In consideration of uneven distribution of seabed nodules and continuous travel of a collector vehicle during deep-sea mining operations, a CFD-DEM coupling approach was used to investigate the effects of particle abundance, traveling speed, and their combined actions on the collection efficiency of a wall-attached jet collector head and particle transport behavior. The results show that under static conditions, when particle abundance increases, more nodule particles enter the effective zone of the wall-attached jet, and collection efficiency rises accordingly. Nevertheless, excessively high particle abundance can lead to massive accumulation of particles in front of the pick-up mechanism, inhibiting continuous particle transport and lowering collection efficiency. It is found that the preferable particle abundance is 12.60 kg/m². Under dynamic working conditions, collection efficiency also exhibits a trend of initial increase followed by a decrease with increasing traveling speed. At too low traveling speed, particle supply cannot remain continuous, while at excessively high speed, the effective interaction time between particles and collector head is reduced. Both scenarios are unfavorable for stable particle transport. And collection performance is satisfactory with the traveling speed at 0.15-0.20 m/s. It is concluded that the particle transport near the pick-up mechanism is jointly governed by particle abundance and traveling speed. Higher collection efficiency depends on the appropriate balance among particle supply, effective interaction time and transport capacity of the pick-up mechanism.

To explore the lateral diffusion law of particle plumes resulting from a midwater discharge of sediment during deep-sea mining, effects of terminal velocity of settling particles and seawater-buoyancy-flux ratio of discharged fluid on plume diffusion process in density-stratified environments was studied by adopting large-eddy simulation. The numerical model was validated based on water-tank test, and it is found that the average relative error of the lateral diffusion radius for single-phase plumes is 2.94%, and the average error for particle plumes at stable stage is 5.3%. The results show that particle settling decreases the residual buoyancy of plume and diffusion layer moves upward. The lateral diffusion radius tends to stabilize after an initial increase with the growth of terminal settling velocity, and the corresponding dimensionless parameter at the critical terminal settling velocity is w_s/U_s≈0.1. The lateral diffusion radius reaches its minimum value when the density of discharged fluid is close to that of ambient seawater (P≈0). This study provides theoretical support for quantitatively optimizing parameters and controlling environmental impact of tailings discharge during deepsea mining operation.

To investigate the flow characteristics of sediments disturbed by the track of a collector vehicle during deep-sea mining, numerical simulations of continuous sediment disturbance by multiple grousers were conducted based on the Eulerian multiphase flow model. The mass and the dispersion velocity of disturbed sediments were analyzed, and the effects of in-situ disturbance, subsidence depth, and bottom-current velocity on the flow characteristics of sediments. The results indicate that when a collector vehicle travels 1.5 meters at a speed of 0.6 m/s, the mass of disturbed sediments at the water-sediment interface reaches 70.8 kg. After 2.5 seconds, the horizontal dispersion velocity of the plume reaches 0.37 m/s and the vertical dispersion velocity is 0.269 m/s. Subsidence depth increases, the dispersion intensity aggregates. In-situ disturbance causes more severe damage to the soil layer. Seabed bottom-current velocity, although being lower, can also bring influence to both the concentration and dispersion range of sediments.

The force acting on material particles in a dry magnetic separator was systematically investigated. It is found that the motion trajectory of particles during the separation is determined by the combined effects of material magnetic permeability, drum rotation speed of magnetic separator and magnetic field intensity. With a certain dry magnetic separator as an example, the dynamic separation process of materials during magnetic separation was calculated, and then verified by performing a test on dry magnetic separation of ilmenite. The results show that the average deviation between the predicted trajectory and the actual trajectory of simulated particles is within 8%. It is concluded that the dynamic simulation method can satisfactorily predict the motion trajectory of liberated magnetic minerals.

To improve low-temperature flotation behavior of the refractory low-grade scheelite ores from Henan, a combined collector HQ-3 (95%FX-6+5%PEG-2000) was developed to enhance the low-temperature flotation separation between scheelite and calcium-containing gangue minerals, and then flotation tests were conducted to determine reagent regime suitable for such scheelite. On that basis, a closed-circuit flotation test by adopting a flowchart consisting of low-temperature roughing and high-temperature cleaning was performed at a temperature ranging from 5 ℃ to 10 ℃, with 1 800 g/t of sodium carbonate as the regulator, 750 g/t of water glass as the depressant and 260 g/t of HQ-3 as the collector in the roughing stage. As a result, a scheelite concentrate grading 28.06% WO₃ was obtained at 85.15% recovery. It is shown that compared with FX-6, the combined collector HQ-3 can improve the recovery of WO₃ from the roughing stage at a low temperature by 10.89 percentage points.

