人工改性纳米nSiO_2对Cd(Ⅱ)在土-水界面分配的影响

Effect of modified artificial nSiO_2 nanoparticles on Cd(Ⅱ) interface distribution in water-soil environment

【目的】研究改性纳米吸附材料nSiO_2对土-水界面上Cd(Ⅱ)分配过程的影响。【方法】人工制备改性纳米二氧化硅(nSiO_2),并对其表征进行分析;以采自陕西杨凌和辽宁抚顺的土样YL和FS为研究对象,通过批处理试验法探讨了nSiO_2对不同粒级组成土壤中Cd(Ⅱ)的界面竞争吸附动力学特征。【结果】成功制备粒径为13~28nm、具有较高分散性、富含-NH2官能团的改性nSiO_2,其对YL和FS土壤溶液中Cd(Ⅱ)的最大吸附量可达143.94mg/g左右。YL土壤的砂粒、粉粒和黏粒对Cd(Ⅱ)的最大吸附量则分别为5.76,9.17和11.48mg/g,FS土壤的砂粒、粉粒和黏粒对Cd(Ⅱ)的最大吸附量分别为6.25,11.54和15.43mg/g。土壤粒径越小,Cd(Ⅱ)吸附量和释放潜力越大,但Cd(Ⅱ)实际释放量不足吸附量的0.1%。土壤中添加改性nSiO_2后,会导致Cd(Ⅱ)在土-水界面的分配系数明显增大,Cd(Ⅱ)的释放量明显减小,且Cd(Ⅱ)在形成的nSiO_2-土-水多元界面体系中具有良好的稳定性。添加改性nSiO_2后,YL土壤砂粒、粉粒和黏粒中Cd(Ⅱ)的分配系数分别增加了2.10,2.28和3.06倍,FS土壤砂粒、粉粒和黏粒中Cd(Ⅱ)的分配系数分别增加了4.61,4.47和4.80倍。Cd(Ⅱ)在nSiO_2-土-水多元体系中的界面分配行为受限于伴随有竞争吸附和扩散释放的复杂的非均相准二级动力学过程。【结论】人工改性nSiO_2进入土壤环境后,可以明显减少Cd(Ⅱ)在水相中的分配,增强土壤固相对Cd(Ⅱ)的固定和吸持,在污染土壤修复中具有良好的应用潜力。

【Objective】This study investigated the effect of artificial nanoparticles on Cd（Ⅱ）interface distribution in soil-water environment.【Method】Modified artificial silicate nanoparticles（nSiO2）were prepared and characterized,and soil samples were collected from Yangling（YL）,Shaanxi and Fushun（FS）,Liaoning.The Cd（Ⅱ）interface competitive adsorption kinetics with different soil compositions were investigated by batch tests.【Result】Highly dispersed amino-group modified nSiO2 particles with diameters of 13-28 nm were obtained.The maximum Cd（Ⅱ）adsorption capacity was 143.94mg/g.Sand,silt and clay fractions of YL soil adsorbed 5.76,9.17,and 11.48 mg/g Cd（Ⅱ）,while those of FS soil adsorbed6.25,11.54 and 15.43mg/g Cd（Ⅱ）,respectively.Cd（II）adsorption process followed the Langmuir adsorption model.Smaller soil particles had greater Cd（Ⅱ）adsorption amount and releasing potential,al-though the actual releasing amounts were less than 0.1%.Adding nSiO2 nanomaterial increased Cd（Ⅱ）distribution coefficients significantly in soil-water interface and decreased releasing amounts,and Cd（Ⅱ）presented good stability in the nSiO2-soil-water combined interface system.Cd（Ⅱ）distribution coefficients increased by 2.10,2.28 and 3.06 times in sand,silt and clay factions of YL soil,and by 4.61,4.47and4.80 times in sand,silt and clay factions of FS soil.Cd（Ⅱ）distribution in the nSiO2-soil-water combined interface system was limited by competitive adsorption and diffusion release combined pseudo-second-order heterogeneous dynamics process.【Conclusion】Modified nSiO2 significantly enhanced Cd（Ⅱ）fixation and adsorption in soil and reduced Cd（Ⅱ）distribution in aqueous solution,and nSiO2 presented acceptable potential in polluted soil remediation.