The tailings from gravity separation of cassiterite in a polymetallic ore from Guangxi Zhuang Autonomous Region were taken for experimental research. Due to its low grade, fine particle size of target minerals therein and similar floatability of tourmaline and cassiterite, a multiple ligand metal-group collector, CSC-BHA-Pb, and a high-efficiency depressant, XY1, were adopted to selectively inhibit gangue minerals dominated by tourmaline while efficiently enrich fine-grained cassiterite. On the basis of iron removal and desulfurization, an open-circuit flotation test of cassiterite, consisting of one roughing, one scavenging and seven cleaning, finally produced a tin concentrate with a Sn grade of 14.05% and a recovery of 28.79%, achieving efficient tin enrichment.

A roasting and acid leaching process was adopted to extract lithium from a low-grade clay-type lithium ore with a Li₂O grade of 0.13%. After exploration of the effects of various factors on lithium leaching rate, including roasting temperature, roasting time, and mass fraction of sulfuric acid, liquid-solid ratio, leaching temperature and leaching time in acid leaching process, the optimal experimental conditions were determined as follows: roasting at 500 ℃ for 1 h, leaching at 95 ℃ for 60 min with sulfuric acid at a mass fraction of 15%, and liquid-solid ratio of 6 mL/g. Under these conditions, the lithium leaching rate can reach 85.26%, indicating that efficient leaching of lithium from such low-grade clay-type lithium ore can be actualized. XRD and SEM analyses of the samples before and after leaching show that lithium leaching is attributed to the exchange between hydrogen ions in the sulfuric acid solution and lithium ions in the mineral.

Heavy metal pollution in Dalong River was assessed by field sampling and detection analysis. Hg(II) and Pb(II) in the water and sediment were adsorbed with sludge-derived biochar for ecosystem restoration in Dalong River, and the restoration effect was then compared with that by using activated carbon. The results indicate that heavy metal pollution in Dalong River is relatively slight, and the contents of heavy metals in the surface water at all sampling points are within a safe range, only the sediment at some sampling points has the heavy metal pollution at a light pollution level. It is shown that sludge-derived biochar has a good adsorption for Hg(II) and Pb(II), with the adsorption process conforming to the Langmuir isotherm (with R² of 0.932 2 and 0.998 9). Compared with activated carbon, the sludge-derived biochar can bring better restoration effect, and its desorption of Hg(II) and Pb(II) also shows that it can have a significantly better fixation effect of heavy metals.

An experimental study was carried out to address problems of higher grade of iron in the tailings from 1^st-stage high intensity magnetic separation (HIMS) and higher metal losses in the production of Lilou Iron Mine in Anhui Province. In the study, the low-intensity magnetic separator (LIMS) used before 1^st-stage HIMS was replaced with a CCT-A high-gradient permanent magnetic drum separator, and the HIMS process consisting of one roughing and one scavenging was optimized to a HIMS process consisting of one roughing and two scavenging. With these measures, both strongly and weakly magnetic minerals can be effectively recovered. The 1^st-stage scavenging tailings have the iron grade decreased by around 1 percentage point, and nearly 40 000 tons of iron concentrate can be recovered annually, which can bring remarkable economic benefits to the mine.

With a copper sulfide ore from Jiangxi Province taken in the research, an experimental study was carried out for enhancing the recovery of associated Au by flash flotation. In a laboratory test, the underflow of secondary-stage classification was subjected to an open-circuit flash flotation consisting of two-stage roughing and two-stage scavenging, leading to the Au grade up from 16.60 g/t to 140.60 g/t, presenting good floatability. Additionally, the Cu grade in the concentrate from flash flotation cell is higher than that in the main process, which proves that flash flotation of classification underflow will not affect the Cu recovery from the main process. Industrial practice demonstrates that with the ores of different Au grade, the Au recovery rate has increased after technical transformation. A size analysis by sieving reveals that those fully liberated minerals within conventional size fraction in classification underflow can be mainly recovered by flash flotation, thus being prevented from overgrinding due to returning to the grinding mill.