To improve the recovery of associated precious metal Ag from an overseas lead-zinc ore, mineral processing tests were carried out based on raw ore process mineralogy. The results show that silver mainly occurs as exposed silver sulfide and encapsulated silver in sulfides. A process consisting of decarbonization and lime-free lead flotation was adopted, with aniline dithiophosphate as a collector, and zinc depressant CB-1 and auxiliary zinc depressant W-1 added in the roughing of lead flotation. As a result, a lead concentrate grading 56.70% Pb, 8.93% Zn and 1 432.30 g/t Ag was obtained, with corresponding recoveries of 80.73%, 2.13% and 59.07%, respectively. It is concluded that compared with the original lime-based process, the recoveries of Pb and Ag can be increased by 2.80 and 4.83 percentage points respectively, while in the lead concentrate, Zn grade can be decreased by 1.30 percentage points and Ag grade up by 35.80 g/t.

To realize quality improvement and desiliconization of high-silicon bauxite, binary and ternary collectors were prepared with sodium oleate as the main component, compounded with benzohydroxamic acid, sodium dodecyl sulfonate, sodium dodecyl sulfate and n-octanol, respectively. The effects of single collector, binary collector and ternary collector on the flotation of high-silicon bauxite were systematically investigated. The interaction mechanisms between diaspore and kaolinite in bauxite and the collectors were revealed via contact angle measurement, zeta potential test, Fourier transform infrared spectroscopy and reagent adsorption capacity analysis. The results indicate that flotation performance of binary collectors is obvious superior to that of single collector. Flotation with sodium oleate combined with benzohydroxamic acid at a total dosage of 800 g/t can produce the concentrate with an Al₂O₃ grade of 56.49% at a recovery of 64.85% and an alumina-to-silica ratio of 2.96. While with a ternary collector composed of sodium oleate, benzohydroxamic acid and sodium dodecyl sulfonate at a total dosage of 1 200 g/t, the flotation can yield the concentrate with an Al₂O₃ grade of 61.17% at a recovery of 79.84% and an alumina-to-silica ratio of 3.80. The contact angle, zeta potential, infrared spectroscopy and adsorption capacity results demonstrate that both the binary collector and the ternary collector interact more strongly with diaspore than with kaolinite, suggesting that the collectors possess better selective collection of diaspore.

Platinum group metals (PGMs) occurs as associated elements in Jinchuan copper-nickel ores and are always recovered together with copper and nickel by flotation. Nevertheless, substantial amounts of PGMs are still lost into tailings, leading to tailings containing 0.07 g/t Pt, 0.06 g/t Pd, alongside 0.074 5 g/t Au and 5.54 g/t Ag. It is found that platinum and palladium mainly exist in the forms of michenerite, merenskyite, and Pd- and Pt-bearing bismuthotelluride minerals, finely disseminated and mostly encapsulated by silicate gangue, valleriite, pyrrhotite and other minerals. With those features taken into consideration, experimental investigations on PGM enrichment were carried out by multi-cycle gravity concentration with fabric-lined sluice. The results show that after five cycles of gravity concentration via fabric-lined sluice followed by grinding and re-concentration, the final tailings are obtained with the grades of Pt and Au decreased to 0.02 g/t and 0.05 g/t at recoveries of 74.48% and 53.04%, respectively. A combined separation process consisting of gravity concentration with fabric-lined sluice, shaking table concentration and low-intensity magnetic separation can lead to Pd primarily enriched into magnetic products, while Pt and Au concentrated in shaking table concentrates. This provides a feasible technical idea and research direction for the efficient recovery and utilization of PGMs in this type of tailings.

A comprehensive recovery test was conducted for a complex refractory copper-cobalt oxide ore from the Democratic Republic of the Congo (DRC). A combined process of copper flotation for enrichment followed by high-intensity magnetic separation (HIMS) for cobalt recovery was adopted. Sodium sulfide was used as activator, butyl xanthate as primary collector, TP as auxiliary collector, and No.2 oil as frother. In a closed-circuit test, a flotation process consisting of two-stage roughing, two-stage scavenging, and two-stage cleaning was adopted to preferentially recover copper, and the flotation tailings were then treated by HIMS to recover weakly magnetic cobalt-bearing minerals. Finally, the closed-circuit test produced a copper concentrate grading 16.31% Cu and 0.24% Co with recoveries of 80.82% Cu and 29.41% Co and a cobalt concentrate grading 0.304% Co at 40.34% recovery. It is concluded that this combined process can enhance the floatability of pseudomalachite and chrysocolla through a synergistic effect of sulfide activation and auxiliary collectors, and can also actualize effective recovery of cobalt minerals by HIMS. Accordingly, the overall recovery of copper and cobalt can be significantly enhanced.

In Yuanjiacun iron mine, the mineral processing water is recycled and then reused in flotation and magnetic processing stage, resulting in dissatisfied processing indicators. To address this problem, simulated wastewater was used to investigate the corresponding treatment technology and the mineral processing performance of the treated wastewater. Based on the verification with the recycle water on site, it is found that polyacrylamide (PAM), blue liquor and Ca²⁺ are the primary water quality factors influencing separation performance, and sodium hypochlorite, potassium ferrate and sodium carbonate can be used respectively to treat the mineral processing water containing them. After treatment, the recycle water is returned to the concentrator, leading to the processing indicators comparable to those obtained with clean water.