Hexavalent Cr is most toxic metal and hazardous compound worldwide. It is also considered to be cellular oxidizing pollutant causing damage, mutagenic and hematopoietic effects to living systems. Present work is focused on synthesis of zero valent iron nano particles (Fe-NPs) using Bacillus subtilis SHB 13, Achromobacter xylosoxidans SHB 204 and Surfactin and their application for Cr (VI) detoxification (100 ppm) in synthetic solutions and polluted sludge, sewage and soil samples about 90-100 % reduction observed with above particles. Qualitative analysis, structural characterization of Fe-NPs, adsorption and recovery of Cr (VI) were carried out using XRD, SEM and TEM. This work explains adsorption isotherm of Cr with iron nano particles (Fe- NPs), was best fitted with Langmuir model and it followed first order rate kinetic reaction. Microcosm studies were carried out using Fe-NPs in sludge, sewage and tannery samples and Cr (VI) was completely (100 %) removed within 72 h. In another microcosm experiment, bacteria were able to reduce (60-70 %) Cr (VI) from soils with and without moisture and glucose. In green house experiments both the bacteria were able to reduce Cr (VI) (65-90%) effectively from both polluted and non-polluted soil and there was increase in root length and shoot length of plant L. esculentum was observed and maximum plant biomass was observed with plants inoculated with SHB 204 and SHB 13.

Keywords: Bacillus subtilis, Achromobacter xylosoxidans, Langmuir, microcosm, L. esculentum