Improved biosorption for Cr(VI) reduction and removal by Arthrobacter viscosus using zeolite

The aim of the present work was to optimize the reduction and removal of chromium from aqueous solutions by a biosorption system consisting of a bacteria supported on a zeolite. The system proposed combines the biosorption properties of Arthrobacter viscosus, with the ion exchange capacity of NaY zeolite. Experiments were also performed without the zeolite for comparison purposes. Experimental parameters such as solution pH, biomass concentration and initial Cr(VI) concentration were investigated in order to assess their influence on the biosorption system. The results revealed that chromium biosorption was highly pH dependent. The lower pH values favored Cr(VI) reduction, while higher solution pH enhanced total chromium removal. After the optimization of the parameters in study, the highest content of chromium in the zeolite (0.9%) and best uptake (13.0 mgCr/gzeolite) were obtained for the experiment at pH 4, biomass concentration of 5 g L−1 and initial Cr(VI) concentration of 100 mg L−1. After the biosorption process, the samples were characterized by chemical analyses (ICP-AES) and X-ray photoelectron spectroscopy (XPS). The XPS spectra of bacteria revealed that the chromium loaded on the biomass surface was in the trivalent form.

► Cr(VI) biosorption by a bacterium supported on a zeolite was studied and optimized.
► Arthrobacter viscosus reduced Cr(VI) to Cr(III) species that can be exchanged by the zeolite.
► To study Cr(VI) removal mechanism, Cr(VI) and total Cr concentrations were analyzed.
► pH was the most important parameter that affected the biosorption of the metal.
► Lower pH values favored Cr(VI) reduction, while higher pH improved total Cr removal.