M Rakib - Academia.edu (original) (raw)
Papers by M Rakib
Environmental Technology, 2020
The objective of this paper was to propose a deepened analyze of a microfiltration membrane fouli... more The objective of this paper was to propose a deepened analyze of a microfiltration membrane fouling by two biomolecules: a protein (Bovine Serum Albumin) and a peptide (Glutathione). In addition to an analysis of flux decline, the mass of biomolecules accumulated on the membrane during filtration was quantified and compared to adsorption experiments, using Fourier Transform Infra Red spectroscopy in Attenuated Total Reflection mode (ATR-FTIR). It was demonstrated that the same quantity of accumulated biomolecules on the apparent membrane area can generate totally different flux declines because of different fouling mechanisms. On the one hand, Glutathione can adsorb in the whole porous media of the membrane, penetrating through the pores, modifying the hydrophilicity at low concentrations and generating pore constriction at high concentrations. On the other hand, BSA organize a dense irreversible fouling in the first minutes of filtration containing a quantity equivalent to more than 45 monolayers, leading to pore blocking and pore constriction. This structure is resistant to rinsing and NaOH cleaning. Then a reversible fouling, containing a quantity equivalent to more than 90 monolayers is settled. The above structure can be removed with an intensive water rinsing and corresponds to a rather porous cake leading to a low resistance to water permeation, whereas the intermediate structure can only be removed with chemical cleaning and has a higher impact on water permeation.
Journal of Experimental Agriculture International, 2017
The electrodeposition of indium from synthetic solution has been tested in sulphuric, hydrochlori... more The electrodeposition of indium from synthetic solution has been tested in sulphuric, hydrochloric and citric acids media or a mixture of citric and sulphuric acids. The best current efficiencies are obtained in sulphuric acid medium and for the low current densities: 13-19 mA.cm -2 . The feasibility of indium recovery from spent CBD of In 2 (O,S) 3 baths is demonstrated. Concentrated solutions of indium (III) are obtained (≈80 g.dm -3) after the leaching of In 2 (O,S) 3 cake. It seems that the titanium is the best material for cathode in indium electrowinning process. The purity of recovered indium is 99.98 %.
A two-compartment membrane electrolysis cell is used to split sodium sulfate into sulfuric acid a... more A two-compartment membrane electrolysis cell is used to split sodium sulfate into sulfuric acid and sodium hydroxide. The cell is equipped with a Na®on â 350 cation-exchange membrane. Due to the dissociation of the strong acid, free hydrogen ions migrate through the membrane together with sodium ions. This transfer decreases current eciency. The transport properties of Na®on â 350 membrane are studied in a laboratory cell. Current eciency varies either with sulfuric acid to total sulfate concentration ratio in the anolyte or with sodium hydroxide concentration depending on the membrane state. Water transport through the membrane is due to electroosmosis. Hydrogen and sodium ions carry three to four molecules of water per ion. Modelling of a continuous feed and bleed process in the steady-state is performed using material balance and transport data obtained in a laboratory scale. Tests in a pilot plant (scaling factor 13) were undertaken. The model predictions agree well with experimental results. As a consequence, the model may be used for industrial purposes. Due to current eciency decrease when salt conversion increases, the use of a cascade of cells in series is advantageous compared to a single stage.
