Ginkgo biloba biochar-based fertilizer prepared with Ginkgo biloba was used for remediation of heavy metal contaminated soil. After 4 d remediation at 30 ℃ by adding 4% ginkgo biloba biochar-based fertilizer, the stabilization efficiencies of Pb, Cd, and Cu can reach 89.5%, 97.5%, and 74.9%, respectively. It is shown that the contents of acid extractable Pb, Cd and Cu decrease from 43.81%, 60.53% and 65.31% to 12.21%, 52.75% and 60.47% respectively; the contents of reducible Pb and Cd decrease from 11.12% and 36.35% to 10.02% and 33.71% respectively; the contents of oxidizable Pb and Cd decrease from 14.36% and 0.76% to 11.61% and 0.74%, respectively, while the content of oxidizable Cu increases from 11.13% to 14.12%; the contents of residual Pb, Cd, and Cu increase from 30.71%, 2.36%, and 22.33% to 66.16%, 12.80%, and 24.19%, respectively. It is concluded that with strong stability and a good remediation effect at low cost, such ginkgo biloba biochar-based fertilizer shows a good application prospect in remediation of heavy metal contaminated soil.

Based on the study on reduction behavior of vanadium during the smelting of vanadium-bearing titanium concentrate in an electric furnace, the comprehensive recovery of vanadium resources was explored through experiments. The vanadium-bearing titanium concentrate from Yunnan Province was taken as raw material to carry out an industrial-scale smelting experiment in an electric furnace with different carbon ratios. Based on the thermodynamic theory, the distribution and influencing factors of vanadium element in slag-iron phase were all analyzed. The results show that with carbon ratio up from 6.5% to 14.0%, the mass fraction of TiO₂ in titanium slag increases from 54.12% to 92.51%, the proportion of vanadium element reduced into molten iron increases from 1.14% to 6.61%, and the proportion of vanadium element left in the titanium slag decreases from 92.95% to 88.17%. It is found that there is a small amount of vanadium in dust, accounting for about 5.5%, which has no significant correlation to carbon ratio. The smelting process of titanium slag is not conducive to vanadium reduction, which is principally attributed to carbon deficiency operation and low-basicity slag system. It is not economically feasible to extract vanadium from molten iron by smelting vanadium-bearing titanium concentrate in an electric furnace, so it is suggested that vanadium should be extracted from the vanadium mud obtained after refining and vanadium removal process of titanium dioxide.

According to the relative position between interbedded surrounding rock and the peripheral holes, the relationship between bedding planes and the connecting line of the adjacent blastholes was classified into three kinds. Mechanism for bedding planes bringing impact to crack propagation in rocks between blastholes by blasting under typical work conditions (with bedding planes on the perpendicular bisector of the connecting line of blastholes) was explored by the LS-DYNA numerical simulation; and the effect of bedding planes in a different relative position to the connecting line of blastholes on the blasting effect of surrounding rock was also studied. It is found that the propagation speed of blasting vibration waves in sandstone is slightly higher than that in sandy mudstone. Under blasting loads, the surrounding rock above both softer layer and the beddings suffer severe damage. The superposition of two-blasthole blasting vibration wave peaks intensifies the damage to the surrounding rock. The blasting effect is poor when the bedding plane penetrates the blastholes, but the blasting effect is ideal if the bedding plane is on the perpendicular bisector of the connecting line of blastholes.

Collophanite ore was taken in a test to explore the influence of fine particle entrainment content in return sand to grinding on grinding efficiency. It is found that the lower the fine particle entrainment content in return sand, the higher yield of the newly generated particles in the size range of -0.074 mm. Nevertheless, the increase in the yield of particles within the range of -0.025 mm has little to do with the entrainment content in return sand.

The effect of Sc on the microstructure and properties of Al-8.5Zn-2.3Mg-2.4Cu alloy was investigated. It is found that an addition of Sc can make the as-cast Al-Zn-Mg-Cu alloy with obviously smaller grain. As the Sc content (mass fraction) increases from 0 to 0.4%, the grain size of alloy decreases from 107.7 μm to 49.96 μm and the hardness increases from 116.8HV to 130.2HV. After hot-rolling process with large deformation quantity followed by 1 hour of solution heat treatment at 470 ℃, the Sc-containing alloy has higher dislocation density compared to the alloy without Sc addition, and the alloy with an addition of 0.4% Sc has a recrystallization rate dropped from 92.4% to 45.7% due to inhibition of its recrystallization behavior. After 24 hours of aging treatment at 120 ℃, the Al-Zn-Mg-Cu alloy with an addition of 0.4% Sc can be observed to have a large amount of spherical Al₃Sc particles and short rod-like η′ (MgZn₂) particles in dispersive distribution. Based on the plotted a crystal structure of Al₃Sc-MgZn₂ with coherent or semi-coherent interface with α (Al), it can be deduced that the Al₃Sc particles provide heterogeneous nucleation sites for η′ (MgZn₂) phase to promote its nucleation, which can promote precipitation hardening of the alloy.

