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Papers by lassaad gzara

RSC Advances, 2016

A facile approach for the rapid and sensitive detection as well as determination of Zn2+ions in w... more A facile approach for the rapid and sensitive detection as well as determination of Zn2+ions in water has been developed.

Desalination, Aug 1, 2004

... Purif. Technol. 14 (1998), pp. 155–162. WR Bowen, AW Mohammad and N. Hilal, Characterisation ... more ... Purif. Technol. 14 (1998), pp. 155–162. WR Bowen, AW Mohammad and N. Hilal, Characterisation of nanofiltration membranes for predictive purpose-use of salts, uncharged solutes and atomic force microscopy, J. Membr. Sci. 126 (1997), pp. 91–105. ...

Case Studies in Thermal Engineering, Dec 1, 2022

Polymers, Jun 16, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Social Science Research Network, 2022

Fibrous membranes of poly(trimethyl hexamethylene terephthalamide) (PA6(3)T) were fabricated by e... more Fibrous membranes of poly(trimethyl hexamethylene terephthalamide) (PA6(3)T) were fabricated by electrospinning and rendered hydrophobic by applying a conformal coating of poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) using initiated chemical vapor deposition (iCVD). A set of iCVD-treated electrospun PA6(3)T fiber membranes with fiber diameters ranging from 0.25 to 1.8 μm were tested for desalination using the air gap membrane distillation configuration. Permeate fluxes of 2−11 kg/m 2 /h were observed for temperature differentials of 20−45°C between the feed stream and condenser plate, with rejections in excess of 99.98%. The liquid entry pressure was observed to increase dramatically, from 15 to 373 kPa with reduction in fiber diameter. Contrary to expectation, for a given feed temperature the permeate flux was observed to increase for membranes of decreasing fiber diameter. The results for permeate flux and salt rejection show that it is possible to construct membranes for membrane distillation even from intrinsically hydrophilic materials after surface modification by iCVD and that the fiber diameter is shown to play an important role on the membrane distillation performance in terms of permeate flux, salt rejection, and liquid entry pressure.

Journal of Applied Membrane Science & Technology, Jul 24, 2023

Desalination is a great technique to address the growing demand for water because it is essential... more Desalination is a great technique to address the growing demand for water because it is essential for humans. Water treatment and desalination are two common uses for the membrane-based, non-isothermal MD (Membrane Distillation) process. It works at low pressure and temperature, and heat from waste and solar energy can meet the process's heat requirements. In MD, dissolved salts and nonvolatile contaminants are rejected as the vapors go through the membrane's pores and start condensing at the permeate side. However, because to the lack of a suitable and adaptable membrane, biofouling, wetting and water efficacy are the main problems for MD. Many researchers have recently worked on membrane composites and attempted to create effective, appealing, and unique membranes for membrane distillation. This review article talks about water shortages in the 21st century, the rise of desalination, the use of membrane distillation (MD), recent developments in membrane distillations, developments in pilot scale MD technologies, New developments in membrane fabrication and modification, the desired properties of membranes, and desalination membranes.

Chemical Engineering Journal, Dec 1, 2009

Cadmium removal from aqueous solution by polyelectrolyte enhanced ultrafiltration (PEUF) with rel... more Cadmium removal from aqueous solution by polyelectrolyte enhanced ultrafiltration (PEUF) with relatively low transmembrane pressure was investigated at varying conditions of polyelectrolyte and cadmium concentrations, transmembrane pressure, ionic strength and pH. The poly(ammonium acrylate), with two average molecular weights (8000 and 15 000 Da) were used as polyelectrolyte. Flux declines during ultrafiltration of polyelectrolyte solutions. An effort has been made to evaluate these resistances independently at different operating conditions. The hydraulic membrane resistance is higher for processing solutions of PAmA 8 than solutions of PAmA 15. The study of ionic strength effect demonstrates that it decreases the retention of cadmium ions and increases the permeate flux. More than 99% of cadmium was retained for a NaNO 3 feed concentration less than 5 × 10 −2 mol L −1. The pH effect study on the cadmium recovery revealed a maximum retention around 98% for pH 4.

