Combination of electroreduction with biosorption for enhancement for removal of hexavalent chromium

Hexavalent chromium is one of the most toxic heavy metals in aqueous solutions. It has been well documented that the brown seaweed can be used as a promising biosorbent for the sequestration of this heavy metal from wastewater. However, the uptake of Cr(VI) is reportedly a rather slower process; the sorption equilibrium can only be established after a few days, much slower than a few hours for the trivalent chromium ion. In this study, we developed a novel technology of electrochemically assisted biosorption (ECAB) system for the enhancement of the treatment efficiency. It was found through our study that the removal efficiencies of Cr(VI) and total chromium were greatly enhanced by 48.1% and 51.3%, respectively, with the application of −1.0 V in the ECAB system. The conversion of Cr(III) due to the electroreduction of Cr(VI) and the higher pH due to the cathodic H2 evolution created a favorable condition for the uptake of chromium onto the modified seaweed (MSW). The reduction and adsorption of Cr(VI) by MSW was proved to play a minor role in the removal. Both direct electroreduction and indirect electroreduction by atomic H* contributed to the reduction of Cr(VI).

Figure optionsDownload high-quality image (134 K)Download as PowerPoint slideHighlights
► A novel technology of electrochemically assisted biosorption (ECAB) was developed.
► Removal efficiencies of Cr(VI) and total Cr were remarkably enhanced in the ECAB.
► Electroreduction of Cr(VI) to Cr(III) led to great enhancement in Cr elimination.
► pH elevation due to cathodic H2 evolution facilitated Cr(III) biosorption.
► Cr(VI) reduction was due to direct electroreduction and reduction by atomic H*.