紫外老化作用对纳米生物炭吸附环丙沙星的影响机制

Mechanism of Ultraviolet Aging Effect on the Adsorption of Ciprofloxacin by Nanobiochar

纳米生物炭的老化行为在自然环境中是不可避免的,然而老化作用对纳米生物炭吸附污染物的影响机制尚不清楚.采用模拟光照老化,通过元素分析、扫描电镜、透射电镜和红外光谱分析老化前后纳米生物炭的组成和结构特性变化,探究了老化纳米生物炭对环丙沙星(CIP)的吸附机制以及溶液p H值和纳米生物炭浓度梯度对吸附的影响.结果表明,老化作用使纳米生物炭C元素含量降低,O元素含量增加,极性增强,芳香性和粒径降低.老化前后纳米生物炭对CIP的吸附在很大程度上取决于溶液p H值,酸性条件下溶液p H值的增加更有利于CIP的吸附.纳米生物炭浓度梯度影响研究表明,纳米生物炭在低浓度条件下更有利于CIP的吸附.老化前后纳米生物炭对CIP的吸附更符合准二级动力学模型,Langmuir模型能更好地描述CIP在老化前后纳米生物炭上的吸附行为,最大吸附量分别为607.69 mg·g^(-1)和920.73 mg·g^(-1),老化纳米生物炭对CIP的吸附性能优于纳米生物炭,且主要的吸附机制为孔隙填充、静电作用和氢键作用.紫外老化作用增强了纳米生物炭对CIP的吸附性能.

The aging behavior of nano-biochar is inevitable in the natural environment;however,the mechanism of aging effects on the adsorption of pollutants by nano-biochar is not clear.The changes in composition and structural properties of nano-biochar before and after aging were analyzed using elemental analysis,scanning electron microscopy,transmission electron microscopy,and infrared spectroscopy.In this study,the adsorption mechanism of aged nano-biochar on ciprofloxacin(CIP)and the effect of solution pH and nano-biochar concentration gradient on adsorption were investigated.The results showed that the aging effect reduced the content of the C element,increased the content of the O element,enhanced the polarity,and decreased the aromatics and particle size of the nano-biochar.The adsorption of CIP on the nano-biochar before and after aging was largely dependent on the solution pH,and the increase in the solution pH under acidic conditions was more favorable to the adsorption of CIP.The study on the effect of the concentration gradient of nanobiochar showed that nano-biochar was more favorable for CIP adsorption under low-concentration conditions.The adsorption of CIP on nano-biochar before and after aging was more consistent with the pseudo-second order kinetic model,and the Langmuir model could better describe the adsorption behavior of CIP on nano-biochar before and after aging;the maximum adsorption amounts were 607.69 mg·g^(−1) and 920.73 mg·g^(−1),respectively.The adsorption performance of aging nano-biochar on CIP was better than that of nano-biochar,and the main adsorption mechanisms were pore filling,electrostatic interaction,and hydrogen bonding.Ultraviolet aging enhanced the adsorption performance of nano-biochar on CIP.