改性粒状凹凸棒石对Cu、Ni、Cd离子的吸附性能研究

ADSORPTION CHARACTERISTICS OF COPPER,NICKEL AND CADMIUM IONS BY MODIFIED GRANULAR PLALYGORSKITE

研究造粒改性、酸改性凹凸棒石对Cu(Ⅱ)、Ni(Ⅱ)、Cd(Ⅱ)的等温吸附、动力学、热力学特征,并研究不同pH值、溶液浓度、温度条件对改性粒状凹凸棒石吸附3种重金属的影响。用Langmuir、Freundlich等温式拟合,Langmuir效果最好,吸附属于单层吸附;准二级动力学方程能较好描述吸附过程,吸附作用主要受化学控制;热力学分析结果显示,吸附3种金属离子△G<0,△H<0,△S<0,说明吸附反应为放热反应且能自发进行;|△H|>|T·△S|说明反应为焓驱动。在研究范围内,不同条件和分析模型中,吸附性能均为Ni>Cu>Cd。在pH>4时,吸附重金属效果良好;吸附性能随温度的升高,先升增强后降低,在20℃出现拐点。

Isothermal adsorption characteristics,dynamic characteristics,thermodynamic characteristics for the modified granular palygorskite adsorbing Cu( Ⅱ),Ni( Ⅱ) and Cd( Ⅱ),and the influences made by different pH,solution concentration,temperature for modified palygorskite absorbing the three heavy metals were reseached. With the Langmuir,Freundlich isotherm fitting,the result of the Langmuir was best,showing that the adsorption belongs to monolayer adsorption;pseudo-second-order kinetic equation described the process of adsorption better,showing that the absorption was controlled by chemical action mainly; the result of thermodynamic analysis showed that △G,△H < 0,△S were negative value,suggesting that the adsorption process for three heavy metals were exothermic and spontaneous; | △H | > | T·△S | indicated that the adsorption was driven by enthalpy. The adsorption property for Ni was better than Cu,and Cu was better than Cd in different conditions and analysis models. When pH > 4,the absorbent effect for heavy metals was best; the adsorption properties increased at first and then decreased with the change of temperature and represented inflection point at 20℃.