用批平衡法研究了Cu^2+在不同pH下对商用腐殖酸(HA)增溶4,4′-二溴联苯醚(BDE-15)的影响,并通过表征HA的Zeta电位和粒径分布特征,探讨了Cu^2+的浓度效应以及pH对增溶过程的影响.结果表明,HA对BDE-15增溶等温曲线在低浓度HA下呈线性,随着HA浓度增大逐渐表现为非线性,其主要机制应为疏水作用与其他形式作用力的联合作用,HA分子对BDE-15的增溶作用受溶液中Cu/C以及pH的影响.在pH为4.0时,Cu^2+对HA增溶BDE-15的影响呈现"U"型曲线关系(低促进高抑制);在pH为6.0时,在实验的Cu^2+浓度范围内均对增溶起促进作用,并且Cu^2+在pH6.0时要比在pH4.0下更能促进HA对BDE-15的增溶作用,同时使增溶非线性现象更显著,这主要是由于pH影响HA官能团的解离程度,从而影响HA与Cu(Ⅱ)复合物的结构以及大小.
The effect of copper ions on the water solubility enhancement of 4,4′-dibromodiphenyl ethers(BDE-15) by a commercial humic acid(HA) has been studied using batch equilibrium technique at various pHs.The characteristics of HA-Cu complex were investigated with the aid of dynamic light scattering and Zeta potential measurements.The results showed that the interaction of BDE-15 with HA could be explained by partition according to the linear isotherms when HA were at lower level,while the non-linear isotherms were observed at higher level of HA.The capability of solubility enhancements was affected by the pH and the ratio of the concentration of copper ions and the concentration of HA.At low pH condition(pH 4.0),solubility enhancement of BDE-15 by HA was facilitated by Cu^2+ at low concentration,but reduced by Cu^2+ at high concentration.While the phenomenon was different at pH 6.0,and Cu^2+ over all investigated concentration range promoted the capability of HA enhancing BDE-15 solubility and .non-linear isotherms became more significant.The different effects of Cu^2+ at pH 4.0 and 6.0 was mainly due to the dissociation of the HA functional groups as pH increased,thus affected the structure and size of HA-Cu complex.