摘要
为了研究过渡金属离子掺杂对锰氧化物作为环境友好材料物理化学性质的影响,在浓盐酸还原高锰酸钾制备水钠锰矿过程中添加氯化钴,在常压回流条件下一步合成了三维纳米微球状水钠锰矿,考察了其铅吸附和砷氧化能力.应用粉晶X射线衍射、化学分析、N2物理吸附、场发射扫描电镜(FE-SEM)、X射线光电子能谱(XPS)等手段表征产物晶体结构、化学组成、微观形貌和元素化学状态.当初始钴锰摩尔比从0.05增加到0.20时,钴的引入没有改变水钠锰矿层状结构和微观形貌,但掺钴水钠锰矿的结晶度有所减弱.化学分析和XPS分析表明,随着钴含量的增加,矿物中锰平均氧化度降低,Mn3+和Mn4+含量分别与钴含量呈正相关和负相关.钴主要以Co(Ⅲ)OOH形式存在于矿物结构中,而且随着水钠锰矿结构中钴含量的增加,羟基氧摩尔分数由未掺钴时的12.79%分别增加到13.05%、17.69%和17.79%.掺钴水钠锰矿对铅的吸附能力和砷氧化能力显著增强.未掺钴水钠锰矿最大铅吸附量为2 538 mmol.kg-1,初始钴锰摩尔比分别为0.05、0.10、0.20时,矿物对铅的最大吸附量分别增加到2 798、2 932和3 146 mmol.kg-1.水钠锰矿对砷的氧化率为76.5%,掺钴水钠锰矿对砷的氧化率分别增加2.0%、12.8%和18.9%.Co3+部分取代了Mn4+进入到矿物晶格中,导致水钠锰矿晶层内的电荷不平衡,层负电荷增加,羟基含量增多,使水钠锰矿对铅的吸附能力显著增强.由于Co3+/Co2+具有比Mn4+/Mn3+/Mn2+更高的氧化还原电位,含钴水钠锰矿对砷的氧化率随着钴含量的增加而相应增加.因此,掺钴水钠锰矿具有更好的处理重金属离子污染水体的性能,本研究为锰氧化物环境友好材料的掺杂改性及其应用提供了思路.
In order to study the effects of transition metal ions on the physic-chemical properties of manganese dioxides as environmental friendly materials,three-dimensional nano-microsphere cobalt-doped birnessite was synthesized by reduction of potassium permanganate by mixtures of concentrated hydrochloride and cobalt（Ⅱ） chloride.Powder X-ray diffraction,chemical analysis,N2 physical adsorption,field emission scanning electron microscopy（FE-SEM） and X-ray photoelectron spectra（XPS） were used to characterize the crystal structure,chemical composition and micro-morphologies of products.In the range of molar ratios from 0.05 to 0.20,birnessite was fabricated exclusively.It was observed that cobalt incorporated into the layers of birnessite and had little effect on the crystal structure and micromorpholgy,but crystallinity decreased after cobalt doping.Both chemical analysis and XPS results showed that manganese average oxidation state decreased after cobalt doping,and the percentage of Mn3 ＋ increased.Co（Ⅲ）OOH existed mainly in the structure.With the increase of cobalt,hydroxide oxygen percentage in molar increased from 12.79% for undoped birnessite to 13.05%,17.69% and 17.79% for doped samples respectively.Adsorption capacity for lead and oxidation of arsenite of birnessite were enhanced by cobalt doping.The maximum capacity of Pb2 ＋ adsorption increased in the order HB（2 538 mmol/kg） CoB5（2 798 mmol/kg） CoB10（2 932 mmol/kg） CoB20（3 146 mmol/kg）.Oxidation percentage of arsenite in simulated waste water by undoped birnessite was 76.5%,those of doped ones increased by 2.0%,12.8% and 18.9% respectively.Partial of Co3 ＋ substitution for Mn^4＋ results in the increase of negative charge of the layer and the content of hydroxyl group,which could account for the improved adsorption capacity of Pb^2 ＋.After substitution of manganese by cobalt,oxidation capacity of arsenite by birnessite increases likely due to the higher standard redox potential of Co^3 ＋/Co^2 ＋ than those of Mn^4＋/Mn^3 ＋/Mn^2 ＋.Therefore,Co-doped birnessite is more applicable for the remediation of water polluted with heavy metal ions,implying new methods of modification of manganese dioxides in practice.
出处
《环境科学》
EI
CAS
CSCD
北大核心
2011年第7期2092-2101,共10页
Environmental Science
基金
国家自然科学基金项目(40771102
40830527)
全国优秀博士学位论文作者专项(200767)
新世纪优秀人才支持计划项目(NCET-09-0399)
关键词
二氧化锰
水钠锰矿
钴掺杂
铅吸附
砷氧化
X射线光电子能谱
manganese dioxide
birnessite
cobalt doping
lead adsorption
arsenite oxidation
X-ray photoelectron spectroscopy
