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The aqueous chemistry of micron-sized lignite particles has essential influences on the dispersion stability of water-lignite slurry. In this work, the adsorption behaviors of dissolved humics on lignite surface in lignite–water slurry were studied through batch adsorption experiments. The influences of adsorbed humics on the surface properties, particle size distribution and dispersion stability of lignite particles in water-lignite slurry were examined by advanced analysis techniques, EDLVO theory and settlement tests. The adsorption results indicate that the adsorption capacity of humics on lignite increases from 4.11 mg·g−1 to 8.25 mg·g−1 with the humics concentration increasing from 100 mg·L−1 to 200 mg·L−1. The adsorption process can be well described by the pseudo-second order kinetic model. The adsorbed humics significantly improves the hydrophilicity and electronegativity of lignite surface and reduces the apparent particle size of lignite. The EDLVO calculation and settlement tests reveal that the total interaction energy of the humics-adsorbed lignite particles at 18 nm of separation distance is enhanced from 0.85 × 10−17 J to 1.45 × 10−17 J with the initial humics concentration increasing from 100 mg·L−1 to 200 mg·L−1. The dispersion stability of micron-sized lignite particles is improved with humics adsorption on lignite surface.

The recycling and utilization of mullite in coal fly ash (CFA) gives rise to environmental and economic profits. The optimal experimental conditions for enhanced recycling of mullite with a flotation and metallurgy process are studied by factorial designs, and further analyzed by thermodynamic and dynamics calculations, and XRD/SEM characterizations. The unburned carbon is firstly removed from the CFA assisted with effective humic acid surfactant in the froth flotation step. The maximum removal rate of carbon is 93.20 ± 0.05%. Then the digesting of glass phase in carbon-free product with mixed acid solutions (HF: H2SO4 = 3:1) is employed in the metallurgy step. The influencing intensity of digesting factor on glass phase decreases in order of acid concentration, agitation intensity, reaction time, reaction temperature. The digesting kinetics of glass phase in mixed acid solution is belonging to diffusion-controlled reaction model. The maximum digesting rate of glass phase can be 97.40 ± 0.16%. The mineralogical phase of the digested residue is mainly mullite. The performance of the refractory obtained from the water-cleaned mullite-enriched product meets the production requirements of refractory materials. This potential process would provide an effective approach for the separation and recycling of valuable components from CFA in further industry applications.

Morphology-controlled synthesis of copper vanadate nanocrystals is of great significance in electrochemical sensing applications. A facile hydrothermal process for synthesizing copper vanadate nanocrystals with various morphologies (e.g., nanoparticles, nanobelts and nanoflowers) was reported. Phase, morphology and electrochemical performance of the as-synthesized copper vanadate nanocrystals were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and cyclic-voltammogram (CV) techniques. The results revealed that the morphologies of the Cu 3 V 2 O 7 (OH) 2 ·2H 2 O (CVOH) nanocrystals could be controlled by changing copper salts, surfactants and pH values. The CVOH samples showed enhanced electrochemical response to ascorbic acid. Comparatively, the CVOH nanobelts had the higher electrochemical sensing performance than those of CVOH nanoparticles and nanoflowers. The CVOH-nanobelts-modified GCEs had a linear relationship between the peak currents in their CVs and ascorbic acid concentration. The CVOH nanocrystals can be used as potential electrochemical active materials for the determination of ascorbic acid.

In order to remove aluminum ions in bauxite processing wastewater, two natural clay minerals (bentonite and kaolin) were used as adsorbents. The adsorption behaviors including kinetics and isotherms were studied at much broader pH range, higher temperature, and higher Al(III) concentration by batch experiments. The adsorption mechanisms were investigated by optical microscope, zeta potential testing, and XRD analysis. The results show that Al(III) adsorption is strongly pH dependent and increases clearly with increasing pH. The pseudo-second-order kinetic model can best describe the adsorption process, and the intra-particle diffusion was not the sole rate-controlling step. The Langmuir–Freundlich model can fit best the adsorption equilibrium data, and the maximum capacities of Al(III) adsorbed on bentonite and kaolin reach to 8.52 mg g–1 and 0.58 mg g–1, respectively, at 35°C. Thermodynamic studies display that the adsorption of Al(III) onto clay minerals is non-spontaneous. The adsorption of Al(...

