Effect of montmorillonite biochar composite amendment on thallium bioavailability in contaminated agricultural soils and its mitigated health risk

Little information is available on the effect of clay minerals and biochar composite on the remediation and bioavailability of thallium in agricultural soils. This study thus investigated the influence of montmorillonite biochar composite (Mnt-BC) amendment on the remediation of agricultural soil contaminated artificially by Tl and its potential health risks. Herein, bok choi was cultured to estimate the efficiency of soil Mnt-BC amendments through the bioavailability of Tl of the vegetable. Results showed that Tl bioavailability was significantly reduced in Mnt-BC-amended soils, mainly ascribed to the elevated soil pH and other improved soil properties of high functional groups (-OH, -COOH), negative charges, and exchangeable cations after amendment. Specifically, the highest immobilization efficiency of Tl in soils was observed in 2.5% treated soils with 79.11%, while in plant leaves the highest reduction of Tl was estimated to be 75.1% compared to the control treatment. Hence, the amendment dosage improved the immobilization of Tl in soil and subsequently reduced Tl uptake by the vegetable. Furthermore, from target hazard quotient (THQ) estimation, Mnt-BC amendment can lower the potential health risk while consuming such cultured bok choi in Tl-contaminated soils. Considering the environmental friendliness and high efficiency of Mnt-BC, it could be used as a potential soil amendment to remediate agricultural soils contaminated by Tl.

Highly efficient removal of thallium in wastewater by MnFe2O4-biochar composite

Thallium (Tl), is a highly toxic trace metal in the natural environment. Emerging Tl pollution in waters has gradually become a global concern. However, limited removal technologies are available for Tl-containing wastewater. Herein, MnFe₂O₄-biochar composite (MFBC) was successfully fabricated via coprecipitation method as a novel and efficient adsorbent for treating Tl(I)-contaminated wastewater. It was found that the MFBC, with a specific surface area of 187.03 m²/g, exhibited high performance across a wide pH range of 4-11, with the superior Tl(I) removal capacity (170.55 mg/g) based on Langmuir model (pH 6.0, a dosage of 1 g/L). The removal mechanisms included physical and chemical adsorption, ion exchange, surface complexation, and oxidation. This investigation revealed that MFBC is a promising and environmentally friendly adsorbent with a low cost, large specific surface area, magnetic properties, and high efficiency for the removal of Tl(I) from wastewater.