KOH活化制备铁基生物质炭及其对四环素和环丙沙星的吸附研究

Preparation of iron-based biochar by KOH activation and its adsorption properties for tetracycline and ciprofloxacin

低代谢程度的抗生素如四环素和环丙沙星会造成较为严重的水体污染,而活性炭对此种污染有一定的吸附作用。活化是改善生物炭吸附特性的主要方法之一。以甘蔗渣为主要研究对象,用KOH为活化剂,以FeCl_(3)·6H 2O为浸渍溶剂,制备了改性生物炭(KFBC),同时制备甘蔗渣生物炭(BC)作为对照。综合多种表征手段分析KOH活化和FeCl_(3)的掺杂对KFBC的结构和理化性质的影响,采用吸附法探究KFBC对溶液中的四环素(TC)或环丙沙星(CIP)的吸附性能和机理。结果表明:KOH活化后会形成更多的碳结构缺陷,影响BC的官能团的种类和数量以及BC的表面电性;FeCl_(3)的掺杂会增强BC的磁性,有利于KFBC的循环利用;吸附反应受pH影响较小,KFBC能够在一个较宽泛的pH范围内进行吸附。KFBC吸附TC或CIP是以化学吸附为主,且是自发、吸热、自由度增加和熵增的过程;KFBC对TC或CIP的理论最大吸附量可达到743和794 mg/g;KFBC的主导机制并非静电吸附,而是以孔隙扩散和π—π作用等为主,氢键和络合作用也发挥了重要作用。

Antibiotics with lower metabolic levels such as tetracycline(TC)and ciprofloxacin(CIP)can cause serious pollution to water bodies,biochar(BC)is commonly used for the treament of wastewater polluted by these antibiotics.Activation is one of the main methods to improve the adsorption properties of biochar.With bagasse as the raw material,a novel modified biochar,namely KFBC,was prepared using KOH as the activator and FeCl_(3)·6H 2O as the impregnating solvent;in the meantime,bagasse BC was also prepared for the study as the control.Firstly,the effects of KOH activation and FeCl_(3)doping on the structural and physicochemical properties of KFBC were analyzed by various characterization methods.Then,the adsorption properties and mechanism of KFBC on tetracycline or ciprofloxacin in solutions were investigated by the adsorption method.The results show that more carbon structure defects form after KOH activation,which affects the type and quantity of functional groups and surface electricity of BC.The doping of FeCl_(3)enhances the magnetic properties of BC and facilitates the recycling of KFBC.In addition,pH has little effect on the adsorption reaction,which indicates that the adsorption by KFBC act in a wide pH range.The adsorption of TC and CIP by KFBC is featured by chemisorption,which is a spontaneous and endothermic process with increasing freedom and entropy.The theoretical maximum adsorption capacity of TC and CIP by KFBC can reach 743 and 794 mg/g.The dominant mechanism of KFBC is not electrostatic adsorption but pore diffusion andπ—πinteraction,hydrogen bond and complexation also play an important role.