Contamination of fresh water resources by acidic and metalliferous effluents emanating from minin... more Contamination of fresh water resources by acidic and metalliferous effluents emanating from mining activities has rendered the environment unsuitable to foster life. Mine effluents from coal and gold mining are mainly acidic and contains elevated levels of toxic chemical species. Due to their toxic nature, this water need to be contained and treated prior discharge to the nearby environments.This book reports on the state of art technologies that were developed for remediation of acid mine drainage using cryptocrystalline magnesite, bentonite clay and mechanochemically synthesized cryptocrystalline magnesite-bentonite clay composite. Laboratory studies proved that the fabricated composite can neutralise acidity in mine effluent and attenuate elevated levels of chemical species. The obtained results were substantiated by PHREEQC geochemical modelling and it was pointed out that chemical species were precipitating as hydroxides, ferric hydroxides, oxyhydrosulphates and carbonates.
remediation of acid mine drainage using cryptocrystalline magnesite: A batch experimental and geo... more remediation of acid mine drainage using cryptocrystalline magnesite: A batch experimental and geochemical modelling approach
The present study reports the optimum conditions for intercalating the Al3+ species to bentonite ... more The present study reports the optimum conditions for intercalating the Al3+ species to bentonite clay matrices and evaluate the potential of using Al3+-modified bentonite clay (Alum-Bent) for removal of oxyanionic species of As, B, Cr, Mo and Se from coal fly ash (FA) leachates. Removal of oxyanionic species was done in batch experimental procedures. Parameters optimized were: contact time, adsorbent dosage, concentration and pH. The adsorption affinity of Al3+-bentonite clay for oxyanionic species varied as follows: B ≈ Se > Mo > Cr ≈ As respectively. The adsorption data fitted better to Langmuir adsorption isotherm than Freundlich adsorption isotherm hence confirming mono-site adsorption. The adsorption kinetics fitted well pseudo-second-order kinetic model hence confirming chemisorption. The fact that most of the oxyanion were adsorbed at pH ≥ pHpzc indicated that both electrostatic and chemical interactions occurred with the clay surface and interlayers. The Al3+-modified ...
Journal of Environmental Chemical Engineering, 2016
Abstract This study assessed the fate of inorganic contaminants post treatment of acid mine drain... more Abstract This study assessed the fate of inorganic contaminants post treatment of acid mine drainage by cryptocrystalline magnesite. To accomplish that, neutralization and metal attenuation were evaluated and complemented with simulations using geochemical modeling. Mineral phase formation and changes during the reaction of magnesite and AMD were also evaluated. The geochemical computer code PHREEQC and WATEQ4 database was used for geochemical modelling of the process water. Interaction of AMD with magnesite at an optimum solid: liquid ratio of 1:100 and contact time of 60 min led to an increase in pH, reaching a maximum pH of 10, resulting in significant precipitation of most metal species. Increase of pH in solution with contact time caused the removal of the metal ions mainly by precipitation, co-precipitation and adsorption. Sulphate concentration was lowered from 4640 down to 1910 mg/L. Fe was mainly removed as Fe(OH) 3 , goethite, and jarosite, Al as basaluminite, boehmite and jurbanite, Al(OH) 3 and as gibbsite and diaspore. Al and Fe precipitated as iron (oxy)-hydroxides and aluminium (oxy)-hydroxides. Mn precipitated as rhodochrosite and manganite. Ca was removed as gypsum. Sulphate was removed as gypsum, and Fe, Al hydroxyl sulphate minerals. Mg was removed as brucite and dolomite. Cryptocrystalline magnesite effectively neutralized AMD and attenuated concentration of inorganic species to within department of water affairs and sanitation (DWAS) water quality guidelines.
