Adsorption of tungstate on kaolinite: adsorption models and kinetics
Adsorption of tungstate on kaolinite: adsorption models and kinetics
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钨酸盐在高岭石上的吸附：吸附模型和动力学
DOI：
10.1039/c5ra24201k
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发表时间：
2016-01-01
期刊：
影响因子：
3.9
通讯作者：
Liu Xitao
中科院分区：
文献类型：
--
作者：
Li Ruiping;Lin Chunye;Liu Xitao
在室温下，采用静态吸附实验研究了钨酸盐在高岭石上的吸附特性。各种操作变量的影响，即，接触时间，初始浓度，溶液pH值，离子强度和竞争性阴离子，进行了研究。发现达到平衡所需的最佳接触时间为48 h。钨酸盐吸附等温线符合Langmuir和Freundlich模型，高岭石样品的最大吸附容量为35.54 mmol kg−1。钨酸盐的吸附在pH值为3-5的范围内增加，并在平均平衡pH值为4.24时达到最大值，但随着pH值从5.35增加到11.03，吸附率从83.7%下降到10.6%。当离子强度从0.001 M增加到0.1 M NaCl时，钨酸盐吸附从71.9%增加到89.4%。随着P/W摩尔比从0增加到10，钨酸盐吸附量从24.38 mmol kg−1减少到21.61 mmol kg−1，而磷酸盐吸附量从-2.09 mmol kg−1增加到27.45 mmol kg−1。这些结果表明，钨酸盐可能是通过内球络合作用吸附到高岭石矿物的钨酸盐专属性吸附位上的。
The adsorption characteristics of tungstate onto kaolinite have been studied using batch experiments under ambient temperature. The effects of various operating variables, viz., contact time, initial concentration, solution pH, ionic strength and competitive anions, have been investigated. The optimum contact time needed to reach equilibrium was found to be 48 h. Tungstate adsorption isotherms fitted well with both Langmuir and Freundlich models and the maximal adsorption capacity of the kaolinite sample is 35.54 mmol kg−1. Tungstate adsorption increases in the pH range of 3–5 and reaches a maximum at an average equilibrium pH of 4.24, but decreases from 83.7% to 10.6% as the pH increases from 5.35 to 11.03. Tungstate adsorption increases from 71.9% to 89.4% as ionic strength increases from 0.001 M to 0.1 M NaCl. As the P/W molar ratio increases from 0 to 10, tungstate adsorption decreases from 24.38 mmol kg−1 to 21.61 mmol kg−1, while phosphate adsorption increases from −2.09 mmol kg−1 to 27.45 mmol kg−1. These results demonstrate that tungstate might be adsorbed onto tungstate-specific adsorption sites of the kaolinite minerals, mainly via inner-sphere complexation.