In order to solve the problem of high water content in JISCO iron concentrate, dewatering tests were conducted by adding filtration aid. The results show that the filtration aid, CYG-1, can improve filtration effect. With the addition of CYG-1 at an amount of 500 g/t, the water content in the filter cake of iron concentrate falls by 2.31 percentage points compared to the practice without adding filtration aid.

In Bangzhong Zinc-Copper Mine in Tibet, a mining method consisting of stoping followed by backfilling is adopted to excavate ores. In order to further improve production efficiency and economic benefits in the mine, rock mass quality was classified based on the investigation of geoengineering and geomechanics and rock mechanics test, and key factors influencing stability of stopes were analyzed in combination with the layout of mining and cutting engineering. On this basis, stope structure parameters were optimized by using a variety of empirical stability charts. The results show that the improved stability chart is highly adaptable and a stop with span extended from 12.5 m to 20 m can still meet safety requirement in the mining production.

Based on an introduction of Japan's operation mechanism for exploiting deep-sea mineral resources, including Japan's marine policies, management and implementation agencies related to ocean mining, as well as Japan's coordination mechanisms for pushing progress in ocean technologies, Japan's cross-ministerial Strategic Innovation Promotion Program is outlined in terms of ocean mining, and the research achievements made by Japan in this field are also summarized. Such research on Japan's management system and program for exploitation of deep-sea mineral resources can be of reference for China in developing strategies, formulating investment mechanism and coordination mechanism for deep-sea mining.

With gold tailings as aggregate and ground gold mine tailings (referred to as gold mine tailings powder) as precursor materials, a kind of backfill material was prepared by alkali activation with sodium hydroxide together with sodium silicate as an activating agent. The effects of several factors, including particle size of gold mine tailings powder, modulus and addition of activating agent, on the mechanical properties of backfill mass were studied. The test results show that when gold mine tailings is ground for 60 min (size d₅₀ of 5.939 μm), modulus and addition of sodium silicate in activating agent are 1.2 and 60% respectively, the prepared backfill mass can have a 28 d compressive strength of 854.2 kPa, completely up to the requirement for backfill mass stipulated in the GB/T 39489—2020 "Technical Specification for Paste Filling with Total Tailings". Due to alkali activation, gold mine tailings powder is subjected to a hydration reaction, yielding a large amount of aluminosilicate gel, which forms a dense and stable structure, resulting in the backfill mass with good mechanical properties.

A commercially applied large ball mill with an effective internal diameter of 4.6 m is taken for study, and the discrete element method (DEM) was introduced to simulate and investigate the influence of filling rate of grinding media (steel balls) on the collision of particles inside the mill and energy consumption. It is found that when the filling rate of grinding media is 30% - 35%, the frequency of ball-ore collision increases gradually. However, the ratio of ore-ore collision frequency to the total collision frequency increases first and then decreases, and the energy loss for ball-ball and ball-liner collisions increases. It can be seen that increasing filling rate of grinding media may not only reduce grinding efficiency and increase energy loss, but also increase liner wear by steel ball, which is not conducive to sustainable usage of mill liner.

A shear creep test was performed for weak intercalation in order to investigate influence of creep characteristics of weak intercalation on slope stability. The obtained curve from the test was fitted according to Cvisc creep constitutive model, and the creep of slope with weak intercalation was calculated by using finite difference method to analyze the variation in long-term displacement and shear strain increment of the slope. The results show that the weak intercalation has typical creep characteristics. The results obtained from the numerical calculation with Cvisc model are basically consistent with the actual monitoring data. The creep characteristics of weak intercalation cause not only increase in the displacement, but also significant changes in the distribution form and orientation of the overall displacement of the slope, especially greater displacement at the top and in the middle of the slope. As a result, the slope body experiences an increment in the shear strain, which is then expanded and finally tends to stable.

Flotation tests were conducted for a complex refractory copper-lead-zinc polymetallic sulfide ore bearing arsenic and silver. By using a new high-efficient sulfide ore collector (CYC) and an environment friendly lead depressant (CYZ), the test with a flowsheet consisting of rough grinding, copper-lead-silver bulk flotation, classification and regrinding, reagent removal and Cu/Pb separation produced a copper concentrate grading 22.42% Cu and 11 549.74 g/t Ag with corresponding recoveries of 73.77% Cu and 83.85% Ag, as well as a lead concentrate grading 13.96% Pb and 6.61% Sb with corresponding recoveries of 19.45% Pb and 11.10% Sb. It is shown that with this technique, an efficient Cu/Pb separation can be actualized, while the associated Ag and Sb minerals can also be reclaimed effectively.

Blown zinc powder, electric furnace zinc powder, zinc alloy powder and distilled zinc powder were respectively taken in the test of cobalt removal by arsenic trioxide purification process to investigate influences of several factors on cobalt removal effect, including an adding amount of zinc powder, temperature and time of reaction, a mole ratio of copper to cobalt and a mole ratio of antimony to cobalt. Results show that when copper sulfate is added with copper and cobalt in a mole ratio of 5.0, potassium antimony tartrate is added with antimony and cobalt in a mole ratio of 0.5, a reaction at 90 ℃ for 90 min, with rotation speed of 300 r/min and addition of zinc powder at an amount of 2 g/L, the cobalt removal rates by using 4 different kinds of zinc powder are 95.73%, 96.15%, 95.94% and 94.87%, respectively, indicating the cobalt removal effect of different powder in the following descending order: electric furnace zinc powder > zinc alloy powder > blown zinc powder > distilled zinc powder.

Based on the environmental characteristics of polymetallic nodules mining zone, different lifting modes for deep-sea polymetallic nodules, including continuous line bucket (CLB) system, autonomous submersible shuttle mining system and pipeline lifting system, were analyzed in terms of characteristics and applicability. With eight factors taken into consideration, including maneuverability, dry ore lifting capacity, launching and recovery efficiency, manufacturing and operation costs, suitability for water depth, adaptability to extreme sea condition and seabed disturbance, as well as environmental friendliness, a mathematical model covering multi-dimensional evaluation indices and an adaptability evaluation system were established. Analysis results show that CLB system and capsule pipeline lift system are not suitable for lifting polymetallic nodules, while autonomous submersible shuttle mining system, due to high cost in R & D, is not economically applicable. Due to the improvement in the reliability of underwater equipment and progress in the solution to sealing of heavy medium, pipeline lift system with heavy medium is expected to become a high-efficient lifting mode for deep-sea polymetallic nodules.

A technique process to remove impurities of calcium and magnesium from the leaching solution obtained after roasting plus leaching process of a sort of lepidolite was studied, and the effects of several factors on washing effect, including amount of sodium carbonate, solution pH, time and temperature of reaction and washing conditions, were all investigated. The results show that removal rates of calcium and magnesium can reach 99.9% and 93.1%, respectively, by adding sodium carbonate as precipitant at an amount of 2.21 mol/L, with pH of solution at 8.0, temperature of 25 ℃and time of 30 min. Then, the obtained calcium-magnesium residue was washed three times with a liquid-solid ratio of 1∶1, and 5 min for each time. As a result, products of calcium carbonate and magnesium carbonate can be obtained. It is concluded that this process, being simple and stable, can be adopted to effectively remove impurities of calcium and magnesium from leaching solution of lepidolite.