针铁矿-高岭石二元体的微观结构与形成机制  

MICROSTRUCTURE OF GOETHITE-KAOLINITE DYAD AND MECHANISM OF ITS FORMATION

作　　者：魏世勇[1,3] 刘凡[1] 冯雄汉[1] 谭文峰[1,2] 

机构地区：[1]农业部亚热带农业资源与环境重点实验室,华中农业大学资源与环境学院,武汉430070 [2]黄土高原土壤侵蚀与旱地农业国家重点实验室,中国科学院水利部水土保持研究所,陕西杨凌712100 [3]湖北民族学院化学与环境工程学院,湖北恩施445000

出　　处：《土壤学报》2011年第2期320-330,共11页Acta Pedologica Sinica

基　　金：国家自然科学基金项目(40671088,40471071);教育部新世纪优秀人才支持计划项目(NCET-08-0781)资助

摘　　要：制备了针铁矿-高岭石复合物,以其混合物为对照,分析了它们的微观结构与形成机制。结果表明,复合物中的针铁矿较好地包被在高岭石表面,而混合物中两固相之间的包被作用微弱。相对针铁矿和高岭石两单体而言,二元体中针铁矿和高岭石的主要晶面间距没有明显变化;复合物的孔体积增多、平均孔径减小,混合物的孔体积和平均孔径都接近两单体的平均值;两种二元体的表面分形度(D)增大,且D混合物>D复合物。红外光谱显示,二元体中≡Fe-OH的振动频率升高,而≡Al-OH、Al-O、Si-O和Fe-O的振动频率降低;高岭石与针铁矿胶结后,核磁共振波谱中29Si和27Al的化学位移均向正方向移动。根据波谱分析的结果推断,针铁矿与高岭石的胶结主要通过针铁矿表面≡FenOH2(n/2)+(n=1,2,3)与高岭石表面≡Si-OH、≡Al-OH02.5+等Lewis酸之间的阳离子交换、高岭石表面≡Si-O-和≡Al-OH0.5-与针铁矿表面铁羟基(≡Fe-OH)间的阴离子交换以及高岭石表面O与针铁矿表面Fe间的配位等作用而实现,其胶结力主要为氢键和静电引力。复合物中≡Fe-OH、≡Al-OH等主要基团的振动频率以及29Si、27Al的化学位移的漂移均大于混合物中的变化量,说明复合物中针铁矿与高岭石间的胶结强度大于混合物中两固相间的胶结作用。Comparison of lab-prepared goethite-kaolinite association with goethite-kaolinite mixture as control was done for analysis of its microstructure and mechanism of its formation. It was found that in the association kaolinite was well wrapped by goethite, but in the mixture they coated neither. Compared to pure goethite or kaolinite, neither goethite or kaolinite in the association showed much change in the distance between major crystal planes; but the association showed a higher micropore volume and a lower average pore diameter. However, both pore parameters of the mixture were close to the average values of monomeric goethite and kaolinite. The surface fractal dimension D of the mixture and the association increased, and Dmixture was higher than Dassociation. Infrared spectra （IR） demonstrated that the vibration frequency of ≡ Fe-OH increased and that of ≡ Al-OH, Al-O, Si-O and Fe-O decreased in the dyads. The magic angle spinning nu- clear magnetic resonance spectroscopy （MAS NMR） showed that the cementation between goethite and kaolinite led to increased chemical shift of ^29Si and ^27Al towards positivity, which implied that cation exchange between ≡ FeOH2（n/2）＋ （n = 1, 2, 3） and ≡Si-OH or ≡Al-OH2^0.5＋, and anion exchange between ≡Fe-OH and ≡Si-O^- or ≡Al-OH^0.5-, surface coordination between O atoms on the surface of kaolinite and Fe atoms on the surface of goethite were the main mechanisms of cementation between goethite and kaolinite, where hydrogen bond and electrostatic attraction served as the main acting forces. Although the IR and NMR parameters of the association and mixture displayed similar changes, the variation of the former was more significant, indicating that the cementation strength between goethite and kaolinite in the association is greater than in the mixture.

关 键 词：针铁矿 高岭石 复合物 微观结构 交互作用 

分 类 号：S153.3[农业科学—土壤学] S153.61[农业科学—农业基础科学]