Highly efficient removal of thallium(I) by facilely fabricated amorphous titanium dioxide from water and wastewater

In this study, amorphous hydrous titanium dioxide was synthesized by a facile precipitation method at room temperature, aiming to effectively remove thallium(I) from water. The titanium dioxide prepared using ammonia as precipitant (TiO₂^I) is more effective for thallium(I) uptake than the one synthesized with sodium hydroxide (TiO₂^II). The TiO₂ obtained particles are amorphous, aggregates of many nanoparticles and irregular in shape. The thallium(I) uptake increases with the rise of solution pH value. Under neutral pH conditions, the maximal thallium(I) adsorption capacities of TiO₂^I and TiO₂^II are 302.6 and 230.3 mg/g, respectively, outperforming most of the reported adsorbents. The amorphous TiO₂ has high selectivity towards thallium(I) in the presence of multiple cations such as K⁺, Ca²⁺, Mg²⁺, Zn²⁺ and Ni²⁺. Moreover, the TiO₂^I is efficient in removing thallium(I) from real river water and mining wastewater. Additionally, the spent TiO₂^I can be regenerated using hydrochloric acid solution and reused. The Tl(I) adsorption is achieved via replacing the H⁺ in hydroxyl group on the surface of TiO₂ and forming inner-sphere surface complexes. Owing to its high efficiency, facile synthesis and environmental friendliness, the TiO₂^I has the potential to be used as an alternative adsorbent to remove Tl(I) from water.