In an experiment, with hydrochloric acid as leaching agent and NaClO₃ as oxidizing agent, lithium was selectively leached from cathode material of spent lithium iron phosphate battery, and the effects of factors, including dosage of hydrochloric acid, solid-liquid ratio and reaction time, on the lithium leaching rate were investigated. It is shown that with an addition of hydrochloric acid at an amount of 1.0 time theoretical value, solid-liquid ratio of 1∶3 and reaction time of 3 h, the average lithium leaching rate can reach 99.33% by using this process. After that, magnesium hydroxide and sodium hydroxide were added into the raffinate in turn to remove impurities of P, Al and Fe. And then, the obtained solution was used to prepare Li₂CO₃ at 95 ℃ by adding anhydrous sodium carbonate. After water washing to remove NaCl, a high purity Li₂CO₃ (99.62%) can be obtained, which meets the industrial standard for industrial-grade lithium carbonate.

The impact of large-diameter pressure-relief borehole arrangement and drilling parameters on roadway stability was studied. It is found that arrangement of boreholes in a two-row pattern, compared to boreholes in a single-row pattern, can benefit stress shift and control of roadway deformation. By adopting the arrangement of boreholes in a single-row pattern and a two-row pattern, the deformation at both sides was reduced by 6.05% and 15.44% respectively, and the original maximum stress was reduced from 39.61 MPa to 33.50 MPa and 32.70 MPa respectively. It is also found that boreholes should be arranged, as much as possible, near the center of two sides, penetrating the plastic zone to the place with the maximum stress. And the spacing between boreholes should be determined based on the horizontal distance of the plastic zone of boreholes, and the burden spacing should be less than the height of stress-relaxed zone.

In the actual production, not only the copper oxide ore has a high content of slime, but also the copper minerals therein are prone to be lost during the beneficiation. In consideration of these problems, a cyclone desliming system was added to process the tailings after the copper sulfide was preferentially floated. The industrial experiment results show that a copper oxide concentrate grading 19.20% Cu can be obtained with the process recovery of 76.24% by adopting a direct sulphidizing flotation process to reclaim copper oxide minerals from copper sulfide flotation tailings, and the copper grade of tailings can be reduced to 0.94%. After copper sulfide flotation tailings were deslimed by cyclone, a process consisting of flotation of copper oxide minerals from underflow and a wet leaching to recover copper resource from fine slime (overflow) was adopted, resulting in a comprehensive copper oxide concentrate with Cu grade of 24.63% and process recovery of 85.55%, and the final tailings with Cu grade reduced to 0.60%. The indices of the copper oxide concentrate from the flowsheet containing cyclone desliming process are obviously superior to those by direct sulphidizing flotation process. Besides, this flow is relatively simple with reduced unit consumption of reagent for copper oxide flotation.

A lead-zinc deposit is rich in valuable metals of gold and silver. In order to improve the economic benefits of products, the associated gold and silver should be enriched in lead concentrate to the maximum extent. Based on the actual situation in the production, the distribution of associated gold and silver in the products after mineral processing was ascertained, and then optimization tests were perform. The results showed that most of the associated gold and silver were concentrated in the lead concentrate, and the recovery of gold and silver was positively correlated with the recovery of lead. Without altering the original reagent regime for lead flotation, ethyl xanthate was introduced as an auxiliary collector in a close-circuit test adopting a flowsheet consisting of one stage of roughing, two stages of cleaning and two stages of scavenging. And the obtained lead concentrate with grade around 50% can have a high enrichment of gold and silver and a low content of zinc. It is concluded that gold and silver resources can be comprehensively recovered, which can bring in the maximized economic benefit.

