ZHANG Cai-hua1,2, ZHANG Jin-hua1, LI Ying2, 3, LIANG Xiao-liang2, HE Hong-ping2
(1. School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China；
2. CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China；3. University of Chinese Academy of Sciences, Beijing 100049, China)
Abstract: The interaction between magnetite and aqueous Fe(Ⅱ) has a strong reduction activity to environmental pollutants. In natural environment, Fe2+ and Fe3+ in the magnetite structure are often isomorphously substituted by transition metals, which significantly changes the structure characteristics, physicochemical properties and surface reactivity of magnetite. In the present study, the effect of isomorphic replacement of zinc on the removal of Cr(Ⅵ) by magnetite coupled with aqueous Fe(Ⅱ) and its mechanism were investigated. Series of Zn substituted magnetites (Fe3-xZnxO4, x=0, 0.25, 0.49, 0.74 and 0.99) were synthesized by a coprecipitation method, followed by systematic characterization of the variation of structure and physicochemical properties of magnetite by Zn substitution, e.g., X-ray diffraction (XRD), thermogravimetry (TG), specific surface area and surface acid/base titration. The characterization results show that all the samples are with spinel structure without obvious alternation by Zn substitution. The BET surface area and surface site density gradually increases with Zn substitution level. In the batch reduction experiment under neutral pH, Cr(Ⅵ) was firstly adsorbed on magnetite surface, then reduced to Cr(Ⅲ) by magnetite and the adsorbed Fe(Ⅱ), and finally immobilized on magnetite surface. With the increase of Zn content in magnetite, the Cr removal efficiency was initially decreased and then changed to be better, ascribed to the decreasing Cr(Ⅵ) reduction and increasing Cr(Ⅵ) adsorption.
Keywords: environmental pollutant; Cr(Ⅵ); isomorphic replacement; magnetite; aqueous Fe(Ⅱ)
ACTA MINERALOGICA SINICA Vol. 37, No. 6, 2017, Page 697-704