Cu-Fe bimetal-carbon nanofiberous catalytic beads for enhanced oxidation of dichlorvos pesticide and simultaneous reduction of Cr(VI) in wet air

Emerging organic pollutants and heavy metals are the most common co-contaminants in water bodies. Efficacy of the Cu-Fe bimetals-dispersed carbon nanofibers (CNFs) grown over activated carbon beads (ACBs) was investigated for remediation of wastewater co-contaminated with dichlorvos (DDVP) (pesticide) and toxic Cr(VI) at moderate temperature and pressure (200 degrees C and 25 bar) using air as an oxidant. The experimental data showed that (similar to)95 and 80% degradation of DDVP (single feed) was achieved in 3 h over Cu-CNF/ACB and Fe-CNF/ACB, respectively, whereas complete degradation was measured during the identical time over Cu-Fe-CNF/ACB. In case of mixed feed (DDVP and Cr), complete degradation of DDVP as well as reduction of Cr(VI) was achieved in only 1 h. DDVP was degraded or mineralized by the hydroxyl radicals ((OH)-O-center dot) through oxidation, whereas Cr(VI) was reduced to Cr(III). Further analysis indicated that reduction of Cr(VI) to Cr(III) was facilitated by the transformed intermediate products of DDVP, which were recognized as the formic and acetic acids. Analysis of the spent water showed complete mineralization of DDVP with simultaneous reduction of Cr(VI) to Cr(III). The toxicity tests showed the spent water to be non-toxic. This is the first study to indicate the successful remediation of wastewater co-contaminated with a recalcitrant organic pollutant and a heavy toxic metal over the catalytic Cu-Fe-CNF/ACB.