Journal of Polymer Engineering, May 12, 2016

Polyethersulfone (PES) is among the most interesting materials for membranes preparation, thanks ... more Polyethersulfone (PES) is among the most interesting materials for membranes preparation, thanks to its outstanding properties, coupled to compatibility with several additives and the facility to be solubilized in several solvents. In this work, flat sheet membranes were prepared by the non-solvent induced phase separation (NIPS) technique, using PES as polymer and polyvinyl pyrrolidone (PVP, 10 kDa) as additive. Preparation and casting conditions were varied and membranes with tailored morphology and properties were obtained. The main objective was to investigate the relationship between selected preparation conditions and membrane features. This may help to understand how to tailor membrane morphology and properties depending on the desired application.

Journal of Power Sources, Jun 1, 2006

3-Methyl-2-oxazolidinone (MeOx) has been mixed to ethylene carbonate (EC) or dimethyl carbonate (... more 3-Methyl-2-oxazolidinone (MeOx) has been mixed to ethylene carbonate (EC) or dimethyl carbonate (DMC) in presence of lithium tetrafluoroborate (LiBF4) or lithium hexafluorophosphate (LiPF6) for use as electrolyte in lithium batteries. The optimized electrolytes in term of conductivity and viscosity are MeOx:EC, x(MeOx)=0.5 and MeOx:DMC, x(MeOx)=0.4 in presence of LiBF4 (1M) or LiPF6 (1M). MeOx:EC electrolytes have a better thermal stability

Journal of Water Science, Apr 12, 2005

The increasing contamination of urban and industrial waste water by toxic métal ions is a worryin... more The increasing contamination of urban and industrial waste water by toxic métal ions is a worrying environmental problem. Thèse inorganic micro-pollutants are of considérable concern because they are non-biodegradable, highly toxic and in some cases hâve a probable carcinogenic effect. If directly discharged into the sewage System they may seriously affect the opération of biological treatment Systems and render the activated sludge unsuitable for application to agricultural land.

Journal of Molecular Liquids, Jun 1, 2014

The aim of this work is to study the interaction between Toluidine Blue (TB), a cationic dye, and... more The aim of this work is to study the interaction between Toluidine Blue (TB), a cationic dye, and an anionic polyelectrolyte, poly (ammonium acrylate) (PANH 4). The UV-Visible spectroscopy study shows that addition of increasing amounts of poly (ammonium acrylate) induces the formation of a metachromatic complex. The stoichiometry of TB-PANH 4 complex evaluated by the molar ratio method is 1:1 and the large hypsochromic absorption shift (73 nm) obtained is attributed to dye H-aggregates. The effects of sodium chloride concentration, pH and Cetyl pyridinium chloride (CPC) concentration, on metachromasy have also been studied. Thermodynamic parameters of interaction ΔG, ΔH and ΔS at different temperatures have been evaluated to determine the stability constant of the complex.

Desalination, Sep 1, 2009

Enhanced ultrafiltration by the addition of poly(ammonium acrylate), with two average molecular w... more Enhanced ultrafiltration by the addition of poly(ammonium acrylate), with two average molecular weight 8000 Da and 15 000 Da, for the removal of Cd(II) from aqueous solutions has been studied. The solution is processed by ultrafiltration using a membrane with pore sizes (10 kDa) small enough to block the passage of the polymer and adsorbed metal ions. Suitable experimental conditions (e.g. pH, polymer and metal concentration, and polymer molecular weight) for cadmium recovery and permeate flux have been optimised. Cadmium rejection coefficient increases with monomer concentration and reaches 99% values at twofold cadmium concentrations. As a consequence, two monomers units (C 2 H 3 COO-) are necessary to coordinate 1 ion mol of cadmium. Based on this experimental result, a simple mathematical model that allows calculating the apparent polymer-metal complex (PMC) formation constant has been established. The influence of pH has been studied to fix the pH for metal retention and polymer regeneration experiments.

