T main goal in upcycling municipal waste as technical components for the building industry is to comply with the pressing requirements coming from NZEB policy adopted in EU framework program Horizon 202020. CITERA research center, in... more
T main goal in upcycling municipal waste as technical components for the building industry is to comply with the pressing requirements coming from NZEB policy adopted in EU framework program Horizon 202020. CITERA research center, in cooperation with Lazio District has developed different components for the building envelope up cycling wood pallet, plastic and glass bottle, tires and aluminum cans, with high thermal and acoustic performance according to Italian latest building energy regulation (D.lgs. 311/2006). This component can be used both for vertical elements and for horizontal floors both for new constructions and for main refurbishment. A first application of this technology is a new model of social housing for elderly coming from the needs expressed in the position paper of Italian government on ageing society regarding the built environment. In fact the planning and design approach will need to incorporate the values and perspectives arising from this new cultural and dem...
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Alkali-activated binders (AABs) stand out as a sustainable alternative to ordinary Portland cement (OPC) as they can be formulated using by-products or waste as raw materials. However, the presence of hazardous compounds in residues can... more
Alkali-activated binders (AABs) stand out as a sustainable alternative to ordinary Portland cement (OPC) as they can be formulated using by-products or waste as raw materials. However, the presence of hazardous compounds in residues can lead to an increase in AABs' toxicity due to the highly alkaline media. Therefore, it is extremely important to evaluate their environmental risks to validate their use as building materials. This study environmentally assessed AABs prepared with two different fractions (0-30 mm and 8-30 mm) of weathered bottom ash (AA-WBA) from WtE plants. The potential leachate toxicity of AA-WBA was assessed using granular and monolithic leaching tests that simulated end-of-life and service life scenarios, respectively. Furthermore, an acute toxicity test with crustacean Daphnia magna as model organisms was conducted to determine the relationship between the leachate metal(loid) concentrations and the ecotoxicity of AA-WBA. The results showed higher metal(loid) concentrations in AA-WBA specimens prepared with the 0-30 mm fraction of WBA. The service life scenario revealed multiple metal(loid)-release mechanisms. The 48 h EC50 value (close to 10%; moderate toxicity) indicated that the use of the coarse fraction of WBA increased the immobilisation of the metal(loid)s. Finally, the correlation between the concentrations of some of the metal(loid)s and toxicity was demonstrated.
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Research Interests: Mechanical Engineering, Geography, Materials Science, Thermodynamics, Energy Conservation, and 10 moreHeat Transfer, Phase Change Material, Thermal Energy Storage, Thermal Analysis, Thermogravimetric Analysis, Interdisciplinary Engineering, Applied Thermal Engineering, Slurry, Heat Storage, and Latent Heat
Abstract Anaerobic digestion is a worldwide technology for the treatment of organic waste streams with clear environmental benefits including generation of methane as renewable energy. However, the need to improve process feasibility of... more
Abstract Anaerobic digestion is a worldwide technology for the treatment of organic waste streams with clear environmental benefits including generation of methane as renewable energy. However, the need to improve process feasibility of existing applications as well as to expand anaerobic digestion to a range of new substrates has raised interest on several intensifications techniques. Among them, the supplementation of inorganic and biological additives has shown good results at improving digesters performance. This manuscript presents a comprehensive review about recent advances in the utilization of inorganic and biological additives. On the one hand, reviewed inorganic additives comprise: (i) macro- (e.g. P, N and S) and micro- (e.g. Fe, Ni, Mo, Co, W and Se) nutrients supplements, (ii) ashes from waste incineration, (iii) compounds able to mitigate ammonia inhibition, and (iv) substances with high biomass immobilization capacity. Among them, iron (Fe 0 and Fe(III)) has shown particularly promising results, which have been mainly related to their action as electron donor/acceptor and cofactor of key enzymatic activities. On the other hand, reviewed biological additives include: (i) the dosage of microbial inocula with high hydrolytic or methanogenic activity (bioaugmentation), and (ii) the addition of enzymes able to facilitate particulate organic matter solubilization.
