title: The effectiveness of ferrous iron and sodium dithionite for decreasing resin-extractable Cr(VI) in Cr(VI)-spiked alkaline soils.
abstract: Ferrous iron, Na(2)S(2)O(4), and a mixture of Fe(II) and Na(2)S(2)O(4) (4:1 mol/mol) were tested for their effectiveness for decreasing resin-extractable Cr(VI) in alkaline Cr(VI)-spiked soils. The results indicated that adding those reductants greatly decreased the amount of resin-extractable Cr(VI) when the application rate of reductants equaled the number of equivalents of dichromate added to the Cr(VI)-spiked soils. This was mainly as a result of the Cr(VI) reduction into Cr(III), as supported by the XANES spectra. Among the tested reductants, a mixture of Fe(II) and Na(2)S(2)O(4) was the most effective to decrease resin-extractable Cr(VI). The extent to which resin-extractable Cr(VI) and soil pH were decreased was affected by the pH of the reductants. Among the tested reductants at various pH, FeSO(4) at pH below 1 was the most effective in decreasing resin-extractable Cr(VI) in alkaline soils. However, the soil pH was the most decreased as well. On the other hand, the mixtures of ferrous iron and dithionite at a wide range of pH were all efficient (>70% efficiency) in decreasing resin-extractable Cr(VI). Moreover, the extent of the decrease in soil pH was much smaller than that by FeSO(4) (pH<1) alone, and thus the possibility of the Cr(III) hazard can be avoided.
authors.affiliation: Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan, ROC.
authors.forename: Chia-Jung
authors.initials: CJ
authors.lastname: Cheng
authors.forename: Tzu-Huei
authors.initials: TH
authors.lastname: Lin
authors.forename: Chiou-Pin
authors.initials: CP
authors.lastname: Chen
authors.forename: Kai-Wei
authors.initials: KW
authors.lastname: Juang
authors.forename: Dar-Yuan
authors.initials: DY
authors.lastname: Lee
mesh_terms: D000327:Adsorption; D002857:Chromium / Q000302:isolation & purification*; D004227:Dithionite / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D019163:Reducing Agents; D012117:Resins, Synthetic; D012989:Soil Pollutants / Q000302:isolation & purification*
chemical_list: D019163:Reducing Agents; D012117:Resins, Synthetic; D012989:Soil Pollutants; D002857:Chromium; D004227:Dithionite; D007501:Iron