Smita Gupta

Response Surface Modelling and Optimization of Mercury Extraction through Emulsion Liquid Membrane

Mercury(II) is a very harmful metal, highly toxic, and carcinogenic in nature. Experiments were carried out using the emulsion liquid membrane (ELM) technique in order to evaluate the maximum extraction of mercury(II) from aqueous solutions of mercuric chloride using 33 factorial design. The ELM consisted of di-2-ethylhexylphosphoric acid as a carrier, toluene as an organic solvent, span 80 as a surfactant, and sulphuric acid with thiourea solution as stripping phase. The three factors for the factorial design were mercury(II) concentration in the aqueous solution, that is, feed phase concentration, carrier concentration in the membrane phase, and sulphuric acid concentration in the stripping phase. The study has also highlighted the effects of various other parameters, such as pH of the feed phase and thiourea concentration on mercury(II) extraction. The optimization of the factors to obtain maximum extraction were carried out by incorporating main effect plots, interaction plots, analysis of variance (ANOVA), normal probability plots, residual plots, surface plots, and contour plots. A reduced model developed by regression analysis was suggested in which the experimental data were fitted very well. The results showed that it is possible to extract mercury(II) up to 98% from aqueous solutions at the optimum conditions.

Removal of Mercury by Emulsion Liquid Membranes: Studies on Emulsion Stability and Scale Up

Emulsion liquid membranes (ELM) have received significant attention in the separation of various metal ions from industrial wastewater. Still efforts are needed to get the desired level of stability to overcome the hindrance in the application of ELM at industrial scale. In this paper, the effects of various parameters such as emulsification speed, concentration of cosurfactant, surfactant, carrier and impeller speed during extraction on the stability of an emulsion liquid membrane are studied. Dispersion destabilization of w/o emulsion is checked by Turbiscan. Drop size distribution and photomicrographs of the emulsions are also analyzed to evaluate stability of the emulsion. Instability of emulsion liquid membrane during extraction process is measured in terms of membrane breakage. A stable emulsion is used for the extraction of mercury from aqueous solution in small scale as well as in large scale.

Application of pseudo-emulsion-based hollow fiber strip dispersion for the extraction of p-nitrophenol from aqueous solutions

ABSTRACT The extraction of p-nitrophenol (PNP) from aqueous solutions through a pseudo-emulsion hollow fiber strip dispersion (PEHFSD) system was conducted in a microporous hydrophobic polypropylene hollow fiber membrane contactor. For the optimization of the process variables, face-centered central composite design (FCCD) has been used. It was observed that initial feed concentration, carrier composition and stripping phase concentration were the three FCCD factors, which influenced the nitrophenol extraction. Using the optimized process conditions for the separation of PNP, experiments were also performed for the separation of other nitrophenols through PEHFSD system. By the FCCD design and analysis, almost 99% extraction of all three nitrophenols was achieved at optimum conditions. A mass transfer model was also developed and aqueous and membrane resistances were evaluated as 196.46 s cm−1 and 50.14 s cm−1, respectively.

Study on Photocatalytic Degradation of Endocrine Disrupting Compound

Propylparaben (PP) is catagorized as endocrine disrupting compounds and is found to be present in urban wastewater comparatively at high concentrations. In the present work, propylparaben was degraded photo-catalytically by optimizing different process parameters such as initial concentration of propylparaben (25mgL-1 to 100 mgL-1), pH of the feed phase and concentration of photocatalyst TiO2 (50 mgL-1 to 200 mgL-1). Finally PP degraded and converted to CO2 and H2O and the degradation was found to follow the first order kinetics.

Isolation and Characterization of Biosurfactant Producing Bacteria for the Application in Enhanced Oil Recovery

In the present study, a biosurfactant producing bacterial strain was isolated, screened and identified. Further, various fermentation conditions (such as pH (5-10), incubation period (24-96h) and incubation temperature (20-60 °C) were optimized for maximum production of biosurfactant. The produced biosurfactant was characterized by measuring emulsification index, foaming characteristics, rhamnolipid detection, interfacial tension between water and oil and stability against pH and temperature for its potential application in oil recovery process. The additional oil recovery for two different sand, sand1 and sand2, was found to be 49% and 38%, respectively.