超声辅助柠檬酸化学淋洗复合污染土壤的研究

Study on Ultrasonic Assisted Citric Acid Chemical Elution of Compound Contaminated Soil

以某尾矿库周边重金属污染土壤作为研究对象,采用超声辅助淋洗方式,使用柠檬酸作为淋洗剂对Th、Fe、Mn进行去除。通过改变淋洗剂浓度、液固比、温度等条件,比较并分析其对去除量的影响并确定最优条件,结合淋洗动力学模型和热力学参数探究淋洗动力学表征与反应特性。结果表明,柠檬酸超声辅助化学淋洗90min,适当提高淋洗剂浓度与温度、扩大液固比可提高重金属去除量,最优条件为:浓度0.1mol/L、液固比为10mL/g、温度45℃。重金属的去除量由大到小依次为Mn>Fe>Th,分别为5 055.09、1 750.98、61.48mg/kg。三种重金属的淋洗动力学均符合双常数模型,Mn的淋洗动力学同时符合抛物扩散模型。Th和Fe为非均相扩散,Mn为抛物扩散、非均相扩散的混合扩散。Mn平均反应速率最大,为0.82,Th的表观活化能最小,为12.90kJ/mol,表明Mn与柠檬酸反应更快,Th更易与柠檬酸反应。

Taking soil contaminated by heavy metals around a tailings pond as research object,Th,Fe and Mn in soil were removed by ultrasound-assisted elution with citric acid as eluant.By changing eluant concentration,L/S,temperature and other conditions to compare removal amount,analyze its influence on removal amount and determine the optimal conditions.Characterization of leaching kinetics was investigated combined with leaching kinetics model and activation energy change.The results show that removal capacity rises by appropriately increasing concentration of eluant and temperature,and expanding L/S after ultrasonic-assisted chemical elution of citric acid for 90 min.The optimal conditions include concentration of 0.1 mol/L,L/S of 10 mL/g,and temperature of 45℃.Removal amount of heavy metals ranges from large to small is Mn> Fe> Th,which is 5 055.09,1 750.98 and 61.48 mg/kg,respectively.Elution kinetics of three heavy metals all conform to double constant model,and elution kinetics of Mn also conform to parabolic diffusion model.Th and Fe are heterogeneous diffusion,Mn is mixture diffusion of parabolic diffusion and heterogeneous diffusion.Mn has the maximum average reaction rate of 0.82,and Th has the minimum apparent activation energy of 12.90 kJ/mol,which indicates that Mn reacts faster with citric acid,and Th reacts more easily with citric acid.