Journal of Analytical Chemistry, Oct 1, 2005

ABSTRACT The behavior of surfactants of different natures and chain lengths was studied in flame ... more ABSTRACT The behavior of surfactants of different natures and chain lengths was studied in flame atomic absorption spectrometry (FAAS) analyses. The variations of absorbance, which arise as a consequence of the surfactant addition to aqueous solutions of Cr(VI) or Cr(III), were measured. Depressions were observed below the critical micelle concentration (CMC), whereas enhancements were observed above the CMC. These depressions are more significant when the surfactant is opposite in charge to the analyte and the longest surfactant chain is used. A mechanism that enables explanation of the effects of a surfactant on FAAS is also suggested. This mechanism is based on the preferential orientation of surfactant molecules to the surface of nebulized droplets.

ABSTRACT The increasing contamination of urban and industrial waste water by toxic metal ions is ... more ABSTRACT The increasing contamination of urban and industrial waste water by toxic metal ions is a worrying environmental problem. These inorganic micro-pollutants are of considerable concern because they are non-biodegradable, highly toxic and in some cases have a probable carcinogenic effect. If directly discharged into the sewage system they may seriously affect the operation of biological treatment systems and render the activated sludge unsuitable for application to agricultural land. The traditional techniques for the removal of metal ions from aqueous effluents are incapable of reducing concentrations to the levels required by law (reduction or lime precipitation) or prohibitively expensive (ion exchange, activated carbon adsorption or electrolytic removal). The use of membrane separation processes to treat waste water containing toxic metal ions is today an attractive and suitable technique, and it can easily be included in the process, which is the reason why membrane separations are being used more and more frequently. Separations can be carried at room temperature, the modular membrane surface can be easily adjusted to the wastewater flows, and various industrial membranes are now available. In order to retain metallic ions, reverse osmosis (or at least nanofiltration) can be used, due to the size of the ions in aqueous solutions. However, the usual permeate fluxes of reverse osmosis membranes are limited and require high transmembrane pressure, which makes the process expensive. During the last decade, there has been a constantly increasing level of interest and research efforts in order to improve the performances of surfactant-based separation processes. In the present study an attempt is made to remove lead(II) ions from synthetic aqueous solutions by micellar-enhanced ultrafiltration (MEUF) using the anionic surfactant sodium dodecylsulfate (SDS). The study has been carried out at a temperature of 318 °K and on a laboratory scale. Ultrafiltration experiments were carried out with a tangential cell system. The inlet flux was held constant (up to 0.5 m·s-1) and the drop in pressure was varied from 1 to 3 bars by restricting the outlet tube. Polysulfone membranes with a molecular weight cut-off (MWCO) of 10,000 Da and an effective filtration area of 30 cm2 were used. The influence of the operating parameters on permeate flux and lead rejection was studied. Rejection coefficients of 99% are reached under optimal conditions of pressure, feed concentration in SDS, tangential velocity of the feed, and percent filtered volume. An ionic exchange model has been used to study the interaction between the lead cation (Pb2+) and sodium dodecylsulfate micelles. The model used to fit the experimental data is an ionic micelle in which the electric double layer is divided into a diffuse outside layer and a Stern layer inside the shear surface. Assuming that divalent cations are strongly attached to the micellar surface and located specifically in the Stern layer of the micelle, it has been found that adsorption in the Stern layer is well described by a Langmuir isotherm. From this isotherm, ion exchange constants for Pb2+ with the Na+ counterion have been determined Ke (Na+/Cd2+) = 1.39, and have been compared with those obtained for other cations (Cd2+, Mg2+) in the same media. In order to determine the performance of the MEUF process in acidic streams, studies were performed at constant cation concentrations and various pH values. The pH variation was obtained by the addition of HCIO4 or H3PO4. Rejection remains higher than 95% provided the pH is maintained higher than 1.8.

