Removal of As(III) and Cr(VI) from aqueous solutions by Bixa orellana leaf biosorbent and As(III) removal using bacterial isolates from heavy metal contaminated site

Abstract

Arsenic and chromium have affected wider area in the world including Gangetic plains of India due to its toxicity and carcinogenic characteristics. Entry of As(III) into food chain has also escalated problem. A novel approach has been adopted to develop remediation technique using bacteria and herbs. The bioremediation study showed Bixa orellana as an accumulator of As(III) of Cr(VI) which was validated by SEM-EDX, FTIR and other kinetic analyses. Maximum percentage removal of Cr(VI) with fixed bio mass of B. orellana is 82.8% for an initial concentration of 3 ppm Cr(VI) concentration whereas maximum percentage removal of As(III) is 40.42 for an initial concentration of 6 ppm As(III).The R2 values and graphs showed that Freundlich as well as Elovich model best fitted to the experimental data. Three bacteria isolated from the coal mines of Rajmahal hills showed As(III) resistance and bioremediation potentials (up to 150 ppm). The 16S rRNA genotyping of these isolates was done (GenBank accession no: MK231250, MK231251 and MK231252) which showed similarity with Stenotrophomonas maltophilia, Uncultured gamma proteobacteria clone and Bacterium E1. Further, the presence of genes involved in arsenic biotransformation like aox, acr and ars was also confirmed in these bacterial isolates. Maximum percentage removal od As(III) in 50 ppm concentration by ASBBRJM16, ASBBRJM85 and ASBBRJM87 bacteria are 60.66%, 28.36% and 10.30% respectively for an initial concentration of 50 ppm As(III). Our results suggest that bacterial isolates may be adopted as an effective tool to remove As(III) from aqueous medium in spite of different cell structures and composition.