes which are produced are highly polluting and persistent. To determine the degradation of those gases, a prototype of a packed bed photoreactor with UV lamps and TiO2 (1%p/p) as catalyst was used. The catalyst is supported on polyester granules. Conversion of each contaminant were determined and the mixture as well. The research found conversions between 72% and 99% giving better results for the treatment of the mixture where all conversions achieved were above 94% for a residence time of 160 min. It was found that an increment in the initial concentration of pollutant can improve the final conversion for components such as ethylbenzene. Finally, kinetic constants were determined for pollutants degradation which ranged between 0.005 and 0.03 min-1
Un estudio fue desarrollado a escala laboratorio de un proceso foto-Fenton con el fin de evaluar ... more Un estudio fue desarrollado a escala laboratorio de un proceso foto-Fenton con el fin de evaluar la factibilidad técnica de un sistema de tratamiento de aguas residuales con colorantes del sector textil. El proceso foto – Fenton fue aplicado como pretratamiento para así obtener un agua compatible con un proceso biológico. Se exploraron diferentes concentraciones Fenton que permitieron aumentar la biotratabilidad (DBO5/DQO) de una solución artificial con colorante y del agua residual real, como también la disminución del color (Abs580). Las soluciones pretratadas con mejores resultados se agregaron a un biorreactor de lodos activados para determinar la tasa específica de consumo de oxígeno (TECO). Los mejores resultados para la solución con colorante fueron obtenidos a concentraciones Fenton de 0.1:10 (Fe (II):H2O2, mM) y una TECO de 14.65(mg/g)/h. Para el agua residual, los resultados fueron con Fenton de 1:10mM y una TECO de 7.81 (mg/g)/h, la cual no estuvo dentro del rango deseado.
An investigation of photo-catalytical degradation to organic pollutants present in waste waters u... more An investigation of photo-catalytical degradation to organic pollutants present in waste waters used in the cleaning of ink in impression cartridges was carried out. In order to accomplish this degradation a titanium dioxide (TiO2-Degussa) supported on activated carbon (TiO2-AC) photo-catalyst was manufactured, so as to allow the organic dissolved species to easily contact the ions and free radicals generated by the oxidizing species exposed to UV light throughout the reactor. The composite particles of TiO2 and activated carbon were prepared using methylene chloride and liquid silicon to generate one dispersion with TiO2 which diffuses into the AC granules for a period of 20 hours at 298K, followed by an hour of thermal treatment at 373K. An advanced catalytic oxidation process was preformed with the aim of determining the photo-catalytic reaction kinetics of the CMYK inks found in the impression cartridges. An accurate kinetic model was developed by measuring the concentration of ...
Water is a vital resource for human survival, so it is the duty of ensuring security of supplies ... more Water is a vital resource for human survival, so it is the duty of ensuring security of supplies in any situation. There have been several studies and found that the savannah of Bogotá has a functional and seismic vulnerability in the event of a natural disaster, in which their systems of water supply fail, leaving a large percentage of affected population. Given the magnitude of the problem, there is an alternative, portable treatment plants that provide the necessary water satisfactorily during the scope of the emergency. For this purpose, we identified the technologies available for water treatment, in order to achieve assess the best con-figuration of such plants to ensure water quality within a limited time.
The generation of membranes has grown in recent years, and that has caused a high business impact... more The generation of membranes has grown in recent years, and that has caused a high business impact. One of the materials used to manufacture membranes are polymers due to properties such as the adoption of different shapes and control over their molecular configurations. There are different methods of separation for the generation of membranes. Polystyrene membranes were performed by extraction and sulfonation. In the method of extraction was varied the percentage by weight of the polymer and solvent, in order to determine the composition and the most suitable solvent for an appropriate pore distribution, while the extractant remained constant. For sulfonation method was used only a percentage by weight of polymer, and by sulfonation reaction sulfonated polystyrene was prepared prior to generating the membrane. After obtaining the membranes, covered with gold, because the samples are not conductive and observed in scanning electron microscopy for characterization and structure determ...
This work describes the preparation of a polymer of acrylic acid (AA) and ethylene glycol (EG) by... more This work describes the preparation of a polymer of acrylic acid (AA) and ethylene glycol (EG) by redox polymerization and the use of the exhausted metal based catalysts (ferric ion) of the process to synthesize zero-valent iron nanoparticles for water remediation applications. The polymerization is done by free radicals in a reaction between a catalyst (FeCl2 or FeSO4) and an initiator (Potassium persulfate). This redox polymerization is the source of the metal ions that are going to be reduced and immobilized simultaneously in the polymer. The creation of a support like polymer hydrogel or membrane pore domain for the immobilization of nanoparticles (NPs) prevents their loss and reduction of active surface. For direct solution-phase (no polymers) synthesis, NPs loss and aggregation occurs, making them unable to recover and possibly increasing the costs in the practice. The novelty of this work is that the nanoparticles are synthesized using the metal catalysts from the polymerizat...
