A liquid membrane (multiple emulsion, water-in-oil-in-water (WIII/OII/WI)) method of separation of chromium(VI) from simulated waste water has been described. The effect of the variation of the oil-membrane constituents and different types of chemical reactions at the II/I interface using aqueous solutions of various strippants (internal phase) have been studied for a critical appraisal of the efficiency of the process. Among others, reductions have been found to be most effective in lowering the chromium(VI) content in waste water below the toxic limit (0.05 ppm, suggested by the World Health Organisation). The ion exchange behaviour of the carriers in the membrane and coupled countertransport have been suggested to be the main cause of chromium(VI) transport. The application of the reaction site model has been found to be reasonably justified. © 1995.

A K CHAKRAVARTI

S B CHOWDHURY

S CHAKRABARTY

T CHAKRABARTY

D C MUKHERJEE

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Liquid membrane multiple emulsion process of chromium(VI) separation from waste waters

Colloids and Surfaces A: Physicochemical and Engineering Aspects

This study deals with the adsorption characteristics of Cd(II) onto rice husk ash, low valued agricultural by-product obtained during the rice processing from rice mill. The influences of pH, contact time, initial metal ion concentration, adsorbent concentration on the selectivity and sensitivity of the removal process were investigated. The optimum pH for adsorption was found to be 5 for Cd(II), and equilibrium was achieved within 2 h of contact time. Maximum adsorption of Cd(II) was obtained at an adsorbent dosage of 75 g/L, which may be considered as optimum adsorbent dosage level Kinetics data were best described by pseudo-second order model The value of effective diffusion coefficient was of the order of 10-10 m2/s. The equilibrium adsorption data were better fitted to Freundlich isotherm models. The adsorption capacity (qmax) of rice husk ash for Cd(II) ions in terms of monolayer adsorption was 35.84 mg/g. The thermodynamic equilibrium constant and the Gibbs free energy were determined for and results indicated the spontaneous nature of the adsorption process. The adsorption energy calculated using Dubinin-Radushke-vich isotherm shows that adsorption of Cd(II) is chemical in nature. © 2009 American Institute of Chemical Engineers Environ Prog.

Environmental Progress and Sustainable Energy

Adsorptive removal of Cd(II) ions from aqueous solutions by rice husk ash

Shrinking Core model, widely accepted in the solid-fluid non-catalytic reaction system was applied to analyze the adsorption of metal ions like Zn(II), Cr(VI), Cd(II) and Pb(II) from the aqueous solutions onto the clarified sludge (CLS). The diffusivities of different metal ions in clarified sludge were determined by global optimization. The depth of penetration was also estimated for different initial concentrations. The experimental concentration profiles at various initial concentrations for all these four different metal ions matched well with the model predictions. © 2009 Springer Science+Business Media, LLC.

Adsorption

Applicability of shrinking core model on the adsorption of heavy metals by clarified sludge from aqueous solution

Present study deals with the adsorption of Pb(II) from aqueous solution on rice husk ash. Rice husk is a by-product generally obtained from rice mill. Rice husk ash is a solid obtained after burning of rice husk. Batch studies were performed to evaluate the influences of various experimental parameters like pH, initial concentration, adsorbent dosage, contact time and the effect of temperature. Optimum conditions for Pb(II) removal were found to be pH 5, adsorbent dosage 5 g/L of solution and equilibrium time 1 h. Adsorption of Pb(II) followed pseudo-second-order kinetics. The effective diffusion coefficient is of the order of 10-10 m2/s. The equilibrium adsorption isotherm was better described by Freuindlich adsorption isotherm model. The adsorption capacity (qmax) of rice husk ash for Pb(II) ions in terms of monolayer adsorption was 91.74 mg/g. The change of entropy (ΔS0) and enthalpy (ΔH0) were estimated at 0.132 kJ/(mol K) and 28.923 kJ/mol respectively. The negative value of Gibbs free energy (ΔG0) indicates feasible and spontaneous adsorption of Pb(II) on rice husk ash. The value of the adsorption energy (E), calculated using Dubinin-Radushkevich isotherm, was 9.901 kJ/mol and it indicated that the adsorption process was chemical in nature. Application study was also carried out to find the suitability of the process in waste water treatment operation. © 2008 Elsevier B.V. All rights reserved.

Journal of Hazardous Materials

The sorption of lead(II) ions on rice husk ash

Clarified sludge is a major waste generating during steel making process. In India and in most industrial countries, the use of clarified sludge as a road ballast and land filter has had a very long history. In present study, clarified sludge has been characterized and used for the removal of Cd(II) from aqueous solutions. The effect of pH, adsorbent dosage, adsorbate concentration, contact time and temperature on adsorption process was studied in batch experiments. Kinetics data were best described by pseudo-second order model. The effective diffusion co-efficient of Cd(II) is of the order of 10-11 m2/s. The maximum uptake was 36.23 mg/g. The adsorption data can be well described by Langmuir isotherm. The result of the equilibrium studies showed that the solution pH was the governing factor affecting the adsorption. Mass transfer analysis was also carried out for the adsorption process. The thermodynamic studies indicated that the adsorption was spontaneous and exothermic in nature. The sorption energy calculated from Dubinin-Radushkevich isotherm indicated that the adsorption process is chemical in nature. Desorption as well as the application studies were carried out considering the economic viewpoint of wastewater treatment plant operations. © 2008 Elsevier Inc. All rights reserved.

Journal of Colloid and Interface Science

Removal of Cd(II) from aqueous solutions using clarified sludge

The removal of Cr(VI) from aqueous solution by batch adsorption technique using different low-cost adsorbents was investigated. Adsorbents such as clarified sludge-a steel industry waste material, rice husk ash, activated alumina, fuller's earth, fly ash, saw dust and neem bark were used to determine the adsorption efficiency. The influence of pH, adsorbent type and concentration, initial Cr(VI) concentration and contact time on the selectivity and sensitivity of the removal process were investigated. Adsorption process was found to be highly pH dependent. The optimum pH range for adsorption of Cr(VI) was found to be between 2 and 3. Kinetics studies were performed to understand the mechanistic steps of the adsorption process and the rate kinetics for the adsorption of Cr(VI) was best fitted with the pseudo-2nd-order kinetic model. Langmuir and Freundlich adsorption isotherms were applicable to the adsorption process and their constants were evaluated. The thermodynamic equilibrium constant and the Gibbs free energy were determined for each system. The adsorption capacity (qmax) calculated from Langmuir isotherm and the Gibbs free energy (ΔGo) value obtained for the different adsorbents showed that clarified sludge was the most effective among the selected adsorbents for the removal of Cr(VI) from aqueous solution. The adsorption efficiencies of rice husk ash and activated alumina were also equally comparable with that of clarified sludge. © 2007.

Journal	Colloids and Surfaces A: Physicochemical and Engineering Aspects
Publisher	-
ISSN	0927-7757