Effect of amorphous silica and silica sand on removal of chromium(VI) by zero-valent iron.
The effect of two surfaces (amorphous silica and silica sand) on the reduction of chromium(VI) by zero-valent iron (Fe(0)) was investigated using batch reactors. The amendment of both surfaces significantly increased the rate and extent of Cr(VI) removal. The rate enhancement by amended surfaces is presumed to result from scavenging of Fe(0)-Cr(VI) reaction products by the provided surfaces, which minimized surface deactivation of Fe(0). The rate enhancing effect was greater for silica compared to sand, and the difference is attributed to silica's higher surface area, greater affinity for reaction products and pH buffering effect. For a given mass of Fe(0), the reactivity and longevity of Fe(0) to treat Cr(VI) increased with increasing dose of silica. Elemental analyses of the reacted iron and silica revealed that chromium removed from the solution was associated with both surfaces, with its mass distribution being approximately 1:1 per mass of iron and silica. The overall result suggests reductive precipitation was a predominant Cr(VI) removal pathway, which involves initial reduction of Cr(VI) to Cr(III), followed by formation of Cr(III)/Fe(III) hydroxides precipitates.
Oh
Young Ju
YJ
Korea Water Resources Corporation, Daejeon, Republic of Korea.
Song
Hocheol
H
Shin
Won Sik
WS
Choi
Sang June
SJ
Kim
Young-Hun
YH
D000327:Adsorption; D002274:Carcinogens, Environmental / Q000737:chemistry / Q000302:isolation & purification*; D011232:Chemical Precipitation; D002857:Chromium / Q000737:chemistry / Q000302:isolation & purification*; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D012822:Silicon Dioxide / Q000737:chemistry*; D018505:Waste Management / Q000379:methods
D002274:Carcinogens, Environmental; D002857:Chromium; C074702:chromium hexavalent ion; D012822:Silicon Dioxide; D007501:Iron