Adsorption Performance and Mechanism of Low Antimonate Concentrations in Water by Zirconium-Modified Biochar

The widespread products using contained antimony and corresponding activities of Sb mining have led to elevated antimony concentrations in water. In order to effectively remove the excessive antimony in water, zirconium-modified peanut shell biochar (BC) was prepared. The effects of different environmental factors on antimony-(V) adsorption and the recycling capacity, and practical application of the material were also studied, and its removal mechanism was revealed. The maximum adsorption capacity of antimony-(V) by zirconium-modified BC reached 72.34 mg·g^-1. When coexisting ions were present, adsorptive inhibition of antimony-(V) adsorption by zirconium-modified BC ranged from 0.74% to 21.68% apart from dihydrogen phosphate and arsenic-(V), indicating selectivity of adsorption. Adsorptive isotherms analyses showed that the adsorption of antimony-(V) by ZrBC was consistent with multilayer adsorption, and kinetic studies indicated that adsorptive procedures were predominantly chemisorptive. Zirconium-modified BC showed 100% removal rate after 4 reuse cycles and adsorption-desorption cycles, and the desorption amount was 6.16 mg·g^-1. The zirconium-modified BC adsorbed 6.97 mg·g^-1 of antimony when treating real wastewater, which has potential for practical applications. Characterizations showed that the antimony-(V) adsorptive mechanism in water mainly includes ligand exchange, complexation, electrostatic interaction, and hydrogen bonding. In summary, zirconium-modified BC can efficiently and stably remove Sb from the aqueous environment and can be a potentially viable option for antimony-containing wastewater treatment.