With the synthesis and functionalization of membranes for selective separations, reactivity, and ... more With the synthesis and functionalization of membranes for selective separations, reactivity, and stimuli responsive behavior arises new and advanced opportunities. The integration of bio-based channels is one of these advancements in membrane technologies. By a layer-by-layer (LbL) assembly of polyelectrolytes, outer membrane protein F trimers (OmpF) or "porins" from Escherichia coli with a central pore of ~2 nm diameter at its opening and ~0.7 × 1.1 nm at its constricted region are immobilized within the pores of poly(vinylidene fluoride) microfiltration membranes, as opposed to traditional ruptured lipid bilayer or vesicles processes. These OmpF-membranes demonstrate selective rejections of non-charged organics over ionic solutes, allowing the passage of salts up to 2 times higher than traditional nanofiltration membranes starting with rejections of 84% for 0.4-1.0 kDa organics. The presence of charged groups in OmpF membranes also leads to pH-dependent salt rejection th...
Functionalized polymer materials with ion-exchange groups and the integration of nanostructured m... more Functionalized polymer materials with ion-exchange groups and the integration of nanostructured materials is an emerging area for catalytic and water pollution control applications. The polymerization of materials such as acrylic acid often requires persulfate initiator and a high-temperature start. However, is generally known that metal ions accelerate such polymerizations starting from room temperature. If the metal is properly selected, then it can be used in environmental applications, adding two advantages simultaneously. This article deals with this by polymerizing acrylic acid using iron as an accelerant and subsequently using it for nanoparticle synthesis in hydrogels and PVDF membranes. Characterizations of hydrogels, membranes, and nanoparticles were carried out with different techniques. Nanoparticles sizes of 30–60 nm were synthesized. Permeability and swelling measurements demonstrate an inverse relationship between the hydrogel mesh size (6.30 to 8.34 nm) and the membrane pore size (222 to 110 nm). The quantitative reduction of trichloroethylene/chloride generation by Fe/Pd nanoparticles in hydrogel/membrane platforms was also performed.
Este resumen pretende dar una visión global de los aportes de la Universidad de los Andes en el t... more Este resumen pretende dar una visión global de los aportes de la Universidad de los Andes en el tratamiento de aguas y suelos con la presencia de compuestos de difícil degradación o tiempo de vida media prolongado, tales como fármacos (Ciclofosfamida), lodos aceitosos y derivados de la industria del petróleo (Tolueno, Xileno, Fenol) derivados de la industria textil, química y pesticidas (Bisphenol A, AMBI, Glifosato, Isoproturon y Metobromuron), usando tecnologías ya sea basadas en procesos biológicos (biorremediación y bioadsorción) o de oxidación avanzada (foto-Fenton).
This summary intends to give a global view of the Universidad de los Andes contributions related to the water and soil treatment in the presence of recalcitrant or long half-life aquatic pollutants such as drugs (Cyclophosphamide), oil sludge and petroleum (Toluene, Xylene and Phenol), textile, chemical (Bisphenol A, AMBI) and pesticides (Glyphosate, Isoproturon, and Metobromuron) industry derived products based on biological (bioremediation and bioadsortion) and advanced oxidation (Photo-Fenton) approaches.
Functionalized microfiltration membranes containing iron nanoparticles are a novel platform for o... more Functionalized microfiltration membranes containing iron nanoparticles are a novel platform for organic pollutant degradation reactions and for selective removal of contaminants such as heavy metals, without the drawback of potential nanoparticle loss to the environment. These environmentally friendly and sustainable technology approaches allow various water treatment applications exploit the enhanced water transport through the membrane pores. The present work deals with “green” techniques to create nanocomposite materials based on sponge-like membranes for water remediation containing chlorinated organic compounds. First, hydrophobic hollow fiber microfiltration membranes (HF) of polyvinylidene fluoride were hydrophilized using a water-based chemistry process with polyvinylpyrrolidone and persulfate. HF and flat sheet membrane pores were then functionalized with poly(acrylic acid) hydrogel followed by a double ion exchange sodium/iron and subsequent in situ synthesis of bimetallic Fe/Pd nanoparticles. The nanocomposite membrane modifications were determined by contact angle, surface free energy and infrared spectroscopy. The synthesized nanoparticles were characterized by electronic microscopy, X-ray spectrometry, image analysis and other techniques. Nanoparticle sizes between 193 and 301 nm were obtained for each of the membranes. Depending on the concentration of the dopant (Pd) in the membrane, the catalytic activity (established by trichloroethylene (TCE) reduction) was enhanced up to tenfold compared to other reported results. Chloride produced in reduction was close to the stoichiometric 3/1 (Cl/TCE), indicating absence of reaction intermediates.
