Nanobiopolymer: Potential Applications in Bioremediation of Cadmium Contaminated Water

Abstract

Nanobiopolymer nanotechnology, bacterial extracellular polymeric substances (EPS), has been used markedly for various water treatments.EPS has polysaccharides, proteins, and lipids, which have functional groups such as amino, sulfhydryl, carboxylic, and phosphate groups that allow binding to metal ions. The accumulation of the metal ions onto the EPS bacterial cell walls is used widely in the bioremediation of cadmium and other metals. This study objectives were extracting EPSs from the bacterium Bacillus subtilis 168 Cd2 and investigating their cadmium adsorption in bead column reactors after being immobilized with calcium alginate. For comparison with the bacterium's role, B. subtilis 168 Cd2 was used before EPS extraction and immobilized with calcium alginate, as well as a comparison with the use of calcium alginate. Cadmium adsorption from solution onto calcium alginate beads with untreated B. subtilis 168 Cd2 and EPS-free B. subtilis 168 Cd2 and under different pH (4.00, 7.00, and 7.50) were studied. The percentages of adsorption onto untreated B. subtilis 168 Cd2 and EPS-free B. subtilis 168 Cd2 were determined and were 89% and 77%, respectively. The adsorption of these were reduced when the pH increased. Scanning electron microscopy (SEM) confirmed the changes in the morphology of the adsorbents, and X-ray fluorescence (XRF) spectrometry analysis recorded the cumulative concentrations of cadmium in the adsorbents after the cadmium adsorption process. EPS in untreated B. subtilis 168 Cd2 significantly enhanced cadmium adsorption percentages. The fewer carboxyl and phosphate groups in EPS-free B. subtilis 168 Cd2 decreased cadmium adsorption. The results obtained in this study are of fundamental significance for applying nano biopolymers nanotechnology environmental biotechnology and bioremediation.