N.R. Bishnoi and R. Kumar (India)
Biosorption, immobilized, calcium alginate, Trichoderma viride and chromium (VI).
This paper investigates the ability of Cr (VI) biosorption with immobilized Trichoderma viride biomass and cell free Ca alginate beads. Biosorption efficiency in the powdered fungal biomass entrapped in polymeric matric of calcium alginate compared with cell free calcium alginate beads. The effect of pH, initial ion concentration, time and biomass dose on the Cr (VI) removal by immobilized and cell free Ca alginate beads were also determined. The biosorption of Cr (VI) was pH dependent and the maximum adsorption was observed at pH 2.0. The adsorption equilibrium was reached in 90 min. The binding sites of biosorbent was also analysed using FTIR Spectro-photometer. The experimental results were fitted satisfactory to the Langmuir and Freundlich isotherm models. microorganisms due to its applications in environmental protection and recovery of toxic or strategic heavy metals [4, 5]. Certain types of microbial biomass are considered to retain relatively high quantities of metals by means of passive process known as biosorption. The process is relatively fast and the fact that is a surface phenomenon facilitates the removal of metal ions from solutions and the subsequent application of the material as biosorbent [6]. Biosorption technology based on the utilization of dead biomass offers certain major advantages such as lack of toxicity constraints, non-requirement of nutrient supply and recovery of bound metal species by an appropriate desorption method [7]. Cr (VI), because of its mutagenic and carcinogenic properties was selected for bioremediation studies by many researchers employing Rhizopus [8, 9], Aspergillus niger, Penicillium janthinellum [1]. These biosorbents were found to be capable of efficiently accumulating heavy metals. Biosorption mechanisms involved in the process may include ion exchange, co-ordination, complexation, adsorption and micro-precipitation [10, 11]. On the other hand, biosorption represents the sum of all passive interactions of cell wall with metal ions [12]. These were adsorption reactions, ion exchange reactions with functional groups at the cell surface and surface complexation reactions. Binding sites for metal ions were carboxylic, hydroxylic and phosphate group of lipids, proteins and polysaccharides localized at the cell surface [13, 14]. For successful detoxification of toxic heavy metals, the native biomass needs to be immobilized to improve its mechanical strength and resistance to the various chemical constituents of aqueous waste. The immobilized biomass beads could be regenerated and reused in more than 25 cycles and the regeneration efficiency was 75-78% [15]. The aim of this study was to investigate the Cr (VI) biosorption efficiency with immobilized T. viride biomass and cell free Ca-alginate beads. The adsorption capacity of the entrapped biomass and cell free Ca-alginate beads were explained by the Freundlich and Langmuir isotherm model.
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