Water pollution is a serious concern in all the aspects of society. Most of the pollutants have t... more Water pollution is a serious concern in all the aspects of society. Most of the pollutants have two main origins: organic compounds and heavy metals. One of these contaminants, Trichloroethylene (TCE), has high interest because their persistency in nature and the difficulties related with their treatment and/or elimination. Nano-structured material synthesis or metal capturing using functionalized membranes with polymers that contain ion exchange groups is a promising research field for water pollution, catalytic and mining applications. The polymerization of such materials requires initiation using strong oxidants and heat. However, a redox reaction can take place using metal ions to accelerate it.
This work describes this redox polymerization in order to synthesize a hydrogel of poly (acrylic acid) (PAA) for Polyvinylidene fluoride (PVDF) membrane functionalization using ferrous ions as accelerant and persulfate as initiator. The iron accelerant selected was subsequently used for nanoparticle synthesis and compared with a process of ion exchange and nanoparticle synthesis developed previously by this group. Redox polymerization resulted exothermic with temperatures around 50°C producing ferric ions contributing to the decrease in pH values around 2.0. Iron nanoparticles sizes of 30-60 nm were synthesized. From the use of the ferrous ions in the polymerization of the hydrogel, 9.2 mg Fe /g PAA were produced. This value is lower compared to ion exchange procedure (450 mg Fe/ g PAA) due to the small concentrations used in the polymerization. Since the functionalization of the membranes carry less PAA inside (8.5 to 13.4% wt), the amount of iron in the membranes was lower.
The PAA hydrogel was also characterized by swelling behavior along with the permeability of the PVDF-PAA membranes. The rate of swelling of the cross-linked PAA hydrogel follows a second order swelling kinetics, making the swelling process faster at higher pH values and higher responsive behavior. It was defined an inverse relationship between the hydrogel mesh size (6.30 to 8.34 nm) and the membrane pore size (222 to 110nm). An increase in the mesh size of the hydrogel creates around 93% of decrease in permeability.
Quantitative TCE/chloride generation by Fe/Pd nanoparticles in hydrogel and functionalized membrane were performed in batch process. Iron nanoparticles followed pseudo-first order reaction kinetics with a higher surface-area constant ksa in hydrogel (2.46 L/ (m2h)) than functionalized membrane (0.10 to 0.13 L/ (m2h)) due to a more open area and larger volume of reaction. The produced chloride using bimetallic Fe/Pd nanoparticles in dechlorination experiments is close to the stoichiometric value, indicating negligible production of intermediates.
The project described was supported by Grant Number P42ES007380 from the National Institute of Environmental Health Sciences. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Environmental Health Sciences or the National Institutes of Health.
During the last two decades, the photocatalytic degradation for the oxidation of volatile organic... more During the last two decades, the photocatalytic degradation for the oxidation of volatile organic compounds (VOC) has gained force since these compounds represents an environmental risk and a public health problem. A particular group of these VOCs: the BTEX (benzene-toluene-ethylbezene-xylene), are often used as a solvent in paints and it is also considerably dangerous on service stations and oil companies. On that way, it is a group of gases that can be present in both environments, indoor and/or outdoor. The fumes which are produced are highly polluting and persistent. To determine the degradation of those gases, a prototype of a packed bed photoreactor with UV lamps and TiO2 (1%p/p) as catalyst was used. The catalyst is supported on polyester granules. Conversion of each contaminant were determined and the mixture as well. The research found conversions between 72% and 99% giving better results for the treatment of the mixture where all conversions achieved were above 94% for a residence time of 160 min. It was found that an increment in the initial concentration of pollutant can improve the final conversion for components such as ethylbenzene. Finally, kinetic constants were determined for pollutants degradation which ranged between 0.005 and 0.03 min^-1
An investigation of photo-catalytical degradation to organic pollutants present in waste waters u... more An investigation of photo-catalytical degradation to organic pollutants present in waste waters used in the cleaning of ink in impression cartridges was carried out. In order to accomplish this degradation a titanium dioxide (TiO2-Degussa) supported on activated carbon (TiO2-AC) photo-catalyst was manufactured, so as to allow the organic dissolved species to easily contact the ions and free radicals generated by the oxidizing species exposed to UV light throughout the reactor. The composite particles of TiO2 and activated carbon were prepared using methylene chloride and liquid silicon to generate one dispersion with TiO2 which diffuses into the AC granules for a period of 20 hours at 298K, followed by an hour of thermal treatment at 373K. An advanced catalytic oxidation process was preformed with the aim of determining the photo-catalytic reaction kinetics of the CMYK inks found in the impression cartridges. An accurate kinetic model was developed by measuring the concentration of the oxidizing agent and the organic pollutants at different time intervals along the process and determining the effects of initial pollutant and oxidizing agent concentrations. Finally, to corroborate the degradation a chemical oxygen demand test (COD) was carried out to evaluate the reduction of organic water pollutants after treatment in the photo-catalytic-reactor. Additionally, a Fourier Transformed Infrared Spectrum analysis was carried out to, both, the starting ink-water sample and the reactor effluent to determine the presence of major organic functionalities, and explore possible means to improve the photo-catalytic degradation process developed.
