氮掺杂多孔碳电极CDI技术对水中四环素和硬度离子的高效去除

Highly effective removal of tetracycline and water hardness ions by the CDItechnology with nitrogen-doped porous carbon electrode

为解决水体中过剩四环素(tetracycline,TC)与水硬度离子(Ca^(2+)和Mg^(2+))等共存带来的复杂环境污染问题,采用分散聚合法将含氮单体聚合成手风琴状碳前驱体并将其碳化后,制备得到氮掺杂多孔碳材料(nitrogendoped porous carbon,NPC),采用电容去离子技术考察了NPC电极同步去除不同水体、pH、初始浓度中TC和水硬度离子的能力。结果表明:Langmuir,Freundlich和Temkin模型对NPC样品电吸附TC的吸附等温线分别进行拟合,发现电吸附过程包含了化学吸附、强静电吸附和物理吸附等机制,吸附过程较为复杂;NPC独特的手风琴状层次结构,使得TC的电吸附容量高达854.3 mg·g^(-1),是传统自吸附的2.4倍(350.6 mg·g^(-1));稳定的层次结构与高导电碳网络结构,协同增强了NPC电极的吸附稳定性、再生性和循环稳定性,使其在自然水体中经过200次吸-脱附后吸附容量仍可保持在78%以上。由此可知,基于CDI技术的氮掺杂多孔碳电极能够有效地同步去除水体中的四环素和硬度离子。该研究结果可为复杂水体污染处理提供参考。

To solve the complex environmental pollution problem caused by the coexistence of excess tetracycline(TC)and water hardness ions(Ca^(2+)and Mg^(2+))in water bodies,nitrogen-containing monomers were polymerized into accordion-like carbon precursors by the dispersion polymerization method,and then they were carbonized and nitrogen-doped porous carbon(NPC)was prepared accordingly.The ability of NPC electrode to remove TC and water hardness ions simultaneously under different water bodies,pHs and initial concentrations was investigated by capacitive deionization technique.The results showed that the Langmuir,Freundlich and Temkin models were used to fit the adsorption isotherms for the electroadsorption of TC on NPC samples,respectively,and it was found that the electroadsorption process contained the mechanisms of chemisorption,strong electrostatic adsorption and physical adsorption,and the adsorption process was complex;the unique accordion-like hierarchical structure of NPC resulted in the electroadsorption capacity of NPC to TC as high as 854.3 mg·L^(-1),which is 2.4 times higher than that of conventional self-adsorption(350.6 mg·L^(-1)).The stable hierarchical structure and high conductive carbon network structure synergistically enhanced the adsorption stability,regeneration and cycling stability of NPC electrode,so that its adsorption capacity could still be maintained at higher than 78%after 200 times of adsorption-desorption in natural water bodies.In conclusion,the nitrogen-doped porous carbon electrode based on CDI technology can effectively and simultaneously remove tetracycline and hardness ions from water bodies.The results of this study can provide an important reference for the treatment of complex water pollution.