On the adsorption/photodegradation of amoxicillin in aqueous solutions by an integrated photocatalytic adsorbent (IPCA): experimental studies and kinetics analysis

Abstract

Activated carbon-supported TiO₂ nanoparticles, termed integrated photocatalytic adsorbents (IPCAs), were prepared using an ultrasonic impregnation technique and investigated for the photocatalytic degradation of amoxicillin (AMO), a β-lactam antibiotic. The IPCAs had high adsorption affinity for AMO with the amount adsorbed proportional to the TiO₂ loading and the highest adsorption was at 10 wt% TiO₂ loading. A pseudo-second-order model was found to fit the experimental data and consistently predicted the amount of AMO adsorbed over the adsorption period. Equilibrium isotherm studies showed that the adsorption followed the Redlich–Peterson model with maximum adsorption capacity of 441.3 mg g⁻¹ for 10% IPCA, 23% higher than the pure activated carbon (AC). Kinetic studies on the photocatalytic degradation of AMO using non-linear regression analysis suggest that the degradation followed Langmuir–Hinshelwood (L-H) kinetics. The adsorption rate constant (K_ad) was considerably higher than the photocatalytic rate constant (k_L-H), indicating that the photocatalysis of AMO is the rate-determining step during the adsorption/photocatalysis process. The 10% IPCA exhibited excellent stability and reusability over four photodegradation cycles.