锰掺杂对针铁矿的结构、表面性质及吸附硒的影响  

Effects of Mn-Doping on Structure, Surface Properties and Selenium Adsorption of Goethite

作　　者：王锐 牛鹏举 许海娟 魏世勇 WANG Rui;NIU Pengju;XU Haijuan;WEI Shiyong(Department of Chemistry and Environmental Engineering,Hubei Minzu University,Enshi,Hubei 445000,China;Hubei Key Laboratory of Biologic Resources Protection and Utilization,Hubei Minzu University,Enshi,Hubei 445000,China)

机构地区：[1]湖北民族学院化学与环境工程学院,湖北恩施445000 [2]生物资源保护与利用湖北省重点实验室(湖北民族大学),湖北恩施445000

出　　处：《土壤学报》2020年第1期108-118,共11页Acta Pedologica Sinica

基　　金：国家自然科学基金项目（41561053）;生物资源保护与利用湖北省重点实验室（PKLHB1904）;湖北省“双一流”建设专项资金资助~~

摘　　要：水热条件下制备了针铁矿(Goe)和不同含量锰掺杂产物(G-Mn0.1、G-Mn0.2、G-Mn0.3和G-Mn0.5),用X-射线衍射(XRD)、透射电镜(TEM)、氮气物理性吸附、Zeta电位分析、酸碱滴定等手段对样品进行了表征,并研究其对亚硒酸盐(Se(Ⅳ))和硒酸盐(Se(Ⅵ))的吸附特性。结果表明:低比例的锰掺杂(锰/铁的摩尔比RMn/Fe=0.1~0.2)显著促进了针铁矿晶体沿b轴方向生长,导致针铁矿颗粒的长径比增大,形貌由短纺锤体形变为大长径比的扁平针状;当RMn/Fe=0.3~0.5时,样品中出现了大量的掺锰磁铁矿,且针铁矿晶体的b轴方向生长受到严重的抑制而a轴方向生长受到一定程度的促进并导致针铁矿颗粒呈纤细状。Goe、G-Mn0.2和G-Mn0.5的比表面积分别为36.78、53.22和71.33 m2·g–1,表面分形度分别为2.31、2.53和2.59,平均孔径分别为13.73、15.59、6.92 nm,Zeta电位零点分别为7.36、6.58和5.31,pH5.0时的Zeta电位分别为40.5、35.3和4.92 mV。3种样品的表面活性羟基密度表现为Goe<G-Mn0.2<G-Mn0.5。随着锰掺杂量升高,样品对不同价态硒的吸附量均不断增加,且对Se(Ⅳ)的吸附量明显高于Se(Ⅵ),初始pH 5.0时,Goe、G-Mn0.2和G-Mn0.5对Se(Ⅳ)的吸附容量分别为11.6、16.8和20.4 mg·g–1,对Se(Ⅵ)的吸附容量分别为7.6、8.5和9.2 mg·g–1。3种样品对Se(Ⅳ)和Se(Ⅵ)的等温吸附数据均适合用Langmuir模型拟合(R2为0.966~0.996),其等温吸附模式主要属于均质性表面的单层吸附。【Objective】Selenium(Se)is an essential micronutrient for human and animals.Ingestion of either an inadequate or excessive amount of Se tends to cause hazard to their health.Bioavailability of Se in soil depends on its forms.Iron oxide is an important component of soil and may interact with Se through desorption/adsorption.Iron and manganese oxides in soil are often cemented together forming binary metal oxides or Mn-doped iron oxides,thus significantly affecting translocation and transformation of nutrient elements and contaminants in the soil.However,so far little has been reported in-depth in the literature about effects of Mn-doped iron oxides on speciation and bioavailability of Se in soil.【Method】Samples of pure goethite(Goe)and Mn-doped products(G-Mn0.1,G-Mn0.2,G-Mn0.3 and G-Mn0.5)were prepared under set hydrothermal conditions and were characterized with the aid of X-ray diffraction(XRD),transmission electron microscopy(TEM),nitrogen physical adsorption,Zeta potential analysis and potentiometric titrations.Moreover,selenite(Se(Ⅳ))and selenate(Se(Ⅵ))adsorption characteristics of the samples were investigated through batch adsorption experiments.【Result】Mn-doping at a low rate with RMn/Fe(Mn(Ⅱ)/Fe(Ⅲ)molar ratio being 0.1-0.2)promoted significantly formation of goethite crystals along Axis b,in the form of flat needles big in length-to-diameter ratio instead of short spindles,whereas Mn-doping at a high rate,0.3-0.5 in RMn/Fe,which means increased Mn(II)content,inhibited significantly formation of goethite crystals along Axis b,while promoting their growth along Axis a by a certain degree and moreover making them tenuous.Additionally,a mass of Mn-doped magnetite appeared in the samples.Of Goe,G-Mn0.2 and G-Mn0.5,the specific surface area was 36.78、53.22 and 71.33 m2·g–1;the surface fractal dimension D,2.31,2.53 and 2.59;the mean pore diameter,13.73,15.59 and 6.92 nm;the isoelectric point,7.36,6.58 and 5.31;and the surface zeta potentials at pH=5.040.5,35.3 and 4.92 mV,respectively.In

关 键 词：针铁矿 锰掺杂 表面性质 吸附 硒 

分 类 号：S153.6[农业科学—土壤学] O647.3[农业科学—农业基础科学]