Nickel, Cobalt and Manganese in the cathode materials of spent ternary lithium-ion batteries were recovered by leaching with a combination of citric acid and hydrogen peroxide. The possible reactions during the leaching process were analyzed, and the effects of factors, including citric acid concentration, mass fraction of hydrogen peroxide, leaching temperature, leaching time and liquid-to-solid ratio on the leaching rates of nickel, cobalt and manganese from cathode materials were also investigated. It is found that after 60 min leaching at 80 ℃ with citric acid at a concentration of 1.5 mol/L, hydrogen peroxide at a mass fraction of 8%, and a liquid-to-solid ratio of 25 mL/g, the leaching rates of nickel, cobalt and manganese are 97.58%, 97.35% and 96.12%, respectively. Then, an antisolvent crystallization method is adopted with ethanol as antisolvent agent to recover metals from the obtained leach liquor, leading to the crystallization rates of nickel, cobalt and manganese at 92.34%, 93.07% and 99.69%, respectively.

In order to find a reasonable disposal method for electrolytic manganese slag (EMS), effect of roasting at medium and high temperature on the content of manganese, sulfur and ammoniacal nitrogen in EMS was explored. The results show that after the EMS is directly roasted at 1 050 ℃ for 60 min, the mass fraction of S in the EMS sample falls from 9.11% to 0.87%, while the mass fraction of Mn goes up from 1.87% to 2.26%. After being washed with water, the EMS sample is then roasted with 3% coal (in mass fraction) at 1 000 ℃ for 60 min. As a result, the mass fractions of S and Mn in the obtained roasted sample drop down to 1.32% and 0.78%, respectively. It is found that after direct roasting process at medium and high temperature, EMS can meet the requirement of mass fraction of S for cement admixture, and also medium and high temperature roasting process can almost remove all ammoniacal nitrogen therein, presenting a good removal effect.

In order to investigate the main factors affecting the service life of graphite anodes used in preparation of rare earth metals, a range of analytical tools, including a digital microscope, an optical microscope, an SEM, XRD, a simultaneous thermal analyzer and a four-probe tester were employed for comparison and comprehensive evaluation of macroscopic and microscopic morphology, crystal structure, graphitization, thermal properties and resistances of graphite anodes with different service lives. The results indicate that the resistance, internal cracks and porosity of graphite anodes contribute mainly to the difference in the service life of graphite anodes. The research results can be of reference for selection of graphite anode in preparation of rare earth metals, thus providing technical assistance for enterprises to realize cost reduction and efficiency improvement.

Vanadium was extracted from vanadium-containing stone coal by adopting a process of sulphuric acid curing and water leaching, and the effects of sulphuric acid curing and water leaching conditions on vanadium leaching rate were investigated. It is found that the vanadium-containing stone coal is firstly subjected to a sulphuric acid curing process at 130 ℃ for 8 h, with an addition of H₂SO₄ at an amount of 25%；and then the obtained product is leached by water at 90 ℃ for 120 min, with liquid-solid ratio of 2∶1, resulting in the vanadium leaching rate of 90.79%. After the vanadium-containing leachate is oxidized with NaClO₃, the vanadium in the oxidized solution is adsorbed with D202, and then the vanadium in the resin is desorbed. The obtained solution after desorption is subjected to calcination, and vanadium pentoxide is produced with a purity up to 99.21%. It is shown that a total recovery rate of vanadium is 85.99%.

A cyanide-free leaching test was performed for the arsenic-carbon bearing gold ore from Laos, and effects of grinding fineness, pH value of pulp, concentration of slurry, and the dosage of golden cicadas environment-friendly leaching agent for gold on gold leaching effect were investigated. The results show that pre-treatment with hydrogen peroxide can improve the leaching rate of gold. With a grinding fineness of -0.074 mm 95% and an agitating speed of 2 000 r/min, the pulp is pre-oxidized with 500 g/t of hydrogen peroxide for 3 h, and then treated by 30 h agitation leaching with addition of lime at an amount of 3 000 g/t and golden cicadas environment-friendly leaching agent for gold at 5 000 g/t, leading to the residue grading 0.25 g/t Au and gold leaching rate of 92.27%. It is shown that this pretreatment with hydrogen peroxide can make gold leaching rate up by 1.96 percentage points.