Natural alumina/silica suspended particles in water to enhance ofloxacin degradation with UVA-H2O2 driven by surface chemistry.

UV-H2O2 is the most widely used oxidizing system with established effectiveness and a high level of technical development for practical application. However, little attention was paid on the effect of suspended particles in natural water on organic contaminants removal via UV-H2O2 technique. In this study, this effect of suspended particles to enhance the contaminant degradation was explored using silica/alumina-based oxides (MCM-41 and Al@MCM-41) as the representative. The results showed that MCM-41 had no effect on OFX degradation compared with UV-H2O2. While the degradation efficiency and reaction rate were greatly enhanced at a pH range of 3.0-9.0 especially at acidic pH values (3.0-5.0) in the presence of Al@MCM-41. The probe experiments proved that OFX adsorption followed by surface reaction process played an important role to enhance the performance of UV-H2O2. Based on the characterization results, the positive effect of suspended particles was not related to their surface area and pore size distribution, but dependent on the chemical composition and surface acid-base property. The suspended particles can provide an active surface composed of acid and base sites. The base site can create a local basic micro-environment by producing more •OH et al. While the dissociated acid sites in Al@MCM-41 with a negative charged surface favor OFX adsorption and then reaction with produced ROS. Our findings suggest that the enhanced performance of UVA-H2O2 induced by suspended particles should be concerned.