Fast Removal of Tetracycline from Aqueous Solution by Aluminosilicate Zeolite Nanoparticles with High Adsorption Capacity

Aluminosilicate zeolite nanoparticles were synthesized in a water-in-oil solvent and applied as an adsorbent for tetracycline (TC) removal from aqueous solutions. The large specific surface area at 495.8 m2 g-1 confirms that the zeolite nanoparticles have mesopores. The zeolite nanoparticles show an excellent removal efficiency for TC, achieving over 97% in the pH range of 4.70-7.17. A fast adsorption kinetics was observed, reaching equilibrium in only 20 min following a pseudo-second-order kinetic model. The adsorption isotherm was found to follow the Langmuir model, with a maximum adsorption capacity of TC of 454.55 mg g-1 at pH 6.7 with no salt added. After 6 cycles of reuse, the removal efficiency of TC remained high at 90.3%. It was understood that the adsorption process is spontaneous and exothermic, with an activation energy of 37.94 kJ mol-1. The high observed adsorption affinity is attributed to hydrogen bonding between TC and the hydroxyl groups on the zeolite nanoparticles and the formation of outer-sphere surface complexes. This study shows a new way to synthesize aluminosilicate zeolite nanoparticles that are an efficient and recyclable adsorbent for effective removal of TC from contaminated water.