凹凸棒石黏土吸附模拟含盐化工废水中Pb(Ⅱ)离子研究

Study on the Sorption of Pb(Ⅱ) onto Attapulgite from Simulated Saliferous Chemical Wastewater

研究了凹凸棒石黏土吸附模拟含盐化工废水中Pb（Ⅱ）离子的动力学和热力学吸附行为。考察了接触时间、吸附剂浓度、pH值、离子强度、不同电解质离子和温度等条件对吸附率的影响,并提出了相应的吸附机理。结果表明：凹凸棒石黏土是一种较好的重金属吸附剂,凹凸棒石黏土吸附Pb（Ⅱ）离子较好地符合假二级动力学方程,吸附过程受pH值和离子强度影响较大,在低pH值下表面络合和离子交换是主要的吸附机理。Pb（Ⅱ）离子在凹凸棒石黏土上的吸附为Langmuir型。在298.15~338.15 K温度范围内,凹凸棒石黏土对Pb（Ⅱ）离子是一个自发的吸热过程,吸附过程的G0分别为-16.96、-20.00和-22.80kJ/mol,而S0和H0基本不随温度的变化而变化,其值分别为146.00J/（mol.K）和（26.50±0.05）kJ/mol。

The kinetics and thermodynamics of Pb（Ⅱ） adsorbed onto attapulgite from simulated saliferous chemical wastewater were studied.The experimental factors such as contact time,solid content,pH value,ionic strength,foreign ions and temperature on the adsorption ratio of Pb（Ⅱ） were investigated,and the corresponding sorption mechanism was proposed.Experimental results indicated that the attapulgite was a suitable sorbent in the preconcentration and solidification of Pb（Ⅱ） from saliferous solutions.The sorption of Pb（Ⅱ） onto attapulgite could be described with pseudosecond-order model and was strongly dependent on pH value and ionic strength.The sorption of Pb（Ⅱ） was mainly dominated by outer-sphere surface complexation and/or ion exchange at low pH value.The Langmuir and Freundlich models were used to simulate the sorption data at temperatures of 298.15,318.15 and 338.15 K,respectivelly,and the process of sorption of Pb（Ⅱ） onto attapulgite was apt to Langmuir model.In the adsorption temperature range of 298.15~338.15 K,the sorption of Pb（Ⅱ） onto attapulgite was spontaneous endothermic process,the calculated thermodynamic parameters of G0 were-16.96,-20.00 and-22.80 kJ/mol,respectivelly,but the S0 and H0 were almost unchangeable in the above temperatures and the values were about 146.00 J/（mol.K） and（26.50±0.05） kJ/mol.