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Passive Fire Protection is currently a field of active interest in building technology. One of the different approaches to obtain a material that provides this protection is to add substances to the initial formulation that are capable to... more
Passive Fire Protection is currently a field of active interest in building technology. One of the different approaches to obtain a material that provides this protection is to add substances to the initial formulation that are capable to absorb heat when the temperature of the material is increased. This is achieved by means of endothermic reactions that these substances undergo at specified temperatures. In the case of a fire scenario huge amounts of heat are released and such heat absorbing reactions delay the achievement of temperatures that can be critical for structural stability. In this work we specifically analyze the behavior of gypsum, which is commonly used in buildings. In order to enrich its endothermic profile we add magnesium hydroxide, calcium hydroxide and calcium carbonate to the sample. These three alkaline earth components have their heat absorbing peaks located along the temperature domain in a way that the temperature rising is reasonably damped. In this work we find, as the main result, that when these three fillers are added to gypsum, the protection offered by the new combination of materials is significantly improved with respect to the behavior of gypsum alone. Under external heating, the component is able to keep itself under critical temperatures for a longer period. For the theoretical description, we first use non isothermal thermogravimetry (TG) to analyze and characterize the kinetic response of each component of the mixture. We propose a conversion function which is based on the correlation between consecutive reactions in neighboring molecules. The heating rate is included in the model as an analytical variable. Later we perform high temperature tests in a tubular furnace and their corresponding numerical simulations where heat transfer is explicitly carried and mass transfer effects are discussed.
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Ammonia nitrogen management is a recurrent problem in intensive livestock areas. Struvite precipitation stands as a mature technology to recover ammonia nitrogen and prevent associated environmental problems. However, the feasibility of... more
Ammonia nitrogen management is a recurrent problem in intensive livestock areas. Struvite precipitation stands as a mature technology to recover ammonia nitrogen and prevent associated environmental problems. However, the feasibility of struvite technology to recover ammonia nitrogen from pig manure is limited by the reagents cost. This research aimed to optimise the formulation of a stabilizing agent (SA) synthesised using an industrial low-grade MgO by-product (LG-MgO) and phosphoric acid for efficient TAN recovery via struvite precipitation. Experimental results showed that the H3PO4/LG-MgO ratio controls the magnesium phosphate mineral phase of the SA (bobierrite and/or newberyite). Newberyite-rich SA showed the highest TAN removal efficiency from pig manure (66-73%) compared to the SA formed by a mixture of newberyite and bobierrite (51-59%) and by bobierrite (26%). Particle size reduction of LG-MgO did not improve the SA's TAN removal efficiency, although XRD patterns showed that the precipitates from the TAN removal experiments contained some unreacted newberyite. The economic analysis showed that the higher reactivity of the SA formulated using higher H3PO4/LG-MgO ratios compensated reagent costs. The SA synthesised with a H3PO4/LG-MgO ratio of 0.98 showed the most economical treatment cost, which was estimated at 7.5 € per kg of ammonia nitrogen from pig manure. Finally, the optimum SA was successfully synthesised in a 200-L pilot plant, with a TAN removal capacity only 10% lower than the one synthesised at lab-scale.
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A hard-burner low-grade MgO (LG-MgO) is used to formulate a chemically bonded phosphate ceramic (CBPC) instead of pure MgO. This by-product is 10 times cheaper than pure MgO. The use of this by-product reduce the cost of the final... more
A hard-burner low-grade MgO (LG-MgO) is used to formulate a chemically bonded phosphate ceramic (CBPC) instead of pure MgO. This by-product is 10 times cheaper than pure MgO. The use of this by-product reduce the cost of the final material and therefore an economical construction material could be obtained. This would reinforce the criteria of sustainability and recyclability. In addition, the inert phases contained on LG-MgO act like inorganic fillers, improving the mechanical properties of this CPBC, which can be considered as a mortar. A range from 55% to 65% of LG-MgO is studied, and boric acid is added in order to improve workability and setting times. Design of Experiments (DoE) approach enabled the evaluation of the influence of each component and the interactions between them. According to the setting times and compressive strength results, a formulation range is proposed.
