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

Abstract

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.