Chang Chien S W, Wang M C, Huang C C
Department of Environmental Engineering and Management, Chaoyang University of Technology, 168 Jifong E. Rd., Wufong Township, Taichung County 41349, Taiwan, ROC.
Chemosphere. 2006 Aug;64(8):1353-61. doi: 10.1016/j.chemosphere.2005.12.041. Epub 2006 Feb 21.
Thermodynamic stability constants of the formation of complexes from the reactions of humic substances with various metals are usually used as parameters to judge the reactivities of both humic substances and metals. However, in calculating the thermodynamic stability constants, complicated processes for the acquisition of activities of components in reactions are absolutely inevitable. In this study, we investigated the average conditional concentration quotients of the complexes formed from the reaction of metals with humic substances and the relations of these quotients to thermodynamic stability constants. The characterized humic substances including HA (MW>1,000), FA (MW>1,000), and FA (MW<1,000) extracted from a swine compost were prepared to react with Pb, Cu, Cd, and Zn at 25 degrees C and at pH 4.00 and 6.50. Reactions of HA (MW>1,000), FA (MW>1,000), and FA (MW<1,000) with the four metals were carried out at 1:0.1, 1:0.5, 1:1, 1:5, and 1:10 ligand:metal stoichiometry. The concentrations of the free ions of Pb, Cu, Cd, and Zn in the reaction systems of metal-HA suspensions and metal-FA solutions were measured by anodic stripping voltammetry (ASV). The sequence of the average conditional concentration quotients of the formed complexes from the reaction of humic substances with metals was FA(MW<1,000)>FA(MW>1,000)>HA(MW>1,000), showing the relative reactivities of the fractions of swine compost-derived humic substances. The sequence of reacting metals with humic substances was Pb>Cu>Cd>Zn, which is in good agreement with the sequence reported by judging the thermodynamic stability constants. The average conditional concentration quotients of the formed complexes from the reaction of humic substances with metals were thus useful parameters that can be directly related to thermodynamic stability constants and other parameters.
腐殖质与各种金属反应形成配合物的热力学稳定性常数通常被用作判断腐殖质和金属反应活性的参数。然而，在计算热力学稳定性常数时，获取反应中各组分活度的复杂过程是绝对不可避免的。在本研究中，我们研究了金属与腐殖质反应形成的配合物的平均条件浓度商，以及这些商与热力学稳定性常数的关系。制备了从猪粪堆肥中提取的特征腐殖质，包括HA（分子量>1000）、FA（分子量>1000）和FA（分子量<1000），使其在25℃、pH值为4.00和6.50的条件下与Pb、Cu、Cd和Zn反应。HA（分子量>1000）、FA（分子量>1000）和FA（分子量<1000）与这四种金属的反应在配体:金属化学计量比为1:0.1、1:0.5、1:1、1:5和1:10的条件下进行。通过阳极溶出伏安法（ASV）测量金属-HA悬浮液和金属-FA溶液反应体系中Pb、Cu、Cd和Zn的游离离子浓度。腐殖质与金属反应形成的配合物的平均条件浓度商顺序为FA（分子量<1000）>FA（分子量>1000）>HA（分子量>1000），表明了猪粪堆肥衍生腐殖质组分的相对反应活性。金属与腐殖质反应的顺序为Pb>Cu>Cd>Zn，这与通过判断热力学稳定性常数报道的顺序高度一致。因此，腐殖质与金属反应形成的配合物的平均条件浓度商是有用的参数，可直接与热力学稳定性常数及其他参数相关联。
