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In the oxygen-enriched side-blown smelting furnace for the treatment of electroplating sludge, fluent was used to simulate the gas–liquid two-phase flow process. The relationship between the lance diameter, lance inclination, bath depth, and the bath evaluation indicators were studied, and the oxygen lance spacing was optimized. The results show that the high velocity and high gas rate areas were near the oxygen lance, while the stirring dead zones with low velocity appeared in the central and bottom areas of the molten pool. The key parameters were optimized using single-factor analysis and multifactor comprehensive optimization. The results showed that the bath evaluation indicators were all at good levels under the optimal parameter conditions. These were comprehensively obtained as the following: the lance diameter was 25 mm, the lance inclination was 15°, the lance spacing was 1050 mm, and the bath depth was 1500 mm. The industrial test carried out in an environmental protection enterprise in Guangdong achieved satisfactory results. The test shows that the electroplating sludge containing 7.24% Cu can be melted at 1300~1400 °C to obtain matte. Compared with industrial copper slag, the smelting slag has a higher CaO and a lower Fe content.

A large amount of spent magnesia–chrome refractories is produced every year from nonferrous metallurgy industry in China. These spent refractories contain not only Mg and Cr but also a large amount of Ag, Pb, Bi, Cu, Sb and other valuable metals. This study proposes a high-efficiency, low-cost and recyclable technology for the treatment of spent magnesia–chromium refractories. In the hydrochloric acid–ferric chloride leaching system, under the conditions of hydrochloric acid concentration of 4.0 mol/L, liquid–solid ratio of 7:1, ferric chloride dosage of 4%, leaching temperature of 70 °C, leaching time of 90 min and stirring intensity of 500 rpm, Cr, Fe and Al are enriched in the leaching residue, and the recoveries are 92.26%, 78.30% and 97.34%, respectively. The extraction rates of Mg, Pb, Bi, Sb, Cu and Ag are 89.04%, 98.88%, 99.82%, 91.48%, 92.64% and 96.38%, respectively. The residue can be used as chromium products, whilst metal ion in the leachate can be precipitated as metallurgical raw materials. According to thermodynamic calculation and experiments, ferric chloride can greatly improve the leaching rate of copper, silver and bismuth in the hydrochloric acid system, depending on its own oxidation ability and increase the concentration of chloride ion.

Environmentally friendly flotation reagent, polyaspartic acid (PAPA), was tested as a potential selective depressant in the flotation separation of chalcopyrite and Cu-activated sphalerite. The depression mechanism of PAPA was revealed by contact angle measurements, Zeta potential measurements, Fourier transform infrared spectroscopy (FT-IR) analysis and inductively coupled plasma (ICP) measurement. The micro-flotation tests with single minerals showed that PAPA selectively depressed Cu-activated sphalerite, while chalcopyrite remained floatable. Moreover, a concentrate containing 31.40% Cu with a recovery of 92.43% was obtained in flotation tests of artificially mixed minerals. Results of contact angle measurements, Zeta potential measurements and FT-IR spectrum revealed that PAPA exerted a much stronger adsorption on Cu-activated sphalerite surface than on chalcopyrite surface, preventing the further adsorption of sodium diethyl dithiocarbamate (DDTC) on its surface. ICP measurements indicated that PAPA had an excellent complexing ability with Cu2+ in flotation pulp, weakening the activation of Cu species on sphalerite surface and producing selective depression.

Pneumatic separation was used to separate the valuable current collectors and harmful separators in spent lithium-ion batteries (LIBs) to avoid the plastic pollution caused by the separators in this study. Theoretical calculations for suspension velocities of the current collectors and separators indicate that they could be separated under special conditions. Furthermore, a special Z-shaped pneumatic separator was used to separate the current collectors and separators for the first time. Experiments for manually cut samples indicate that the efficiency of pneumatic separation is approximately 100% with the sizes and airflow velocities in the range of 3–4 cm and 6.96–7.8 m/s, respectively. Furthermore, industrial experiments of pneumatic separation indicate that the recoveries of the current collectors and separators are approximately 99.23% and 98.64%, respectively. Computer simulations of the separation process indicate that the turbulence and the changes in high-speed zones in the pneumatic separator benefit the separation of current collectors and separators. In conclusion, pneumatic separation is a promising technology to separate crushed current collectors and separators.

The application of waste alkali liquids as a substitute of sodium hydroxide for the saponification to improve the collection performance of fatty acids was investigated by saponification reaction test and flotation test. The results of the saponification reaction test indicated that the optimal conditions for the saponification were stirring rate of 55 r/min, initial temperature of 40 °C and stirring time of 45 min. Meanwhile, the laboratory scale and industrial scale flotation experiments showed that the fatty acid salt synthesized by wastewater achieved an index comparable to fatty acid sodium synthesized by sodium hydroxide. As a consequence, it was feasible to replace sodium hydroxide with the wastewater from zeolite production for fatty acid saponification. The cross-border utilization of waste alkali liquids not only reduced environmental pollution, but also produced excellent economic benefits.

The depression mechanism of zinc sulfate (ZnSO4) and sodium dimethyl dithiocarbamate (DMDC) as the combined depressant on sphalerite was investigated by micro-flotation experiments, ion complexing tests, contact angle tests and X-ray photoelectron spectroscopy (XPS) analysis. The micro-flotation tests revealed that ZnSO4+DMDC had a better selective depression effect on sphalerite than using single ZnSO4 or DMDC. Ion complexing tests confirmed that DMDC had a strong complexing capacity with lead ions or hydroxy complexes. Contact angle tests illustrated that ZnSO4+DMDC makes the sphalerite surface more hydrophilic than ZnSO4 or DMDC. XPS analysis indicated that the combined depressant could prevent collector adsorbing on the Pb-activated sphalerite surface by a competitive adsorption method, while the combined depressant and collector were co-adsorbed on galena surface.

