Hydrometallurgy

Abstract

Hydrometallurgy, which involves the use of aqueous solutions for the recovery of metals from ores, concentrates, and recycled or residual material, plays an integral role in the multi-billion dollar minerals processing industry. It involves either the selective separation of various metals in solution on the basis of thermodynamic preferences, or the recovery of metals from solution through electro-chemical reductive processes or through crystallisation of salts. There are numerous hydrometallurgical process technologies used for recovering metals, such as: agglomeration; leaching; solvent extraction/ion exchange; metal recovery; and remediation of tailings/waste. Hydrometallurgical processes are integral across various stages in a typical mining recovery and mineral processing circuits be it in situ leaching (where solution is pumped through rock matrices); heap leaching (of the ROM or crushed ore); tank/autoclave leaching (of the concentrate/matte obtained from floatation); electro-refining (of the blister product from smelting routes); and the treatment of waste tailings/slags from the aforementioned processes. Modern hydrometallurgical routes to extract metals from their ores are faced with a number of issues related to both the chemistry, geology and engineering aspects of the processes involved. These issues include declining ore grade, variations in mineralogy across the deposits and geo-metallurgical locations of the ore site; which would influence the hydrometallurgical route chosen. The development of technologies to improve energy efficiency, water/resources consumption and waste remediation (particularly acid-rock drainage) across the circuit is also an important factor to be considered. Therefore, there is an ongoing development of novel solutions to these existing problems at both fundamental scales and pilot plant scales in order to implement environmentally sustainable practices in the recovery of valuable metals. The Present IssueWe are delighted to be the Guest Editors for this Special Issue of Hydrometallurgy published in the journal Metals. With a total of 22 papers covering both fundamental and applied research, this issue covers all aspects of hydrometallurgy from comprehensive review articles [1,2] [12][13][14], nanoparticle preparation [15,16] and the development of novel and/or environmentally sustainable methods for the treatment of wastes and effluents for the recovery of valuable metals and products [17][18][19][20][21][22]. The number and of quality of submissions makes this Special Issue of Metals the most successful to date. As Guest Editors, we would especially like to thank Dr. Jane Zhang, Managing Editor for her support and active role in the publication. We are also extremely grateful to the entire staff of the Metals Editorial Office, who productively collaborated

Management of e-waste

“…Hydrometallurgy is a process where an aqueous solution is used for the recovery of metals from ores or concentrates, recycled or discarded materials. There are various hydrometallurgical processes available out of which leaching is best suited for the recovery of metals from ewaste stream [3]. Whereas, the process of pyrometallurgy involves the use of high temperatures for either purification or extraction of the useful metals [1].…”

Possibilities for the Environmental Processing of Gold-Bearing Ores

“…Hydrometallurgical processing of gold-bearing ores represents an important group of methods used in gold mining and is formed by a combination of several elementary processes using aqueous solutions to recover metals from ores, concentrates, and recyclable or residual material [9,10]. Hydrometallurgy is a process which is usually divided into four general areas such as leaching, concentration, solution purification, and the regeneration of metals.…”

“…NaAsS 2 + Na 2 S → Na 3 AsS 3 (9) Dissolving elemental sulfur in sodium hydroxide is also used as a solvent for the alkaline sulfide leaching of arsenic. The combination of sodium hydroxide and elemental sulfur leads to the formation of sodium polysulfide (Na 2 S X ) and sodium thiosulfate (Na 2 S 2 O 3 ) together with sulfides [37].…”

Chalcopyrite leaching by amino acid solutions in the presence of hydrogen peroxide

“…Recently, considerable attention has been paid to the hydrometallurgical process, in which the most important stage is leaching, where ores, concentrates, semi-products and production wastes are treated with aqueous solutions of chemical reagents (Yoo et al, 2010;Safarzadeh et al, 2012;Choubey et al, 2018;Martínez-Gómez et al, 2018;Moyo et al, 2018;Beiza et al, 2019;Moyo et al, 2019;Tiburcio-Munive et al, 2020). Hydrometallurgical methods have the following advantages (Bhargava et al, 2016): provide efficient processing of low-grade ores and extraction of more valuable components through complex processing of raw materials; involve selective chemical reactions and low operating temperatures; require lower energy and economic costs; include safer working conditions (no dust and toxic gases), and reduce environmental pollution by hazardous substances. Hydrometallurgical metal extraction, where leaching, separation, concentration and reduction to metal are carried out at close to ambient temperature, is becoming increasingly competitive compared to conventional high-temperature processes.…”