American Chemical Science Journal, 2015
ABSTRACT The study was to assess health hazard of metal concentation in groundwater of Bangladesh... more ABSTRACT The study was to assess health hazard of metal concentation in groundwater of Bangladesh for drinking purposes. A number of 13 deep tube wells were selected purposively for collecting groundwater samples from the different sampling location of the study area. The study was carried out by laboratory analysis of chemical parameters which were analyzed by ion Chromatograph (IC) and atomic absorption spectrophotometer methods (AAS). The result shown that the concentration of iron and manganese were found to be more than permissible limit according to Bangladesh and WHO standard. The descriptive statistics revealed that most of the heavy metal concentrations like As, Cd, Fe and Mn were found to be range from 0.00 to 0.02 mg/l, 0.00 to 0.20 mg/l, 0.11 to 24.20 mg/l, 0.06 to 16.00 mg/l respectively within accessible limit for drinking according to Bangladesh and WHO standard except some water sampling locations were exceed the permissible limits. Pearson correlation matrix results were depicted that a strong positive correlation between the parameters such as Na+ and SO4 2- and K+ and NH3 - while low negative correlation were existed between Dissolved Oxygen and Mn+. From the analysis of result, it suggests that using groundwater for drinking purposes in the study area is slightly detrimental to human health hazard and thier surrouding environment.
American Chemical Science Journal, 2014
ABSTRACT The present study aimed to investigate hydrogeochemistry and its suitability for drinkin... more ABSTRACT The present study aimed to investigate hydrogeochemistry and its suitability for drinking and irrigation purposes and to determine the contamination of estuary water of ship breaking activities in Sitakunda region, Chittagong, Bangladesh. The study was carried out by in-situ field measurement of physical parameters while chemical parameters were followed by atomic absorption spectrometry (AAS) methods of laboratory analyses of 12 estuary water samples. The result shows that the PH value was average 7.08 indicated neutral water while Eh, EC, TDS and TH value was average -24.65 mv, 8586.5 μS/cm, 5495.36 μS/cm and 432.41 mg/l respectively, indicated that the estuary water is not safe and suitable for domestic and irrigation purposes. Inferential statistical results were depicted that a strong positive correlation (ρ) between the parameters such as EC, TDS, TH, Ca2+, Na+, K+, Cl-, Br2-, SO4 2-, PO4 2-, NO3 - while negative correlation (ρ) were existed between Mg2+ and HCO3 -. According to most abundance of major cations were Na+>Ca2+>Mg2+>K+ whereas major anions were Cl->SO4 2->HCO3 ->Br->NO3 ->PO4 -. The concentration of cations and anions in the study area exceeded drinking standards according to the World Health Organization (WHO) and the Directorate of Environment (DOE), Bangladesh. Irrigation quality index (SAR and PI) indicated that the quality of water is not suitable for irrigation. The origin of solutes in estuary water was influenced by chloride dissolution, although weathering of silicate and cation exchange also added to the water chemistry. This is not conclusive but it may be suggested that the sampled water is not ionically balanced and is highly contaminated due to ship breaking activities.
International Journal of VLSI Design & Communication Systems, 2011
In this paper, we have proposed a new design technique of BCD Adder using newly constructed rever... more In this paper, we have proposed a new design technique of BCD Adder using newly constructed reversible gates are based on NMOS with pass transistor gates, where the conventional reversible gates are based on CMOS with transmission gates. We also compare the proposed reversible gates with the conventional CMOS reversible gates which show that the required number of Transistors is significantly reduced.