International Journal of Modern Physics B, Jul 29, 2022

This research paper investigates the heat and mass transport characteristics in an unsteady flow ... more This research paper investigates the heat and mass transport characteristics in an unsteady flow of Maxwell nanofluid (NF). While examining heat transfer properties, thermal radiation is taken into account. Further, copper oxide with water-based NF is considered. The mass transfer and effective thermal conductivity of nanofluid flow are scrutinized by Koo and Kleinstreuer–Li (KKL) NF model. Through apt transformations, relevant flow expressions are converted to ordinary differential equations (ODEs). The numerical approach Runge–Kutta–fourth–fifth Fehlberg’s order process (RKF-45) algorithm with shooting technique is utilized to solve the generated ODEs. Results reveal that, the rise in values of unsteadiness parameter has a positive impact on both concentration and thermal profiles. The Deborah number has constructive impact on heat transport and reverse influence on velocity field. The improved heat transport is seen for augmented values of radiation and heat source/sink parameters. The Brownian motion parameter has positive influence on heat transport and reverse effect on mass transport.

Polymers, Aug 3, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Environmental Chemical Engineering, 2021

Abstract Exergy analyses are becoming important tools in identifying the less efficient component... more Abstract Exergy analyses are becoming important tools in identifying the less efficient components of plants through the evaluation of the energy lost in entropy production. In this work, this type of analysis was considered for desalination plants based on membrane operations, with specific emphasis on membrane distillation and membrane crystallization for the improvement of the water recovery factor and the recovery of valuable salts from produced brines. The state of the art in the field was firstly presented and discussed. In all literature works, the thermal supply was the highest contributor to exergy losses. However, the use of waste heat or renewable energies can significantly improve the exergy efficiency of the process, as the feed is heated by the available source and enters the process already at the desired temperature. Furthermore, it resulted that the gain for the sale of salts produced by membrane crystallization was able to cover the desalination costs, even without waste heat availability. Then, the exergy analysis of membrane distillation (MD) and membrane crystallization (MCr) working on four different feeds was experimentally carried out. Commercial modules equipped with capillary polypropylene membranes (0.2 μm pore size) were used at fixed feed temperature and flow rate. A high exergy efficiency (72%) was obtained with the Synthetic RO feed (79.9 g/L), together with a high water recovery factor (79%) and brine concentration (around 476 g/L).

Development and Prospective Applications of Nanoscience and Nanotechnology, 2018

RSC Advances, 2016

A facile approach for the rapid and sensitive detection as well as determination of Zn2+ions in w... more A facile approach for the rapid and sensitive detection as well as determination of Zn2+ions in water has been developed.

Desalination, Aug 1, 2004

... Purif. Technol. 14 (1998), pp. 155–162. WR Bowen, AW Mohammad and N. Hilal, Characterisation ... more ... Purif. Technol. 14 (1998), pp. 155–162. WR Bowen, AW Mohammad and N. Hilal, Characterisation of nanofiltration membranes for predictive purpose-use of salts, uncharged solutes and atomic force microscopy, J. Membr. Sci. 126 (1997), pp. 91–105. ...

Case Studies in Thermal Engineering, Dec 1, 2022

Polymers, Jun 16, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Social Science Research Network, 2022

Fibrous membranes of poly(trimethyl hexamethylene terephthalamide) (PA6(3)T) were fabricated by e... more Fibrous membranes of poly(trimethyl hexamethylene terephthalamide) (PA6(3)T) were fabricated by electrospinning and rendered hydrophobic by applying a conformal coating of poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) using initiated chemical vapor deposition (iCVD). A set of iCVD-treated electrospun PA6(3)T fiber membranes with fiber diameters ranging from 0.25 to 1.8 μm were tested for desalination using the air gap membrane distillation configuration. Permeate fluxes of 2−11 kg/m 2 /h were observed for temperature differentials of 20−45°C between the feed stream and condenser plate, with rejections in excess of 99.98%. The liquid entry pressure was observed to increase dramatically, from 15 to 373 kPa with reduction in fiber diameter. Contrary to expectation, for a given feed temperature the permeate flux was observed to increase for membranes of decreasing fiber diameter. The results for permeate flux and salt rejection show that it is possible to construct membranes for membrane distillation even from intrinsically hydrophilic materials after surface modification by iCVD and that the fiber diameter is shown to play an important role on the membrane distillation performance in terms of permeate flux, salt rejection, and liquid entry pressure.

