不同钙离子浓度下铜对磺胺嘧啶在土壤中的吸附/解吸特征

Effects of copper on the adsorption-desorption characteristics of sulfadiazine in soil at different calcium ion concentrations

为探究重金属-抗生素共存时环境条件对土壤吸附/解吸抗生素的影响,通过批次平衡试验研究不同Ca^(2+)浓度下Cu^(2+)对磺胺嘧啶(SDZ)在土壤上的吸附和解吸行为及其交互作用。结果表明,Cu^(2+)浓度的增大显著促进了土壤对SDZ的吸附,同时Ca^(2+)的竞争吸附会抑制这种促进作用。Freundlich、Langmuir模型能较好地拟合SDZ在土壤中的吸附曲线,其拟合相关系数(R2)均大于0.90,而滞后系数(HI)在0.726~1.155,接近于1,表明土壤对SDZ的吸附和解吸过程中没有明显的滞后现象。吉布斯自由能变化量(ΔG)在-20.051~-17.468 kJ/mol,|ΔG|均低于40 kJ/mol,是物理吸附;而进一步的傅里叶红外光谱(FTIR)分析表明,Cu^(2+)和SDZ在土壤中的主要吸附机制是物理吸附,伴随着氢键效应和络合作用。从一定意义上说明,Cu^(2+)可明显提高SDZ在土壤中固持能力,降低其环境迁移的危险性。

To explore the effect of environmental conditions on the adsorption-desorption of antibiotic in soil during heavy metal-antibiotic coexistence,the aim of this study was to evaluate the adsorption and desorption of Cu^(2+)and sulfadiazine(SDZ)on soil at different calcium ion concentrations through batch experiments.The results indicated that:(1)The coexistence of Cu^(2+)significantly promoted the adsorption of SDZ by soil,and the increase of Ca^(2+)concentration attenuated this promotion.(2)The adsorption and desorption of SDZ was well fitted by the Langmuir and Freundlich equations with the R 2 levels more than 0.90,and the lag coefficient HI was between 0.726 and 1.155,close to 1,which indicated that no hysteresis occurred during adsorption and desorption of SDZ.(3)the Gibbs free energy(ΔG)of the adsorption process was between-20.051 and-17.468 kJ/mol,which|ΔG|less than 40 kJ/mol indicated the physical adsorption of SDZ occurred in soil,and the further FTIR analysis showed that the main absorption mechanism of Cu and SDZ in soil was physical adsorption accompanied by hydrogen bonding effect and complexation reactions.The present study indicated in a certain sense that Cu^(2+)coexistence could significantly improve the adsorption capacity of SDZ in soil and reduce the risk of its environmental transfer.