Separation and Purification Technology, 2011
Extinguishments of large scale solvent res produce large amounts of water that may contain variou... more Extinguishments of large scale solvent res produce large amounts of water that may contain various uorinated surfactants depending on the type of reghting foam used. Due to their chemical nature, uorinated parts of uorinated compounds are highly resistant to biochemical and advanced oxidation processes. Therefore the current treatment for the degradation of
Progress in Photovoltaics: Research and Applications, 2001
ABSTRACT
Progress in Photovoltaics: Research and Applications, 2002
Cadmium sulfide thin layers for polycrystalline solar cells are produced by chemical bath deposit... more Cadmium sulfide thin layers for polycrystalline solar cells are produced by chemical bath deposition (CBD). This process generates wastes containing mainly ammonia and cadmium. We have implemented and described in a previous paper a process to recover 90% of ammonia and to confine cadmium as a cake which is a mixture of cadmium sulfide and cadmium cyanamide. The present paper concerns cadmium recycling to the CBD step. The cake is first dissolved in a moderate sulfuric acid solution 0.2–0.5 mol/l mixed with hydrogen peroxide (about 1 mol/l). This last component must be used in large excess (molar ratio H2O2/Cd ≥ 5) and must be completely removed from the solution before recycling or cadmium electrowinning. Hydrogen peroxide decomposition is electrochemically catalyzed by platinized platinum immersed into the solution. The resulting solution contains cadmium sulfate 0.2 mol/l, sodium and ammonium sulfate. One can either recycle it as a chemical bath, or recover the cadmium content by electrowinning; in this case the residual concentration of hydrogen peroxide is electrochemically reduced at the beginning of cadmium electrolysis. The raffinate solution is recycled into the stripping reactor. The pure cadmium metal recovered may be dissolved in a dilute sulfuric acid solution by means of internal electrolysis with two electrodes: a platinized platinum grid as cathode and the cadmium metal as anode. According to the mass of cadmium dissolved it is possible to obtain a concentrated solution of pure cadmium sulfate. The global process recovers at least 99.999% of cadmium and generates only solid sulfur and a liquid effluent containing traces of cadmium (< 10 μg/l). Copyright © 2002 John Wiley & Sons, Ltd.
Procedia Engineering, 2012
Procedia Engineering, 2012
Surfactants play an important role as cleaning, wetting, dispersing, emulsifying and foaming agen... more Surfactants play an important role as cleaning, wetting, dispersing, emulsifying and foaming agents in many practical applications and products. The molecules of surfactants are composed of two different parts: a hydrophilic head and a hydrophobic tail. This kind of amphiphilic molecules are known to self-assemble into a variety of aggregate structures in aqueous solution, such as micelles, bilayers, vesicle, and lamellae 1. Another fundamental property of surfactants is their tendency to adsorb at surfaces/interfaces from the bulk solution 2. Because of their surface activity, surfactants are frequently used in industry and they are also one of the most discharged organic materials in wastewaters that are to be treated by membrane processes. However, it might be a huge obstacle for reverse osmosis (RO) membrane since the surfactant molecules will accumulate on the surface (considered as non-pores) and cause fouling to the membrane and adversely affect both the quantity (permeate flux) and quality (solute concentration) of the product water, resulting in loss of performance of the membrane 3,4. Although RO membranes have received much attention from both academy and industry, the fouling mechanisms of solutes (especially surfactants) on RO membranes are still not fully understood. Recently, Dissipative Particle Dynamics (DPD) simulation has been proved to be a valuable tool to study the dynamic and static structure of the assembly surfactants and can provide a detailed, mesoscopic level insight into the structure of the studied systems 5,6 .
Procedia Engineering, 2012
Journal of Membrane Science, 2004
Splitting of ammonium nitrate to nitric acid and ammonia was achieved by a coupled process includ... more Splitting of ammonium nitrate to nitric acid and ammonia was achieved by a coupled process including bipolar membrane electrodialysis and in situ ammonia stripping. The effect of homopolar ion-exchange membranes on current efficiency led to the selection of AW (Solvay) and CMB (Tokuyama Soda) membranes. The main parameters influencing the current efficiency were acid and ammonia concentrations. Proton leakage through the anion-exchange membrane is proportional to acid concentration. Ammonia diffuses through the membranes independently of the current. Higher current efficiency was obtained at higher current density. Batch and continuous processing were compared.
