Regulation of synthesis pH value and post-treatment of ZSM-5 for improving adsorption and photocatalytic properties of TiO2/ZSM-5 composites

TiO 2 /ZSM-5 composites with enhanced adsorption and photocatalytic properties were synthesized via regulation of synthesis pH value and post (acid/alkali) treatment of ZSM-5. The influences of synthesis pH values and post-treatment of ZSM-5 on microstructure, adsorption and photocatalytic properties of the composites were investigated. The methyl orange was used to assess the adsorption and photocatalytic properties of the samples. The results showed that the synthesis pH values and acid/alkali treatment had significant influences on the microstructure, adsorption and photocatalytic properties of TiO 2 /ZSM-5 composites. The composites synthesized at pH 7 had a relatively higher TiO 2 content, smaller anatase crystallite size, greater specific surface area, the most effective separation of photogenerated electron-hole pairs, the fastest interfacial charge transfer, and therefore exhibited excellent adsorption and photocatalytic properties. Acid treatment could significantly increase the specific surface area, Si/Al ratio of ZSM-5, the separation efficiency of photogenerated electron-hole pairs, and amount of produced active free radicals •O 2 – and •OH. The TiO 2 /acid-treated ZSM-5 exhibited excellent photodegradation with 99.3 % methyl orange in 150 min, which is higher than that of the TiO 2 /ZSM-5 and TiO 2 /alkali-treated ZSM-5.