Nature Environment and Pollution Technology

Kshama A. Shroff ¹, Varsha K. Vaidya ¹

Affiliations
1 Department of Microbiology, Institute of Science, 15, Madam Cama Road, Mumbai-400 032, Maharashtra, IN

Abstract

The kinetics and equilibrium of biosorption of hexavalent chromium from aqueous solution was carried out using the dead physico-chemically treated biomass of Rhizopus arrhizus in a batch system. The biosorption characteristics of Cr(VI) ions were studied with respect to well-established parameters including pH, temperature, rotational speed, biosorbent dosage, initial metal ion concentration and contact time. The uptake of Cr(VI) decreased with an increase in pH and biomass concentration whereas it increased with an increase in the Cr(VI) concentration, temperature and rotational speed. Biosorption equilibrium was established in about 180 min. The adsorption data were analysed using the first and the second-order kinetic models as well as intra-particular rate expressions. The first-order equation was the most appropriate equation to predict the biosorption capacities of the fungal biosorbent. The sorption data obtained at pH 2.0 conformed well to both the Langmuir and Freundlich isotherm models. The reusability of the biosorbent was tested in five consecutive adsorption-desorption cycles and the regeneration efficiency was above 95%. From the practical viewpoint, the abundant and inexpensive dead fungal biomass of Rhizopus arrhizus could be used as an effective, low cost and environmental friendly biosorbent for the detoxification of Cr(VI).

Keywords

Biosorption, Hexavalent Chromium, Rhizopus arrhizus, Dead Gungal Biomass, Isotherm Models.

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Kshama A. Shroff ¹, Varsha K. Vaidya ¹

Affiliations
1 Department of Microbiology, Institute of Science, 15, Madam Cama Road, Mumbai-400 032, Maharashtra, IN

Abstract

The biosorption of Cr (VI) and Ni (II) ions, both singly and in a binary system, by dried biomasses of Rhizopus arrhizus and Mucor hiemalis was investigated in a batch system as a function of initial pH. The working initial pH values for Cr (VI) and Ni (II) in a single biosorption system were determined as 2.0 and 8.0 respectively. In a binary system, the optimum pH for sorption of Cr (VI) remained the same (2.0) while for Ni (II) it changed to 5.0. Although both the biomasses had a higher adsorption capacity for Cr (VI) and Ni (II) at singlecomponent situation due to the initial pH of the solution, the equilibrium uptakes of Cr (VI) and Ni (II) in the binary mixture were found to be decreasing because of the antagonistic interaction between the components. It was observed that the co-ion effect on the equilibrium uptake became more pronounced as pH level increased for Cr (VI) and decreased for Ni (II). Adsorption isotherms were developed for the dual-metal ion system at these two pH values and expressed by the mono-component Langmuir and Freundlich adsorption models. The model parameters were estimated by the non-linear regression.

Keywords

Cromium (VI), Nickel (II), Biosorption, Binary System, Adsorption Models, Isotherms.

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