粉煤灰磁性吸附剂的制备及磷吸附机理

Synthesis and Phosphorus Adsorption of Coal-Fly-Ash Magnetic Adsorbents

通过化学沉淀法制备了CMS@La_2O_3磁性磷吸附剂。结构及磁性表征显示,氧化镧较均匀的包覆在粉煤灰磁珠表面;样品的比磁化强度达20.35 emu·g^(-1),可实现高效磁分离。利用钼酸铵分光光度法对所得磁性吸附剂的磷吸附性能进行了试验研究。研究表明,其最高磷比饱和吸附量可达19.50 mg·g^(-1),吸附时间、pH值、共存阴离子等因素对磷吸附效果均具有显著影响。吸附动力学拟合表明,CMS@La_2O_3对含磷离子的吸附符合准二级动力学方程,以化学吸附为主,磁性吸附剂对含磷离子的吸附反应过程可由La_2O_3表面羟基化-离子交换模型解释。吸附磷后的CMS@La_2O_3吸附剂经处理后可多次循环使用。

Magnetic phosphorus adsorbent coal-fly-ash magnetic sphere@La2 O3（CMS@La2O3） was synthesized by a chemical precipitation method, using CMS as magnetic core. Structural and magnetic characterization shows that Lanthanum oxide is uniformly coated on the surface of CMSs. The magnetism of the prepared CMS@La2O3 is measured as 20.35 emu·g^（-1）, which is strong enough for effective magnetic separation. The P adsorption performance of the CMS@La2O3 was investigated by the ammonium molybdate spectrophotometric method. It is found that the P adsorption of CMS@La2O3 is closely related to the adsorption time, pH value, and coexisting anions in the wastewater. The highest P adsorption was measured as 19.50 mg·g^（-1）. CO3^（2-） and SO42-in the waste water could sharply reduce the P adsorption even in a very low concentration by occupying the P-adsorption site on the La2O3 surface, while the existing of Cl-ions has very little effect on the P adsorption. The P adsorption of CMS@La2O3 is well accordant with the pseudo-second order kinetics equation, indicating that it is dominated by the chemical adsorption. The adsorption reaction could be explained by the ＂surface hydroxylation-ion exchange＂ model on the La2O3 surface. The used CMS@La2O3 adsorbent could be recycled for several times after appropriate treatment.