ABSTRACTThe present study focused on the usability of scallop shell coated Fe2O3 nanoparticles as an eco-friendly new absorbent in the treatment of tetracycline (TC). The process performance in terms of TC removal was investigated at different operating conditions, i.e. at solution pH of 3-11, Fe2O3-scallop dosage of 0.4-2.4 g L-1, initial TC content of 20-120 mg L-1 and temperature of 25-55°C. Solution pH of 7 yielded the highest TC removal efficiency (99%). At this pH value, almost complete TC removal was achieved at a Fe2O3-scallop shell nanocomposite dose of 1.6 g L-1 and 25°C. The responsible TC removal mechanism is suggested as the non-electrical π-π dispersion interaction between the bulk π system on the absorbent surface and TC molecules bearing both benzene rings and double bonds at this solution pH. TC removal efficiency appreciably enhanced up to the Fe2O3-scallop dosage of 1.6 g L-1 being an optimum. Adsorption rate was found to be fast at lower initial TC concentrations than 40 mg L-1. The effect of temperature on TC removal efficiency was insignificant. Adsorption followed the pseudo-second-order kinetic model. Experimental data perfectly fitted by the Langmuir equation. The maximum adsorption capacity was calculated as 49.26 mg g-1. Thermodynamic analysis demonstrated that adsorption process was spontaneous process and endothermic. The results obtained from the present study proved the excellent performance of scallop shell coated Fe2O3 nanoparticles as an eco-friendly adsorbent in TC treatment.
Keywords: Adsorption; Fe2O3; antibiotic; scallop shell; tetracycline.