Journal of Membrane Science, 2006
Abstract Regeneration of hydrochloric acid and sodium hydroxide from sodium chloride solution has... more Abstract Regeneration of hydrochloric acid and sodium hydroxide from sodium chloride solution has been carried out by membrane electrolysis where the anode was replaced by a membrane-electrode assembly (MEA). Hydrogen diffusion electrode and a Nafion ® 117 membrane were assembled tightly in order to prevent platinum poisoning by chloride ions. The use of this electrode to produce H + may be compared to the use of metallic electrodes where H + is produced by water oxidation with oxygen evolution. The reversible cell voltage is reduced by 1.23 V. The current efficiency of hydrogen oxidation in the MEA is 100% if, at least, the stoichiometric flow of hydrogen is insured. Acid production is then only limited by H + leakage through the anion-exchange membrane. The undesirable flux of H + through this membrane was found proportional to the acid concentration in the anolyte. The value of the rate constant of proton leakage is about 0.080 dm 3 faraday −1 . The current efficiency decreases when acid concentration increases. Water transfer was also studied. Transfer towards the base solution is higher than transfer to the acidic solution. When a current density of 3 kA m −2 is applied the anodic voltage remains below 300 mV for acid concentration lower than 3 mol dm −3 and increases notably for higher acid concentrations probably due to poisoning of platinum by chloride ions that leak through the membrane owing to their high concentration in solution.
Journal of Membrane Science, 2009
The aim of this work is to model the two-compartment bipolar membrane electrodialysis for organic... more The aim of this work is to model the two-compartment bipolar membrane electrodialysis for organic salts acidification. The salt studied is sodium formate which splits into formic acid and sodium hydroxide thanks to water splitting by bipolar membrane. The contamination of sodium hydroxide by formate ion is due to diffusion of molecular formic acid through the bipolar membrane and to leakage of formate ion through the same membrane under the applied current. The cation-exchange membrane does not participate to contamination of sodium hydroxide. But the leakage of hydroxide ion through the cation-exchange membrane is the major factor that influences the current efficiency of electrodialysis. The average current efficiency decreases with time principally because the sodium hydroxide concentration increases. The development of a membrane with limited hydroxide leakage is desirable.
Journal of Membrane Science, 2006
Waters containing low amounts of sodium formate and sodium hydroxide were processed in order to r... more Waters containing low amounts of sodium formate and sodium hydroxide were processed in order to regenerate formic acid. The treatment was performed in three steps: wastewaters neutralization, sodium formate concentration by conventional electrodialysis (ED), and sodium formate splitting into formic acid and sodium hydroxide by bipolar membrane electrodialysis (BMED). A coupling of these processes was performed. ED was carried out
Journal of Materials Chemistry, 2001
The crystal structure of cadmium cyanamide was investigated by X-ray powder analysis and refined ... more The crystal structure of cadmium cyanamide was investigated by X-ray powder analysis and refined using the Rietveld method. Very fine powders of CdCN2 in the nanometre range were obtained by chemical bath deposition. The size, shape and microstrain were characterised by X-ray diffraction and transmission electron microscopy. The refined structure is very close to that of MgCN2. Infrared spectroscopy and thermogravimetric analysis were also performed to fully characterise the compound.
A process coupling membrane electrolysis and electrodialysis is implemented to treat ammonium nit... more A process coupling membrane electrolysis and electrodialysis is implemented to treat ammonium nitrate wastewater. Membrane electrolysis produces ammonia and nitric acid while electrodialysis reconcentrates the depleted salt solution. Ammonia is removed continuously by in situ stripping; thus allowing gas production with a constant current efficiency (about 70%). Nitric acid up to 8 mol L-1 is obtained. The current efficiency of
Hydrometallurgy, 1996
ABSTRACT Vanadium complex formation with sulphate anions was investigated. The ionic strength was... more ABSTRACT Vanadium complex formation with sulphate anions was investigated. The ionic strength was allowed to vary and was accounted for using a usual expression for the activity coefficients. Numerical treatment of the experimental data (vanadium distribution ratio between sulphate solutions and an organic solution where 1-decanol is the extractant) allowed identification of the complex-forming species as SO42− and determination of the thermodynamic formation constant of the complex VO2SO4− at 25°C as log β1 = 1.30 ± 0.02. We also determined the range of the thermodynamic hydrolysis constant Kh of the pervanadyl ion, 3.65 ≤ pKh ≤ 4.3, the best determination being pKh = 3.84.
