Selective Adsorption of AuIII from Aqueous Solution Using 2,5‑Dimercapto‑1,3,4‑thiadiazole Modified Persimmon Tannin

Sijing Zhang,Fengjiao Ao,Junxue Zhao,Yongliang Ji,Yongping Wang,Shuangli Chen

doi:10.21577/0103-5053.20180022

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.

Highlights

In the current information age, a growing amount of electronic waste from all sorts of abandoned electronic gadgetry creates environmental problems
The peak at 3423 cm-1 is attributed to the O−H stretching vibration, and this indicates that persimmon tannin (PT) has a large amount of hydroxyl groups, whereas the peak at 1636 cm-1 in PT spectrum is assigned to the stretching vibrations of C=O
DMTD-PT achieved AuIII removal of 97.7% under similar conditions, and this was very close to that (98.2%) obtained in the single AuIII system at comparable concentrations. These findings indicated that AuIII can be selectively separated from coexisting base metal ions using DMTD-PT

Summary

Introduction

In the current information age, a growing amount of electronic waste from all sorts of abandoned electronic gadgetry creates environmental problems. Effect of the solution pH The species of metals in solution are greatly dependent on pH,[18] and the solution pH can affect both the dissociation state of the binding sites and the aqueous chemistry of the metal adsorbed in terms of coordination, redox potentials and hydrolysis.[19] Figure 3 shows plots of the AuIII adsorption at different values of initial pH on PT and DMTD-PT.

Results

Conclusion