典型重金属和药物在活性炭上的共吸附机制及强化去除方法

The combined pollution of heavy metals and pharmaceuticals becomes more serious in the aquatic environment, resulting in increased stability and toxicity as well as the water safety risk. However, the coadsorption mechanism of heavy metals and pharmaceuticals by activated carbon is not well understood. This study aims to use copper, cadmium and lead as the target heavy metal ions, use sulfamethoxazole, ciprofloxacin and tetracycline as the target pharmaceuticals to examine the coadsorption mechanism and removal enhancement of heavy metals and pharmaceuticals by activated carbon. The research is intended to (1) determine the stability constant of heavy metals with pharmaceuticals, analyze the complexation behavior, then study the coadsorption behavior of heavy metals and pharmaceuticals by activated carbon, discuss the effect of water quality parameters on heavy metals and pharmaceuticals coadsorption, (2) clarify the coadsorption mechanism of activated carbon by pre-adsorption and desorption experiments, adsorption strength analysis, activated carbon characterization before and after adsorption, (3) modify the surface of activated carbon and reveal the relationship between the surface chemical properties of activated carbon and the removal efficiency of heavy metals and pharmaceuticals, (4) and finally propose an surface modification method for removal enhancement of heavy metals and pharmaceuticals by activated carbon using the speciation plots of pollutants and other results of the present study. The findings of this study will provide a theoretical and technical support to solve the threat of heavy metals and pharmaceuticals combined pollution.

水环境中重金属和药物复合污染现象日趋严重，导致污染物稳定性及毒性增加，造成潜在的水质风险加大。针对目前这种复合污染在活性炭上共吸附机制缺乏的现状，本项目拟以典型的重金属离子（铜、铅、镉）和药物（磺胺甲恶唑、环丙沙星、四环素）为对象，研究其在活性炭上的共吸附机制及强化去除方法。通过测定络合常数，解析重金属与药物的络合行为，研究其在活性炭上的共吸附行为，并探讨水质参数的影响；通过预吸附与解吸实验、污染物吸附强弱分析及活性炭吸附前后的表面表征，阐明活性炭的共吸附机制；通过表面改性活性炭，解析活性炭表面性质对污染物共去除的影响规律；针对污染物分布形态，结合已有研究结果，提出活性炭表面改性方法以强化其去除。本项目的研究结果可以为重金属和药物复合污染的控制提供理论依据和技术参考。

水环境中普遍存在重金属和药物复合污染现象，导致污染物稳定性及毒性增加，造成潜在的水质风险加大。项目以活性炭为吸附剂，研究典型重金属和药物在活性炭上的共吸附机制和强化方法。取得的主要研究成果：（1）解析了水中典型药物与重金属的络合行为。采用电位滴定法，研究了三种典型药物（四环素TC、环丙沙星CIP和磺胺甲恶唑SMZ）与三种典型重金属离子（Cu2+、Pb2+和Cd2+）在水中的络合行为。计算得出药物与重金属离子的络合常数（logK）。TC-Me络合形态主要为MeHTC+和MeTC0；CIP-Me络合形态主要为MeCIP2+、MeCIP22+和MeCIP2+；SMZ-Me络合形态主要为MeSMZ+。以药物-Cu2+体系为例，通过XANES和ATR-FTIR谱图分析，推测出药物与Cu2+的络合位置。（2）考察了药物和重金属在活性炭上的吸附与共吸附行为。在单一污染体系中，活性炭对药物的吸附量大小为TC≈CIP>SMZ，对重金属的吸附量小于10%。在复合污染体系中，重金属抑制了药物在活性炭上的吸附，吸附速率和吸附量均减小。（3）强化了活性炭对药物和重金属的共去除。采用硝酸氧化法改性椰壳活性炭强化药物和重金属的共去除。硝酸改性明显提高了活性炭对TC和Cu(II)的吸附，其中对Cu(II)的吸附提高了一个数量级，证明了表面酸性官能团在吸附中起到重要作用。在复合污染体系中，Cu(II)能促进TC在活性炭上的吸附，但降低了TC的吸附速率。TC也能促进Cu(II)在活性炭上的吸附，但降低了Cu(II)的吸附速率。pH影响研究表明，TC和Cu(II)的去除率均随着pH的升高而升高。（4）阐明了药物和重金属在改性活性炭上的共吸附机制。采用FTIR和XPS表征吸附前后的活性炭，分析结果表明，TC和Cu(II)在活性炭表面上以桥连的方式进行吸附。