Journal of Applied Membrane Science & Technology, Jul 24, 2023

Desalination is a great technique to address the growing demand for water because it is essential... more Desalination is a great technique to address the growing demand for water because it is essential for humans. Water treatment and desalination are two common uses for the membrane-based, non-isothermal MD (Membrane Distillation) process. It works at low pressure and temperature, and heat from waste and solar energy can meet the process's heat requirements. In MD, dissolved salts and nonvolatile contaminants are rejected as the vapors go through the membrane's pores and start condensing at the permeate side. However, because to the lack of a suitable and adaptable membrane, biofouling, wetting and water efficacy are the main problems for MD. Many researchers have recently worked on membrane composites and attempted to create effective, appealing, and unique membranes for membrane distillation. This review article talks about water shortages in the 21st century, the rise of desalination, the use of membrane distillation (MD), recent developments in membrane distillations, developments in pilot scale MD technologies, New developments in membrane fabrication and modification, the desired properties of membranes, and desalination membranes.

Chemical Engineering Journal, Dec 1, 2009

Cadmium removal from aqueous solution by polyelectrolyte enhanced ultrafiltration (PEUF) with rel... more Cadmium removal from aqueous solution by polyelectrolyte enhanced ultrafiltration (PEUF) with relatively low transmembrane pressure was investigated at varying conditions of polyelectrolyte and cadmium concentrations, transmembrane pressure, ionic strength and pH. The poly(ammonium acrylate), with two average molecular weights (8000 and 15 000 Da) were used as polyelectrolyte. Flux declines during ultrafiltration of polyelectrolyte solutions. An effort has been made to evaluate these resistances independently at different operating conditions. The hydraulic membrane resistance is higher for processing solutions of PAmA 8 than solutions of PAmA 15. The study of ionic strength effect demonstrates that it decreases the retention of cadmium ions and increases the permeate flux. More than 99% of cadmium was retained for a NaNO 3 feed concentration less than 5 × 10 −2 mol L −1. The pH effect study on the cadmium recovery revealed a maximum retention around 98% for pH 4.

Journal of Polymer Engineering, May 12, 2016

Polyethersulfone (PES) is among the most interesting materials for membranes preparation, thanks ... more Polyethersulfone (PES) is among the most interesting materials for membranes preparation, thanks to its outstanding properties, coupled to compatibility with several additives and the facility to be solubilized in several solvents. In this work, flat sheet membranes were prepared by the non-solvent induced phase separation (NIPS) technique, using PES as polymer and polyvinyl pyrrolidone (PVP, 10 kDa) as additive. Preparation and casting conditions were varied and membranes with tailored morphology and properties were obtained. The main objective was to investigate the relationship between selected preparation conditions and membrane features. This may help to understand how to tailor membrane morphology and properties depending on the desired application.

Journal of Power Sources, Jun 1, 2006

3-Methyl-2-oxazolidinone (MeOx) has been mixed to ethylene carbonate (EC) or dimethyl carbonate (... more 3-Methyl-2-oxazolidinone (MeOx) has been mixed to ethylene carbonate (EC) or dimethyl carbonate (DMC) in presence of lithium tetrafluoroborate (LiBF4) or lithium hexafluorophosphate (LiPF6) for use as electrolyte in lithium batteries. The optimized electrolytes in term of conductivity and viscosity are MeOx:EC, x(MeOx)=0.5 and MeOx:DMC, x(MeOx)=0.4 in presence of LiBF4 (1M) or LiPF6 (1M). MeOx:EC electrolytes have a better thermal stability

Journal of Water Science, Apr 12, 2005

The increasing contamination of urban and industrial waste water by toxic métal ions is a worryin... more The increasing contamination of urban and industrial waste water by toxic métal ions is a worrying environmental problem. Thèse inorganic micro-pollutants are of considérable concern because they are non-biodegradable, highly toxic and in some cases hâve a probable carcinogenic effect. If directly discharged into the sewage System they may seriously affect the opération of biological treatment Systems and render the activated sludge unsuitable for application to agricultural land.

