Thermodynamic and kinetic coupling modeling for thallium(I) sorption at a heterogeneous titanium dioxide interface

New insights into thallium(I) behaviors at birnessite surfaces: Effects of an organic buffer and goethite

Understanding the environmental behavior of thallium (Tl) is crucial due to its high toxicity and increasing anthropogenic presence. This study investigated the adsorption and redox behaviors of Tl(I) with acid birnessite (AcBi) in the presence of 1,4-piperazine-diethanesulfonic acid (PIPES) and goethite under diffusion-limited conditions using Donnan reactors in aerobic and anaerobic environments. Our findings indicate that Tl(I) preferentially adsorbs onto AcBi, with capacities 20 to 100 times higher than onto goethite, even when AcBi is partial reduced by PIPES. No net Tl(I) oxidation occurred in the Donnan reactors, likely due to complex electron transfer processes between Tl(I), birnessite, and PIPES. Any Tl(III) generated from Tl(I) oxidation by birnessite was rapidly reduced back to Tl(I) by PIPES. This was confirmed in batch experiments where reduced Tl(III) on birnessite surfaces and in Tl(III) salts. These findings highlight the need to assess the impact of Good's buffers on redox reactions involving manganese oxides and Tl, while also providing insights into the competitive retention of Tl on manganese and iron (hydr)oxides, with implications for Tl mobility and bioavailability in natural environments.

Mechanisms for thallium(I) adsorption by zinc sulfide minerals under aerobic and anaerobic conditions

The highly toxic heavy metal thallium is widely distributed in sulfide ores and released into the environment by sulfide mining. However, the interface between the sulfide minerals and Tl(I) is unclear. In this study, the capacity for adsorption of thallium(I) by a common sulfide mineral (zinc sulfide) was investigated in aerobic and anaerobic environments, which revealed three mechanisms for adsorption on the ZnS surface (surface complexation, electrostatic action and oxidation promotion). Batch experiments indicated that the Tl(I) adsorption capacity of ZnS in an aerobic environment was approximately 9.3% higher than that in an anaerobic environment and was positively correlated with the pH. The adsorption kinetic data showed good fits with the pseudosecond-order model and the Freundlich isotherm model. The Tl(I) adsorption mechanism varied in different oxidative and pH environments. XPS, FTIR, and EDS results implied that complexation with surface hydroxyl groups was involved in the adsorption process. pH experiments and zeta analyses suggested that electrostatic attraction was also involved. Surface complexation and electrostatic attraction were the dominant mechanisms at pH values above 6. Furthermore, oxidative dissolution of ZnS and hydrolysis of Zn2+ enhanced the complexation with hydroxyl groups on the mineral surface and facilitated Tl adsorption. In this study, this interface mechanism provided new insights into thallium migration in sulfurized mineral environments in aerobic and anaerobic transition regions.

Mn/Ce@HKUST-1 for Efficient Removal of Gaseous Thallium: Insights from Kinetic and Experimental Studies

Gaseous thallium (Tl) pollution events, primarily caused by non-ferrous mineral refineries and fossil fuel combustion, have increased over the past few decades. To prevent gaseous Tl distribution from flue gas, MnO2/CeO2@HKUST-1 (MCH) was synthesized and found to achieve a gaseous Tl(I) removal level of up to 90% at 423 K, a weight hourly space velocity (WHSV) of 2000 h-1/mL with an Mn dose of 10%, maintained over 10 h. The best Mn/Ce ratio was found to be 9:1. To further investigate surface kinetic behavior, four commonly used kinetic models were applied, including the Eley-Rideal (ER) model, Langmuir-Hinshelwood (LH) model, Mars-van Krevelen (MVK) model, and pseudo-first-order (PFO) model. While the ER and LH models had the slightest deviation, the MVK model was the most reliable. The CatMAP software was also used to match the simulation deviation. This work demonstrated the Tl removal mechanism and provided insights into the accuracy of kinetic models on minor-radius heavy metal. Thus, this research may help promote the design of reactors, heavy metal removal rates, and flue gas purification technology selection.

Dynamic retention of thallium(I) on humic acid: Novel insights into the heterogeneous complexation ability and responsiveness

Widely distributed soil humic acid (HA) would significantly affect the environmental migration behavior of Tl(I), but a quantitative and mechanistic understanding of the dynamic Tl(I) retention process on HA is limited. A unified kinetic model was established by coupling the humic ion-binding model with a stirred-flow kinetic model, which quantified the complexation constants and responsiveness coefficients during dynamic Tl(I)-HA complexation. Furthermore, the heterogeneous complexation mechanism of HA and Tl(I) was revealed by batch adsorption experiments, stirred-flow migration experiments, and 2D-FTIR-COS analysis. An increase in pH significantly improved the responsiveness of HA organic binding sites, promoting Tl(I) dynamic retention. Monodentate carboxyl groups induced rapid Tl(I) complexation (k_d = 1.9 min^-1) in strongly acidic environments. Under weakly acidic conditions, Tl(I) retention on HA was mainly attributed to the synergistic complexation effect of carboxyl and amide groups. Among the groups, multidentate carboxyl-phenolic hydroxyl sites could achieve sustained Tl(I) retention due to their stable complexing properties (logK = 4.48∼7.46) and slow response (k_d = 1.1 × 10^-3 min^-1). These findings are crucial for a comprehensive understanding of the environmental interactions of Tl(I) with humic substances in swamp environments.

Magnetic hydrochar derived from waste lignin for thallium removal from wastewater: Performance and mechanisms

Waste lignin, such as black liquor (BL) from paper and pulping industries, is an agro-industrial biowaste while its reuse raised global concerns. In this work, a hydrothermal carbonization procedure was employed to convert BL into magnetic lignin-based hydrochar (MLHC) for thallium elimination from wastewater. The results exhibited water purification potential due to a wider working pH window (2-9) with the magnetization intensity of 11.12 emu/g. The maximum adsorption capacity for Tl(III) was 278.9 mg/g, while the contribution of various mechanisms was elucidated with the order: surface precipitation (31.3 %), complexation (20.6 %), physical adsorption (18.2 %), chemical reduction (15.0 %), and ion exchange (14.9 %). This study revealed that hydrothermal treatment could be a potential and promising method to convert waste lignin into magnetic bio-adsorbent to recycle pulping black liquor and apply it for thallium pollution control.

Recent Advances in Thallium Removal from Water Environment by Metal Oxide Material

Thallium is widely used in industrial and agricultural development. However, there is still a lack of systematic understanding of its environmental hazards and related treatment methods or technologies. Here, we critically assess the environmental behavior of thallium in aqueous systems. In addition, we first discuss the benefits and limitations of the synthetic methods of metal oxide materials that may affect the practicality and scalability of TI removal from water. We then assess the feasibility of different metal oxide materials for TI removal from water by estimating the material properties and contaminant removal mechanisms of four metal oxides (Mn, Fe, Al, and Ti). Next, we discuss the environmental factors that may inhibit the practicality and scalability of Tl removal from water. We conclude by highlighting the materials and processes that could serve as more sustainable alternatives to TI removal with further research and development.