Recovery of Zinc and Silver from Zinc Acid-Leaching Residues with Reduction of Their Environmental Impact Using a Novel Water Leaching-Flotation Process

Yunpeng Du,Qiang Song,Hanxu Yang,Xian Xie,Xiong Tong,Wenjie Zhang

doi:10.3390/min11060586

Abstract

Zinc-leaching residue (ZLR) is a strongly acidic hazardous waste; it has poor stability, high heavy metal levels, and releases toxic elements into the environment. ZLR has potential as a valuable resource, because it contains elevated levels of zinc and silver. In this paper, the recovery of zinc (Zn) and silver (Ag) from ZLR wastes from zinc hydrometallurgy workshops using water leaching followed by flotation was studied. During water leaching experiments, the zinc and copper recovery rates were 38% and 61%, respectively. Thereafter, various flotation testing parameters were optimized and included grinding time, reagent dosages, pulp density, flotation time, and type of adjuster. Experimental results demonstrated this flotation method successfully recycled Ag and Zn. A froth product containing more than 9256.41 g/t Ag and 12.26% Zn was produced from the ZLR with approximately 80.32% Ag and 42.88% Zn recoveries. The toxicity characteristic leaching procedure (TCLP) results indicated the water-leaching flotation process not only recycled valuable metals such as zinc and silver in zinc-containing hazardous wastes but lowered the hazardous waste levels to those of general wastes and recycled wastes in an efficient, economical, and environmentally friendly way.

Highlights

Zinc hydrometallurgy, regardless of whether using traditional wet zinc smelting, high temperature, and high acid leaching or direct oxygen leaching, inevitably produces a huge amount of zinc-leaching residue (ZLR) [1,2]
ZLR contains a significant amount of valuable metals, such as zinc, silver, indium, lead, and copper [3], which means the zinc-leaching slag has high economic and industrial value and places an emphasis on developing a method for their recovery [4,5]
Most metals in the zinc-leaching residue occur as sulfates, and except for lead sulfate, almost all of them leach into rainwater [6,7]

Summary

Introduction

Regardless of whether using traditional wet zinc smelting, high temperature, and high acid leaching or direct oxygen leaching, inevitably produces a huge amount of zinc-leaching residue (ZLR) [1,2]. ZLR contains a significant amount of valuable metals, such as zinc, silver, indium, lead, and copper [3], which means the zinc-leaching slag has high economic and industrial value and places an emphasis on developing a method for their recovery [4,5]. Most metals in the zinc-leaching residue occur as sulfates, and except for lead sulfate, almost all of them leach into rainwater [6,7]. Heavy metal ions and sulfate ions can enter the surface via rainwater and pollute the environment [8], which must be processed by high-temperature smelting. The massive discharge of zinc-containing liquids and solid wastes causes serious environmental pollution but negatively impacts the human body and is classified as a hazardous waste [11,12]

Objectives

Methods

Results

Conclusion