Reduction of hexavalent chromium using Aerva lanata L.: Elucidation of reduction mechanism and identification of active principles

•Hexavalent chromium was reduced using aqueous extract of Aerva lanata L.•Batch experiments were used to identify the equilibrium point.•Mechanism of Cr(VI) reduction was identified by Cyclic voltammetry and FTIR.•ICP-MS analysis was used to quantify the chromium in hexavalent and trivalent form.•Ferulic acid, kaempherol and β-carboline may responsible for Cr(VI) reduction. The effluent discharge treatment for controlling the environment from non biodegradable metal contaminants using plant extract is an efficient technique. The reduction of hexavalent chromium by abundantly available weed, Aerva lanata L. was investigated using batch equilibrium technique. The variables studied were Cr(VI) concentration, Aerva lanata L. dose, contact time, pH, temperature and agitation speed. Cyclic voltammetry and ICP-MS analysis confirmed the reduction of Cr(VI) to Cr(III). Electrochemical analysis proved that, the chromium has not been degraded and the valency of the chromium has only been changed. ICP-MS analysis shows that 100ng/L of hexavalent chromium was reduced to 97.01ng/L trivalent chromium. These results suggest that components present in the Aerva lanata L. are responsible for the reduction of Cr(VI) to Cr(III). The prime components ferulic acid, kaempherol and β-carboline present in the Aerva lanata L. may be responsible for the reduction of Cr(VI) as evident from LC-MS analysis.