Ce-Mn复合氧化物对As(V)的吸附行为与机制

Adsorption of As (V) on Ce-Mn binary oxide:Behavior and mechanism

采用氧化共沉淀法制备了新型Ce-Mn复合氧化物吸附剂,通过批式实验,系统地研究了其对As(V)的吸附行为,并采用FTIR、XPS等表征技术研究了其对As(V)的吸附机制.研究结果表明,随着Mn的引入,铈锰复合氧化物对As(V)的吸附产生了协同效应,对As(V)的吸附容量显著高于单一组分的CeO_(2)与MnO_(2),尤其当Ce/Mn摩尔比为3∶1时;As(V)吸附速率较快,4 h吸附量达平衡吸附量的90.8%;吸附剂对As(V)具有较高的吸附容量,且酸性条件有利于As(V)的吸附,在pH 5.0、7.0、9.0时最大吸附容量分别为77.8、63.5、39.0 mg·g^(-1);Freundlich模型能较好地拟合其对As(V)的吸附过程,离子强度对As(V)的吸附影响不大,溶液中PO^(3-)_(4)与SiO^(2-)_(3)对As(V)吸附存在竞争作用,Ca^(2+)与Mg^(2+)则有助于促进As(V)吸附.机制研究结果表明,As(V)主要通过在Ce-Mn复合金属氧化物表面形成单齿单核和双齿双核的内层配合物而从溶液去除.

A novel Ce-Mn binary oxide adsorbent was synthesized via oxidation and co-precipitation method.As(V)adsorption behavior on Ce-Mn bimetal oxide was systematically investigated by batch experiments.As(V)adsorption mechanism was studied using FTIR and XPS techniques.The results indicated that the introduction of manganese oxides into CeO_(2)emerged a synergistic effect on As(V)adsorption,which was evidently proved by the much higher adsorption capacity of Ce-Mn bimetal oxide than that of the pure CeO_(2)and MnO_(2),especially at the Ce/Mn molar ratio of 3∶1.The adsorption of As(V)was relatively fast and over 90.8%of the equilibrium adsorption capacity was obtained within 4 h.Ce-Mn bimetal oxide had good performance for As(V)adsorption,especially under acidic conditions.The maximum adsorption capacity was 77.8,63.5 and 39.0 mg·g^(-1)at pH 5.0,7.0 and 9.0,respectively.Freundlich model was more suitable to describe the adsorption isotherm data.The ionic strength had little influence on the adsorption.The coexisting anions PO^(3-)_(4)and SiO^(2-)_(3)inhibited As(V)adsorption,whereas the cations Ca^(2+)and Mg^(2+)slightly enhanced As(V)adsorption.Mechanism investigations suggested that As(V)was probably removed from the solution by forming monodentate mononuclear and didentate dinuclear complexes on the surface of Ce-Mn bimetal oxide.