The generation of membranes has grown in recent years, and that has caused a high business impact... more The generation of membranes has grown in recent years, and that has caused a high business impact. One of the materials used to manufacture membranes are polymers due to properties such as the adoption of different shapes and control over their molecular configurations. There are different methods of separation for the generation of membranes. Polystyrene membranes were performed by extraction and sulfonation. In the method of extraction was varied the percentage by weight of the polymer and solvent, in order to determine the composition and the most suitable solvent for an appropriate pore distribution, while the extractant remained constant. For sulfonation method was used only a percentage by weight of polymer, and by sulfonation reaction sulfonated polystyrene was prepared prior to generating the membrane. After obtaining the membranes, covered with gold, because the samples are not conductive and observed in scanning electron microscopy for characterization and structure determination. Was found for the extraction method that the best structure is obtained for a rate of 5% polymer using chloroform as solvent, with a pore size of 0,1 μm and an asymmetrical structure; for the membrane produced from sulfonation, the pore size was greater and the structure was asymmetrical too.
Water is a vital resource for human survival, so it is the duty of ensuring security of supplies ... more Water is a vital resource for human survival, so it is the duty of ensuring security of supplies in any situation. There have been several studies and found that the savannah of Bogotá has a functional and seismic vulnerability in the event of a natural disaster, in which their systems of water supply fail, leaving a large percentage of affected population. Given the magnitude of the problem, there is an alternative, portable treatment plants that provide the necessary water satisfactorily during the scope of the emergency. For this purpose, we identified the technologies available for water treatment, in order to achieve assess the best con-figuration of such plants to ensure water quality within a limited time.
Un estudio fue desarrollado a escala laboratorio de un proceso foto-Fenton con el fin de evaluar ... more Un estudio fue desarrollado a escala laboratorio de un proceso foto-Fenton con el fin de evaluar la factibilidad técnica de un sistema de tratamiento de aguas residuales con colorantes del sector textil. El proceso foto – Fenton fue aplicado como pretratamiento para así obtener un agua compatible con un proceso biológico. Se exploraron diferentes concentraciones Fenton que permitieron aumentar la biotratabilidad (DBO5/DQO) de una solución artificial con colorante y del agua residual real, como también la disminución del color (Abs580). Las soluciones pretratadas con mejores resultados se agregaron a un biorreactor de lodos activados para determinar la tasa específica de consumo de oxígeno (TECO). Los mejores resultados para la solución con colorante fueron obtenidos a concentraciones Fenton de 0.1:10 (Fe (II):H2O2, mM) y una TECO de 14.65(mg/g)/h. Para el agua residual, los resultados fueron con Fenton de 1:10mM y una TECO de 7.81 (mg/g)/h, la cual no estuvo dentro del rango deseado.
Various studies have showed the effect of nano-structured materials in decontamination of water. ... more Various studies have showed the effect of nano-structured materials in decontamination of water. Some of these materials use functionalized membranes with polymers that have ion exchange functional groups for nanoparticle synthesis. These systems prevent the loss of nanoparticles and have a high surface area that increases their reactivity. In order to improve the detoxification of water, it is necessary to explore different platforms like functionalized hydrogels or hollow fiber (HF)/spongy-like microfiltration membranes.
The present work takes hydrogels of poly (acrylic acid) (PAA) and membranes of polyvinylidene fluoride (PVDF) with PAA, to immobilize iron and iron/palladium nanoparticles to treat aqueous solutions with different chloro-organic pollutants and heavy metals like Selenium. Is worth mentioning that functionalization of HF membranes with functional polymers and nanoparticles has not been applied yet in detoxification studies. The functionalization of HF was also preceded by a hydrophilization with poly(vinyl pyrrolidone). The PAA hydrogel was also characterized by swelling behavior, and also the permeability of the membranes.
Quantitative detoxification by iron and iron/palladium nanoparticles in hydrogels and membranes were performed in batch process. Iron nanoparticles follow pseudo-first order degradation reaction kinetics. Using hydrogels, the surface-area normalized rate constant is higher than using membranes and similar results between hydrogel and solution phase were found. Produced chloride is close to the stoichiometric value, indicating negligible intermediate production. Comparative analysis of iron loading between platforms from previous and current works were also made.
This research is supported by the NIEHS-SRP grant P42ES007380 and by an NSF EPSCoR grant. HF Membranes were synthesized at the SMTC, NTU (Singapore, Singapore). Flat sheet membranes used are from EMD Millipore (Billerica MA, USA) and Ultura (Oceanside CA, USA).
