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水合氧化铈吸附水中三价砷和五价砷的研究
The Study of Adsorption of Arsenate and Arsenite by Hydrous Ceric Oxide in Aquatic Conditions
【作者】 甄青；
【导师】 欧阳通；
【作者基本信息】 厦门大学 ， 环境工程， 2008， 硕士
【摘要】 本文从稀土材料的充分利用以及高效除砷吸附材料开发与应用的角度出发,系统的研究了稀土材料水合氧化铈对As(Ⅲ)和As(Ⅴ)的基本吸附性能和反应机理,确定了解吸的最佳条件,并初步探讨了再生吸附效果及动态柱状试验。研究结果表明:水合氧化铈在较宽的pH值范围(4.0～9.0)内对As(Ⅲ)和As(Ⅴ)均表现出较强的吸附能力,其吸附容量都能达到110 mg/g以上。水合氧化铈吸附As(Ⅲ)的最佳pH值范围为中性偏碱,吸附As(Ⅴ)的最佳pH值范围为弱酸性。无论As(Ⅲ)还是As(Ⅴ),在开始阶段吸附速率非常快,随着时间的延长逐渐达到平衡。水合氧化铈对于As(Ⅲ)与As(Ⅴ)的吸附可以很好地用Langmuir方程式进行定量描述.其吸附接近于单分子层描述的化学吸附。水合氧化铈对As(Ⅲ)和As(Ⅴ)的吸附反应是自发进行的吸热过程,As(Ⅲ)和As(Ⅴ)的反应标准吸附热分别为22.02 kJ/moL和20.41 kJ/moL。温度对吸附的影响相对较小,在正常季节温度变化范围内能够稳定发挥其吸附特性。水合氧化铈粒径的改变对As(Ⅲ)和As(Ⅴ)的吸附效果影响不大,共存离子对水合氧化铈对As(Ⅲ)和As(Ⅴ)的吸附效果影响也很小。经过TCLP测试证明吸附后的吸附剂对环境不造成二次污染。水合氧化铈的最佳解吸条件为:解吸液选择NaOH溶液,解吸液浓度2mol/L,体积50 mL。As(Ⅲ)和As(Ⅴ)解吸速率都是相当明显的,在1h解吸时间内就可实现砷的最大限度的解吸脱附。再生实验证明水合氧化铈吸附材料具有解吸后重复利用的可行性。通过柱状试验可知,对于As(Ⅲ)和As(Ⅴ)来说,穿透体积分别为180BV和140BV。水合氧化铈材料中的表面活性羟基在As(Ⅲ)和As(Ⅴ)的吸附中起着重要的作用,其主要吸附反应机理趋向于以化学吸附为主。
【Abstract】 In view of taking full advantage of rare earth materials and development and utilization of high effective arsenic adsorption material,this research had studied the adsorption/desorption of arsenate and arsenite onto hydrous ceric oxide(HCO).And the adsorption mechanisms were also investigated.It was found that the adsorption capacity of HCO absorbent was constant around a value of 110mg/L over a wide pH range(4.0～9.0).The arsenite was better adsorbed in slight basic medium while arsenate was favorably adsorbed in an acidic pH range. The kinetics of arsenic adsorption by HCO involved an initial fast adsorption process followed by a slower uptake process as time progresses.The adsorption data fit the Langmuir isotherm and its linearized form well.The thermodynamic data revealed that the adsorption was a spontaneous,endothermic and entropy increasing process. The standard enthalpy changes(△H~0) for arsenate and arsenite were 22.02 and 20.42kJ/mol,respectively.The adsorption capacity of arsenate and arsenite did not increase much along with the minishing particle diameter of HCO.And the effect of coexist ions in water were tiny to the adsorption capacity.The TCLP results showed that the spent material was suitable for discharge in landfill deposits.We chose NaOH solution to desorption the arsenic and the best qualification was 50mL 2mol/L of NaOH solution.Both the arsenate and arsenite had their maximum desorption capacity in one hour.Regeneration experiment of HCO powder indicated that the HCO adsorbent was feasible for using repeatedly.The breakthrough volumes for As(Ⅲ) and As(Ⅴ) are 180BV and 140BV.The FTIR analysis demonstrated that the characteristic adsorption made a very important effect during the adsorption of As(Ⅲ) and As(Ⅴ) by HCO,and the substitution of Ce-OH groups made a very important effect during the adsorption of As(Ⅲ) and As(Ⅴ) by HCO.