Desorption Behaviour of Oxytetracycline onto Natural Sediment: A Case Study for the Middle Reaches of Weihe River in Shaanxi, China

摘要

Desorption behaviour of oxytetracycline (OTC) onto natural sediment from the middle reaches of Weihe River was described. The impact factors in the process of desorption, such as contact time, temperature (simulative range of summer and winter), ionic strength and colloidal concentration were determined by experiments. The results indicated that desorption of OTC reached equilibrium in about 40 min, and its kinetics were found to follow a pseudo-first-order model. Thermodynamic parameters such as Gibbs-free energy change (?G°), enthalpy change (?H°) and entropy change (?S°) were calculated, and the results demonstratedthat desorption of OTC was feasible, spontaneous, exothermic in nature, and the desorption capacity decreased with increasing temperature, especially at the range of 296 to 302 K. The desorption process approached to saturation at a temperature range of 275 to 281 K. In addition, the presence of colloid and electrolytes in aqueous solution had a negative effect on OTC desorption onto sediment sample. Such results may help to provide the theoretical basis for the effective prevention of OTC pollution to the groundwater system in the Weihe River basin.