Ultrasonic spray pyrolysis synthesis of TiO(2)/Al(2)O(3) microspheres with enhanced removal efficiency towards toxic industrial dyes

Developing low-cost and highly effective adsorbent materials to decolorate wastewater is still challenging in the industry. In this study, TiO(2)-modified Al(2)O(3) microspheres with different TiO(2) contents were produced by spray pyrolysis, which is rapid and easy to scale up. Results reveal that the modification of γ-Al(2)O(3) with TiO(2) reduced the crystallite size of Al(2)O(3) and generated more active sites in the composite sample. The as-synthesized Al(2)O(3)–TiO(2) microspheres were applied to remove anionic methyl orange (MO) and cationic rhodamine B (RB) dyes in an aqueous solution using batch and continuous flow column sorption processes. Results show that the Al(2)O(3) microspheres modified with 15 wt% of TiO(2) exhibited the maximum adsorbing capacity of ∼41.15 mg g(−1) and ∼32.28 mg g(−1) for MO and RB, respectively, exceeding the bare γ-Al(2)O(3) and TiO(2). The impact of environmental complexities on the material's reactivity for the organic pollutants was further delineated by adjusting the pH and adding coexisting ions. At pH ∼5.5, the TiO(2)/Al(2)O(3) microspheres showed higher sorption selectivity towards MO. In the continuous flow column removal, the TiO(2)/Al(2)O(3) microspheres achieved sorption capacities of ∼31 mg g(−1) and ∼19 mg g(−1) until the breakthrough point for MO and RB, respectively. The findings reveal that TiO(2)-modified Al(2)O(3) microspheres were rapidly prepared by spray pyrolysis, and they effectively treated organic dyes in water in batch and continuous flow removal processes.