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... Study of the effect of eafd in polymer composites usig DoE. Niubó Eslava, Maria; Fernández, Ana Inés; Haurie Ibarra, Laia; Capdevila, XG; Martínez, M; Velasco Perero, José Ignacio. Diseño y caracterización de mezclas EVA/plastómero... more
... Study of the effect of eafd in polymer composites usig DoE. Niubó Eslava, Maria; Fernández, Ana Inés; Haurie Ibarra, Laia; Capdevila, XG; Martínez, M; Velasco Perero, José Ignacio. Diseño y caracterización de mezclas EVA/plastómero para su empleo en compuestos de ...
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Although waste-to-energy plants allow reducing the mass and volume of municipal solid waste (MSW) incinerated, an average around 30 % of the total content remains as bottom ash (BA) and air pollution control (APC) ashes at the end of... more
Although waste-to-energy plants allow reducing the mass and volume of municipal solid waste (MSW) incinerated, an average around 30 % of the total content remains as bottom ash (BA) and air pollution control (APC) ashes at the end of combustion process. While weathered bottom ash (WBA) is considered a non-hazardous residue that can be revalorized as a secondary aggregate, APC fly ashes generated during the flue gas treatment are classified as hazardous waste and are handled in landfill disposal after stabilization, usually with Portland cement (OPC). However, taking into account the amount of APC residues produced and the disposing cost in landfill, their revalorization is an important issue that could be effectively addressed. As MSW can be incinerated producing bottom ashes (BA) or air pollutant control (APC) residues, the development of a mortar formulated with APC fly ash as secondary building material is a significant risk to the environment for their content of heavy metals. I...
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Controlled struvite formation has been attracting increasing attention as a near mature technology to recover nutrients from wastewater. However, struvite feasibility is generally limited by the high cost of chemical reagents. With the... more
Controlled struvite formation has been attracting increasing attention as a near mature technology to recover nutrients from wastewater. However, struvite feasibility is generally limited by the high cost of chemical reagents. With the aim to understand and control reagent use efficiency, experiments and equilibrium model simulations examined inorganic nitrogen (TAN) removal from pig manure via struvite with added magnesium and phosphate reagents. Four industrial magnesium oxide (MgO), a commercial product and three by-products from magnesite calcination, were tested with phosphate added as a highly soluble potassium salt. TAN removal extents with the MgOs ranged from 47 to 72%, with the highest grade MgO providing the greatest extent of TAN removal. However, model analysis showed that all the MgO reagents were poorly soluble (only about 40% of added magnesium actually dissolved). The model results suggested that this poor dissolution was due to kinetic limitations, not solubility constraints. A further set of additional reagents (termed stabilization agents) were prepared by pre-treating the MgO reagents with phosphoric acid, and were tested separately as a source of both magnesium and phosphate. Results showed that acid pre-treatment of moderate to highly reactive MgOs (soft to medium-burnt) primarily formed bobierrite as the stabilizing agent, whereas the pre-treatment of very low reactivity MgOs (dead-burnt) mostly formed newberyite. The newberyite stabilizing agents achieved very high TAN removal extents of about 80%, which is significant, considering that these were formed from dead-burnt/low-grade MgOs. However, the bobierrite stabilizing agents achieved a substantially lower TAN removal extent than their medium-to-high reactivity precursor MgOs. Again, model analysis showed that the bobierrite stabilizing agents were poorly soluble, due to kinetic limitations, not solubility constraints. In contrast, the model suggested that the newberyite stabilizing agents almost completely dissolved to very effectively form struvite. A mechanism was proposed by which conditions near a dissolving reagent particle surface causes unwanted struvite nucleation onto and overgrowth of the reagent particle, inhibiting further dissolution and markedly reducing reagent efficiency. The findings of the study could have implications for reagent efficiency with struvite in general, even when using other solid reagents such as magnesium hydroxide or other MgOs.
