Adsorption of arsenate and arsenite by iron-treated activated carbon and zeolites: Effects of pH, temperature, and ionic strength
Adsorption of arsenate and arsenite by iron-treated activated carbon and zeolites: Effects of pH, temperature, and ionic strength
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DOI：
10.1081/ese-200048254
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发表时间：
2005-01-01
影响因子：
2.1
通讯作者：
Abel-Fattah, TM
中科院分区：
文献类型：
--
作者：
Payne, KB;Abel-Fattah, TM
天然存在的砷对包括美国在内的许多国家的地下水造成污染，其浓度超过世界卫生组织目前的指导值10μgl(-1)，增加了数百万人患皮肤癌、肺癌、膀胱癌和肾癌的风险。砷的毒性取决于其化学形态；亚砷酸盐的毒性更大，因为它比砷酸盐对蛋白质具有更高的亲和力。这项研究支持全球范围内的研究工作，以获得砷含量低于 10 mu g l(-1) 的饮用水。进行批量吸附动力学和等温线研究，以比较和评估铁处理吸附剂从水介质中去除砷酸盐和亚砷酸盐的效果。研究了两种铁处理以及不同 pH 值、温度和离子强度增加对吸附效果的影响。选择活性炭和天然沸石（斜发沸石和菱沸石）等吸附材料是因为它们的成本相对较低，而且沸石是减轻地下水砷污染的潜在使用点材料。选择分子筛、八面沸石 (13X) 和 Linde A 型 (5A) 是因为它们为与之前的研究进行比较提供了基础，并且代表了良好表征的材料。经过铁处理的活性炭和菱沸石作为低成本砷吸附剂最有希望；活性炭去除了大约60%的砷酸盐和亚砷酸盐，而菱沸石去除了大约50%的砷酸盐和30%的亚砷酸盐。使用 Langmuir 和 Freundlich 等温线表达式对这些吸附剂对砷酸盐和亚砷酸盐的吸附进行建模，确定了吸附剂从水介质中去除砷的能力。通过铁处理的活性炭和斜发沸石去除砷最适合朗缪尔模型。通过铁处理菱沸石去除砷以及通过活性炭、菱沸石和斜发沸石去除亚砷酸盐最符合 Freundlich 模型。应用铁改性活性炭有效去除砷酸盐需要 pH 值在 7 到 11 之间，菱沸石在 4 到 5 之间，斜发沸石在 3 到 7 之间。通过铁改性活性炭去除亚砷酸盐需要 pH 值在 7 到 11 之间，菱沸石在 7 到 10 之间，斜发沸石在 4 到 11 之间。提高温度可以提高活性炭和沸石的吸附性能。离子强度的增加提高了铁处理活性炭和沸石的性能。
Naturally occurring arsenic contaminates groundwater in many countries, including the United States, at levels greater than 10 mu g l(-1), the current WHO guideline value, increasing the risk of skin, lung, bladder, and kidney cancer-in millions of people. Arsenic toxicity is dependent on its chemical form; arsenite is more toxic due to its higher affinity for protein than arsenate. This study supports worldwide research efforts to obtain drinking water with arsenic levels below 10 mu g l(-1). Batch adsorption kinetic and isotherm studies were conducted to compare and evaluate iron-treated adsorbents for arsenate and arsenite removal from aqueous media. Two iron treatments were investigated as well as the effects of varied pH, temperature, and ionic strength increases on adsorption effectiveness. Adsorbent materials such as activated carbon and naturally occurring zeolites (clinoptilolite and chabazite) were selected because of their relative low cost and because the zeolites are potential point-of-use materials for mitigating arsenic contaminated groundwater. Molecular sieves, Faujasite (13X) and Linde type A (5A) were selected because they provide a basis for comparison with previous studies and represent well-characterized materials. Iron-treated activated carbon and chabazite showed the most promise as low-cost arsenic adsorbents; activated carbon removed approximately 60% of arsenate and arsenite while chabazite removed approximately 50% of arsenate and 30% of arsenite. Modeling arsenate and arsenite adsorption by these adsorbents using the Langmuir and Freundlich isotherm expressions determined the adsorbents' capacity for arsenic removal from aqueous media. Arsenate removal by iron-treated activated carbon and clinoptilolite best fit the Langmuir model. Arsenate removal by iron-treated chabazite and arsenite removal by activated carbon, chabazite, and clinoptilolite best fit the Freundlich model. Applications of iron-modified activated carbon for effective arsenate removal would require pH values between 7 and 11, chabazite between 4 and 5, and clinoptilolite between 3 and 7. Arsenite removal by iron-modified activated carbon would require pH values between 7 and 11, chabazite between 7 and 10, and clinoptilolite between 4 and 11. Increasing temperature improved adsorption performance for activated carbon and the zeolites. Increasing ionic strength improved performance of iron-treated activated carbon and zeolites.