Superior removal of Tl(I) from aqueous solution by facilely engineered MnxOy@potassium-rich biowaste-biochar

Potassium(K)-rich biochar (BC) synthesized from waste banana peels were designed as green adsorbents for removal of TI(I) from aqueous solution. Co-precipitation and solid surface deposition method were adopted to fabricate two distinct manganese oxide biochars, i.e., H-Mn3O4@BC and S- MnxOy@BC, respectively, which showed remarkably higher efficiency but with less dosage in treating Tl(I)-containing aqueous solution with the maximum adsorption capacities at 122.91 mg/g and 136.94 mg/g, respectively, than most adsorbents reported. Besides, H-Mn3O4@BC and S-MnxOy@BC exhibited strong resistance to co-existing cations and organics interference on Tl(I) removal. Specially, DTPA and EDTA could coordinate with Mn(III) to promote the oxidation and removal of Tl(I). According to FTIR, H-Mn3O4@BC and S-MnxOy@BC were enriched with abundant functional groups such as O-H and Mn-O, while the original C--O on BC surface was oxidized by MnO4- . The results of SEM-EDS and XPS revealed that cation exchange and oxide-coprecipitation were the main mechanisms of Tl(I) removal by H- Mn3O4@BC and S- MnxOy@BC. This study proposes a novel approach on facile design of potassium-rich biochars, which exhibited highly effective performance on Tl(I) removal from aqueous solution. The findings provide favorable alternative for synthesis of specially designed functional materials from naturally K-rich biowastes and show promising potential in efficient treatment with increasing occurrence of Tl(I)containing wastewater.