Mousumi Chakraborty

Process intensification : Extraction of chromium(VI) by emulsion liquid membrane

Abstract Electroplating is one of the important processes involved in surface finishing and metal deposition for better life of articles and for decoration. Chromium(VI) is the most commonly used metal for electroplating. Thus, the waste water of such industries contains Chromium(VI) ions. Emulsion Liquid Membrane (ELM) separation technique provides a potentially powerful technique for the removal of Chromium(VI) ions from the waste water. In the present study, the effect of different parameters such as pH, different carriers concentration, synergistic effect caused by a mixture of two appropriate carriers concentration, effect of electrostatic surface potential and effects of composition of a dilute polymer solution; which will intensify the extraction efficiency of Chromium(VI); are systematically investigated using Aliquat 336 and tri‐n‐octyl amine as extractant, sorbitan mono‐oleate (span 80) as surfactant, kerosene as membrane phase and sodium hydroxide as stripping solution.

Photocatalytic degradation of malachite green dye using doped and undoped ZnS nanoparticles

Photocatalytic degradation of malachite green dye using doped and undoped ZnS nanoparticles In the present study, ZnS nanoparticles were prepared using the mechanochemical method. The ZnS nanoparticles prepared were doped with different concentrations of manganese using metal acetate and manganese acetate by mechanochemical method. The as-prepared particles were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The photocatalytic activity of the prepared nanoparticles samples, in the photocatalytic degradation of malachite green, had been investigated. The nanoparticles were photo induced, generating hole transfer for photocatalytic activity. The photodegradation of malachite green was observed at different pH (2-5) values, dye concentrations (10-100mg/L) and amount of ZnS nanoparticles (1-2.5 g/L). About 95% degradation of dye was observed on the addition of 2 g/L ZnS in 50 mg/L dye solution after 90 minutes illumination at 125 W. Degradation has been increased up to 99% using UV/nanoparticles/H2O2 (50 mL/L) combined process. The degradation efficiency was also compared using Mn doped ZnS nanoparticles (Zn1-x MnxS, where x = 0.01, 0.22 and 0.3). Maximum of 97% degradation was observed with 0.01% concentration of Mn. Kinetics study and performance of UV/ZnS, UV/ZnS/H2O2, UV/doped ZnS processes were evaluated to compare the efficiency of different processes.

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.

Benzene hydrogenation over highly active monodisperse Ru/γ-Al2O3 nanocatalyst synthesized by (w/o) reverse microemulsion

Ruthenium nanoparticles (10–40xa0nm) were synthesized by the reduction of aqueous ruthenium trichloride in aqueous sodium borohydride by the water-in-oil (w/o) reverse microemulsion method at atmospheric temperature. The synthesized Ru nanoparticles (Ru content 1–5xa0wt%) were dispersed on γ-alumina of high surface area by a high speed mechanical stirrer. The nanocatalysts (Ru/γ-Al2O3) were characterized by transmission electron microscopy, X-ray diffraction, N2-physisorption, BET surface area, hydrogen chemisorption and thermogravimetric analysis (TG/DTA). The activity of the nanocatalyst was tested in the gas–liquid phase hydrogenation reaction of benzene to cyclohexane at 40–100xa0°C and 20xa0bar hydrogen pressure. The activities of the catalysts were studied by varying different parameters such as Ru loading (wt% of Ru), reaction temperatures, catalyst recycling, thiophene (catalyst poison) concentration, stirring speed and metal nanoparticles size etc. The results showed that maximum activity (100xa0% conversion of benzene) was obtained at 80xa0°C and 20xa0bar pressure with 4xa0wt% (Ru content) catalyst. The activation energy and TOF were found to be 27.9xa0kJxa0molxa0−1 and 1416.8xa0h−1, respectively, which indicated higher activity of Ru/γ-Al2O3 catalyst than conventional catalyst for the hydrogenation of benzene to cyclohexane.

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.

Mechanochemical Synthesis and Characterization of Group II-VI Semiconductor Nanoparticles

Synthesis of metal sulfide semiconductor nanoparticles of group II-VI; namely ZnS, PbS, CdS, and CuS; by mechanochemical method was carried out in a high energy ball mill from corresponding metal acetates and sodium sulfide. The samples were continuously milled for 10 h with sample withdrawal at 2 h time interval. Structural properties of nanoparticles were studied by x-ray diffraction (XRD), transmission electron microscope (TEM), and ultraviolet-visible spectra. Particle size distribution and stability of 10 h milled samples were examined using particle size analyzer and Turbiscan. It was found that nanoparticles synthesized by mechanochemical method had mean particle sizes as small as 2–25 nm, low agglomeration, narrow size distribution, and uniformity of particle structure and morphology.

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 196.46u2005su2005cm−1 and 50.14u2005su2005cm−1, respectively.

Microwave Assisted Synthesis of Schiff Bases: A Green Approach

Abstract In the present study Schiff’s bases are synthesized by the conventional as well as by microwave irradiation. Excellent yield within short reaction time is obtained using microwave irradiation along with other advantages like mild reaction condition, non-hazardous and safer environmental conditions. The effects of temperature, reactant molar ratio, and microwave power variation on yield are observed. Mathematical model has been developed using matlab software to obtain the yield as a function of microwave power. Kinetic study of the reaction has also been attempted. Schiff’s bases structures are confirmed by IR, 1HNMR, Mass Spectra and elemental analysis.

Microwave Assisted Synthesis of Poly(ether sulfone) – An Efficient Synthetic Route to Control Polymer Chain Structure

A novel synthetic process for the efficient control over molecular weight of the poly(ether sulfone) has been studied. The application of microwave irradiation for the condensation polymerization to synthesize poly(ether sulfone) is demonstrated. Microwave assisted polymerization results in significant reduction of reaction time. Microwave based process is also feasible at lower temperature for the synthesis of poly(ether sulfone). Polymers synthesized have been characterized using NMR and FTIR spectroscopy. Polymer film morphology and surface composition have been studied using SEM and EDX. An increase in the molecular weight is observed with increasing microwave irradiation time.

Influence of pH on the Stability of Alumina and Silica Nanosuspension Produced by Wet Grinding

Effects of suspension pH on stability and surface properties of alumina and silica nanosuspension were investigated. Nanosuspensions of alumina and silica used in the present study were produced by wet grinding in stirred media mill. The electrostatic stabilization of two types of nanosuspension was conducted by zeta potential and turbiscan analysis as a function of pH. The long-term stability analysis of alumina and silica nanosuspension was investigated using an optical analyzer. It was observed that particles gradually aggregated and settled with storage time and can be easily redispersed by mere shaking of suspensions under desirable pH conditions. Transmission electron microscopy images obtained at different suspension pH for both alumina and silica nanoparticles show that the state of aggregation is highly dependent on pH and found to affect particles morphology.