Although cyanide is a widespread leaching reagent for the recovery of precious metals, there still are continuing investigations on alternative processes due to the related environmental problems concerned. Thiosulphate leaching of precious metals is one of the processes that were developed as an alternative and nontoxic technique to conventional cyanidation. The aim of this experimental study was to investigate the possibilities of leaching gold and silver in ammoniacal thiosulphate solutions on a laboratory scale. Samples used in the experiments were taken from Ovacık Gold Mine, located in the Bergama region of Turkey. The influence of temperature, copper sulphate concentration, ammonia concentration, thiosulphate concentration, sodium sulfite concentration, and solid–liquid ratio on gold and silver leaching recoveries was investigated and optimum leaching conditions were determined. At these conditions, 99.57% Au and 95.87% Ag leaching recoveries were achieved.

Many industries, especially mining and metallurgy, deal with solutions containing ions. In some cases, these metal ions need to be concentrated and recovered from solutions and sometimes removed from wastewater. The ion flotation method has been applied for wastewater and water...

In this study, solvent extraction is applied for extracting nickel from sulfate solutions containing iron and cobalt ions. This process can also be applied for the cleaning of waste solutions and for increasing solution concentrations after the leaching of low-grade nickel ores. Di-2-Ethylhexyl phosphoric acid (D2EHPA) was used as an extractant for this purpose. Effects of pH, aqueous/organic (A/O) phase ratio, iron, and cobalt ion contents of the solution on nickel extraction efficiency were investigated. The McCabe-Thiele diagrams for extraction and stripping steps were developed to determine the number of stages required. A total of two stages were required for 96.3% of Ni extraction and a total of two stages to strip nickel with 98% efficiency.

Recycling provides environmental benefits, such as energy savings, reduced volumes of waste, and reduced emissions associated with energy savings. Cell (mobile) phones are widely circulated in much of the world at the same time. Less than one percent of the millions of cell phones retired and discarded annually are recycled. Almost all the materials used to manufacture a cell phone can be recovered where metals, plastics, batteries, and packaging materials can be recycled and turned into new products. In this study, recycling technologies are summarized and, as a case study; the possibility of recovering valuable metals from waste cell phones by using acidic leaching was studied. The process steps include dismantling waste mobile phones, pre-processing to liberate the materials, and directing them to final treatment processes. In the leaching experiments, sulfuric, nitric, and hydrochloric acids are used. In the sulfuric acid leaching experiment, the effects of acid concentration, temperature, peroxide addition, and leaching periods on metal dissolution efficiencies are investigated. Leaching efficiencies of 97.9% Fe in 8 M H2SO4 solutions, 89% Pb, 100% Ni, 90.4% Co, and 4.1% Cu in 1M HNO3 solutions, 100% Pb, and 100% Al in 4 M HCl solutions were found in one hour.

Pyrometallurgical extraction of metallic copper from copper concentrates generates several by-products, among which copper slag constitutes one of the most voluminous solid residues. These slags are generally composed of iron oxides, silica, calcium oxide, alumina, and varying amounts of unrecovered copper. Despite their common disposal by stockpiling or use as landfill material, copper slags may still host appreciable quantities of valuable metals occurring as entrapped metallic particles, sulphide phases, or oxidized compounds. For this reason, different recovery routes have been investigated and applied, including mineral processing methods as well as pyro-, hydro-, and combined pyro-hydrometallurgical treatments. Among these approaches, flotation is particularly important in copper slag beneficiation and is already integrated into several industrial smelting circuits. This review examines the characteristics of smelting, converting, refining, and ancient copper slags formed during pyrometallurgical copper production, together with the main strategies proposed for recovering metals from these secondary resources. Selected examples from laboratory-scale studies carried out on various industrial copper slags from Turkey are also presented. In addition, the environmental implications of copper slag management and the sustainability aspects of slag treatment are considered.