Membranes provide selective barriers that allow certain molecules to pass through them based on c... more Membranes provide selective barriers that allow certain molecules to pass through them based on charge and size restriction and provide an avenue for chemical separation that requires less energy than more common thermal separation processes. To introduce viewers to the key variables governing membrane selectivity, this poster will first address the differences in the rejection of various divalent salts by a nanofiltration membrane. Even more impressive than artificial membranes are the biological membranes that nature offers, with higher selectivity, resistance to fouling, and regenerative capabilities. Thus, incorporating into membranes the structures responsible for high biological performance could potentially increase stimulus-responsive behavior and salt rejection while attaining larger fluxes than other highly selective membranes. In order to achieve proper alignment and stabilization of biomolecules, certain techniques are utilized. The second focus of this research is to explain the process and behavior of the layer-by-layer assembly of polycations and polyanions. Multilayers of electrolytes have been shown to increase the number of immobilized biomolecules by 25-fold with insignificant distortion of biomolecules.
Porins, or cylindrical beta barrel protein pores, are the biomolecule of interest in this research. Membranes with solely porins acting as their channels could produce novel behaviors and transport only small metabolites while rejecting macromolecules. These beta barrel proteins are immobilized within the pores of polyvinylidene fluoride (PVDF) membranes using layers of poly(acrylic acid) (PAA) hydrogel intercalated through in situ free radical polymerization and poly(allylamine) hydrochloride (PAH) accumulated during convective flow. The major challenge with this study is achieving an orientation of the porins parallel to the length of membrane pores so fluids may flow through their channels. The number of electrolytic layers, methods of functionalizing the membranes and immobilizing the porins, and the effect of the polyion chosen for the final layer are examined to achieve proper porin alignment and stability.
Functionalization of polymeric membranes of polyvinylidene fluoride (PVDF) for water purification... more Functionalization of polymeric membranes of polyvinylidene fluoride (PVDF) for water purification is an extensive field of study. Most studies of functionalization have been done in flat sheet membranes for pH and temperature responsive applications. In order to improve the detoxification of water, it is necessary to explore different platforms such as hollow fiber (HF) or thicker (spongy-like) flat sheet (FS) microfiltration membranes. HF functionalization has been made on other materials different than PVDF and there are relatively very few studies describing this application as well in thicker membranes.
This work explores the dechlorination of TCE in aqueous solution using iron/palladium nanoparticles (NPs) immobilized in HF and FS membranes functionalized with a functional polymer (polyacrylic acid). The applicability of these systems has been proven in scale-up modules in water polluted with chloro-organic compounds. These systems prevent nanoparticle loss and have a high surface-area that increases their reactivity. Changing the pH of the functionalization process has an impact in the particle size and inter-particle distance as well in the swelling behavior during the dechlorination reactions. It is worth mentioning that functionalization of HF membranes with functional polymers and nanoparticles have not been applied in detoxification studies. TCE degradation with NPs (174 to 280 nm) follows a first-order rate law. The surface-normalized-area rate constants are 0.08 and 0.39 L/ (m2h) for HF and FS, respectively. Up to 75% of TCE degradation is achieved.
This research is supported by the NIEHS-SRP grant P42ES007380. HF Membranes were synthesized at the SMTC, NTU (Singapore). Flat sheet membranes used are from Nanostone (Oceanside, CA - USA).
This work describes the preparation of a polymer of acrylic acid (AA) and ethylene glycol (EG) by... more This work describes the preparation of a polymer of acrylic acid (AA) and ethylene glycol (EG) by redox polymerization and the use of the exhausted metal based catalysts (ferric ion) of the process to synthesize zero-valent iron nanoparticles for water remediation applications. The polymerization is done by free radicals in a reaction between a catalyst (FeCl2 or FeSO4) and an initiator (Potassium persulfate). This redox polymerization is the source of the metal ions that are going to be reduced and immobilized simultaneously in the polymer. The creation of a support like polymer hydrogel or membrane pore domain for the immobilization of nanoparticles (NPs) prevents their loss and reduction of active surface. For direct solution-phase (no polymers) synthesis, NPs loss and aggregation occurs, making them unable to recover and possibly increasing the costs in the practice. The novelty of this work is that the nanoparticles are synthesized using the metal catalysts from the polymerization to form PAA hydrogel. Previous reported studies involved polymerization by free radicals but the Fe ions are ion exchanged in the COOH functional groups after the hydrogel synthesis which was followed by zero-valent iron formation with sodium borohydride. The amount of iron in the solution phase is measured by Atomic Absorption and the counter ion (Chloride) is quantified by a ion selective probe. By material balance, the amount of iron inside the polymer is calculated. Characterization of the polymer and the presence of iron nanoparticles within are done by SEM and TGA techniques.
The polymer hydrogel-nanoparticles system is also studied for toxic chloro-organic degradation from water. In addition to the direct use of NPs immobilized charged hydrogels, polymerization was also conducted in PVDF microfiltration membrane pores to study their functionalization and application towards the pollutant degradation process in batch and convective flow modes. This research was supported by the NIEHS-SRP program.
