Amor Hafiane

Removal of hexavalent chromium by nanofiltration

Abstract Removal of chromate CrO42− from water was investigated using nanofiltration as a possible alternative to the conventional methods of CrVI removal from aqueous solution. Retention measurements with single reference salt revealed that Donnan exclusion plays an important role. The phenomenological parameters σ and P were calculated using the Spiegler-Kedem equation. The rejection rate depends on the ionic strength and pH. The increasing of ionic strength decreases the retention. The effect of pH was clarified by using a stable diagram of the CrVIH2O system. Better retention was obtained at basic pH.

Removal of Eriochrome Blue Black R from wastewater using micellar-enhanced ultrafiltration

Micellar-enhanced ultrafiltration (MEUF) represents a potentially attractive tool for the removal of different contaminants from wastewater. In this study, MEUF was carried out to investigate the retention of Eriochrome Blue Black R (EBBR), an anionic dye, from aqueous stream. N-Alkyltrimethylammonium bromide i.e. dodecyltrimethylammonium bromide (C(12)TAB), tetradecyltrimethylammonium bromide (C(14)TAB), cetyl-trimethylammonium bromide (C(16)TAB) and octadecyltrimethylammonium bromide (C(18)TAB) were taken as cationic surfactants, and NaCl, Na(2)SO(4), Na(2)HPO(4) as electrolytes. A hydrophilic membrane made of cellulose (molecular weight cut-off 10000 Da) was used in a cross-flow ultrafiltration unit. The removal of EBBR was studied as a function of dye and surfactant concentrations, ionic strength, transmembrane pressure and pH. The MEUF experiments showed that the highest dye rejection was about 99% for the used range of dye and surfactant concentrations. This retention depended slightly on dye and surfactant concentrations, ionic strength, pH and transmembrane pressure. However, permeate flux changed significantly with those parameters due mainly to concentration polarisation and osmotic pressure.

Spectral study of Eriochrome Blue Black R in different cationic surfactant solutions

Interactions of anionic dye Eriochrome Blue Black R (EBBR) with various cationic micelles of surfactants n-alkyltrimethylammonium CnTAB (n=12; 14; 16 and 18) have been investigated spectrophotometrically at 25°C in premicellar and postmicellar region. The results have shown that with increasing the alkyl chain length of surfactants, the maximum absorbance of EBBR shifted to a higher wavelength and the binding constants of EBBR to cationic micelles (Kb) increases. This confirms that the surfactant micelle, which has a longer alkyl hydrocarbon chain, enables greater solubilization of dye. Thus, the hydrophobic interaction of the dye with micelles increases in the order: C12TAB

Nitrate removal from aqueous solution by direct contact membrane distillation using two different commercial membranes

AbstractIn the present work, the removal of nitrate from aqueous solution by direct contact membrane distillation (DCMD) using flat sheets polypropylene (PP) and polyvinylidene fluoride (PVDF) membranes was studied. Effect of operating parameters, such as feed temperature, feed flow rate, initial nitrate concentration, feed ionic strength, and competing co-existing anions on permeate flux and nitrate rejection, was investigated. In all DCMD experimental runs, an almost complete nitrate rejection was achieved (higher than 99.90%) and the permeate nitrate concentration was largely below the maximum permissible level in potable water. Under the same operating conditions, PVDF hydrophobic membrane showed a higher permeate flux of 37.21 L/m2h than PP membrane with a permeate flux of 4.12 L/m2h. For both the membranes, feed temperature is the important operating parameter which enhanced exponentially the permeate flux. Likewise, a positive effect on permeate flux was found when feed flow rate was increased. How...

Investigation on the interaction of Safranin T with anionic polyelectrolytes by spectrophotometric method.

