Removal of Cr(VI) in groundwater by controlled release materials based on nano zero-valent iron and activated carbon

The use of nano zero-valent iron (nZVI) materials for groundwater Cr(VI) removal encountered challenges of agglomeration and low removal efficiency. Controlled release materials (CRMs) gradually release reactive substances or reducing agents, prolonging the release time. Here, we report the development of novel CRMs containing nZVI and activated carbon (AC). During the removal of Cr(VI) in groundwater, the prepared AC/nZVI/CRMs slowly released nZVI, greatly reducing the agglomeration of nZVI. The adsorption capacity of AC-containing CRMs prolonged the residence time of Cr(VI) in water, improving the removal efficiency of the AC/nZVI/CRMs. We found that lower pH enhanced the removal of Cr(VI) by the AC/nZVI/CRMs from simulated groundwater. The removal efficiency of the AC/nZVI/CRMs was also affected by the simulated groundwater environment and decreased with the increasing flow rate of the groundwater. Our results suggested that these novel nZVI-containing CRMs minimized agglomeration during the removal of Cr(VI) by nZVI, exhibited enhanced efficiency under acidic conditions, and facilitated Cr(VI) removal from similar groundwater environments.