El agua es uno de los recursos vitales para la subsistencia del ser humano, por lo cual es obliga... more El agua es uno de los recursos vitales para la subsistencia del ser humano, por lo cual es obligación del mismo garantizar su suministro en cualquier situación. Se han realizado varios estudios y se encontró que la Sabana de Bogotá presenta una vulnerabilidad funcional y sísmica en caso de una catástrofe natural, en la cual sus sistemas de suministro de agua potable fallarían dejando un gran porcentaje de población afectada. Teniendo en cuenta la magnitud de la problemática, se planteó una solución alternativa: plantas de tratamiento móvil ó portátil que provean satisfactoriamente el agua necesaria durante el alcance de la emergencia. Para tal fin se identificaron las tecnologías disponibles para el tratamiento de agua para así lograr evaluar cual sería la mejor configuración de tales plantas que garanticen la calidad del agua en un tiempo limitado.
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This summary intends to give a global view of the Universidad de los Andes contributions related to the water and soil treatment in the presence of recalcitrant or long half-life aquatic pollutants such as drugs (Cyclophosphamide), oil sludge and petroleum (Toluene, Xylene and Phenol), textile, chemical (Bisphenol A, AMBI) and pesticides (Glyphosate, Isoproturon, and Metobromuron) industry derived products based on biological (bioremediation and bioadsortion) and advanced oxidation (Photo-Fenton) approaches.
pollutant degradation reactions and for selective removal of contaminants such as heavy metals, without the drawback of potential nanoparticle loss to the environment. These environmentally friendly and sustainable technology approaches allow various water treatment applications exploit the enhanced water transport through the membrane pores. The present work deals with “green” techniques to create nanocomposite materials based on sponge-like membranes for water remediation containing chlorinated organic compounds. First, hydrophobic hollow fiber microfiltration membranes (HF) of polyvinylidene fluoride were hydrophilized using a water-based chemistry process with polyvinylpyrrolidone and persulfate. HF and flat sheet membrane pores were then functionalized with poly(acrylic acid) hydrogel followed by a double ion exchange sodium/iron and subsequent in situ synthesis of bimetallic Fe/Pd nanoparticles. The nanocomposite membrane modifications were determined by contact angle, surface free energy and infrared spectroscopy. The synthesized nanoparticles were characterized by electronic microscopy, X-ray spectrometry, image analysis and other techniques. Nanoparticle sizes between 193 and 301 nm were obtained for each of the membranes. Depending on the concentration of the dopant (Pd) in the membrane, the catalytic activity (established by trichloroethylene (TCE) reduction) was enhanced up to tenfold compared to other reported results. Chloride produced in reduction was close to the stoichiometric 3/1 (Cl/TCE), indicating absence of reaction intermediates.
This work describes this redox polymerization in order to synthesize a hydrogel of poly (acrylic acid) (PAA) for Polyvinylidene fluoride (PVDF) membrane functionalization using ferrous ions as accelerant and persulfate as initiator. The iron accelerant selected was subsequently used for nanoparticle synthesis and compared with a process of ion exchange and nanoparticle synthesis developed previously by this group. Redox polymerization resulted exothermic with temperatures around 50°C producing ferric ions contributing to the decrease in pH values around 2.0. Iron nanoparticles sizes of 30-60 nm were synthesized. From the use of the ferrous ions in the polymerization of the hydrogel, 9.2 mg Fe /g PAA were produced. This value is lower compared to ion exchange procedure (450 mg Fe/ g PAA) due to the small concentrations used in the polymerization. Since the functionalization of the membranes carry less PAA inside (8.5 to 13.4% wt), the amount of iron in the membranes was lower.
The PAA hydrogel was also characterized by swelling behavior along with the permeability of the PVDF-PAA membranes. The rate of swelling of the cross-linked PAA hydrogel follows a second order swelling kinetics, making the swelling process faster at higher pH values and higher responsive behavior. It was defined an inverse relationship between the hydrogel mesh size (6.30 to 8.34 nm) and the membrane pore size (222 to 110nm). An increase in the mesh size of the hydrogel creates around 93% of decrease in permeability.
Quantitative TCE/chloride generation by Fe/Pd nanoparticles in hydrogel and functionalized membrane were performed in batch process. Iron nanoparticles followed pseudo-first order reaction kinetics with a higher surface-area constant ksa in hydrogel (2.46 L/ (m2h)) than functionalized membrane (0.10 to 0.13 L/ (m2h)) due to a more open area and larger volume of reaction. The produced chloride using bimetallic Fe/Pd nanoparticles in dechlorination experiments is close to the stoichiometric value, indicating negligible production of intermediates.
The project described was supported by Grant Number P42ES007380 from the National Institute of Environmental Health Sciences. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Environmental Health Sciences or the National Institutes of Health.
