Selective adsorption of AuIII from aqueous solution using 2,5‑Dimercapto‑1,3,4‑thiadiazole modified persimmon tannin

Abstract

A one-pot synthesized persimmon tannin (PT)-based novel biosorbent modified with 2,5-dimercapto-1,3,4-thiadiazole (DMTD) was prepared for the selective adsorption of AuIII from aqueous mixtures. The synthesized biosorbent was designated as DMTD-PT and characterized using elemental analysis, zeta potential, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The batch adsorption experiments in a model electronic waste leachate revealed that both DMTD-PT and PT had poor affinity for coexisting base metal ions, however, DMTD-PT and PT adsorbed 97.7 and 32.7%, respectively, of AuIII with an initial AuIII concentration of 78.0 mg L-1 in the mixtures with a dosage of 2.5 g L-1 each at pH 3.0 at ambient temperature. The adsorption results indicate the superior selectivity of DMTD-PT for AuIII compared to that of PT. The continuous column experiments further proved that DMTD-PT can be used to separate AuIII from aqueous mixtures. The maximum adsorption capacity of DMTD-PT for AuIII was determined to be 0.42 mmol g-1. A kinetic study in combination with XPS and FTIR analyses of fresh and spent DMTD-PT further revealed that the potential biosorption mechanism can be attributed to the collaboration of electrostatic interactions and coordination.