Li Aimin, Dai Jingyu
College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
Water Res. 2006 Jun;40(10):1951-6. doi: 10.1016/j.watres.2006.03.008. Epub 2006 May 2.
Sorption of copper on kaolinite in the absence and presence of four fulvic acid (FA) fractions fractionated using XAD-8 resin, including F4.8, F7.0, F11.0 and Feth fractions (eluted by pH4.8 buffer, pH7.0 buffer, pH11.0 buffer, and ethanol (95%), respectively, was investigated by batch experiments. Results showed that the binding of Cu(II) by pure kaolinite increased with an increase in pH values. The presence of each FA fraction significantly affects the sorption of Cu(II) to kaolinite. Below pH 6.3, Cu(II) sorption was pronouncedly promoted after adding FA fraction to binary systems, compared to that in pure kaolinite suspensions. Magnitude in enhancement of Cu(II) sorption to solid phase, which was caused by FA fractions, followed an order of F4.8>F7.0>11.0>Feth. Above pH 6.3, nearly all the Cu(II) were removed from solution in pure koalinte system, while a portion of Cu(II) left in aqueous phase via formation of dissolved Cu-FA complexes, was observed in systems in the presence of FA fractions. The largest Cu(II) distribution coefficients (K(d)) between solid phase and aqueous solution at pH 3.15-5.7, are obtained from the ternary system with F4.8 fraction. The smallest K(d) are from system in the presence of Feth fraction. Conversely, over a pH range from 5.7 to 7.0, the highest K(d) values are from system with Feth fraction. Overall, F4.8 fraction exhibited the greatest effect on Cu(II) pH-dependent sorption to kaolinite, and Feth fraction had the least. Functional groups such as carboxyl, phenolic moieties of FA played the vital role in Cu(II) sorption to kaolinite at lower pH conditions, and solubility under neutral conditions.
采用分批实验法研究了在不存在和存在用XAD - 8树脂分级得到的四种富里酸（FA）组分（包括F4.8、F7.0、F11.0和Feth组分，分别用pH4.8缓冲液、pH7.0缓冲液、pH11.0缓冲液和乙醇（95%）洗脱）的情况下，高岭土对铜的吸附作用。结果表明，纯高岭土对Cu(II)的吸附量随pH值的升高而增加。每种FA组分的存在均显著影响Cu(II)对高岭土的吸附。在pH 6.3以下，与纯高岭土悬浮液相比，向二元体系中添加FA组分后，Cu(II)的吸附明显增强。FA组分引起的Cu(II)对固相吸附增强的幅度顺序为F4.8>F7.0>11.0>Feth。在pH 6.3以上，纯高岭土体系中几乎所有的Cu(II)都从溶液中去除，而在存在FA组分的体系中，观察到一部分Cu(II)通过形成溶解的Cu - FA络合物而留在水相中。在pH 3.15 - 5.7时，含F4.8组分的三元体系获得了固相和水溶液之间最大的Cu(II)分配系数（K(d)）。含Feth组分的体系K(d)最小。相反，在pH 5.7至7.0的范围内，含Feth组分的体系K(d)值最高。总体而言，F4.8组分对高岭土上Cu(II)的pH依赖性吸附影响最大，而Feth组分影响最小。FA的羧基、酚基等官能团在较低pH条件下对高岭土吸附Cu(II)以及在中性条件下的溶解性中起着至关重要的作用。