This summary intends to give a global view of the Universidad de los Andes contributions related to the water and soil treatment in the presence of recalcitrant or long half-life aquatic pollutants such as drugs (Cyclophosphamide), oil sludge and petroleum (Toluene, Xylene and Phenol), textile, chemical (Bisphenol A, AMBI) and pesticides (Glyphosate, Isoproturon, and Metobromuron) industry derived products based on biological (bioremediation and bioadsortion) and advanced oxidation (Photo-Fenton) approaches.
pollutant degradation reactions and for selective removal of contaminants such as heavy metals, without the drawback of potential nanoparticle loss to the environment. These environmentally friendly and sustainable technology approaches allow various water treatment applications exploit the enhanced water transport through the membrane pores. The present work deals with “green” techniques to create nanocomposite materials based on sponge-like membranes for water remediation containing chlorinated organic compounds. First, hydrophobic hollow fiber microfiltration membranes (HF) of polyvinylidene fluoride were hydrophilized using a water-based chemistry process with polyvinylpyrrolidone and persulfate. HF and flat sheet membrane pores were then functionalized with poly(acrylic acid) hydrogel followed by a double ion exchange sodium/iron and subsequent in situ synthesis of bimetallic Fe/Pd nanoparticles. The nanocomposite membrane modifications were determined by contact angle, surface free energy and infrared spectroscopy. The synthesized nanoparticles were characterized by electronic microscopy, X-ray spectrometry, image analysis and other techniques. Nanoparticle sizes between 193 and 301 nm were obtained for each of the membranes. Depending on the concentration of the dopant (Pd) in the membrane, the catalytic activity (established by trichloroethylene (TCE) reduction) was enhanced up to tenfold compared to other reported results. Chloride produced in reduction was close to the stoichiometric 3/1 (Cl/TCE), indicating absence of reaction intermediates.
This work describes this redox polymerization in order to synthesize a hydrogel of poly (acrylic acid) (PAA) for Polyvinylidene fluoride (PVDF) membrane functionalization using ferrous ions as accelerant and persulfate as initiator. The iron accelerant selected was subsequently used for nanoparticle synthesis and compared with a process of ion exchange and nanoparticle synthesis developed previously by this group. Redox polymerization resulted exothermic with temperatures around 50°C producing ferric ions contributing to the decrease in pH values around 2.0. Iron nanoparticles sizes of 30-60 nm were synthesized. From the use of the ferrous ions in the polymerization of the hydrogel, 9.2 mg Fe /g PAA were produced. This value is lower compared to ion exchange procedure (450 mg Fe/ g PAA) due to the small concentrations used in the polymerization. Since the functionalization of the membranes carry less PAA inside (8.5 to 13.4% wt), the amount of iron in the membranes was lower.
The PAA hydrogel was also characterized by swelling behavior along with the permeability of the PVDF-PAA membranes. The rate of swelling of the cross-linked PAA hydrogel follows a second order swelling kinetics, making the swelling process faster at higher pH values and higher responsive behavior. It was defined an inverse relationship between the hydrogel mesh size (6.30 to 8.34 nm) and the membrane pore size (222 to 110nm). An increase in the mesh size of the hydrogel creates around 93% of decrease in permeability.
Quantitative TCE/chloride generation by Fe/Pd nanoparticles in hydrogel and functionalized membrane were performed in batch process. Iron nanoparticles followed pseudo-first order reaction kinetics with a higher surface-area constant ksa in hydrogel (2.46 L/ (m2h)) than functionalized membrane (0.10 to 0.13 L/ (m2h)) due to a more open area and larger volume of reaction. The produced chloride using bimetallic Fe/Pd nanoparticles in dechlorination experiments is close to the stoichiometric value, indicating negligible production of intermediates.
The project described was supported by Grant Number P42ES007380 from the National Institute of Environmental Health Sciences. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Environmental Health Sciences or the National Institutes of Health.
factibilidad técnica de un sistema de tratamiento de aguas residuales con colorantes del sector textil.
El proceso foto – Fenton fue aplicado como pretratamiento para así obtener un agua compatible con
un proceso biológico. Se exploraron diferentes concentraciones Fenton que permitieron aumentar la
biotratabilidad (DBO5/DQO) de una solución artificial con colorante y del agua residual real, como
también la disminución del color (Abs580). Las soluciones pretratadas con mejores resultados se
agregaron a un biorreactor de lodos activados para determinar la tasa específica de consumo de
oxígeno (TECO). Los mejores resultados para la solución con colorante fueron obtenidos a
concentraciones Fenton de 0.1:10 (Fe (II):H2O2, mM) y una TECO de 14.65(mg/g)/h. Para el agua
residual, los resultados fueron con Fenton de 1:10mM y una TECO de 7.81 (mg/g)/h, la cual no estuvo
dentro del rango deseado.