Research Interests: Water, Multidisciplinary, Animals, Struvite, Nitrogen, and 3 moreSwine, Phosphates, and Magnesium Oxide
ABSTRACT The transposition of a sustainable wet flue gas desulfurization (WFGD) process from a discontinuous batch reactor at laboratory scale to a pilot scale scrubber was performed by means of three transposition variables: time of... more
ABSTRACT The transposition of a sustainable wet flue gas desulfurization (WFGD) process from a discontinuous batch reactor at laboratory scale to a pilot scale scrubber was performed by means of three transposition variables: time of saturation (tS), liquid-to-gas ratio (L/G) and pH. Thus, the results obtained by the authors in the past studies at laboratory scale were extrapolated to the design and set-up of a pilot scale packed column. The present study describes the methodology employed during the up-scaling of the WFGD process using the optimum MgO by-product (LG-MgO). According to the results obtained, the pH of saturation (pHS) was well predicted by the discontinuous batch reactor. Moreover, the transposition process was confirmed by comparing the average consumption values (kg of by-product per m3 of SO2 for a 100% removal efficiency) at laboratory (2.9 ± 0.6 kg·m− 3 for diluted conditions) and pilot (2.3 ± 0.03 kg·m− 3) scales. Therefore, the high contact between phases promoted by the packing in the scrubber can be well predicted by a discontinuous batch reactor in diluted conditions. Consequently, saturation time (tS) is a suitable parameter from predicting the desulfurization behaviour of this kind of by-products at different scales. In order to avoid managing the acidic effluents and reduce the risk of material corrosion at the pHS, several desulfurization tests were performed at a pH 5. These trials included the testing of high SO2 concentrations (up to 30,000 mg·Nm− 3), where desulfurization was improved by the increase of the driving force of the process.
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ABSTRACT The reutilisation of MSWI natural weathered bottom ash (WBA) in many applications such as road and underground constructions, embankments or as an aggregate replacement is a common practice in many developed countries. Its... more
ABSTRACT The reutilisation of MSWI natural weathered bottom ash (WBA) in many applications such as road and underground constructions, embankments or as an aggregate replacement is a common practice in many developed countries. Its potential environmental risk has regularly been evaluated from the point of view of the leaching of heavy metals and metalloids. Nevertheless, the influence over steel rebar when reinforced concrete is exposed to the contact with WBA has been poorly assessed before. In this study, it has been possible to evaluate in terms of days the probability of corrosion in a common case of WBA reutilisation, which is in contact with reinforced concrete formulated with conventional Portland cement. The corrosion monitoring indicates that the probability of corrosion of steel rebar is higher than 90 % with a corrosion rate (CI) estimated to be 11.6 µm year−1. The aggressive conditions imposed by WBA suppose an important withdrawal if the application of reutilisation involves contact with steel rebar.
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The continued great dependency on fossil fuels entails increasing SO
ABSTRACT The reutilization of the by-products from the calcination of natural magnesite for environmental solutions is conditioned by the availability of MgO, CaO and other compounds. In order to overcome their great heterogeneity, an... more
ABSTRACT The reutilization of the by-products from the calcination of natural magnesite for environmental solutions is conditioned by the availability of MgO, CaO and other compounds. In order to overcome their great heterogeneity, an exhaustive chemical and physical characterization is necessary in order to assess their potential applications. In this study, the acid neutralization capacity (ANC) test was used to categorize three types of by-products (LG-MgO, LG-D and LG-F), which mainly differed according to source ore and processing conditions. The experimental data concerning the leaching of Mg2 +, Ca2 +, Fe2 + and SO42 − was corroborated with geochemical predictions using the modelling software Visual MINTEQ. Likewise, the main solubility-controlling mineral phases were also identified. According to the results, there is a buffer capacity within the pH 8–10 range, mainly dominated by the neutralization of MgO/Mg(OH)2, equilibrium with a small contribution from the carbonate content at lower pH values. The release of sulphates showed a non-pH dependency attributed to the solubility of CaSO4 and elemental sulphur present in petcoke. For dust materials, leaching of Fe was minimal above pH 6 owing to the insoluble nature of the Fe2O3/Fe3O4 pair. Accordingly, the by-products labeled as LG-D and LG-F are better suited for stabilizing solid wastes or wastewater that are acid while LG-MgO is more appropriate for alkaline residues such as contaminated soils. In both cases, a suitable pH range in which pH-dependent heavy metals and metalloids show minimum solubility can be obtained. The use of these by-products guarantees an environmentally friendly alkali reservoir for the long-term stabilization of heavy metals and metalloids at a very competitive price as a substitute for the widely used lime.
