Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Leaching is a primary extractive operation in hydrometallurgical processing, by which a metal of interest is transferred from naturally occurring minerals into an aqueous solution. In essence, it involves the selective dissolution of valuable minerals, where the ore, concentrate, or matte is brought into contact with an active chemical solution known as a leach solution. Currently, the hydrometallurgical processes have a great number of applications, not only in the mining sector—in particular, for the recovery of precious metals—but also in the environmental sector, for the recovery of toxic metals from wastes of various types, and their reuse as valuable metals, after purification. Therefore, there is an increasing need to develop novel solutions, to implement environmentally sustainable practices in the recovery of these valuable and precious metals, with particular reference to critical metals; those included in materials that are indispensable to modern life and for which an exponential increase in consumption is already a reality, or will be in a short-term perspective. For publication in this Special Issue, consideration has been given to articles that contribute to the optimization of the kinetic conditions of innovative hydrometallurgical processes—economic and of low environmental impact—applied to the recovery of valuable and critical metals.

eudialyte --- rare earth elements --- dry digestion --- leaching --- neural network --- uranium --- contaminated groundwater --- permeable reactive barrier --- zero-valent iron --- Al-Ni alloys --- aluminothermic reactions --- reaction rate --- Al master alloys --- kinetics --- Hydrometallurgical processes --- Chalcopyrite --- low-pressure leaching --- mining waste --- hydrometallurgical processes --- leaching kinetic --- thiosulphate leaching --- electrowinning --- gold --- waste printed circuit board --- iodide --- iodine --- ascorbic acid --- precipitation --- thiosulfate oxidation --- catalysis --- oxygen --- high alumina fly ash --- desilication rate --- physical–chemical activation --- alumina silica mass ratio --- refractory gold concentrate --- resources depletion --- reducing harmful emissions --- arsenic --- nitric acid --- shrinking core model --- pyrite --- arsenopyrite --- clays --- nanoscale zero-valent iron --- groundwater --- wastewater --- geochemical characteristics --- pitchblende --- U neutral leaching --- ELZPA ore deposit in Pakistan --- n/a --- physical-chemical activation

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Unit metallurgical operations processes are usually separated into three categories: 1) hydrometallurgy (leaching, mixing, neutralization, precipitation, cementation, and crystallization); 2) pyrometallurgy (roasting and smelting); and 3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). In hydrometallurgy, the aimed metal is first transferred from ores and concentrates to a solution using a selective dissolution (leaching or dry digestion) under an atmospheric pressure below 100 °C and under a high pressure (40-50 bar) and high temperature (below 270°C) in an autoclave. The purification of the obtained solution was performed using neutralization agents such as sodium hydroxide and calcium carbonate or more selective precipitation agents such as sodium carbonate and oxalic acid. The separation of metals is possible using a liquid/liquid process (solvent extraction in mixer-settler) and solid–liquid (filtration in filter-press under high pressure). Crystallization is the process by which a metallic compound is converted from a liquid into a solid crystalline state via a supersaturated solution. The final step is metal production using electrochemical methods (aqueous electrolysis for basic metals such as copper, zinc, silver, and molten salt electrolysis for rare earth elements and aluminum). Advanced processes, such as ultrasonic spray pyrolysis and microwave-assisted leaching, can be combined with reduction processes in order to produce metallic powders.

Technology: general issues --- History of engineering & technology --- Mining technology & engineering --- zirconium --- eudialyte --- hydrometallurgy --- basic sulfate precipitation --- macroporous polymer --- goethite --- factorial design --- desorption --- tailings reprocessing --- early stage cost estimation --- magnetic separation --- leaching --- flotation --- silica --- ultrasonic spray pyrolysis --- synthesis --- acid mine drainage --- red mud --- neutralization --- immobilization --- precipitation --- nitinol --- continuous vertical cast (CVC), NiTi rod --- atomic layer deposition --- corrosion properties --- potentiodynamic test --- electrochemical impedance spectroscopy --- rare earth elements --- recycling --- NdFeB --- magnet --- non-ferrous metals --- cavitation erosion --- optical microscopy --- electron microscopy --- atomic force microscopy --- aluminium --- thin-layer electrolysis --- molten salts --- halides --- capillary cell --- electrorefining --- non-commercial copper anode --- waste solution --- high content --- Ni --- Pb --- Sn --- Sb --- passivation --- anode slime --- pentlandite --- oxidation --- reaction mechanism --- phase analysis --- silver --- copper --- nanoparticles --- antibacterial --- MnO2 --- cobalt oxide Co3O4 --- perovskite materials --- oxygen reduction in alkaline media --- electrocatalyst --- Pt catalyst --- nanocomposite --- mixed oxides --- NiAl2O4 --- ZnAl2O4 --- electrocatalysis --- nanocatalyst --- noble metal nanoparticles --- leachate --- metal ions extraction --- selectivity --- Fe removal --- electrodeposition --- conductometry --- n/a

