土霉素在4种人工湿地基质上的吸附-解吸特性

为了研究土霉素在人工湿地基质床中的行为机制,本实验采用批量平衡方法研究了壤土、煤灰渣、粗砂和细砂等4种人工湿地基质材料对土霉素的吸附、解吸特性。结果表明,土霉素在人工湿地基质材料上的吸附可分为前4小时的快速吸附阶段和之后的慢速吸附阶段,14 h后达到吸附平衡,这一吸附平衡时间明显低于一般人工湿地系统的水力停留时间。可以认为,土霉素在人工湿地中有足够的时间吸附于基质层上,其吸附量的大小主要取决于基质材料的性质。土霉素在4种基质材料上的等温吸附实验表明,吸附等温线均呈非线性,用Freundlich方程能较好地对吸附数据进行非线性拟合。在4种人工湿地基质材料中,煤灰渣对土霉素的吸附作用最强,通过Freundlich方程拟合的吸附容量参数(KF)为280.2;其次为壤土,KF值为129.3;粗砂和细砂的吸附作用较弱,KF值分别为53.2和64.5。人工湿地基质材料对土霉素的吸附能力主要与基质有机质含量、粘粒含量、Fe2O3含量、阳离子交换量和Al2O3含量呈正相关。土霉素在4种人工湿地基质材料上的解吸均存在滞后现象,相对于壤土和煤灰渣,吸附于粗砂和细砂上的土霉素更容易被解吸下来。

Adsorption and desorption of oxytetracycline in four constructed wetland substrates

To explore the behavioural mechanisms of oxytetracycline (OTC) in constructed wetland, the adsorption and desorption characteristics of OTC in constructed wetland substrates were investigated in laboratory according to the OECD guideline 106. Four constructed wetland substrates; soil, coal ash, grit and fine sand, were used for the sorption of OTC in this study. The result indicated that OTC was strongly and rapidly adsorbed to the four constructed wetland substrates and Freundlich model was the best isotherm to describe all experimental data of adsorption. Among the tested four constructed wetland substrates, coal ash and soil had the strong adsorption of OTC, with the adsorption capacity (K_F) of 280.2 and 129.3, respectively, and the adsorption of fine sand and grit were less effective, the K_F of which were 53.2 and 64.5, respectively. The adsorption amount of OTC in the constructed wetland substrates was correlated positively with the contents of organic matter, clay and iron oxides. The adsorbed OTC was difficult to be desorbed with desorption H of 1.594 for soil, 1.236 for grit, 1.268 for fine sand and 1.830 for coal ash. It shows that the OTC adsorbed on the grit and fine sand was relatively easy to be desorption.