Environmental Technology, 2020
The objective of this paper was to propose a deepened analyze of a microfiltration membrane fouli... more The objective of this paper was to propose a deepened analyze of a microfiltration membrane fouling by two biomolecules: a protein (Bovine Serum Albumin) and a peptide (Glutathione). In addition to an analysis of flux decline, the mass of biomolecules accumulated on the membrane during filtration was quantified and compared to adsorption experiments, using Fourier Transform Infra Red spectroscopy in Attenuated Total Reflection mode (ATR-FTIR). It was demonstrated that the same quantity of accumulated biomolecules on the apparent membrane area can generate totally different flux declines because of different fouling mechanisms. On the one hand, Glutathione can adsorb in the whole porous media of the membrane, penetrating through the pores, modifying the hydrophilicity at low concentrations and generating pore constriction at high concentrations. On the other hand, BSA organize a dense irreversible fouling in the first minutes of filtration containing a quantity equivalent to more than 45 monolayers, leading to pore blocking and pore constriction. This structure is resistant to rinsing and NaOH cleaning. Then a reversible fouling, containing a quantity equivalent to more than 90 monolayers is settled. The above structure can be removed with an intensive water rinsing and corresponds to a rather porous cake leading to a low resistance to water permeation, whereas the intermediate structure can only be removed with chemical cleaning and has a higher impact on water permeation.
Journal of Experimental Agriculture International, 2017
The electrodeposition of indium from synthetic solution has been tested in sulphuric, hydrochlori... more The electrodeposition of indium from synthetic solution has been tested in sulphuric, hydrochloric and citric acids media or a mixture of citric and sulphuric acids. The best current efficiencies are obtained in sulphuric acid medium and for the low current densities: 13-19 mA.cm -2 . The feasibility of indium recovery from spent CBD of In 2 (O,S) 3 baths is demonstrated. Concentrated solutions of indium (III) are obtained (≈80 g.dm -3) after the leaching of In 2 (O,S) 3 cake. It seems that the titanium is the best material for cathode in indium electrowinning process. The purity of recovered indium is 99.98 %.
A two-compartment membrane electrolysis cell is used to split sodium sulfate into sulfuric acid a... more A two-compartment membrane electrolysis cell is used to split sodium sulfate into sulfuric acid and sodium hydroxide. The cell is equipped with a Na®on â 350 cation-exchange membrane. Due to the dissociation of the strong acid, free hydrogen ions migrate through the membrane together with sodium ions. This transfer decreases current eciency. The transport properties of Na®on â 350 membrane are studied in a laboratory cell. Current eciency varies either with sulfuric acid to total sulfate concentration ratio in the anolyte or with sodium hydroxide concentration depending on the membrane state. Water transport through the membrane is due to electroosmosis. Hydrogen and sodium ions carry three to four molecules of water per ion. Modelling of a continuous feed and bleed process in the steady-state is performed using material balance and transport data obtained in a laboratory scale. Tests in a pilot plant (scaling factor 13) were undertaken. The model predictions agree well with experimental results. As a consequence, the model may be used for industrial purposes. Due to current eciency decrease when salt conversion increases, the use of a cascade of cells in series is advantageous compared to a single stage.
American Chemical Science Journal, 2015
ABSTRACT The study was to assess health hazard of metal concentation in groundwater of Bangladesh... more ABSTRACT The study was to assess health hazard of metal concentation in groundwater of Bangladesh for drinking purposes. A number of 13 deep tube wells were selected purposively for collecting groundwater samples from the different sampling location of the study area. The study was carried out by laboratory analysis of chemical parameters which were analyzed by ion Chromatograph (IC) and atomic absorption spectrophotometer methods (AAS). The result shown that the concentration of iron and manganese were found to be more than permissible limit according to Bangladesh and WHO standard. The descriptive statistics revealed that most of the heavy metal concentrations like As, Cd, Fe and Mn were found to be range from 0.00 to 0.02 mg/l, 0.00 to 0.20 mg/l, 0.11 to 24.20 mg/l, 0.06 to 16.00 mg/l respectively within accessible limit for drinking according to Bangladesh and WHO standard except some water sampling locations were exceed the permissible limits. Pearson correlation matrix results were depicted that a strong positive correlation between the parameters such as Na+ and SO4 2- and K+ and NH3 - while low negative correlation were existed between Dissolved Oxygen and Mn+. From the analysis of result, it suggests that using groundwater for drinking purposes in the study area is slightly detrimental to human health hazard and thier surrouding environment.
