Oxidative removal of thallium(I) using Al beverage can waste with amendments of Fe: Tl speciation and removal mechanisms

The emerging occurrence of thallium (Tl) in environments arouses the imposition of effective technology for its remediation. Due to the low solubility of Tl(III), the oxidation-precipitation of Tl(I) is considered as an promising removal method. Here, we recycled Al beverage can powder (AlCP) as the substitute for zero-valent Al to conduct the Fenton-like reaction for Tl(I) oxidation and subsequently induced the Tl(III) precipitation via the alkalinization at pH 9.5. The Tl(I) removal mechanisms in AlCP systems with amendments of Fe(III) or Fe(II) were determined in relation to its speciation for both dissolved and solid phases. Results showed that although additions of Fe(III)/Fe(II) prompted the Tl(I) oxidation as compared with the pure AlCP system, they were detrimental to the Tl removal upon the alkalinization. While the greatest removal efficiency was ~ 92% in AlCP/Fe(III)/Fe(II) systems, up to 99.8% of total Tl could be removed from the pure AlCP system. The Tl-XANES data indicated that although Tl(III) dominated the Tl inventory (92 – 95%) on all solids collected upon the alkalinization, it preferred to precipitate as stable Tl₂O₃ in pure AlCP system but as labile Tl(III) in AlCP/Fe(III)/Fe(II) systems, which might sorb on precipitated Al (hydr)oxides. Such sorbed Tl(III) is subject to reduction and the further dissolution, accounting for the lower removal efficiency for Tl in the presence of Fe(III)/Fe(II). This study corroborated the comparable Tl(I) removal efficiency of AlCP to that of state-of-the-art (nano)composites, providing a niche opportunity to give consideration to both interests in hazard remediation and the waste reduction/reuse.