Journal of environmental chemical engineering, Jun 1, 2019
Abstract In this work, magnetite nanoparticles functionalized with Moringa oleifera plant leaf ex... more Abstract In this work, magnetite nanoparticles functionalized with Moringa oleifera plant leaf extracts were synthesized and investigated as potential nanosorbents in the extraction of nitroaromatic explosive compounds from aqueous solution. The predicted maximum adsorption capacity towards the nitroaromatic explosive compounds was 282 μg g−1. Batch studies confirmed that the pseudo second order model explained the extent of the adsorption while the absorption mechanism followed the Langmuir model. The order of selectivity for the nitroaromatic explosive compounds studied was observed as follows: 2-nitrotoluene >3-nitrotoluene >4-nitrotoluene > nitrobenzene >2,6-dinitrotoluene >1,3-dinitrobenzene. The limits of detection ranged from 0.4 to 4.5 mg L−1. Even though the recovery values for the target analytes are relatively low (14–46%), the method has shown great potential and repeatability with an average RSD value of 2.33%. The Moringa oleifera functionalized magnetite nanoparticles are therefore a viable nanosorbent that can be used as a sorbent to effectively extract nitroaromatic explosive compounds from polluted water.
International Journal of Environmental Analytical Chemistry, Jul 5, 2010
The objectives of this study were to evaluate the mobility of heavy metals (HMs) in two types of ... more The objectives of this study were to evaluate the mobility of heavy metals (HMs) in two types of soils (acidic forest soil and neutral agricultural soil) by leaching with calcium chloride solution in column experiments. The screening properties of neutral agricultural soil towards pollution by heavy metals (Ni, Cu, Zn and Cd) are approximately 10 times higher than those of
Soil and Sediment Contamination: An International Journal, Dec 23, 2010
Adsorption of Cu, Cd, Ni, and Zn in single and multi-metal solutions by agricultural and forest s... more Adsorption of Cu, Cd, Ni, and Zn in single and multi-metal solutions by agricultural and forest soils was investigated in batch sorption experiments. The results showed significant differences in sorption capacities of the studied soils. The selectivity order was as follows: agricultural soil≫ top forest soil > bottom forest soil. The adsorption sequence Cu > Zn > Ni > Cd
The reviews cover important critical parameters that are often optimized in a supported liquid me... more The reviews cover important critical parameters that are often optimized in a supported liquid membrane extraction technique in both flat sheet and hollow fibre designs for ionizable organic molecules. Understanding of these parameters can enable one to predict the behavior of the compound before hand and thus reduce the number of optimization experiments. Moreover, less number of experiments can be also generated using statistical techniques which are now becoming more commonly used. Supported liquid membrane extraction optimal parameters such as the conditions of the pH of the acceptor and donor phases should easily be fixed from the pKa values of the compounds. Other parameters, including the polarity of the compound can help to predict the partitioning into the membrane and the behavior of the compound. The influence of parameters such as temperature on the mass transfer in supported liquid membrane depends on the design of the module, experimental design and type of mass transfer controlling the extraction process.
This work aimed at optimizing the QuEChERS method with PSA and then comparing it with Moringa Ole... more This work aimed at optimizing the QuEChERS method with PSA and then comparing it with Moringa Oleifera seed protein as a clean-up sorbent for the extraction of endocrine-disrupting chemicals. The response surface methodology approach was used in the optimization. A design of experiment (DoE) was used to investigate the effect of the sample mass (0.5–3 g), centrifuge speed (3400–4000 rpm) and time (5–20 min), the mass of N a C l and MgSO 4 1 − 3 g , and solvent extraction volume (5–10 mL). The analysis was done using GC-ECD and GC × GC TOFMS. The PSA method which was later replaced with Moringa Oleifera seed protein presented optimal values of 3 g of sample, 150 mg PSA, 4000 rpm for 6 min centrifuge conditions, including 2 g NaCl and 2 g MgSO 4 extracted in 10 mL methanol, respectively. Moringa Oleifera seed protein gave better selectivity, and the detection limits ranged between 0.16 and 1.77 μ g kg − 1 with RSD values ≤ 13.32 % , respectively. Moreover, recoveries were betwee...
