Evaluation of the performance of activated carbon and titanium dioxide composites for pharmaceutical adsorption and photocatalysis in water

摘要

In this project the adsorptive properties of activated carbons (AC) are coupled with the photocatalytic properties of titanium dioxide (TiO2) to create a synergistic composite - an integrated photocatalytic adsorbent (IPCA) - that can adsorb and photodegrade pollutants better than the two materials separately. Two active pharmaceutical ingredients, famotidine and solifenacin succinate, were chosen as model pollutants in this study. Active pharmaceutical ingredients are an important group of organic environmental contaminants that have the potential to cause health risks for humans as well as biota. An ultrasonication preparation method was used to combine the AC and TiO2 to prepare the IPCA.udCharacterisation of the IPCA using SEM, EDX and FESEM analysis revealed that TiO2 particles approximately 25 nm in diameter were dispersed across the AC surface. XRD analysis provided information on the molecular structure of the IPCAs and TiO2. Adsorption studies indicated that TiO2 has limited adsorption capacity. The AC and IPCA have higher adsorption capacity but require long equilibrium times due to rate limiting intraparticle diffusion.udIPCA photodegradation studies at an initial concentration of 100 mg/L can remove more solifenacin from solution than either TiO2 or AC separately; however for famotidine removal the IPCAs showed no improvement compared to AC or TiO2 controls. The contrast is postulated to be the high adsorption strength of famotidine compared to solifenacin, which retards migration from the adsorption sites on the AC to the TiO2 on the IPCA surface. This lowers the photodegradation rate for famotidine but not solifenacin. These results suggest that substrate desorption is required to prepare effective IPCAs. Future work would involve IPCA photodegradation studies of compounds similar to famotidine to confirm this hypothesis.