Evaluating the efficiency of different natural clay sediments for the removal of chlortetracycline from aqueous solutions

Natural clay sediments were collected from ten different localities in Saudi Arabia (S-1 from eastern, S-2 to S-4 from middle and S-5 to S-10 from western regions), characterized and evaluated for their efficiency towards chlortetracycline (CTC) removal from aqueous solutions. Sediment S-4 exhibited highest surface area (288.5 m(2) g(-1)), followed by S-5, S-9, and S-1 (252.1, 249.6, and 110.4 m(2) g(-1), respectively). Sediments S-5, S-9, S-2, and S-4 showed the highest cation exchange capacities (CEC) (62.33, 56.54, 52.72, and 46.85 cmol kg(-1), respectively). The pH range of 3.5-5.5 was optimum for the highest CTC removal. Freundlich model was best fitted to CTC sorption data (R-2 = 0.96-0.99), followed by Dubinin-Radushkevich model (R-2 = 0.89-0.97). The sediments S-4, S-5, and S-9 exhibited the highest CTC removal efficiency (98.80-99.05%), which could be due to higher smectite and kaolinite contents, CEC, surface area and layered structure. Post-sorption XRD patterns shown new peaks and peak shifts confirming the sorption of CTC. Electrostatic interactions, interlayer sorption and H-pi bonding were the potential CTC sorption mechanisms. Therefore, natural clay sediments with high sorption capacities could efficiently remove CTC from contaminated aqueous media.