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Adsorption of phosphate on a novel nanostructured Ce-Mn binary oxide: Behavior and mechanism

摘要：采用共沉淀法制备了一种新型铈锰复合氧化物吸附剂,对其进行了表征,并对磷吸附行为与机制进行了研究.表征结果分析表明,此氧化物由纳米级颗粒组成;铈锰复合氧化物中的铈氧化物有类似水合氧化铈的无定形结构;BET比表面积为157 m² · g^-1,等电点为6.5.吸附实验结果表明,Langmuir吸附等温线模型可以更好地拟合铈锰复合氧化物对磷的吸附,最大吸附量为28.6 mg · g^-1(pH=7.0);铈锰复合氧化物对磷具有较高的吸附速率,更符合准二级动力学模型;溶液pH对铈锰复合氧化物吸附磷的影响较为明显,随pH升高,吸附量降低;离子强度则影响不大;共存阴离子对吸附影响的大小顺序为SiO₃^2->CO₃^2->Cl^-≥SO₄^2-.通过对铈锰复合氧化物吸附磷前后Zeta电位和红外谱图(FTIR)分析,可以推断磷在铈锰复合氧化物表面发生了特性吸附,磷酸根主要通过取代复合氧化物表面的金属羟基而被吸附去除.

Abstract：A novel cerium-manganese binary oxide adsorbent was prepared via co-precipitation. The as-prepared Ce-Mn binary oxide was characterized by SEM, XRD and BET surface areas measurement. The adsorption behavior and mechanism of phosphate were also investigated. The Ce-Mn binary oxide is in amorphous form and is aggregates of nanosized particles. It has a high specific area of 157 m² · g^-1 and an isoelectric point of 6.5. The Langmuir model is more suitable for describing the adsorption behavior of phosphate and the maximal adsorption capacity is as high as 28.6 mg · g^-1 at pH 7.0. The phosphate adsorption is quick and the kinetic data is well fitted by the pseudo second order model. Additionally, the phosphate adsorption on Ce-Mn binary oxide is pH-dependent, and decreases with increasing solution pH. However, ionic strength has little effect on phosphate adsorption. The effects of coexisting anions on phosphate adsorption decrease in the order of: SiO₃^2->CO₃^2->Cl^-≥SO₄^2-. Specific adsorption occurs at the aqueous phosphate/Ce-Mn binary oxide interface and the replacement of surface hydroxyl groups by the phosphate species is the main removal mechanism.