Augmented photocatalytic degradation of antibiotics in a solid-liquid interfacial system using Ag-TiO2–laced graphene oxide sponge

Abstract

There are inherent flaws in using pristine nano-photocatalysts for aqueous organic contaminants photo-degradation such as fast electron-hole recombination rates, low photon harvesting, large band gap, difficulty in separating nano-sized photocatalysts from aqueous solution after degradation, and poor reusability. These have led to the search for photo-degradation catalysts that suppress these flaws. Thus, pristine TiO 2 nano-photocatalysts was doped with Ag ion to yield Ag-TiO 2 which was then evenly laced on graphene oxide sponge (GOS) to obtain a final composite product (Ag-TiO-GOS). The Ag-TiO-GOS was extensively characterized and employed in the photo-degradation of ciprofloxacin (CPF) and tetracycline (TC). The Ag-TiO-GOS exhibited enhanced physicochemical and optical properties including lowered agglomeration of Ag-TiO 2 , high surface area and pore diameter compared to the GOS, lowered band gap, and enhanced photon absorption compared to TiO 2 and Ag-TiO 2 , as well as high adsorption of antibiotics onto the GOS. The experimental CPF and TC degradation data showed that these improved properties worked in tandem to enhance the photo-degradation with maximal efficiencies of ≈90 and 100%, respectively, at optimum conditions including photon harvesting, pH of 7, concentration (≈7.3 mg/L), and an average photon irradiation time of 200 min. These maximal efficiencies (≥90%) were comparatively far higher than those of the Ag-doped-TiO 2 recorded at ≈32 and 22%, respectively. The initial Ag-TiO-GOS enhanced efficiencies for CPF and TC were retained even after 4 reuse cycles; hence, the Ag-TiO-GOS demonstrated excellent reusability with high efficiency. Application of the Ag-TiO-GOS composite may be practically feasible in real water treatment due to its easy handling, easy removal from treated water, easy washing and reuse, and consistent efficiency over several reuse cycles. This may be especially so for the degradation of low concentrations of both TC and CPF which are common in most environmental water sources. • Ag-doped TiO 2 was coupled to graphene oxide sponge (GOS) to obtain Ag-TiO-GOS composite • Ag-TiO-GOS exhibited enhanced optical and physicochemical properties including lower band gap energy • Antibiotic degradation efficiencies exceeded over 90% • Ag-TiO-GOS has excellent reusability after 4 reuse-cycles with consistent efficiency and it is easy to handle