American Chemical Science Journal, 2014
ABSTRACT The present study aimed to investigate hydrogeochemistry and its suitability for drinkin... more ABSTRACT The present study aimed to investigate hydrogeochemistry and its suitability for drinking and irrigation purposes and to determine the contamination of estuary water of ship breaking activities in Sitakunda region, Chittagong, Bangladesh. The study was carried out by in-situ field measurement of physical parameters while chemical parameters were followed by atomic absorption spectrometry (AAS) methods of laboratory analyses of 12 estuary water samples. The result shows that the PH value was average 7.08 indicated neutral water while Eh, EC, TDS and TH value was average -24.65 mv, 8586.5 μS/cm, 5495.36 μS/cm and 432.41 mg/l respectively, indicated that the estuary water is not safe and suitable for domestic and irrigation purposes. Inferential statistical results were depicted that a strong positive correlation (ρ) between the parameters such as EC, TDS, TH, Ca2+, Na+, K+, Cl-, Br2-, SO4 2-, PO4 2-, NO3 - while negative correlation (ρ) were existed between Mg2+ and HCO3 -. According to most abundance of major cations were Na+>Ca2+>Mg2+>K+ whereas major anions were Cl->SO4 2->HCO3 ->Br->NO3 ->PO4 -. The concentration of cations and anions in the study area exceeded drinking standards according to the World Health Organization (WHO) and the Directorate of Environment (DOE), Bangladesh. Irrigation quality index (SAR and PI) indicated that the quality of water is not suitable for irrigation. The origin of solutes in estuary water was influenced by chloride dissolution, although weathering of silicate and cation exchange also added to the water chemistry. This is not conclusive but it may be suggested that the sampled water is not ionically balanced and is highly contaminated due to ship breaking activities.
International Journal of VLSI Design & Communication Systems, 2011
In this paper, we have proposed a new design technique of BCD Adder using newly constructed rever... more In this paper, we have proposed a new design technique of BCD Adder using newly constructed reversible gates are based on NMOS with pass transistor gates, where the conventional reversible gates are based on CMOS with transmission gates. We also compare the proposed reversible gates with the conventional CMOS reversible gates which show that the required number of Transistors is significantly reduced.
