Chromium (VI) biosorption by immobilized Aspergillus niger in continuous flow system with special reference to FTIR analysis.

ABSTRACT

Aspergillus niger was treated with acid and immobilized in calcium alginate matrix. The dynamic removal of Cr (VI) ion was studied using continuously fed column packed with immobilized biosorbent beads. Column experiments were carried out to study the effect of various bed heights (20, 30, 40 cm) under different flow rates (5, 7.5, 10 ml min-1) on efficiency of biosorption. The maximum time (1020 minutes; 17 hr) before breakthrough point was observed in case of 40 cm bed height with flow rate of 5ml min-1. FTIR analysis of acid treated immobilized A.niger was used for a qualitative and preliminary analysis of chemical functional groups present on its cell wall which provided the information on nature of cell wall and Cr (VI) interaction during the process of biosorption. The IR spectra of biosorbent recorded before and after chromium biosorption had shown some changes in the band patterns, which were finally analyzed and was found that chemical interaction such as ion-exchange between carboxyl (-COOH), hydroxyl (-OH) and amine (-NH2) group of biosorbent and Chromium ion were mainly involved in biosorption of Cr (VI) onto A. niger cell wall surface. The biosorbed metal was eluted from biosorbent by using 0.1 M H2SO4 as eluant. Immobilized biosorbent could be reused for, five consecutive biosorption and desorption cycles without apparent loss of efficiency after its reconditioning. Considering all above factors together this paper discusses the efficient chromium biosorption process carried out by immobilized A. niger biosorbent.