[Treatment of Cr( VI) in deoxygenated simulated groundwater using nanoscale zero-valent iron].
Laboratory experiments and theoretical modeling studies were performed to investigate the mechanisms of Cr( VI) removal from deoxygenated simulated groundwater using nanoscale zero-valent iron, and to evaluate influencing factors and kinetics based on zeta potential, redox potential, ferrous concentrations, and the pe-pH diagram of Fe-Cr-H2O system. Experimental results demonstrate that the removal efficiency of Cr(VI) decreases with the increasing Cr( VI)/Fe mass ratio. When the Cr(VI)/Fe mass ratios are 0.025, 0.050, 0.075, and 0.100, the corresponding Cr(VI) removal rates are 100.0%, 85.6%, 72.7% and 39.6%, respectively. The Cr( VI) removal is favorable at acidic pH with fixed Cr(VI)/Fe mass ratio of 0.100. When pH are 3.0, 5.0, 7.0, 9.0 and 11.0, the Cr(VI) removal rates are 73.4%, 57.6%, 39.6%, 44.1%, and 41.2%, accordingly. The Cr(VI) removal follows the pseudo second-order kinetics. When pH is 7.0 and Cr(VI)/nZVI mass ratio is 0.025, the rate of Cr(VI) removal is the highest with rate constant at 9.76 x 10(-3) g x (mg x min)(-1). The conversion from Cr2O7(2-) to Cr3+ should be instantaneous when Cr2O7(2-) is absorbed on the surface of Fe. The Cr(VI) was reduced to Cr(III), which was subsequently incorporated into the FeOOH shell and formed a Cr-Fe film. The film once formed could further inhibit the electron transfer between Cr2O7(2-) and Fe. Then Cr(V) removal was primary controlled by the adsorption process.
Wu
Jia
J
Department of Municipal and Environmental Engineering, Beijing Jiaotong University, Beijing 100044, China. polarisxxx@126.com
Tian
Xiu-jun
XJ
Wang
Jin
J
Jing
Chuan-yong
CY
D002274:Carcinogens, Environmental / Q000737:chemistry / Q000302:isolation & purification; D002857:Chromium / Q000737:chemistry / Q000302:isolation & purification*; D005290:Ferric Compounds / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods
D002274:Carcinogens, Environmental; D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; C000499:ferric oxide; D007501:Iron