土霉素(OTC)在东北典型黑土上的吸附行为及其影响因素

摘要

The batch equilibrium method was employed to research the kinetic characteristics of the oxytetracycline (OTC) adsorption onto the typical black soil, and the effects of the ionic strength, temperature as well as the dissolved organic matter (DOM) extracted from decomposed caw dung on the thermodynamics of OTC adsorption onto the black soil.The experimental results showed that the kinetics of OTC adsorption onto black soil included two processes, rapid adsorption and slow adsorption, which can be fitted well by pseudo-second order kinetic equation.The kinetics of OTC adsorption was an endothermic entropy increase reaction was controlled by the entropy increase, and in which the chemical adsorption was dominant.The thermodynamic processes of OTC onto black soil under the different influencing factors all can be described well by Freundlich equation.The adsorption of OTC onto black soil was inhibited by the increase of ionic strength, and OTC adsorption onto black soil in the presence of different ionic strength followed this order 0.00 1 mol/L>0.01 mol/L>0.1 mol/L.On the contrary, the adsorption of OTC onto black soil was enhanced by the increase of temperature, and OTC adsorption onto black soil under different temperatures followed the order 35 ℃>25 ℃>15 ℃.Furthermore, the adsorption of OTC onto black soil was inhibited by DOM, whose inhibition increased with DOM concentrationincreasing.The adsorption of OTC changed with different addition orders of OTC, which followed TS (simultaneous addition of DOM and OTC)>TO(first addition of OTC)>TD(first addition of DOM).%采用批量平衡法研究了东北地区典型黑土对四环素类抗生素土霉素(OTC)的吸附动力学特征,以及离子强度、温度和腐熟牛粪DOM对黑土吸附OTC的热力学影响.结果表明:OTC在黑土上的吸附动力学过程包括快速吸附和慢速吸附2个阶段,而且可以较好地被准二级动力学方程拟合.黑土对OTC的吸附过程为吸热熵增反应,属熵增控制过程,且黑土对DOM的吸附以化学吸附为主.Freundlich模型对不同因素影响下DOM在黑土上的吸附热力学过程均能进行较好地描述.离子强度的增加抑制了OTC在黑土上的吸附,不同离子强度作用下黑土对OTC的吸附能力顺序为0.001 mol/L>0.01 mol/L>0.1 mol/L.温度的增加促进了OTC在黑土上的吸附,不同温度作用下黑土对OTC的吸附能力顺序为35 ℃>25 ℃>15 ℃.DOM的存在抑制了黑土对OTC的吸附,而且抑制作用随着DOM浓度的增大而增大.黑土对OTC的吸附能力随着OTC添加顺序的不同而改变,符合以下规律:Ts (DOM与OTC同时加入)>TO(先加入OTC)>TD(先加入DOM).