Separation and Purification Technology, 2011
Extinguishments of large scale solvent res produce large amounts of water that may contain variou... more Extinguishments of large scale solvent res produce large amounts of water that may contain various uorinated surfactants depending on the type of reghting foam used. Due to their chemical nature, uorinated parts of uorinated compounds are highly resistant to biochemical and advanced oxidation processes. Therefore the current treatment for the degradation of
Progress in Photovoltaics: Research and Applications, 2001
ABSTRACT
Progress in Photovoltaics: Research and Applications, 2002
Cadmium sulfide thin layers for polycrystalline solar cells are produced by chemical bath deposit... more Cadmium sulfide thin layers for polycrystalline solar cells are produced by chemical bath deposition (CBD). This process generates wastes containing mainly ammonia and cadmium. We have implemented and described in a previous paper a process to recover 90% of ammonia and to confine cadmium as a cake which is a mixture of cadmium sulfide and cadmium cyanamide. The present paper concerns cadmium recycling to the CBD step. The cake is first dissolved in a moderate sulfuric acid solution 0.2–0.5 mol/l mixed with hydrogen peroxide (about 1 mol/l). This last component must be used in large excess (molar ratio H2O2/Cd ≥ 5) and must be completely removed from the solution before recycling or cadmium electrowinning. Hydrogen peroxide decomposition is electrochemically catalyzed by platinized platinum immersed into the solution. The resulting solution contains cadmium sulfate 0.2 mol/l, sodium and ammonium sulfate. One can either recycle it as a chemical bath, or recover the cadmium content by electrowinning; in this case the residual concentration of hydrogen peroxide is electrochemically reduced at the beginning of cadmium electrolysis. The raffinate solution is recycled into the stripping reactor. The pure cadmium metal recovered may be dissolved in a dilute sulfuric acid solution by means of internal electrolysis with two electrodes: a platinized platinum grid as cathode and the cadmium metal as anode. According to the mass of cadmium dissolved it is possible to obtain a concentrated solution of pure cadmium sulfate. The global process recovers at least 99.999% of cadmium and generates only solid sulfur and a liquid effluent containing traces of cadmium (< 10 μg/l). Copyright © 2002 John Wiley & Sons, Ltd.
Procedia Engineering, 2012
Procedia Engineering, 2012
Surfactants play an important role as cleaning, wetting, dispersing, emulsifying and foaming agen... more Surfactants play an important role as cleaning, wetting, dispersing, emulsifying and foaming agents in many practical applications and products. The molecules of surfactants are composed of two different parts: a hydrophilic head and a hydrophobic tail. This kind of amphiphilic molecules are known to self-assemble into a variety of aggregate structures in aqueous solution, such as micelles, bilayers, vesicle, and lamellae 1. Another fundamental property of surfactants is their tendency to adsorb at surfaces/interfaces from the bulk solution 2. Because of their surface activity, surfactants are frequently used in industry and they are also one of the most discharged organic materials in wastewaters that are to be treated by membrane processes. However, it might be a huge obstacle for reverse osmosis (RO) membrane since the surfactant molecules will accumulate on the surface (considered as non-pores) and cause fouling to the membrane and adversely affect both the quantity (permeate flux) and quality (solute concentration) of the product water, resulting in loss of performance of the membrane 3,4. Although RO membranes have received much attention from both academy and industry, the fouling mechanisms of solutes (especially surfactants) on RO membranes are still not fully understood. Recently, Dissipative Particle Dynamics (DPD) simulation has been proved to be a valuable tool to study the dynamic and static structure of the assembly surfactants and can provide a detailed, mesoscopic level insight into the structure of the studied systems 5,6 .
Procedia Engineering, 2012
Journal of Membrane Science, 2004
Splitting of ammonium nitrate to nitric acid and ammonia was achieved by a coupled process includ... more Splitting of ammonium nitrate to nitric acid and ammonia was achieved by a coupled process including bipolar membrane electrodialysis and in situ ammonia stripping. The effect of homopolar ion-exchange membranes on current efficiency led to the selection of AW (Solvay) and CMB (Tokuyama Soda) membranes. The main parameters influencing the current efficiency were acid and ammonia concentrations. Proton leakage through the anion-exchange membrane is proportional to acid concentration. Ammonia diffuses through the membranes independently of the current. Higher current efficiency was obtained at higher current density. Batch and continuous processing were compared.
