Cadmium ion adsorption on different carbon adsorbents from aqueous solutions. Effect of surface chemistry, pore texture, ionic strength, and dissolved natural organic matter.
Cadmium ion adsorption on different carbon adsorbents from aqueous solutions. Effect of surface chemistry, pore texture, ionic strength, and dissolved natural organic matter.
复制标题
DOI：
10.1021/la049253m
复制
发表时间：
2004-09
期刊：
影响因子：
--
通讯作者：
C. Moreno-Castilla;M. A. Álvarez-Merino;M. López-Ramón;J. Rivera-Utrilla
中科院分区：
文献类型：
--
作者：
C. Moreno-Castilla;M. A. Álvarez-Merino;M. López-Ramón;J. Rivera-Utrilla
研究了颗粒活性炭、活性炭纤维和活性炭布三种活性炭吸附剂对pH = 5条件下Cd（II）的吸附。采用原位吸附剂和氧化吸附剂。由于引入了羧基，氧化后镉（II）的吸附量大大增加。使用缓冲溶液来控制pH值，通过吸附所使用的一种化合物，邻苯二甲酸盐阴离子，使碳的表面化学发生了一些变化。离子强度的增加减少了Cd（II）在接收碳和氧化碳上的吸收，这是由于屏蔽了Cd（II）正电荷和负电荷之间的静电吸引力，在接收碳的情况下，Cd（II）正电荷来自于吸附的双邻苯二甲酸阴离子，而氧化碳来自于羧基。单宁酸被用作天然有机物的模型化合物。氧化后对Cd（II）的吸附剂吸附量大大降低，单宁酸预吸附后的碳吸附剂对Cd（II）的吸收率增加。在Cd（II）与单宁酸分子竞争吸附的情况下，接收碳对Cd（II）的吸收减少，而氧化碳则相反。这些结果说明了碳表面化学在这种竞争吸附过程中的重要性。最后，在所使用的所有实验条件下，当比较相同条件下碳的吸附容量时，其增加的顺序为：颗粒活性炭<活性炭纤维<活性炭布。
Adsorption of Cd(II) species at pH = 5 was studied on three carbon adsorbents: granular activated carbon, activated carbon fiber, and activated carbon cloth. As-received and oxidized adsorbents were used. Cd(II) adsorption greatly increased after oxidation due to the introduction of carboxyl groups. The use of a buffer solution to control the pH introduced some changes in the surface chemistry of carbons through the adsorption of one of the compounds used, biphthalate anions. The increase in ionic strength reduced Cd(II) uptake on both as-received and oxidized carbons due to a screening of the electrostatic attractions between the Cd(II) positive species and the negative surface charge, which in the case of as-received carbons derived from the biphthalate anions adsorbed and in the oxidized ones from the carboxyl groups. Tannic acid was used as a model compound for natural organic matter. Its adsorption was greatly reduced after oxidation, and most of the carbon adsorbents preadsorbed with tannic acid showed an increase in Cd(II) uptake. In the case of competitive adsorption between Cd(II) species and tannic acid molecules, there was a decrease in Cd(II) uptake on the as-received carbon whereas the contrary occurred with the oxidized carbons. These results illustrate the great importance of carbon surface chemistry in this competitive adsorption process. Finally, under all experimental conditions used, when the adsorption capacity of carbons was compared under the same conditions it increased in the following order: granular activated carbon < activated carbon fiber < activated carbon cloth.