Chalcopyrite is one of the most important copper minerals; however, the extracted efficiency of chalcopyrite is still not satisfactory in hydrometallurgy owing to its high lattice energy which leads to its low dissolution kinetics. To overcome the difficulties, many advanced technologies have been developed, including the selection of high effectively bacteria, the inhibition of the passivation film adhered onto the minerals surface, and the maintenance of solution redox potential under an optimum range. Up to date, considerable researches on the first two terms have been summarized, while the overview of the last term has been rarely reported. Based on corresponding works in recent years, key trends and roles of solution redox potential in copper hydrometallurgy, including its definition, effect and maintenance, have been introduced in this review.

Waste printed circuit boards (WPCBs) are an essential component in electronic waste (e-waste), and contain a number of valuable metals (e.g., Cu, Sn) as well as non-metal resources (e.g., brominated epoxy resin). Currently, most of the non-metals are disposed of in landfills, causing environmental problems. In this study, a combination of pyrolysis and physical separation is proposed to recover valuable resources, including both metals and non-metals, from WPCBs. The WPCBs were pyrolyzed at 700°C under a nitrogen atmosphere. Pyrolysis oil and gas can be reused as fuel for the pyrolysis of WPCBs. Metals like copper, tin, and iron in the pyrolysis residues were separated by selective crushing, sieving, gravity separation, and magnetic separation. Finally, rich copper (Cu 82.21%, Sn 1.47%), rich tin (Cu 53.20%, Sn 13.43%), rich iron (Fe > 63%), and non-metal products were obtained, and the total recoveries of copper, tin, and iron were 95%, 86%, and 76%, respectively.

Xanthan gum (XG), a clean, non-toxic macromolecular polysaccharide, was studied as a depressant in the flotation separation of scheelite from calcite. Its selective inhibition mechanism was investigated by adsorption experiments, fourier transform infrared spectroscopy (FTIR) analysis and X-ray photoelectron spectroscopy (XPS) analysis. It was found that the XG exhibited a strong selective depressive effect on calcite. However, XG had minimal effect on the flotation recovery of scheelite. Adsorption experiments indicated that the adsorption density of XG on the surface of calcite was much higher than that of scheelite. FTIR results indicated that XG was selectively chemisorbed on calcite surface, while sodium oleate (NaOL) can still be chemisorbed on scheelite surface in the presence of depressant XG. XPS results indicated that the carboxyl groups ( COO−) of the XG can be chemically chelated with the calcium ions species on calcite surface. It was intuitively observed by atomic force microscopy (AFM) that the coverage and adsorption density of XG on calcite surface were higher than that of the scheelite surface. As such, the calcite surface adsorbed more depressant XG than that of scheelite, which hindered the further adsorption of the collector NaOL. This greatly deteriorated the flotation of calcite and achieved flotation separation between the two minerals.

In this paper, the effect of a probe tip on the contact angle measurements and the formation process of nanobubbles based on line tension and pinning theory was investigated. In this investigation, the images of nanobubbles and micropancakes on mica(001) and molybdenite(0001) surfaces were obtained during an alcohol-water exchange by means of atomic force microscopy (AFM) in tapping mode (TMAFM). Based on the image characteristics and the theory of line tension and pinning, a new point of view is presented: the contact angle of a nanobubble is not always a large obtuse angle but is an uncertain value; its true value is affected by the curvature radius of the AFM probe tip, and the value is close to the macroscopic contact angle. Meanwhile, the formation of nanobubbles is affected by the surface tension, line tension and pinning.

The influence of humic acid on the flotation of galena under different redox conditions was studied based on micro-flotation experiment. The results showed that the humic acid was an effective inhibitor for moderately oxidized galena. Adsorption tests indicated that the surface oxidation played an incredibly important role in the adsorption of humic acid on galena surface. Explorations on identifying the mechanism for the selective adsorption of humic acid on the surface of oxidized galena were carried out by Zeta potential, XPS and FT-IR analysis. The results indicated that the oxidation of galena caused significant changes in surface components, which was beneficial to the adsorption of humic acid. The elemental sulfur formed by the oxidation of galena is one of the adsorption sites for humic acid besides lead sulfate.

In this paper, pectin, a polymer polysaccharide, was studied for its depression during the selective flotation separation of scheelite from calcite. Zeta potential experiment, FTIR analysis and XPS analysis were used to explain the selective depression mechanism of pectin on the two minerals. The microflotation experiment showed that the pectin had a strong depressive effect on the calcite, but had little effect on the floatability of the scheelite in the pH range of 7–9. The flotation recovery of calcite dropped sharply to 4.56%, while scheelite still maintained a high flotation recovery of 71.01% at pH 7.5. A series of mechanism experiments showed that the localized ions on the surface of scheelite and calcite were mainly tungstate and calcium species, and the dominant component on the calcite surface was mainly positively charged calcium species. The carboxyl groups on the pectin molecular chains can be chemically chelated with the calcium species on the calcite surface and adsorbed on the calcite surface. The large amount of adsorption of pectin hindered the further adsorption of the collector sodium oleate (NaOL) on calcite surface, thereby greatly reducing the floatability of calcite, and finally achieving the flotation separation of the two minerals. Finally, the adsorption model of pectin and the separation model between the two minerals can be obtained.