不同pH条件下针铁矿表面磷的配位形式及转化特点

COORDINATION FORMS AND TRANSFORMATIONS OF PHOSPHATE ADSORBED BY GOETHITE SURFACE ON DIFFERENT pH

应用XPS技术研究了不同pH条件下针铁矿表面磷的配位形式及转化特点。结果表明：磷浓度一定时，低pH值有利于形成磷的单基配位，高pH值有利于形成磷的双基配位。体系pH值升高，针铁矿表面的单基配位磷即较快地向双基配位磷转化；pH降低，双基配位磷则缓慢地向单基配位磷转化．分析认为，体系pH通过影响溶液中磷酸根的离子类型来影响针铁矿表面吸附磷的配位形式，pH变化引起表面磷酸根质子的解离和缔合，是导致针铁矿表面磷配位形式转变的重要原因。双基配位磷的稳定性比单基配位磷的高，原因在于两种表面配合物的键能和结构不同。

X-ray photoelectron spectroscopy (XPS) tecnique was used to study the coordination forms and transformation characterishcs of P on goethite surfaces atdifferent pH. The results showed that the chemical forms of P on goethite surfaceschanged from the dondnance of monofadical ligands to that of biradical ones with increasing pH of the solutions. For a given P concentration, increasing the pH of suspension could cause a faster transformation of monoradical ligands of P to thebiradical ones on goethite surfaces, while lowering the pH the biradical ligands converted slowly to the monoradical ones. By influencing types of phosphate ions inthe solution, pH affected the coordination forms of P on goethite surfaces. Thedissociation and association of protons of the sorbed P caused by pH changes wereconsidered as a major reason leading to the transformation of the coordination forms of P on the surfaces. The stability of biradical ligands of P was greater than that of monoradical ones, and the possible reasons were disscussed in the paper.