An experimental study on flotation separation was conducted for a gold-antimony concentrate with grade of Sb and Au at 20.66% and 98.95 g/t, respectively, from Russia. In an experiment on antimony floatation while suppressing sulfur by adding efficient sulfur depressant of BK526, activator of lead nitrate, and collector of ammonium dibutyl dithiophosphate, the gold-antimony concentrate was ground to a fineness of -0.045 mm 86%, sodium sulfide and activated carbon was added to remove reagent and sulfuric acid was used to adjust the pulp pH to be acidic. Finally, it produced an antimony concentrate grading 51.56% Sb at 86.06% recovery, and a gold concentrate grading 108.35 g/t Au and 4.41% Sb, with gold recovery of 71.20%. It is shown that stibnite and gold-bearing pyrite can be efficiently separated.

Based on analysis of chemical composition, mineral composition, main mineral properties and disseminated grain size of slag from smelting of nickel laterite ore, a series of exploratory experiments were carried out. The iron in the slag was recovered by magnetizing roasting and magnetic separation. The magnetizing roasting is performed for 40 min at 750 ℃ with a coal powder at a ratio of 2%. The roasted ore is subjected to a two-stage low-intensity magnetic separation (LIMS) after being ground to a fineness of -0.045 mm 80%, and an iron concentrate grading 60.38% Fe can be obtained at recovery of 71.55%.

In combination with experiments and multi-step finite element simulation, the residual stress distribution in components manufactured by laser powder bed fusion (LPBF) and the influence of the initial residual stress field on the laser shock peening (LSP)-induced compressive residual stress field. The validity of the simulation results was verified by the residual stress values measured with X-ray diffraction. The results show that the thermal stress of the lower and middle layer materials in the component fabricated by LPBF undergoes a transition from zero stress, compressive stress, tensile stress to compressive stress, while the top layer material shows a transition from zero stress, compressive stress to tensile stress, thus leading to tensile residual stress occurred on the surface layer of LPBF fabricated component, while compressive residual stress in the lower part. The action of initial residual stress field results in the reduced peak value but increased depth of LSP-induced compressive residual stress. The initial residual tensile stress field of LPBF components can exert a suppressive and dragging effect on the reverse plastic deformation caused by surface waves, leading to reduced intensity and changed position of the “residual stress hole”, which can improve the uniformity of LSP-induced residual stress distribution.

In Meishan Iron Mine, the iron concentrate produced on the site has SiO₂ grade more than 6.0%. Aiming at this problem, an experimental study was carried out based on the microscopic identification of different concentrate products by using a new process flow, in which the magnetic field intensity of low-intensity magnetic separation (LIMS) was reduced for roughing, and a process of regrinding and re-separation was added for the scavenging concentrate by high-intensity magnetic separation (HIMS). The effects of those technical transformation on the TFe grade of iron concentrate and the content of impurity SiO₂ therein were explored. The results show that after such technical transformation, the LIMS can produce a concentrate grading 63.57% TFe and 3.37% SiO₂ with corresponding recoveries of 72.79% and 12.94%, with a yield of 52.21%; while the HIMS can produce a concentrate grading 44.79% TFe and 9.07% SiO₂ with corresponding recoveries of 17.20% and 11.67%, with a yield of 17.51%. This new flowchart can produce the concentrate grading 58.85% TFe and 4.80% SiO₂ at corresponding recoveries of 89.98% and 24.61%, with a total yield of 69.72%. It is shown the SiO₂ content in the total concentrate of Meishan Mine can be greatly reduced.

To extract rare earth elements (REE) of yttrium (Y) and cerium (Ce) from yttrium aluminium garnet (YAG) fluorescent powder, experiments were performed for YAG by adopting direct acid leaching and roasting-acid leaching process, respectively. The effects of various factors on the leaching rates of Y and Ce were investigated, including roasting agent types and dosage, roasting temperature, roasting time, as well as leaching temperature and leaching time. It is shown that YAG fluorescent powder is stable in structure, while Y and Ce elements therein, not in the form of simple oxides, cannot be effectively extracted by direct acid leaching; a roasting pretreatment can effectively destroy the structure of YAG fluorescent powder, and convert the rare earth elements into oxides, which is beneficial to the following acid leaching process. After 2 h roasting at 900 ℃ with YAG and Na₂CO₃ in a mass ratio of 1∶0.5, and then 1 h leaching at 60 ℃ with HCl at a concentration of 3 mol/L, a liquid-solid ratio of 20 mL/g, and 1.2 mL/g of hydrogen peroxide, the leaching rates of Y and Ce can reach 97.23% and 84.91%, respectively.