Adsorption-photocatalytic degradation of Acid Red 88 by supported TiO2: Effect of activated carbon support and aqueous anions

TiO2 nanoparticles supported on activated carbons (TiO2/AC) were synthesized for the synergistic removal of Acid Red 88 (AR) via photocatalytic degradation and adsorption. Great enhancement of photocatalytic efficiency was achieved by supporting TiO2 on two ACs, Darco-G60 and Norit SA UF. The surface hydrophilic properties and pore size distribution of ACs have significant influences on TiO2 deposition on the supports, resulting in remarkable different performances of the two TiO2/AC composites in the degradation of AR. TiO2 loaded on Norit SA UF (TiO2/AC-N) had a more dispersed coverage on the AC support but lower AR adsorption capacity due to larger degree of pores blockage by the TiO2 nanoparticles which were also shielded from incident UV. In comparison, TiO2 loaded on Darco-G60 (TiO2/AC-D) showed higher photocatalytic activity and better durability in cyclic reuse. The synergistic adsorption-photocatalysis was observed, and the optimal TiO2-to-AC mass ratio was 80–20 for the highest photocatalytic activity. Inorganic anions exhibited varying impacts on the performance of TiO2/AC. In general, the AC support could greatly abate TiO2 deactivation by inorganic anions. Sulfate promoted the AR degradation over both TiO2/AC-D and TiO2/AC-N while chloride and nitrate exhibited no influence on TiO2/AC-D but positive effect on TiO2/AC-N. Phosphate and bicarbonate could deactivate the TiO2/AC composites but to a less extent compared to their effects on the TiO2 without AC support.

► TiO2/AC was developed for synergistic adsorption-photocatalysis of Acid Red 88.
► Surface properties and pore size distribution of activated carbons have significant influence on TiO2/AC performance.
► TiO2-to-AC mass ratio of 80–20 gives the highest photocatalytic activity.
► AC support could greatly abate TiO2 deactivation by inorganic anions.