Understanding the role played by chemical additives such as NaCl salt, acid and Cetylpyridinium Chloride (CPC) surfactant on the interaction between dye and polyelectrolyte contributes to optimization of processes using polyelectrolytes in the removal of dye from aqueous solution. Herein we focus in the interaction between Safranin T, a cationic dye, with two anionic polyelectrolytes, poly(ammonium acrylate) and poly(acrylic acid) using spectrophotometric method and conductivity measurement. In aqueous solution, each of anionic polyelectrolytes forms a complex with the dye and induces a metachromasy indicated by the blue shift of the absorbance of the dye. The stoichiometry of complexes evaluated by the molar ratio method are 1:1 for Safranin T poly(ammonium acrylate) and 2:1 in the case of Safranin T poly(acrylic acid). The effect of additives on the stability of complexes has been studied by varying concentrations of the salt and the surfactant and pH of the solution. The thermodynamic parameters of interaction ΔG, ΔH and ΔS at different temperatures were evaluated to determine the stability constant of the complexes.

Electrodialytic Removal of Cadmium from Brackish Water: Effects of Operating Parameters

The continuous increase of environmental regulations make interesting to find effective and efficient methods for processing effluents containing metal ions. This research focuses on cadmium removal from brackish water by an electro-membrane process: The electrodialysis. Experiments were carried out on synthetic brackish water solutions and using a laboratory scale electrodialysis system. The influence of several parameters on process efficiency was investigated. The efficiency of this process was assessed by the determination of five parameters: The demineralization rate, the removal rate and the transport flux of cadmium, the current efficiency and the specific power consumption. The applied voltage, the feed flow rate, the pH and cadmium initial concentration of the feed solution have a significant effect on the process efficiency and mainly on the cadmium transfer from dilute to concentrate compartment. In contrast, feed ionic strength seems to affect only the SPC and not the R(Cd).

Separation of zinc ions from synthetically prepared brackish water using electrodialysis: effect of operating parameters

AbstractThe removal of zinc(II) at low concentrations from an aqueous saline solution was investigated using a five-compartment electrodialysis cell. In this work, the effect of key operating parameters such as initial zinc ions concentration, solution pH, applied voltage, and feed flow rate on process efficiency was studied. The separation performance was evaluated in terms of mass transfer, energy consumption, and current efficiency. The results showed that increasing the initial concentration of Zn(II) and applied voltage improves the cell performance. However, separation performance decreases with an increase in the flow rate. It was also found that specific power consumptions (SPC) are strongly dependant on ionic strength as the increase of ionic strength leads to an increase of the solution conductivity. Zinc removal rate and SPC were virtually constant and increased sharply when pH values ranged in the alkaline region.

The effect of surfactant on dye removal by polyelectrolyte enhanced ultrafiltration

AbstractPolyelectrolyte-based separation of toxic dyes is studied to estimate the potential of polyelectrolyte enhanced ultrafiltration (PEUF) using polyethylene glycol (PEG). Removal of methyl orange (MO) an azo dye from aqueous solutions, by continuous polymer enhanced ultrafiltration (PEUF) was investigated. The permeate flux profile and obtained retention of MO were studied as a function of polyelectrolyte concentrations, transmembrane pressure, ionic strength and pH in the absence and in the presence of surfactant (CTAB). The experiments showed that retention of MO in the presence of PEG of different concentrations was 65%. This may be due to that the PEG polyelectrolyte cannot bind MO to form aggregates to enhance UF process. However, when the CTAB was applied at a fixed concentration below CMC, MO decolourization increased and reached a limiting value of 99%. The high rejection for MO dye is due to the formation of H aggregates in the aqueous solution. This result was confirmed by the change of the...

The effect of operating conditions on the retention of Toluidine blue by polyelectrolyte-enhanced ultrafiltration

In the present work, we study the effect of experimental conditions on the performance of polyelectrolyte-enhanced ultrafiltration for the removal of Toluidine blue from aqueous solution. The dye solution was processed by ultrafiltration using a regenerate cellulose membrane with pore sizes small enough to block the passage of the polymer and then the complexed dye ions. The experiments showed that retentions as high as 99% and 97% were obtained for PAA and PANH4, respectively, due to the strong electrostatic interaction between anionic polyelectrolytes and cationic dye. The increase of retention was linked to the complexation of the dye by polyelectrolyte while the decrease of the permeate flux was attributed to the accumulated macromolecular complex near the membrane.