暗棕壤吸附铜离子特征及其影响因素研究

应用平衡吸附法,研究了不同pH、离子强度、温度、Cu~(2 )浓度和接触时间条件下,暗棕壤对Cu~(2 )的吸附作用,并利用热力学和动力学方程对实验结果进行了拟合。结果表明:(1)随pH提高,Cu~(2 )的吸附率增加,pH 8时的吸附率约为91%。(2)随体系离子强度增加,Cu~(2 )的吸附量先下降后增加。(3)随溶液中Cu~(2 )浓度增加,Cu~(2 )在暗棕壤上的吸附量也增加,并且在低浓度时增加比较迅速。吸附等温线可用Frendlich,Langmiur和Temkin方程很好的描述,其中又以Langmiur方程拟合程度最好。根据Langmiur方程中平衡常数(k_L)得到的热力学参数指出,反应是自发的、吸热的,但增温却没有改变Cu~(2 )在暗棕壤表面的混乱度。(4)随接触时间延长,暗棕壤对Cu~(2 )的吸附量也增大,具体表现为吸附开始的快速反应阶段和经过一段时间后的慢速反应阶段。双常数能更好地拟合暗棕壤对Cu~(2 )的吸附动力学曲线,根据一级动力学方程的反应速率常数(k_D),计算出了Cu~(2 )吸附的活化能和活化热力学参数,指出温度升高有利于提高反应的速率。

Adsorption of Cu(II)and Its Affecting Factors in Dark-brown Soil

Adsorption processes of Cu~(2 ) to dark-brown soil were studied by batch equilibrium technique under different pH,ionic strength,temperature,Cu~(2 ) concentration and contact time.The results showed:(1) The adsorption rate of Cu~(2 ) increased with an increase of solution pH.When the solution pH was 8,the ad- sorption rate achieved 91%.(2)With an increase of ionic strength,the adsorption of Cu~(2 ) reduced firstly, and then increased.(3)The amount adsorbed increased with an increase of the Cu~(2 ) concentration,and in- creased rapidly at low concentration.The Langmuir model was better than the Freundlich and Temkin mod- els for describing the Cu~(2 ) adsorption isotherms.According to k_L value of Langmuir model,the thermody- namic parameters were calculated,which indicated that the reaction was a spontaneous and endothermic process,but its disorder was the same.(4)The kinetics of adsorption experiment could be divided into two stages,rapid and slow adsorption.The dual-constant models can be the best model that used to describe the Cu~(2 ) adsorption rate on dark-brown soil.According to k_Dvalue from the first-order kinetic model,activation energy and thermodynamics parameter were calculated,which confirmed a fact that increasing temperature was propitious to improve the reactive rate.