Surfactant-modified clay as adsorbent for chromate
Surfactant-modified clay as adsorbent for chromate
复制标题
DOI：
10.1016/s0169-1317(01)00039-4
复制
发表时间：
2001-09-01
影响因子：
5.6
通讯作者：
Prakash, BSJ
中科院分区：
文献类型：
--
作者：
Krishna, BS;Murty, DSR;Prakash, BSJ
铬酸根的含氧阴离子的吸附没有得到太多的关注，这可能是由于粘土是带负电荷的，未改性的粘土矿物表面对铬酸根没有亲和力。粘土经阳离子表面活性剂改性后，对铬酸盐有较好的吸附效果。采用十六烷基三甲基溴化铵（HDTMA）对高岭石、蒙脱石、柱撑蒙脱石等粘土矿物进行表面改性。蒙脱石对HDTMA的吸附量相当于阳离子交换容量。高岭石和柱撑粘土对表面活性剂的吸附量相对较小，在pH I及以下时，铬酸盐的吸附量最大，且与固定在载体上的HDTMA的量成正比。在pH 2 ~ 6范围内，铬酸盐的吸附量为pH 1时的一半，而在pH 8以上，吸附量可忽略不计。铬酸盐吸附的pH依赖性归因于pH依赖平衡HCr 2 O 7-可逆箭头Cr2 O 72-可逆箭头CrO 42-。吸附数据符合Langmuir吸附等温式。计算了铬酸盐的吸附动力学（扩散常数），提出了吸附机理。(C)2001 Elsevier Science B. V.保留所有权利。
The adsorption of oxyanion of chromate was not given much attention, perhaps due to the fact that clays are negatively charged and unmodified clay mineral surface shows no affinity for chromate. After modification by cationic surfactant, clay was found to adsorb considerable amounts of chromate. Hexadecyl trimethylammonium (HDTMA) bromide was used to modify the surface of clay minerals such as kaolinite, montmorillonite, and pillared montmorillonite. Montmorillonite adsorbed a quantity of HDTMA equivalent to the cation exchange capacity. Kaolinite and pillared clay adsorbed relatively small amounts of the surfactant.The amount of chromate adsorbed was maximum at and below pH I and proportional to the amount of HDTMA fixed on motmorillonite. The amount of chromate adsorbed between pH 2 and 6 was one half of that at pH 1, and above pH approximate to 8 the adsorption was negligible. The pH dependence of chromate adsorption was attributed to the pH dependent-equilibria HCr2O7- reversible arrow Cr2O72- reversible arrow CrO42-. The adsorption data obtained was well described by Langmuir adsorption isotherm. Kinetics of chromate adsorption (diffusion constant) was calculated and a mechanism for the adsorption is proposed. (C) 2001 Elsevier Science B.V. All rights reserved.