The present work takes hydrogels of poly (acrylic acid) (PAA) and membranes of polyvinylidene fluoride (PVDF) with PAA, to immobilize iron and iron/palladium nanoparticles to treat aqueous solutions with different chloro-organic pollutants and heavy metals like Selenium. Is worth mentioning that functionalization of HF membranes with functional polymers and nanoparticles has not been applied yet in detoxification studies. The functionalization of HF was also preceded by a hydrophilization with poly(vinyl pyrrolidone). The PAA hydrogel was also characterized by swelling behavior, and also the permeability of the membranes.
Quantitative detoxification by iron and iron/palladium nanoparticles in hydrogels and membranes were performed in batch process. Iron nanoparticles follow pseudo-first order degradation reaction kinetics. Using hydrogels, the surface-area normalized rate constant is higher than using membranes and similar results between hydrogel and solution phase were found. Produced chloride is close to the stoichiometric value, indicating negligible intermediate production. Comparative analysis of iron loading between platforms from previous and current works were also made.
This research is supported by the NIEHS-SRP grant P42ES007380 and by an NSF EPSCoR grant. HF Membranes were synthesized at the SMTC, NTU (Singapore, Singapore). Flat sheet membranes used are from EMD Millipore (Billerica MA, USA) and Ultura (Oceanside CA, USA).
Even more impressive than artificial membranes are the biological membranes that nature offers, with higher selectivity, resistance to fouling, and regenerative capabilities. Thus, incorporating into membranes the structures responsible for high biological performance could potentially increase stimulus-responsive behavior and salt rejection while attaining larger fluxes than other highly selective membranes. In order to achieve proper alignment and stabilization of biomolecules, certain techniques are utilized. The second focus of this research is to explain the process and behavior of the layer-by-layer assembly of polycations and polyanions. Multilayers of electrolytes have been shown to increase the number of immobilized biomolecules by 25-fold with insignificant distortion of biomolecules.
Porins, or cylindrical beta barrel protein pores, are the biomolecule of interest in this research. Membranes with solely porins acting as their channels could produce novel behaviors and transport only small metabolites while rejecting macromolecules. These beta barrel proteins are immobilized within the pores of polyvinylidene fluoride (PVDF) membranes using layers of poly(acrylic acid) (PAA) hydrogel intercalated through in situ free radical polymerization and poly(allylamine) hydrochloride (PAH) accumulated during convective flow. The major challenge with this study is achieving an orientation of the porins parallel to the length of membrane pores so fluids may flow through their channels. The number of electrolytic layers, methods of functionalizing the membranes and immobilizing the porins, and the effect of the polyion chosen for the final layer are examined to achieve proper porin alignment and stability.
This work explores the dechlorination of TCE in aqueous solution using iron/palladium nanoparticles (NPs) immobilized in HF and FS membranes functionalized with a functional polymer (polyacrylic acid). The applicability of these systems has been proven in scale-up modules in water polluted with chloro-organic compounds. These systems prevent nanoparticle loss and have a high surface-area that increases their reactivity. Changing the pH of the functionalization process has an impact in the particle size and inter-particle distance as well in the swelling behavior during the dechlorination reactions. It is worth mentioning that functionalization of HF membranes with functional polymers and nanoparticles have not been applied in detoxification studies. TCE degradation with NPs (174 to 280 nm) follows a first-order rate law. The surface-normalized-area rate constants are 0.08 and 0.39 L/ (m2h) for HF and FS, respectively. Up to 75% of TCE degradation is achieved.
This research is supported by the NIEHS-SRP grant P42ES007380. HF Membranes were synthesized at the SMTC, NTU (Singapore). Flat sheet membranes used are from Nanostone (Oceanside, CA - USA).
The creation of a support like polymer hydrogel or membrane pore domain for the immobilization of nanoparticles (NPs) prevents their loss and reduction of active surface. For direct solution-phase (no polymers) synthesis, NPs loss and aggregation occurs, making them unable to recover and possibly increasing the costs in the practice. The novelty of this work is that the nanoparticles are synthesized using the metal catalysts from the polymerization to form PAA hydrogel. Previous reported studies involved polymerization by free radicals but the Fe ions are ion exchanged in the COOH functional groups after the hydrogel synthesis which was followed by zero-valent iron formation with sodium borohydride. The amount of iron in the solution phase is measured by Atomic Absorption and the counter ion (Chloride) is quantified by a ion selective probe. By material balance, the amount of iron inside the polymer is calculated. Characterization of the polymer and the presence of iron nanoparticles within are done by SEM and TGA techniques.
The polymer hydrogel-nanoparticles system is also studied for toxic chloro-organic degradation from water. In addition to the direct use of NPs immobilized charged hydrogels, polymerization was also conducted in PVDF microfiltration membrane pores to study their functionalization and application towards the pollutant degradation process in batch and convective flow modes. This research was supported by the NIEHS-SRP program.