Biosorption of Metal Ions by Exopolysaccharide Produced by <i>Azotobacter chroococcum</i> XU1

Abstract

This paper deals with adsorption of Pb and Hg on the exopolysaccharide produced by Azotobacter chroococcum XU1. The adsorption of metal ions was significantly affected by the pH of metal solutions (Pb(NO 3 ) 2 and Hg(NO 3 ) 2 ), metal ions concentration and exopolysaccharide concentrations. At optimum pH the uptakes of the metals were 40.48% and 47.87% respectively. The metal ions biosorption was high at 4, 5-5.

Removal of Silver from Aqueous Solution by <i>Azotobacter chroococcum</i> XU1 Biomass and Exopolysaccharide

“…where q is the metal uptake by polysaccharide (mg•l −1 ), C f is the equilibrium concentration of metal in solution (mg•l −1 ), (b, q max ) and (K f , n) are empirical constants of Langmuir and Freundlich isotherms respectively [5].…”

“…Then, the solution consisting of insoluble EPS was filtered through filter paper and the filtrate used for metal analysis. In order to account the effect of filter paper on adsorption of heavy metals, a separate set of control experiment was done with the same conditions for all experiments [5].…”

“…EPS in the supernatant then precipitated adding cold ethanol in 1:2 (v/v). Precipitated EPS filtered out, dried and weighed [5].…”

“…In recent years, increasing attention has been paid on exopolysaccharides produced by several bacteria genera in particular Bacillus [4] [7], Azotobacter [5], Pseudomonas [8], Paenibacillus [9], Shewanella [10] and Methylobacterium [11]. It is interesting that most bacterial polysaccharides are characterized by the presence of uronic acids, pentoses, a polypeptide moiety or other nonsaccharide components, such as organic (e.g., acetyl, pyruvyl, succinyl group) or inorganic (e.g., sulphate or phosphate group) substituents [12] [13], have been documented for EPS synthesis, metal adsorption properties.…”

“…A wide variety of microorganisms have been found to possess natural capability to se-quester heavy metals [1]- [3]. Besides, certain types of microbial exopolysaccharides (EPS) can adsorb relatively high quantities of metals by means of passive processes known as biosorption, which is dependent on the affinity between the metallic species or its ionic forms and the binding sites on the molecular structure of the microbial EPS [4] [5]. The employment of microbial EPS for the metal removal treatment of effluents is a perspective suggested by many researchers dealing with metal-EPS interactions.…”