Post-calcination as an effective approach to enhance adsorption of arsenic and antimony anions by Mg/Al layered double hydroxide-decorated spent coffee ground biochars: Role of charge properties and active sites

초록

This study evaluated the effects of post-calcination on the charge properties and active sites of Mg/Al layered double hydroxide-decorated spent coffee ground biochars (LDHMgAl@SCGB) governing adsorption behaviors and mechanisms of arsenic (As-V) and antimony (Sb-V) anions from aqueous phases. Post-calcinated LDHMgAl@SCGB (PLDHMgAl@SCGB) exhibited higher adsorption capacities for As-V and Sb-V compared to spent coffee ground biochars (SCGB) and LDHMgAl@SCGB as post-calcination of LDHMgAl@SCGB enhanced the charge properties (surface zeta potential at pH 7.0: SCGB = -21.8 mV, LDHMgAl@SCGB = 28.5 mV, and PLDHMgAl@SCGB = 34.4 mV) and increased active sites by eliminating the anions (i.e., Cl- ions) and water molecules at its interlayers. The calculated kinetic, intra-particle diffusion, and isotherm parameters indicated that the chemisorption and intra-particle diffusion were mainly responsible for the adsorption of As-V and Sb-V by SCGB, LDHMgAl@SCGB, and PLDHMgAl@SCGB. Moreover, post-calcination of LDHMgAl@SCGB enhanced its selectivity toward As-V and Sb-V by reinforcing the electrostatic surface complexation via its improvement of charge properties. Since PLDHMgAl@SCGB exhibited the excellent reusability for the adsorption of As-V (reuse efficiency >63.6%) and Sb-V (reuse efficiency >52.1%), it can be concluded that post-calcination of LDHMgAl@SCGB is a promising method for improving the adsorption capacities for As-V and Sb-V in real water matrices.

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