Applications of zerovalent iron(ZVI)for water treatment under aerobic conditions include sequestration of metals(e.g.,in acid mine drainage)and decolorization of dyes(in wastewaters from textile manufacturing).The processes responsible for contaminant removal can be a complex mixture of reduction,oxidation,sorption,and co-precipitation processes,which are further complicated by the dynamics of oxygen intrusion,mixing,and oxide precipitation.To better understand such systems,the removal of an azo dye(Orange I)by micron-sized granular ZVI was studied in open(aerobic)stirred batch reactors,by measuring the kinetics of Orange I decolorization and changes in “geochemical” properties(DO,Fe2+,Eh,and pH),with and without two treatments that might improve the long-term performance of this system: sulfidation by pretreatment with sulfide,and magnetization by application of a weak magnetic field(WMF).The results show that the changes in solution chemistry are coupled to the dynamics of oxygen intrusion,which was modeled as analogous to dissolved oxygen sag curves.Both sulfidation and magnetization increased Orange I removal rates 2.4-71.8 fold,but there was little synergistic benefit to applying both enhancements together.Respike experiments showed that the enhancement from magnetization carries over from magnetization to sulfidation,but not the reverse.
Azo dyes Zerovalent iron Decolorization Reduction Sulfidation Magnetization Oxygenation Respike Modeling Oxygen sag curves
Chunhua Xu Bingliang Zhang Yahao Wang Qianqian Shao Weizhi Zhou Dimin Fan Joel Z.Bandstra Zhenqing Shi Paul G.Tratnyek
School of Environmental Science and Engineering Shandong University,Jinan,Shandong,250100,P.R.China U.S.Environmental Protection Agency,Office of Superfund Remediation and Technology Innovation,Arling School of Sciences,Saint Francis University 117 Evergreen Drive,Loretto,PA 15940 USA School of Environment and Energy South China University of Technology Guangzhou,Guangdong 510006,P.R Institute of Environmental Health Oregon Health & Science University 3181 SW Sam Jackson Park Road,P