Journal of Molecular Liquids, Jun 1, 2014

The aim of this work is to study the interaction between Toluidine Blue (TB), a cationic dye, and... more The aim of this work is to study the interaction between Toluidine Blue (TB), a cationic dye, and an anionic polyelectrolyte, poly (ammonium acrylate) (PANH 4). The UV-Visible spectroscopy study shows that addition of increasing amounts of poly (ammonium acrylate) induces the formation of a metachromatic complex. The stoichiometry of TB-PANH 4 complex evaluated by the molar ratio method is 1:1 and the large hypsochromic absorption shift (73 nm) obtained is attributed to dye H-aggregates. The effects of sodium chloride concentration, pH and Cetyl pyridinium chloride (CPC) concentration, on metachromasy have also been studied. Thermodynamic parameters of interaction ΔG, ΔH and ΔS at different temperatures have been evaluated to determine the stability constant of the complex.

Desalination, Sep 1, 2009

Enhanced ultrafiltration by the addition of poly(ammonium acrylate), with two average molecular w... more Enhanced ultrafiltration by the addition of poly(ammonium acrylate), with two average molecular weight 8000 Da and 15 000 Da, for the removal of Cd(II) from aqueous solutions has been studied. The solution is processed by ultrafiltration using a membrane with pore sizes (10 kDa) small enough to block the passage of the polymer and adsorbed metal ions. Suitable experimental conditions (e.g. pH, polymer and metal concentration, and polymer molecular weight) for cadmium recovery and permeate flux have been optimised. Cadmium rejection coefficient increases with monomer concentration and reaches 99% values at twofold cadmium concentrations. As a consequence, two monomers units (C 2 H 3 COO-) are necessary to coordinate 1 ion mol of cadmium. Based on this experimental result, a simple mathematical model that allows calculating the apparent polymer-metal complex (PMC) formation constant has been established. The influence of pH has been studied to fix the pH for metal retention and polymer regeneration experiments.

Journal of Analytical Chemistry, Oct 1, 2005

ABSTRACT The behavior of surfactants of different natures and chain lengths was studied in flame ... more ABSTRACT The behavior of surfactants of different natures and chain lengths was studied in flame atomic absorption spectrometry (FAAS) analyses. The variations of absorbance, which arise as a consequence of the surfactant addition to aqueous solutions of Cr(VI) or Cr(III), were measured. Depressions were observed below the critical micelle concentration (CMC), whereas enhancements were observed above the CMC. These depressions are more significant when the surfactant is opposite in charge to the analyte and the longest surfactant chain is used. A mechanism that enables explanation of the effects of a surfactant on FAAS is also suggested. This mechanism is based on the preferential orientation of surfactant molecules to the surface of nebulized droplets.

