Zn_xCa2-x-Fe吸附剂的制备及其除磷机制

Preparation of Zn_xCa_(2-x)-Fe Adsorbent and Mechanisms of Phosphate Adsorption

为研究ZnxCa（2-x）-Fe系LDHs（层状双金属氢氧化物）对P的吸附去除特性,在室温下采用化学共沉淀法制备一系列不同配比的ZnxCa（2-x）-Fe系LDHs,通过XRD（X射线衍射）、FTIR（傅里叶变换红外光谱）、Zeta电位测试对吸附剂的微观结构和表面电荷进行分析,采用静态吸附试验考察了投加量、接触时间及溶液初始p H对ZnxCa（2-x）-Fe系LDHs除P性能的影响.结果表明：ZnxCa（2-x）-Fe系LDHs与含P水接触4 h后,达到吸附平衡;其中0~1 h为快速吸附阶段,之后为缓慢吸附阶段,吸附过程符合准二级动力学方程.Ca2.0-Fe、Zn2.0-Fe对P的吸附符合Langmuir等温吸附模型,经计算所得理论最大吸附量分别为228.31和95.23 mg/g.结合Zeta电位与FTIR的测试结果,推测ZnxCa（2-x）-Fe系LDHs主要通过静电吸引、离子交换、配位交换及化学沉淀的协同作用实现水中P的去除.ZnxCa（2-x）-Fe系LDHs的饱和吸附量均高于同类吸附剂,能有效去除自然水体和市政污水中的P.

ZnxCa（2-x）-Fe layered double hydroxides（ LDHs） were synthesized by co-precipitation method at room temperature to study the characteristics of LDHs phosphorus adsorption removal. The microstructure and surface charge of LDHs were characterized using XRD,FTIR and Zeta potential measurements. The phosphate removal performances of LDHs were determined by an adsorption experiment. The amount of LDHs,contact time and initial p H of the phosphate solution were varied to explore their effects. The adsorption was rapid in the first hour and then gradually reached equilibration in 4 hours for most of LDHs. The behavior was well modeled by pseudo second order kinetics. The phosphate adsorption isotherm using Ca2. 0-Fe and Zn2. 0-Fe as adsorbents were fitted with the Langmuir model. The maximum adsorption amounts were calculated as 228. 31 and 95. 23 mg/g,respectively. The FTIR and Zeta potential measurements shed light on the mechanism that phosphate species were removed via electrostatic attraction,ionic exchange,ligand exchange and chemical precipitation. In conclusion,ZnxCa（ 2-x）-Fe adsorbent with high adsorption capacities will be a promising material for phosphate removal from natural water and municipal wastewater.