Experiments of roasting and leaching of some sulfur concentrate were performed, and the effects of two schemes with fixed bed roasting and fluidized bed roasting on gold extraction were analyzed. The results showed that with the sulfur concentrate at a sizing of 80% -0.074 mm, the proper conditions for a fixed bed roasting included a roasting temperature of 650 ℃ and roasting time of 4 h; while the proper conditions for a fluidized bed roasting included a roasting temperature of 650 ℃ and roasting time of 3 h, roasting gas and material in a ratio of 2.1 m³/kg. The calcines obtained by these two roasting methods were then separately leached for 24 h with the slurry concentration of 33% and pH of 11.5, 2 h alkali treatment and CG505 dosage of 10 kg/t, resulting in the leaching rate of gold reaching 69.45% and 69.92% respectively. It is shown that the fluidized bed roasting can bring in a better gold extraction result. This research results can provide a technical basis for recovery of valuable elements from sulfur concentrate.

The concentration of plume caused by hydraulic collecting system during deep-sea polymetallic nodules mining under different working conditions were analyzed. Test results show that the concentration of discharged plume from conveying system is much higher than that of sediment plume caused by the disturbance of capture system, which is one of the main causes of turbidity current in the sea. In the test, the curve of slurry concentration presented a steep upward trend line followed by a steep downward line. Increasing oil pressure of the pump of capture system will lead to higher concentration of slurry. However, the oil pressure of the pump of conveying system won't result in obvious variation in slurry concentration.

An orthogonal experiment was performed for laser welding of 5 mm ZL114A and 6061 aluminum alloys, and the influences of welding parameters on the microstructure and mechanical properties of welded joint were investigated. It is shown that the influences of three parameters of laser welding power, defocus and welding speed are in a descending order. With laser welding power of 3 kW, welding speed of 16 mm/s and the defocus of -3 mm, the welded joint has an average tensile strength of 208.03 MPa and the elongation of 5.16%. Compared to ZL114A and 6061 aluminum alloy, the tensile strength is reduced to 64.14% and 65.60%, respectively, while the elongation is reduced to 41.38% and 33.70%, respectively. The welded joint presents a mixed mode of brittle and ductile fracture when failing under tensile.

The spent cathode carbon block after aluminum electrolysis was treated by acid leaching with a mixed solution of sulfuric acid and ammonium sulfate, and the effects of factors, such as molar ratio of sulfuric acid to ammonium sulfate, liquid-solid ratio, leaching temperature and time, on the leaching rate of cryolite from this spent cathode carbon sulfate were investigated. The results show that at a leaching temperature of 70 ℃, with liquid-solid ratio of 8 mL/g, sulfuric acid and ammonium sulfate in a molar ratio of 4, a 120-min leaching process can lead to the leaching rate of cryolite up to 99.48%. The leaching residue, being composed of carbon and calcium fluoride and free of leaching toxicity, can be treated as a general solid waste.

A complex precipitation method was adopted to synthesize CuO nanoparticles, and its morphology and structure were characterized. Then, the CuO nanoparticles were taken as the activator in the degradation of ofloxacin with persulfate. Based on the advanced technology of activated persulfate oxidation, the influences of different parameters, including concentration of K₂S₂O₈ and an initial pH of the ofloxacin solution, on the degradation activity of ofloxacin in the wastewater were investigated. It is found that the degradation rate can reach 95.6% with 10 mg/L of ofloxacin in the wastewater with an initial pH of 3.5, by adding 0.003 0 g/L CuO and 1.0 mmol/L K₂S₂O₈. The experiments on capturing free radicals show that SO₄^-· and O₂^-· are active species for the catalytic degradation of ofloxacin, which is possibly the catalytic reaction mechanism.

ZnO narowires were synthesized by adopting hydrothermal synthesis, and ZnO/activated carbon composite material was then prepared by compounding activated carbon powder and nano-ZnO. The research on the sensing performance of such composite to ethanol gas shows that the sensor with ZnO/activated carbon composite presents good response and recovery characteristics to ethanol gas at 150 ℃. Its sensitivity to the ethanol with concentration of 5 × 10^-6 can be up to 4.75, and will increase positively with the increase of ethanol concentration, which presents a reproducibility and stability.