ABSTRACT The increasing contamination of urban and industrial waste water by toxic metal ions is ... more ABSTRACT The increasing contamination of urban and industrial waste water by toxic metal ions is a worrying environmental problem. These inorganic micro-pollutants are of considerable concern because they are non-biodegradable, highly toxic and in some cases have a probable carcinogenic effect. If directly discharged into the sewage system they may seriously affect the operation of biological treatment systems and render the activated sludge unsuitable for application to agricultural land. The traditional techniques for the removal of metal ions from aqueous effluents are incapable of reducing concentrations to the levels required by law (reduction or lime precipitation) or prohibitively expensive (ion exchange, activated carbon adsorption or electrolytic removal). The use of membrane separation processes to treat waste water containing toxic metal ions is today an attractive and suitable technique, and it can easily be included in the process, which is the reason why membrane separations are being used more and more frequently. Separations can be carried at room temperature, the modular membrane surface can be easily adjusted to the wastewater flows, and various industrial membranes are now available. In order to retain metallic ions, reverse osmosis (or at least nanofiltration) can be used, due to the size of the ions in aqueous solutions. However, the usual permeate fluxes of reverse osmosis membranes are limited and require high transmembrane pressure, which makes the process expensive. During the last decade, there has been a constantly increasing level of interest and research efforts in order to improve the performances of surfactant-based separation processes. In the present study an attempt is made to remove lead(II) ions from synthetic aqueous solutions by micellar-enhanced ultrafiltration (MEUF) using the anionic surfactant sodium dodecylsulfate (SDS). The study has been carried out at a temperature of 318 °K and on a laboratory scale. Ultrafiltration experiments were carried out with a tangential cell system. The inlet flux was held constant (up to 0.5 m·s-1) and the drop in pressure was varied from 1 to 3 bars by restricting the outlet tube. Polysulfone membranes with a molecular weight cut-off (MWCO) of 10,000 Da and an effective filtration area of 30 cm2 were used. The influence of the operating parameters on permeate flux and lead rejection was studied. Rejection coefficients of 99% are reached under optimal conditions of pressure, feed concentration in SDS, tangential velocity of the feed, and percent filtered volume. An ionic exchange model has been used to study the interaction between the lead cation (Pb2+) and sodium dodecylsulfate micelles. The model used to fit the experimental data is an ionic micelle in which the electric double layer is divided into a diffuse outside layer and a Stern layer inside the shear surface. Assuming that divalent cations are strongly attached to the micellar surface and located specifically in the Stern layer of the micelle, it has been found that adsorption in the Stern layer is well described by a Langmuir isotherm. From this isotherm, ion exchange constants for Pb2+ with the Na+ counterion have been determined Ke (Na+/Cd2+) = 1.39, and have been compared with those obtained for other cations (Cd2+, Mg2+) in the same media. In order to determine the performance of the MEUF process in acidic streams, studies were performed at constant cation concentrations and various pH values. The pH variation was obtained by the addition of HCIO4 or H3PO4. Rejection remains higher than 95% provided the pH is maintained higher than 1.8.

International Journal of Modern Physics B, Jul 29, 2022

This research paper investigates the heat and mass transport characteristics in an unsteady flow ... more This research paper investigates the heat and mass transport characteristics in an unsteady flow of Maxwell nanofluid (NF). While examining heat transfer properties, thermal radiation is taken into account. Further, copper oxide with water-based NF is considered. The mass transfer and effective thermal conductivity of nanofluid flow are scrutinized by Koo and Kleinstreuer–Li (KKL) NF model. Through apt transformations, relevant flow expressions are converted to ordinary differential equations (ODEs). The numerical approach Runge–Kutta–fourth–fifth Fehlberg’s order process (RKF-45) algorithm with shooting technique is utilized to solve the generated ODEs. Results reveal that, the rise in values of unsteadiness parameter has a positive impact on both concentration and thermal profiles. The Deborah number has constructive impact on heat transport and reverse influence on velocity field. The improved heat transport is seen for augmented values of radiation and heat source/sink parameters. The Brownian motion parameter has positive influence on heat transport and reverse effect on mass transport.

Polymers, Aug 3, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Environmental Chemical Engineering, 2021

Abstract Exergy analyses are becoming important tools in identifying the less efficient component... more Abstract Exergy analyses are becoming important tools in identifying the less efficient components of plants through the evaluation of the energy lost in entropy production. In this work, this type of analysis was considered for desalination plants based on membrane operations, with specific emphasis on membrane distillation and membrane crystallization for the improvement of the water recovery factor and the recovery of valuable salts from produced brines. The state of the art in the field was firstly presented and discussed. In all literature works, the thermal supply was the highest contributor to exergy losses. However, the use of waste heat or renewable energies can significantly improve the exergy efficiency of the process, as the feed is heated by the available source and enters the process already at the desired temperature. Furthermore, it resulted that the gain for the sale of salts produced by membrane crystallization was able to cover the desalination costs, even without waste heat availability. Then, the exergy analysis of membrane distillation (MD) and membrane crystallization (MCr) working on four different feeds was experimentally carried out. Commercial modules equipped with capillary polypropylene membranes (0.2 μm pore size) were used at fixed feed temperature and flow rate. A high exergy efficiency (72%) was obtained with the Synthetic RO feed (79.9 g/L), together with a high water recovery factor (79%) and brine concentration (around 476 g/L).

Development and Prospective Applications of Nanoscience and Nanotechnology, 2018