Li Hui, Liu Fan, Zhu Mengqiang, Feng Xionghan, Zhang Jing, Yin Hui
Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
J Environ Sci (China). 2015 Aug 1;34:77-85. doi: 10.1016/j.jes.2015.02.006. Epub 2015 May 26.
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 (MeCo, 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 Cr(3+) to be HCrO4(-) and remove 45%-66% of the total Cr in the reaction systems by adsorption and fixation, and they have enhanced Pb(2+) 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.
隐钾锰矿是一种活性氧化锰，已被用于去除废水中的重金属。通过常压回流合成了共掺杂隐钾锰矿，并用粉末X射线衍射、扫描电子显微镜、X射线光电子能谱和扩展X射线吸收精细结构光谱对其进行了表征，并研究了其从水溶液中去除Pb(2+)和Cr(3+)的性能。共掺杂对隐钾锰矿的结构和形态影响可忽略不计，但增加了比表面积和锰的平均氧化态。锰和钴K边扩展X射线吸收精细结构光谱（EXAFS）分析表明，钴对锰的原子配位环境影响不大，边共享和角共享的Co-Me（Me为Co、Mn）对的距离比相应的Mn-Me对短，这意味着Co(III)取代了骨架中的Mn(III)。这些共掺杂隐钾锰矿能迅速将Cr(3+)氧化为HCrO4(-)，并通过吸附和固定作用去除反应体系中45%-66%的总铬，且它们对Pb(2+)的吸附能力有所增强。因此，这些材料是用于重金属修复的有前景的吸附剂。研究结果展示了环境友好型氧化锰材料的设计与改性，有助于我们理解过渡金属与氧化锰的相互作用机制。
