Ternary Mg-B-S co-modified Ficus virens biochar for ultra-high adsorption of rhodamine B in lab-scale and field-scale application: Adsorption behavior and mechanisms

To boost the adsorption activity of Ficus virens biochar for dye removal, S-doped biochar was co-modified by MgO and B2O3 (Mg-B/S-BC) via one-pot sulfurization. Mg-B/S-BC exhibits the higher adsorption capacity than S -doped biochar, MgO/biochar and B2O3/biochar for rhodamine B (RhB). The adsorption capacity of optimal Mg-B/S-BC is 1195.25 mg g-1, and declines to 1142.97 mg g-1 after nine cycles. The adsorption isotherms and kinetics of S-biochar based composites are well matched with Langmuir and second-order models, respectively. The mechanism of RhB adsorption on 4d-Mg-B/S-BC composites is through electrostatic attraction, H-bonding and ion exchange interactions, and it is a spontaneous process of physical adsorption and heat absorption. The field-scale results suggest that the adsorption capacity of optimal Mg-B/S-BC is 487.01 mg g-1, while reduces to 429.63 mg g-1 for RhB after nine cycles. The optimal Mg-B/S-BC exhibits the excellent adsorption activity for field-scale removal of tetracycline hydrochloride, ciprofloxacin, and methyl orange. Hence, Mg-B/S-BC com-posite is a promising material for industrial application in wastewater purification.