Structure and properties of Co-doped cryptomelane and its enhanced removal of Pb^(2+) and Cr^(3+) from wastewater  

作　　者：Hui Li Fan Liu Mengqiang Zhu Xionghan Feng Jing Zhang Hui Yin 

机构地区：[1]Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture,College of Resources and Environment, Huazhong Agricultural University [2]Department of Ecosystem Science and Management, University of Wyoming [3]Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences

出　　处：《Journal of Environmental Sciences》2015年第8期77-85,共9页环境科学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (Nos.41271253 and 41401250);the Huazhong Agricultural University Doctoral Start-up Fund (Grant 52902-0900206162)

摘　　要：Cryptomelane is a reactive Mn oxide and has been used in removal of heavy metal from wastewaters. Co-doped cryptomelane was synthesized by refluxing at ambient pressure and characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and extended X-ray absorption fine structure spectroscopy, and its performances for removal of Pb^2＋ and Cr^3＋ from aqueous solutions were investigated. Co doping has a negligible effect on the structure and morphology of cryptomelane but increases the specific surface area and Mn average oxidation state. Mn and Co K-edge extended X-ray absorption fine structure spectroscopy（EXAFS） analysis shows that Co barely affects the atomic coordination environments of Mn, and distances of edge- and corner-sharing Co–Me（Me_Co, Mn） pairs are shorter than those of the corresponding Mn–Me pairs, implying the replacement of framework Mn（III） by Co（III）. These Co-doped cryptomelanes can quickly oxidize Cr3＋to be HCr O4-and remove 45%–66% of the total Cr in the reaction systems by adsorption and fixation, and they have enhanced Pb2＋adsorption capacities. Thus these materials are promising adsorbents for heavy metal remediation. The results demonstrate the design and modification of environmental friendly Mn oxide materials and can help us understand the interaction mechanisms of transition metals with Mn oxides.Cryptomelane is a reactive Mn oxide and has been used in removal of heavy metal from wastewaters. Co-doped cryptomelane was synthesized by refluxing at ambient pressure and characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and extended X-ray absorption fine structure spectroscopy, and its performances for removal of Pb^2＋ and Cr^3＋ from aqueous solutions were investigated. Co doping has a negligible effect on the structure and morphology of cryptomelane but increases the specific surface area and Mn average oxidation state. Mn and Co K-edge extended X-ray absorption fine structure spectroscopy（EXAFS） analysis shows that Co barely affects the atomic coordination environments of Mn, and distances of edge- and corner-sharing Co–Me（Me_Co, Mn） pairs are shorter than those of the corresponding Mn–Me pairs, implying the replacement of framework Mn（III） by Co（III）. These Co-doped cryptomelanes can quickly oxidize Cr3＋to be HCr O4-and remove 45%–66% of the total Cr in the reaction systems by adsorption and fixation, and they have enhanced Pb2＋adsorption capacities. Thus these materials are promising adsorbents for heavy metal remediation. The results demonstrate the design and modification of environmental friendly Mn oxide materials and can help us understand the interaction mechanisms of transition metals with Mn oxides.

关 键 词：Cryptomelane Co doping EXAFS Pb2＋adsorption Cr^3＋oxidation 

分 类 号：X703[环境科学与工程—环境工程] P579[天文地球—矿物学]