NSRRC Activity Report 2022

Environmental and Earth Sciences 067 T hallium (Tl) is an emerging environmental pollutant. The research group of Yu-Ting Liu (National Chung- Hsing University) used recycled aluminum (Al) beverage cans to remove Tl(I) from wastewater and determined the removal mechanism using X-ray absorption spectroscopy at TPS 44A . 1 Because of the low solubility of Tl(III), oxidation- precipitation is regarded as a promising method for the Tl(I) removal. Recycled Al beverage can powder (AlCP) was applied as the substitute for zero-valent Al (ZVAl) to catalyze a Fenton-like reaction for Tl(I) oxidation. The system was subsequently alkalinized to a pH of 9.5 to induce the precipitation of Tl(III) ( Fig. 1 ). In the oxidation process, the addition of Fe(III)/Fe(II) into the AICP system increased Tl(I) oxidation as compared with that of pure AlCP; however, Fe was detrimental to Tl removal during alkalinization. The highest Tl(I) removal efficiency of the AlCP/ Fe(III)/Fe(II) system was approximately 92%, whereas that of pure AICP was 99.8% ( Fig. 1 ). To clarify the removal mechanism, Tl L 3 -edge X-ray absorption near edge structure (XANES) data were acquired to investigate the distribution of Tl chemical species on the removed solids ( Fig. 2 ). The XANES results indicated that although Tl(III) dominated the Tl inventory (92–95%) on all solids obtained upon alkalinization, it was prone to precipitate as stable Tl 2 O 3 in Oxidative Removal of Thallium(I) fromWastewater by Recycled Aluminum Beverage Cans Recycled aluminum beverage can powder facilitates oxidation-precipitation of thallium(I). Fig. 1 : Schematic illustration for the mechanism underlying Tl(I) removal and the chemical species of Tl on solids precipitated upon alkalinization. [Reproduced from Ref. 1] Fig. 2 : Normalized Tl L 3 -edge XANES spectra for (a) references, including labile Tl(I) (TlNO 3 ), labile Tl(III) [Tl(NO 3 ) 3 ·6H 2 O], Tl(III) precipitates: Tl 2 O 3 , Al/Tl(III) coprecipitate [Al-Tl(III)], and Fe/Tl(III) coprecipitate [Fe-Tl(III)]. The Tl-XANES data for solids obtained during the incubation (5–180 min) of 100 μM Tl(I) in oxic and acidic (pH 1.0) suspensions containing (b) only 8 g L −1 AlCP (AlCP-NoFe) and (c,d) both AlCP and 1,000 μM Fe(III)/Fe(II) [AlCP- 1000Fe(III)/Fe(II)] as well as for that collected upon alkalinization are showed as open circles along with the linear combination fitting results showed as solid lines. [Reproduced from Ref. 1]