Indium oxide/Halloysite composite as highly efficient adsorbent for tetracycline Removal: Key roles of hydroxyl groups and interfacial interaction

Abstract Indium oxide/halloysite nanotubes (In2O3/HNTs) composites used as adsorbents for tetracycline (TC) removal were synthesized through a simple hydrothermal method. The influences of adsorbent dosage, pH value, temperature and TC concentration on adsorption efficiency were investigated. The adsorption behavior of In2O3/HNTs toward TC could be described by Langmuir isotherm and pseudo second–order kinetic models. The adsorption results indicated that the adsorption efficiency and capacity of 20% In2O3/HNTs were 7 times and 10 times as those of In2O3 as well as both 4 times as those of HNTs, respectively. Adsorption mechanism studies suggested that the electrostatic attraction was primarily responsible for the improvement of adsorption performance. The abundant hydroxyl groups of HNTs and the interfacial interaction between In2O3 and HNTs contributed to more negative surface charges of In2O3/HNTs, which was favorable for enhancing the adsorption efficiency. This work provides an efficient adsorbent for pollutant removal and contributes a feasible idea for constructing the potential adsorbents using natural minerals with abundant hydroxyl groups.