Adsorption of Chlortetracycline from Water by Rectories

The removal of antibiotics from water by clay minerals has become the focus of research due to their strong adsorptive ability. In this study, adsorption of chlortetracycline (CTC) onto rectories was conducted and the effects of time, concentration, temperature and pH were investigated. Experimental results showed that adsorption equilibrium was reached in 8 h. Based on the Langmuir model, the maximum adsorption capacity of CTC on rectories was 177.7 mg·g−1 at room temperature. By the study on adsorption dynamics, it is found that the kinetic date fit the pseudo-second-order model well. The adsorption of CTC by rectories is endothermic and the free energy is in the range of −10 to −30 kJ·mol−1. The pH value of solution has significant effects on adsorption and the optimal pH is at acidity (pH=2–6). At concentration of 2500 mg·L−1, the intercalated CTC produces an interlayer space with a height of 1.38 nm, which is 1.12 nm in raw rectories, suggesting that the adsorption occurs between layers of rectories.