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ABSTRACT Low-grade magnesium hydroxide is being used with very promising results as flame retardant filler in polymeric materials and as aggregate in the formulation of mortars for passive fire protection, combining an economic and... more
ABSTRACT Low-grade magnesium hydroxide is being used with very promising results as flame retardant filler in polymeric materials and as aggregate in the formulation of mortars for passive fire protection, combining an economic and sustainable solution. Simultaneous TGA–DSC was used to evaluate low-grade magnesium hydroxide thermal decomposition in order to examine the suitability of this product for a broad range of temperatures. Thermal analysis in air shows an unexpected exothermic peak, as well as the endothermic peaks corresponding to the decomposition of magnesium hydroxide, magnesite and dolomite. Thermal decomposition using nitrogen as gas flow does not show the exothermic peak, whereas a new endothermic peak corresponding to decomposition of calcite appears. In situ XRD patterns collected in air atmosphere at high temperature allows determining the presence of anhydrite, which was related to direct sulphation of calcite from the sulphur trioxide generated during the combustion of petcoke adsorbed on the particle surface of the low-grade magnesium hydroxide.
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Hydromagnesite is a basic magnesium carbonate that undergoes an endothermic decomposition with water and carbon dioxide release in the temperature range of 200–550°C. Due to this thermal behaviour it has been studied as flame retardant... more
Hydromagnesite is a basic magnesium carbonate that undergoes an endothermic decomposition with water and carbon dioxide release in the temperature range of 200–550°C. Due to this thermal behaviour it has been studied as flame retardant filler for polymers in cable applications. For this purpose the particle size distribution should be optimized, as it is in most cases responsible for decrease
Research Interests: Materials Engineering, Carbon Dioxide, FTIR spectroscopy, Magnesium, Differential scanning calorimetry, and 11 moreStructural Change, Thermogravimetry, X ray diffraction, Thermal Stability, Particle Size, Flame Retardant, Thermogravimetric Analysis, Thermal Decomposition, Particle Size Distribution, thermal behaviour, and Mechanical Property
During the annealing process of cold-drawn copper with small amounts of impurities a multiple-sigmoidal behavior has been found, related to the overlapping of two or more process steps, corresponding to a simultaneous recrystallization of... more
During the annealing process of cold-drawn copper with small amounts of impurities a multiple-sigmoidal behavior has been found, related to the overlapping of two or more process steps, corresponding to a simultaneous recrystallization of the copper matrix and the impurities placement processes. A kinetic equation is introduced to describe the overall process by means of an auto-catalytic kinetic model which
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This paper reports the experimental results obtained after casting concrete formulated with different mix proportions of municipal solid waste incineration (MSWI) by-products, bottom ash (BA) and air pollution control fly ash (APCFA), as... more
This paper reports the experimental results obtained after casting concrete formulated with different mix proportions of municipal solid waste incineration (MSWI) by-products, bottom ash (BA) and air pollution control fly ash (APCFA), as aggregates. Several tests were performed to determine the properties of the mixed proportions. Mechanical properties of the formulations, such as compressive strength, were also determined, and two different leaching tests were performed to study their environmental effects. Some suitable concrete formulations were obtained for the 95/5 and 90/10 BA/APCFA mix proportions. These formulations showed the highest compressive strength test results, above 15 MPa, and the lowest amount of released trace metals in reference to the leaching test. The leaching mechanisms involved in the release of trace metals for the best formulations were also studied, revealing that the washing-off process may play an important role. Given the experimental data it can be concluded that these concrete mix proportions are suitable for use as non-structural concrete.