Contamination of fresh water resources by acidic and metalliferous effluents emanating from minin... more Contamination of fresh water resources by acidic and metalliferous effluents emanating from mining activities has rendered the environment unsuitable to foster life. Mine effluents from coal and gold mining are mainly acidic and contains elevated levels of toxic chemical species. Due to their toxic nature, this water need to be contained and treated prior discharge to the nearby environments.This book reports on the state of art technologies that were developed for remediation of acid mine drainage using cryptocrystalline magnesite, bentonite clay and mechanochemically synthesized cryptocrystalline magnesite-bentonite clay composite. Laboratory studies proved that the fabricated composite can neutralise acidity in mine effluent and attenuate elevated levels of chemical species. The obtained results were substantiated by PHREEQC geochemical modelling and it was pointed out that chemical species were precipitating as hydroxides, ferric hydroxides, oxyhydrosulphates and carbonates.
remediation of acid mine drainage using cryptocrystalline magnesite: A batch experimental and geo... more remediation of acid mine drainage using cryptocrystalline magnesite: A batch experimental and geochemical modelling approach
The present study reports the optimum conditions for intercalating the Al3+ species to bentonite ... more The present study reports the optimum conditions for intercalating the Al3+ species to bentonite clay matrices and evaluate the potential of using Al3+-modified bentonite clay (Alum-Bent) for removal of oxyanionic species of As, B, Cr, Mo and Se from coal fly ash (FA) leachates. Removal of oxyanionic species was done in batch experimental procedures. Parameters optimized were: contact time, adsorbent dosage, concentration and pH. The adsorption affinity of Al3+-bentonite clay for oxyanionic species varied as follows: B ≈ Se > Mo > Cr ≈ As respectively. The adsorption data fitted better to Langmuir adsorption isotherm than Freundlich adsorption isotherm hence confirming mono-site adsorption. The adsorption kinetics fitted well pseudo-second-order kinetic model hence confirming chemisorption. The fact that most of the oxyanion were adsorbed at pH ≥ pHpzc indicated that both electrostatic and chemical interactions occurred with the clay surface and interlayers. The Al3+-modified ...
Journal of Environmental Chemical Engineering, 2016
Abstract This study assessed the fate of inorganic contaminants post treatment of acid mine drain... more Abstract This study assessed the fate of inorganic contaminants post treatment of acid mine drainage by cryptocrystalline magnesite. To accomplish that, neutralization and metal attenuation were evaluated and complemented with simulations using geochemical modeling. Mineral phase formation and changes during the reaction of magnesite and AMD were also evaluated. The geochemical computer code PHREEQC and WATEQ4 database was used for geochemical modelling of the process water. Interaction of AMD with magnesite at an optimum solid: liquid ratio of 1:100 and contact time of 60 min led to an increase in pH, reaching a maximum pH of 10, resulting in significant precipitation of most metal species. Increase of pH in solution with contact time caused the removal of the metal ions mainly by precipitation, co-precipitation and adsorption. Sulphate concentration was lowered from 4640 down to 1910 mg/L. Fe was mainly removed as Fe(OH) 3 , goethite, and jarosite, Al as basaluminite, boehmite and jurbanite, Al(OH) 3 and as gibbsite and diaspore. Al and Fe precipitated as iron (oxy)-hydroxides and aluminium (oxy)-hydroxides. Mn precipitated as rhodochrosite and manganite. Ca was removed as gypsum. Sulphate was removed as gypsum, and Fe, Al hydroxyl sulphate minerals. Mg was removed as brucite and dolomite. Cryptocrystalline magnesite effectively neutralized AMD and attenuated concentration of inorganic species to within department of water affairs and sanitation (DWAS) water quality guidelines.
