Recovery of Gold from Chloride Solution by TEMPO-Oxidized Cellulose Nanofiber Adsorbent

Shila Jafari,Mika Sillanpää,Minna Hakalahti,Mari Lundström,Benjamin Wilson,Tekla Tammelin,Eero Kontturi

doi:10.3390/su11051406

Abstract

The goal of this study was to assess the sustainability of a modified cellulose nanofiber material for the recovery of precious gold from chloride solution, with a special focus on gold recovery from acidic solutions generated by cupric and ferric chloride leaching processes. TEMPO-oxidized cellulose nanofiber in hydrogel (TOCN), dry (H-TOCN, F-TOCN) and sheet form (S-TOCN) was examined for gold adsorptivity from chloride solution. Additionally, this work describes the optimum conditions and parameters for gold recovery. The data obtained in this investigation are also modeled using kinetic (pseudo first-order and pseudo second-order), isotherm best fit (Freundlich, Langmuir and Langmuir-Freundlich), and thermodynamic (endothermic process) parameters. Results demonstrate that high levels of gold removal can be achieved with TEMPO-oxidized cellulose nanofibers (98% by H-TOCNF) and the interaction characteristics of H-TOCN with gold suggests that other precious metals could also be efficiently recovered.

Highlights

At present, the gold content in specific scrap materials like electronic waste can be 10–100 times higher than that available in many naturally-occurring ores [1,2]
The dominating state-of-the-art technology for gold containing metal rich waste relies on pyrometallurgical treatment as part of primary copper production or via the secondary raw material smeltery through copper electorefining/electrowinning into a precious metal plant [4]
Several precious metal plants are known to operate in hydrochloric acid media at very high acidity [7] and, gold chloride is purported to undergo faster dissolution during leaching than the corresponding cyanide salt [4]

Summary

Introduction

The gold content in specific scrap materials like electronic waste can be 10–100 times higher than that available in many naturally-occurring ores [1,2]. The dominating state-of-the-art technology for gold containing metal rich waste relies on pyrometallurgical treatment as part of primary copper production or via the secondary raw material smeltery through copper electorefining/electrowinning into a precious metal plant [4]. This process route can recover the main base metals, such as Cu and Ni, and precious metals, such as Ag, Au, Pt, and Pd efficiently, the loss of several critical and rare earth metals present in the secondary raw materials is evident [2]. Several precious metal plants are known to operate in hydrochloric acid media at very high acidity [7] and, gold chloride is purported to undergo faster dissolution during leaching than the corresponding cyanide salt [4]

Objectives

Methods

Results