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Unit metallurgical operations processes are usually separated into three categories: 1) hydrometallurgy (leaching, mixing, neutralization, precipitation, cementation, and crystallization); 2) pyrometallurgy (roasting and smelting); and 3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). In hydrometallurgy, the aimed metal is first transferred from ores and concentrates to a solution using a selective dissolution (leaching or dry digestion) under an atmospheric pressure below 100 °C and under a high pressure (40-50 bar) and high temperature (below 270°C) in an autoclave. The purification of the obtained solution was performed using neutralization agents such as sodium hydroxide and calcium carbonate or more selective precipitation agents such as sodium carbonate and oxalic acid. The separation of metals is possible using a liquid/liquid process (solvent extraction in mixer-settler) and solid–liquid (filtration in filter-press under high pressure). Crystallization is the process by which a metallic compound is converted from a liquid into a solid crystalline state via a supersaturated solution. The final step is metal production using electrochemical methods (aqueous electrolysis for basic metals such as copper, zinc, silver, and molten salt electrolysis for rare earth elements and aluminum). Advanced processes, such as ultrasonic spray pyrolysis and microwave-assisted leaching, can be combined with reduction processes in order to produce metallic powders.

Technology: general issues --- History of engineering & technology --- Mining technology & engineering --- zirconium --- eudialyte --- hydrometallurgy --- basic sulfate precipitation --- macroporous polymer --- goethite --- factorial design --- desorption --- tailings reprocessing --- early stage cost estimation --- magnetic separation --- leaching --- flotation --- silica --- ultrasonic spray pyrolysis --- synthesis --- acid mine drainage --- red mud --- neutralization --- immobilization --- precipitation --- nitinol --- continuous vertical cast (CVC), NiTi rod --- atomic layer deposition --- corrosion properties --- potentiodynamic test --- electrochemical impedance spectroscopy --- rare earth elements --- recycling --- NdFeB --- magnet --- non-ferrous metals --- cavitation erosion --- optical microscopy --- electron microscopy --- atomic force microscopy --- aluminium --- thin-layer electrolysis --- molten salts --- halides --- capillary cell --- electrorefining --- non-commercial copper anode --- waste solution --- high content --- Ni --- Pb --- Sn --- Sb --- passivation --- anode slime --- pentlandite --- oxidation --- reaction mechanism --- phase analysis --- silver --- copper --- nanoparticles --- antibacterial --- MnO2 --- cobalt oxide Co3O4 --- perovskite materials --- oxygen reduction in alkaline media --- electrocatalyst --- Pt catalyst --- nanocomposite --- mixed oxides --- NiAl2O4 --- ZnAl2O4 --- electrocatalysis --- nanocatalyst --- noble metal nanoparticles --- leachate --- metal ions extraction --- selectivity --- Fe removal --- electrodeposition --- conductometry --- zirconium --- eudialyte --- hydrometallurgy --- basic sulfate precipitation --- macroporous polymer --- goethite --- factorial design --- desorption --- tailings reprocessing --- early stage cost estimation --- magnetic separation --- leaching --- flotation --- silica --- ultrasonic spray pyrolysis --- synthesis --- acid mine drainage --- red mud --- neutralization --- immobilization --- precipitation --- nitinol --- continuous vertical cast (CVC), NiTi rod --- atomic layer deposition --- corrosion properties --- potentiodynamic test --- electrochemical impedance spectroscopy --- rare earth elements --- recycling --- NdFeB --- magnet --- non-ferrous metals --- cavitation erosion --- optical microscopy --- electron microscopy --- atomic force microscopy --- aluminium --- thin-layer electrolysis --- molten salts --- halides --- capillary cell --- electrorefining --- non-commercial copper anode --- waste solution --- high content --- Ni --- Pb --- Sn --- Sb --- passivation --- anode slime --- pentlandite --- oxidation --- reaction mechanism --- phase analysis --- silver --- copper --- nanoparticles --- antibacterial --- MnO2 --- cobalt oxide Co3O4 --- perovskite materials --- oxygen reduction in alkaline media --- electrocatalyst --- Pt catalyst --- nanocomposite --- mixed oxides --- NiAl2O4 --- ZnAl2O4 --- electrocatalysis --- nanocatalyst --- noble metal nanoparticles --- leachate --- metal ions extraction --- selectivity --- Fe removal --- electrodeposition --- conductometry