Journal of environmental chemical engineering, Jun 1, 2019
Abstract In this work, magnetite nanoparticles functionalized with Moringa oleifera plant leaf ex... more Abstract In this work, magnetite nanoparticles functionalized with Moringa oleifera plant leaf extracts were synthesized and investigated as potential nanosorbents in the extraction of nitroaromatic explosive compounds from aqueous solution. The predicted maximum adsorption capacity towards the nitroaromatic explosive compounds was 282 μg g−1. Batch studies confirmed that the pseudo second order model explained the extent of the adsorption while the absorption mechanism followed the Langmuir model. The order of selectivity for the nitroaromatic explosive compounds studied was observed as follows: 2-nitrotoluene >3-nitrotoluene >4-nitrotoluene > nitrobenzene >2,6-dinitrotoluene >1,3-dinitrobenzene. The limits of detection ranged from 0.4 to 4.5 mg L−1. Even though the recovery values for the target analytes are relatively low (14–46%), the method has shown great potential and repeatability with an average RSD value of 2.33%. The Moringa oleifera functionalized magnetite nanoparticles are therefore a viable nanosorbent that can be used as a sorbent to effectively extract nitroaromatic explosive compounds from polluted water.
International Journal of Environmental Analytical Chemistry, Jul 5, 2010
The objectives of this study were to evaluate the mobility of heavy metals (HMs) in two types of ... more The objectives of this study were to evaluate the mobility of heavy metals (HMs) in two types of soils (acidic forest soil and neutral agricultural soil) by leaching with calcium chloride solution in column experiments. The screening properties of neutral agricultural soil towards pollution by heavy metals (Ni, Cu, Zn and Cd) are approximately 10 times higher than those of
Soil and Sediment Contamination: An International Journal, Dec 23, 2010
Adsorption of Cu, Cd, Ni, and Zn in single and multi-metal solutions by agricultural and forest s... more Adsorption of Cu, Cd, Ni, and Zn in single and multi-metal solutions by agricultural and forest soils was investigated in batch sorption experiments. The results showed significant differences in sorption capacities of the studied soils. The selectivity order was as follows: agricultural soil≫ top forest soil > bottom forest soil. The adsorption sequence Cu > Zn > Ni > Cd
The reviews cover important critical parameters that are often optimized in a supported liquid me... more The reviews cover important critical parameters that are often optimized in a supported liquid membrane extraction technique in both flat sheet and hollow fibre designs for ionizable organic molecules. Understanding of these parameters can enable one to predict the behavior of the compound before hand and thus reduce the number of optimization experiments. Moreover, less number of experiments can be also generated using statistical techniques which are now becoming more commonly used. Supported liquid membrane extraction optimal parameters such as the conditions of the pH of the acceptor and donor phases should easily be fixed from the pKa values of the compounds. Other parameters, including the polarity of the compound can help to predict the partitioning into the membrane and the behavior of the compound. The influence of parameters such as temperature on the mass transfer in supported liquid membrane depends on the design of the module, experimental design and type of mass transfer controlling the extraction process.
This work aimed at optimizing the QuEChERS method with PSA and then comparing it with Moringa Ole... more This work aimed at optimizing the QuEChERS method with PSA and then comparing it with Moringa Oleifera seed protein as a clean-up sorbent for the extraction of endocrine-disrupting chemicals. The response surface methodology approach was used in the optimization. A design of experiment (DoE) was used to investigate the effect of the sample mass (0.5–3 g), centrifuge speed (3400–4000 rpm) and time (5–20 min), the mass of N a C l and MgSO 4 1 − 3 g , and solvent extraction volume (5–10 mL). The analysis was done using GC-ECD and GC × GC TOFMS. The PSA method which was later replaced with Moringa Oleifera seed protein presented optimal values of 3 g of sample, 150 mg PSA, 4000 rpm for 6 min centrifuge conditions, including 2 g NaCl and 2 g MgSO 4 extracted in 10 mL methanol, respectively. Moringa Oleifera seed protein gave better selectivity, and the detection limits ranged between 0.16 and 1.77 μ g kg − 1 with RSD values ≤ 13.32 % , respectively. Moreover, recoveries were betwee...
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