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The release of heavy metals from MSWI bottom ash has been the key concern in the management of this material. The leaching distribution values obtained from 100 freshly quenched bottom ash samples, according to the German DIN 38414-S4... more
The release of heavy metals from MSWI bottom ash has been the key concern in the management of this material. The leaching distribution values obtained from 100 freshly quenched bottom ash samples, according to the German DIN 38414-S4 procedure test, showed the release of lead, zinc and copper to be the main hazards associated with bottom ash utilisation as a secondary building material. Currently, natural weathering of MSWI bottom ash, for an estimated period of 1-3 months, is the most economic treatment available to ensure the eventual utilisation of this material. The leaching of natural weathered bottom ash in the short-term (up to 9 months) was studied. The most significant changes in the bottom ash were found to occur in the first 90 days. At pH values greater than 12, lead, zinc and copper were the main heavy metals to be released from the MSWI freshly quenched bottom ash samples studied. Natural weathering for a period of about 90 days reduced the leaching of heavy metals, stabilising the bottom ash pH to minimise the solubility of metal hydroxides, and enabled the residue to be used as secondary building material. The profile of the pH neutralisation curve is similar to that described by carbonates, which would suggest that the reaction is controlled by CO(2). The formation of insoluble oxides as well as carbonates control the immobilisation of certain heavy metals, e.g. lead and zinc. The leaching of aluminium increases during this short natural weathering stage due to elemental metal oxidation. Aluminium solubility is controlled by the precipitation of gibbsite or other aluminium-sulphate neoformations. The latter may contribute to the immobilisation of heavy metals.
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The particles with diameter >1 mm present in the bottom ash of Municipal solid waste incinerator (MSWI) were characterized by identifying the main constituent materials. This characterization may be used to evaluate the potential... more
The particles with diameter >1 mm present in the bottom ash of Municipal solid waste incinerator (MSWI) were characterized by identifying the main constituent materials. This characterization may be used to evaluate the potential applications of bottom ash and its environmental ...
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This work evaluates the feasibility of incorporating electric arc furnace dust (EAFD), as filler in a polymer matrix, to obtain a moldable heavyweight sheet, useful for acoustic insulation in automotive industry. For this purpose EAFD... more
This work evaluates the feasibility of incorporating electric arc furnace dust (EAFD), as filler in a polymer matrix, to obtain a moldable heavyweight sheet, useful for acoustic insulation in automotive industry. For this purpose EAFD from a steel factory that manufactures high quality steels, was characterized and different formulations of composites were prepared. Physical and mechanical properties, as well as fire behaviour were tested and compared with a polymer composite compounded with common mineral fillers. Optimum formulation with 25% EAFD fulfils the RoHs Directive used by automotive industry to regulate heavy metals content. Leaching test was also performed on prepared composites to classify the material after use.
Research Interests: Engineering, Acoustics, Physical Chemistry, Construction Materials, Automotive Industry, and 13 morePolymers, Heavy metals, Industry, Steel, Heavy Metal, Hazardous Materials, Electric arc furnace, Mechanical Stress, Industrial Waste, Refuse disposal, Conservation of Natural Resources, Dust, and Physical and Mechanical Properties
A granular material (GM) to be used as road sub-base was formulated using 80% of weathered bottom ash (WBA) and 20% of mortar. The mortar was prepared separately and consisted in 50% APC and 50% of Portland cement. A pilot-scale study was... more
A granular material (GM) to be used as road sub-base was formulated using 80% of weathered bottom ash (WBA) and 20% of mortar. The mortar was prepared separately and consisted in 50% APC and 50% of Portland cement. A pilot-scale study was carried on by constructing three roads in order to environmentally evaluate the performance of GM in a real scenario. By comparing the field results with those of the column experiments, the overestimations observed at laboratory scale can be explained by the potential mechanisms in which water enters into the road body and the pH of the media. An exception was observed in the case of Cu, whose concentration release at the test road was higher. The long-time of exposure at atmospheric conditions might have favoured oxidation of organic matter and therefore the leaching of this element. The results obtained showed that immobilization of all heavy metals and metalloids from APC is achieved by the pozzolanic effect of the cement mortar. This is, to the knowledge of the authors, the only pilot scale study that is considering reutilization of APC as a safe way to disposal.