Journal of Membrane Science, 2006
Abstract Regeneration of hydrochloric acid and sodium hydroxide from sodium chloride solution has... more Abstract Regeneration of hydrochloric acid and sodium hydroxide from sodium chloride solution has been carried out by membrane electrolysis where the anode was replaced by a membrane-electrode assembly (MEA). Hydrogen diffusion electrode and a Nafion ® 117 membrane were assembled tightly in order to prevent platinum poisoning by chloride ions. The use of this electrode to produce H + may be compared to the use of metallic electrodes where H + is produced by water oxidation with oxygen evolution. The reversible cell voltage is reduced by 1.23 V. The current efficiency of hydrogen oxidation in the MEA is 100% if, at least, the stoichiometric flow of hydrogen is insured. Acid production is then only limited by H + leakage through the anion-exchange membrane. The undesirable flux of H + through this membrane was found proportional to the acid concentration in the anolyte. The value of the rate constant of proton leakage is about 0.080 dm 3 faraday −1 . The current efficiency decreases when acid concentration increases. Water transfer was also studied. Transfer towards the base solution is higher than transfer to the acidic solution. When a current density of 3 kA m −2 is applied the anodic voltage remains below 300 mV for acid concentration lower than 3 mol dm −3 and increases notably for higher acid concentrations probably due to poisoning of platinum by chloride ions that leak through the membrane owing to their high concentration in solution.
Journal of Membrane Science, 2009
The aim of this work is to model the two-compartment bipolar membrane electrodialysis for organic... more The aim of this work is to model the two-compartment bipolar membrane electrodialysis for organic salts acidification. The salt studied is sodium formate which splits into formic acid and sodium hydroxide thanks to water splitting by bipolar membrane. The contamination of sodium hydroxide by formate ion is due to diffusion of molecular formic acid through the bipolar membrane and to leakage of formate ion through the same membrane under the applied current. The cation-exchange membrane does not participate to contamination of sodium hydroxide. But the leakage of hydroxide ion through the cation-exchange membrane is the major factor that influences the current efficiency of electrodialysis. The average current efficiency decreases with time principally because the sodium hydroxide concentration increases. The development of a membrane with limited hydroxide leakage is desirable.
Journal of Membrane Science, 2006
Waters containing low amounts of sodium formate and sodium hydroxide were processed in order to r... more Waters containing low amounts of sodium formate and sodium hydroxide were processed in order to regenerate formic acid. The treatment was performed in three steps: wastewaters neutralization, sodium formate concentration by conventional electrodialysis (ED), and sodium formate splitting into formic acid and sodium hydroxide by bipolar membrane electrodialysis (BMED). A coupling of these processes was performed. ED was carried out
Journal of Materials Chemistry, 2001
The crystal structure of cadmium cyanamide was investigated by X-ray powder analysis and refined ... more The crystal structure of cadmium cyanamide was investigated by X-ray powder analysis and refined using the Rietveld method. Very fine powders of CdCN2 in the nanometre range were obtained by chemical bath deposition. The size, shape and microstrain were characterised by X-ray diffraction and transmission electron microscopy. The refined structure is very close to that of MgCN2. Infrared spectroscopy and thermogravimetric analysis were also performed to fully characterise the compound.
A process coupling membrane electrolysis and electrodialysis is implemented to treat ammonium nit... more A process coupling membrane electrolysis and electrodialysis is implemented to treat ammonium nitrate wastewater. Membrane electrolysis produces ammonia and nitric acid while electrodialysis reconcentrates the depleted salt solution. Ammonia is removed continuously by in situ stripping; thus allowing gas production with a constant current efficiency (about 70%). Nitric acid up to 8 mol L-1 is obtained. The current efficiency of
Hydrometallurgy, 1996
ABSTRACT Vanadium complex formation with sulphate anions was investigated. The ionic strength was... more ABSTRACT Vanadium complex formation with sulphate anions was investigated. The ionic strength was allowed to vary and was accounted for using a usual expression for the activity coefficients. Numerical treatment of the experimental data (vanadium distribution ratio between sulphate solutions and an organic solution where 1-decanol is the extractant) allowed identification of the complex-forming species as SO42− and determination of the thermodynamic formation constant of the complex VO2SO4− at 25°C as log β1 = 1.30 ± 0.02. We also determined the range of the thermodynamic hydrolysis constant Kh of the pervanadyl ion, 3.65 ≤ pKh ≤ 4.3, the best determination being pKh = 3.84.