土壤胡敏素结构特征及对铜离子的吸附特性  

Structure and Cu(Ⅱ) Adsorption of Soil Humin

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作  者:范春莹 谢修鸿[2] 燕爱春 张晋京[1] FAN Chunying;XIE Xiuhong;YAN Aichun;ZHANG Jinjin(Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases,College of Resource and Environmental Science,Jilin Agricultural University,Changchun 130118,China;College of Landscape Architecture,Changchun University,Changchun 130022,China)

机构地区:[1]吉林农业大学资源与环境学院,吉林省商品粮基地土壤资源可持续利用重点实验室,长春130118 [2]长春大学园林学院,长春130022

出  处:《土壤学报》2018年第6期1460-1471,共12页Acta Pedologica Sinica

基  金:国家自然科学基金项目(41471196)资助.

摘  要:以棕壤和赤红壤为供试土壤,在对土壤胡敏素进行结构表征的基础上,采用批量平衡法研究不同反应温度下其对铜离子(Cu^2+)的吸附动力学和热力学特征,利用同步辐射X-射线吸收光谱技术探测了Cu^2+在胡敏素表面吸附的微观局域结构。结果表明:与胡敏酸相比,胡敏素具有较高的脂族性和极性,但其分子中甲氧基碳、羰基碳、木质素类化合物和酚类化合物的比例较低;随溶液Cu^2+浓度、接触时间和反应温度的增加,胡敏素对Cu^2+的吸附量也增加;吸附动力学曲线符合假二级动力学方程,吸附过程是需要能量和吸热的缔合反应;吸附等温线符合Freundlich和Langmuir方程,吸附反应是自发、吸热和自由度增加的过程;与胡敏酸类似,胡敏素表面吸附态Cu^2+是以扭曲的八面体构型存在,第一配位层(Cu-O)由原子间距为1.91~1.97A的4个O原子构成,第二配位层(Cu-C)由原子间距为2.80~2.83A的2个C原子组成,证实Cu^2+主要以内层复合物形式吸附在胡敏素表面的有机官能团上。上述结果指出,尽管胡敏素的化学组成不同于胡敏酸,但Cu^2+在这两种腐殖物质组分表面的局域配位结构相似。【Objective】The knowledge about chemical composition and interactions of humic substances with metal ions in the soil is of paramount importance to elucidating behaviors and fates of trace metals in the environments. Adsorption is one of the most important interactions between humic substances and metal ions. Among the three fractions of humic substances, i.e., humic acid, fulvic acid and humin, the last is the least studied because of its hard-to-dissolve nature. So far, it is still unclear how humin adsorbs metal ions and its mechanism. 【Method】In this study, humin was extracted from two zonal soils of East China, i.e., brown soil (Argosol) and lateritic red soil (Ferrosol), with 0.1 mol·L^-1 NaOH+0.1 mol·L^-1 Na4P2O7 extraction, treated with 10% (v/v) HF-HCl and then prepared into samples for analysis. Structure of the humin was characterized with elemental analysis, solid-state carbon-13 cross-polarization magic-angle-spinning nuclear magnetic resonance (13C CPMAS NMR) spectroscopy and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) techniques. On such a basis, the batch equilibrium method was used to study adsorption of Cu(Ⅱ) on humin as a function of exposure duration, adsorbate concentration and reaction temperatures. Local chemical structure of the Cu(Ⅱ) adsorbed onto the humin was explored with the synchrotron-based X-ray absorption near edge structure (XANES) spectrum and the extended X-ray absorption fine structure (EXAFS) spectrum. Furthermore, comparison was also made between humin and humic acid in chemical compositions and Cu(Ⅱ) adsorption feature. 【Result】Compared with humic acid, humin is relatively higher in content of C, H, alkyl C, carbohydrate C, di-O-alkyl C, polysaccharides and fatty acids, but lower in content of N, S, O, methoxyl C, aryl C, phenol C, carbonyl C, lignin, phenols and nitrogen-containing compounds. With rising duration of exposure, Cu(Ⅱ) concentration, and reaction temperature, Cu(Ⅱ) adsorption on humin increased, too. Kinetics of the adsorpt

关 键 词:胡敏素 铜离子 吸附动力学 吸附热力学 同步辐射X-射线吸收光谱 

分 类 号:S153[农业科学—土壤学;农业科学—农业基础科学]

 

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