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Caustic calcined magnesia from natural magnesite has been widely employed as a source of magnesium. This mineral, depending on the origin, may contain heavy metals and metalloids that can exceed the regulatory limits in some applications.... more
Caustic calcined magnesia from natural magnesite has been widely employed as a source of magnesium. This mineral, depending on the origin, may contain heavy metals and metalloids that can exceed the regulatory limits in some applications. In most cases, heavy metals and metalloids form solid solutions with the mineral phases of the main impurities, or even magnesium oxide itself, replacing other ions in the crystal lattice. Compared with magnesium oxide, most of these impurities such as silica and silicates are much more chemically stable even in concentrated mineral acids under normal temperature and pressure conditions. In this study, the partitioning of the trace metals was monitored using a sequential extraction procedure (SEP), and their potential solubility was determined using the pH-static leaching test. Only a small fraction of magnesium oxide derived from heavily calcined magnesia is soluble in slightly acidic media. The release of the trace metals and metalloids contained in the soluble fractions was less than 40% as determined by total digestion. It can be concluded that SEP is more accurate than total chemical digestion for setting the maximum limits of the undesirable trace metals.
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ABSTRACT In Spain, the stabilization of electric arc furnace (EAF) dust prior to landfill is mainly carried out using a mixture of lime and Portland cement. This paper describes the treatment of EAF dust with low-grade MgO (LG MgO) and... more
ABSTRACT In Spain, the stabilization of electric arc furnace (EAF) dust prior to landfill is mainly carried out using a mixture of lime and Portland cement. This paper describes the treatment of EAF dust with low-grade MgO (LG MgO) and the results are compared to those obtained with a lime and Portland cement mixture used as a stabilizer agent. The effectiveness of the treatment was assessed with leaching tests results. The use of LG MgO allows us to manage this waste as a nontoxic residuc according to tests decreed by Spanish regulations. Low-grade MgO acts as a buffering agent giving the final pH mixture a value within the range of minimum heavy metal solubility.
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ABSTRACT BACKGROUND: Low grade magnesium oxide (LG-MgO) is a by-product from the calcination of natural magnesite that is currently hydrated to magnesium hydroxide by storing it in the open for up to 6 months. It is eight to ten times... more
ABSTRACT BACKGROUND: Low grade magnesium oxide (LG-MgO) is a by-product from the calcination of natural magnesite that is currently hydrated to magnesium hydroxide by storing it in the open for up to 6 months. It is eight to ten times cheaper than pure magnesium oxide and therefore the revalorization of this by-product is very attractive for those applications requiring great quantities of magnesium hydroxide for which high purity is not required. Here the hydration of LG-MgO is studied as a function of two parameters: hydrating agent and temperature. RESULTS: Addition of acetic acid during the hydration of LG-MgO improved the effectiveness of treatment. At 50 °C, the maximum percentage hydration was 40% in pure water and increased to 65% and 70% using aqueous solutions of 0.5 and 1.0 mol L -1 acetic acid. Increase of temperature also had a positive effect on the final degree of hydration. When the treatment was carried out with 0.5 mol L -1 acetic acid, the hydration increased from 50 to 65 and 80% at 25, 50 and 90 °C respectively. Accordingly under the optimum conditions of 90 °C and 0.5 mol L -1 acetic acid 80% hydration was achieved within 8 h. CONCLUSIONS: The results showed that much shorter hydration times are possible and therefore an industrial alternative to the spontaneous process could satisfy an increasing demand for magnesium hydroxide. Moreover, agitation is not needed as the reaction is chemically controlled. © 2012 Society of Chemical Industry.
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... (14). L. Guzman et al. / Hydrometallurgy 36 (1994) 187-199 195 1,2 1,0 mx 0,8 i 0,4 0,2 0,0 , 0 100 I~ = 1.05 = 19.13 rain . z6o ~oo 400 s6o 600 rum (m=) Fig. 7. Fraction reacted against time plot for a pan concentrate of auriferous... more
... (14). L. Guzman et al. / Hydrometallurgy 36 (1994) 187-199 195 1,2 1,0 mx 0,8 i 0,4 0,2 0,0 , 0 100 I~ = 1.05 = 19.13 rain . z6o ~oo 400 s6o 600 rum (m=) Fig. 7. Fraction reacted against time plot for a pan concentrate of auriferous sands from Delta d'Ebre (Tarragona, Spain). ...