Adsorption and visible-light photocatalytic degradation of tetracycline hydrochloride from aqueous solutions using 3D hierarchical mesoporous BiOI: Synthesis and characterization, process optimization, adsorption and degradation modeling

Presence of antibiotics in aquatic environment has raised public concerns due to potential adverse effects. In this study, we synthesized two different bismuth oxyiodide (BiOI) by hydrolysis (BiOI-H) and solvothermal (BiOI-ST) methods and characterized using FTIR, XRD, FESEM, N-2 adsorption-desorption isotherm, DRS and PLS. The results of characterization tests showed that the BiOI-ST sample is a better adsorbent and may be more active in photocatalytic reactions as the result of more surface area, higher light absorption ability lower band-gap energy and PL intensity, than BiOI-H. Tetracycline hydrochloride (TCH) antibiotic was selected to evaluate adsorption and photocatalytic efficiency of BiOI-ST using Response Surface Methodology. The optimum conditions of contact time, TCH initial concentration, BiOI dosage and pH for adsorption and photocatalytic processes were obtained 37.5 min, 2.1 mg/L, 1.5 g/L, 8.5 and 101.5 min, 2 mg/L, 0.68 g/L, respectively. Based on kinetic and isotherm studies, experimental data fitted to pseudo-second order kinetics model and followed the Freundlich and D-R isotherm models. The apparent pseudo-first order rate constant of BiOI-ST was higher than that of BiOI-H. Therefore, BiOI-ST can be used as a promising option to treat low level concentration of TCH in hospital wastewaters. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.