title: Rapid reduction of Cr(VI) coupling with efficient removal of total chromium in the coexistence of Zn(0) and silica gel.
abstract: The effect of silica gel on the efficiency enhancement of Zn(0) for the reduction of Cr(VI) and removal of total chromium was investigated in this study. The batch experiment was carried at 4 ≤ pH ≤ 10 with 50 μM initial Cr(VI) concentration, and mass loading of 0-40 g/L for silica gel and 0-8 g/L for Zn(0). Results showed limited Cr(VI) reduction in the Zn(0)/H(2)O system, which was attributed to the formation of passivating films on the Zn(0) surface. However, a complete reduction of Cr(VI) by Zn(0) in the presence of silica gel could be achieved at the all tested pHs. The rate of Cr(VI) reduction was markedly enhanced with a pH decrease, an increase of silica gel or Zn(0) loading, and specific surface area of silica gel. Almost complete removal of total chromium was also observed, suggesting that Cr(III) yielded from the reduction of Cr(VI) was adsorbed onto the silica gel and ZnO surface or existed in Zn-Cr mixed oxides or other Zn-Cr co-precipitates. The possible pathways for Cr(VI) reduction and total chromium removal were proposed in this study, revealing the potential mechanism responsible for the rapid reduction of Cr(VI) coupling with the efficient removal of total chromium in the coexistence of Zn(0) and silica gel.
authors.affiliation: College of Sciences, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Guo
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Runan
authors.initials: R
authors.lastname: Dai
authors.forename: Yeqing
authors.initials: Y
authors.lastname: Lan
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D002840:Chromates / Q000737:chemistry; D002857:Chromium / Q000737:chemistry* / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D010084:Oxidation-Reduction; D017680:Potassium Compounds / Q000737:chemistry; D058428:Silica Gel / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
chemical_list: D001391:Azo Compounds; D002840:Chromates; D007202:Indicators and Reagents; D017680:Potassium Compounds; D002857:Chromium; C027373:potassium chromate(VI); D058428:Silica Gel; C100258:methyl orange; D015032:Zinc