Study on adsorption of tetracycline by Cu-immobilized alginate adsorbent from water environment

Widespread concern had been given raise to the pollution of antibiotics including tetracyclines in water environment in recent years. A novel Cu-immobilized alginate adsorbent had been synthesized successfully through a facile fabrication way called sol-gel method, and its adsorption performance had been investigated for the tetracycline removal at various conditions, including the pH, temperature, the dosage of adsorbent, concentration and contact time. The adsorbent was characterized with SEM, EDX, FT-IR and XPS analyses to confirm its properties before and after adsorption. The equilibrium data was fitted well with the Freundlich isotherm model and the maximum adsorption capacity for tetracycline was 53.26 mg·g^-1 at pH 3, 318.15 K, and 90 mg·L^-1 tetracycline solution. The pseudo-second-order kinetic and Freundlich isotherm models combining with the correlative analysis implied that the tetracycline adsorption onto the Cu-immobilized alginate adsorbent was administrated by the n-π electron-donor-acceptor interaction (n-π EDA interaction), hydrogen bond and the cation bonding bridge. Moreover, thermodynamic study demonstrated that the nature of tetracycline adsorption was endothermic, feasible and spontaneous. Compared with the other adsorbents, the as-prepared adsorbent had an excellent tetracycline adsorption capacity, and was expected to be widely applied in the adsorption treatment of tetracycline wastewater.