Decoration of Mg/Fe layered double hydroxides on coffee waste biochars for enhanced adsorption and selectivity of phosphate ions: Mechanistic studies

초록

This study rigorously evaluated the viability of Mg/Fe layered double hydroxides (LDH) decorated biochars produced from coffee wastes (MF-L@CB) for the selective and effectual adsorption of phosphate (PO43-) ions. A higher adsorption capacity of MF-L@CB (6.6 mg/g) toward PO4 3- ions than coffee waste biochars (CB; 2.4 mg/g) was mainly because of the increased metal and anion components through the Mg/Fe LDH decoration. Based on the obtained experimental results, the adsorptive removal of PO4 3- ions by CB and MF-L@CB was chiefly governed by chemisorption and intra-particle diffusion. In addition, the removal of PO4 3- ions by CB and MF-L@CB occurred endothermically and spontaneously. The variations in the main adsorptive removal mechanisms of PO4 3- ions by CB from the ligand exchange with alcohol functional groups to the anion exchange with Cl and electrostatic surface complexation with metal contents via the Mg/Fe LDH decoration could significantly improve the selectivity of PO4 3- ions (decreasing rate of Qe under the co-existing anions: CB = 26.7-98.7 % and MF-L@CB = 1.9-44.2 %). Hence, the decoration of the Mg/Fe LDH particles on the surfaces of CB might be a promising method to improve the adsorption capacity and selectivity of PO4 3- ions.

키워드