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| Effects of Cu2+ and Zn2+ polarization by electric fields on the colloid aggregation of black soil |
| Received:September 23, 2017 |
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| KeyWord:black soil colloid;heavy metal;specific ion effect;light scattering;active energy;ion polarization |
| Author Name | Affiliation | E-mail | | GAO Xiao-dan | Key Laboratory of Arable Land Conservation(Northeast China), Ministry of Agriculture, College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | | | XU Ying-de | Key Laboratory of Arable Land Conservation(Northeast China), Ministry of Agriculture, College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | | | ZHANG Guang-cai | Key Laboratory of Arable Land Conservation(Northeast China), Ministry of Agriculture, College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | | | ZHANG Yun | Key Laboratory of Arable Land Conservation(Northeast China), Ministry of Agriculture, College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | | | LI Song | Key Laboratory of Arable Land Conservation(Northeast China), Ministry of Agriculture, College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | | | LI Shao-bo | Key Laboratory of Arable Land Conservation(Northeast China), Ministry of Agriculture, College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | | | AN Yu-xin | Key Laboratory of Arable Land Conservation(Northeast China), Ministry of Agriculture, College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | | | WANG Jing-kuan | Key Laboratory of Arable Land Conservation(Northeast China), Ministry of Agriculture, College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | j-kwang@163.com |
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| Abstract: |
| The behavior of metal ions at the solid-liquid interfaces of soil considerably affects the aggregation of soil colloids, which subsequently influences the movement and transformation of nutrients and contaminants in soil solutions. To analyze the effects of interfacial behaviors by Cu2+ and Zn2+ on soil colloid aggregation, the aggregation kinetics of black soil colloids were monitored using a dynamic/static light scattering instrument. The aggregate process was induced by specifically adsorbed Cu2+ and Zn2+ ions. The aggregation of black soil colloids was induced by Cu2+ and Zn2+ through similar mechanisms. The soil colloids underwent reaction-limited cluster aggregation at low electrolyte concentrations and diffusion-limited cluster aggregation(DLCA) at high electrolyte concentrations. In the DLCA regime, the total average colloid aggregation rate was relatively unaffected by ion species. Strong ion-specific effects were observed for Cu2+ and Zn2+ during the aggregation of black soil colloids. The critical coagulation concentration of Zn2+ was 3.51 times higher than that of Cu2+, and the difference between the two systems' activation energies increased with declining electrolyte concentrations. Two explanations were proposed for the observed differences in the aggregation behaviors of soil colloids induced by Cu2+ and Zn2+. Cu2+ had a stronger affinity for organic ligands than Zn2+. Moreover, the strong polarization of ions by strong electric fields at the surface of black soil colloids amplified the minor differences in the structure of the two ions. |
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