Depassivation of micro current in hexavalent chromium reduction by zero valent iron

In order to overcome the low removal efficiency for hexavalent chromium(Cr(Ⅵ)) due to the passivation when zero valent iron(ZVI) is used as permeable reactive barriers(PRB) reactive media, the micro current depassivation advanced method was proposed by loading low-DC voltage on the reactive media. In the PRB column flow simulation test, the industrial scrap ZVI powder(0.15-0.35 mm) was used as reactive media, the different micro voltage was loaded on ZVI, and thus the Cr(Ⅵ) removal performance and mechanism were investigated. The results showed that the micro current could solve the ZVI passivation to some extent and enhance the utilization efficiency of ZVI. When Cr(Ⅵ) removal efficiency reached 60%, the effluent volume of the experimental groups with 1 V, 3 V, 7 V loaded on ZVI were 1.42, 1.88, and 2.75 times as many as that of the control group unloaded voltage, respectively. Cr(Ⅵ) removal efficiency was increased with the increase of voltage loaded on ZVI. The micro current could not affect the precipitation of trivalent chromium significantly, but it can influence the precipitation of ferrous or ferric iron.