The existence of sulfur and silica in bauxite influence the product quality of Bayer alumina. The synchronous desulfurization and desilication of low-grade and high-sulfur bauxite through reverse flotation processes were studied using modified starch as depressants in this work. The effects of depressant dosage, modified depressant dosage and collector dosage on flotation performance were investigated. The results show that the sulfur and silica in bauxite were successfully decreased through the reverse flotation. With an optimal condition of 10% solid density, particle size of −74 µm of 75%, pulp pH 9, temperature 30 °C, modified depressant dosage of 50 g/t, copper sulfate dosage of 20 g/t, combined collector dosage of 220 g/t, and terpenic oil dosage of 120 g/t, the recovery of Al2O3 reached to 76.41%. The sulfur content of concentrate was decreased from 2.87 to 0.27%, with an aluminum to silicon ratio (A/S) increasing from 3.36 to 8.09.

The recovering of valuable metals in spent lithium-ion battery cathodes brings about economic and environmental benefits. A stepwise leaching-flotation-precipitation process is adopted to separate and recover Li/Fe/Mn from the mixed types of cathode materials (hybrid wastes of LiFePO 4 and LiMn 2 O 4 ). The optimal operating conditions for the stepwise recovery process are determined and analyzed by factorial design, thermodynamics calculation, XRD and SEM characterization in this study. First, Li/Fe/Mn ions are released from the cathode using HCl assisted with H 2 O 2 in the acid leaching step. The leachability of metals follows the series Li > Fe > Mn in the acidic environment. Then Fe 3+ ions are selectively floated and recovered as FeCl 3 from the leachate in the flotation step. Finally, Mn 2+ /Mn 3+ and Li + ions are sequentially precipitated and separated as MnO 2 /Mn 2 O 3 and Li 3 PO 4 using saturated KMnO 4 solution and hot saturated Na 3 PO 4 solution, respectively. Under the optimized and advisable conditions, the total recovery of Li, Fe and Mn is respectively 80.93 ± 0.16%, 85.40 ± 0.12% and 81.02 ± 0.08%. The purity for lithium, ferrum and manganese compounds is respectively 99.32 ± 0.07%, 97.91 ± 0.05% and 98.73 ± 0.05%. This stepwise process could provide an alternative way for the effective separation and recovery of metal values from spent Li-ion battery cathodes in industry.

The existence of pyrite results in high soda consumption, iron pollution of alumina oxide and pipeline corrosion in the utilization of high-sulfur bauxite during the production of Bayer alumina. The flotation desulfurization of high-sulfur diasporic bauxite with modified 2-mercaptobenzimidazole (MBI) collector was studied in this work. The effects of pulp pH, collector dosage, activator dosage and frother dosage on flotation performance (the sulfur content in concentrate and Al2O3 recovery) were examined. The results indicate that the sulfur in bauxite was successfully decreased through the reverse flotation. With an optimal condition of 10% solid density, particle size of −74 µm of 75%, pulp pH 9, temperature 30 °C, collector dosage of 120 g/t, copper sulfate dosage of 20 g/t, and terpenic oil dosage of 120 g/t, the recovery of Al2O3 reached to 77.58%. The sulfur content of concentrate was decreased from 2.87 to 0.66%, with an aluminum to silicon ratio (A/S) increasing from 3.36 to 4.43.

The flotation desulfurization is generally used for the removal of sulfur impurities in the high sulfur bauxite. 1-butyl-2-mercaptobenzimidazole (DMBI) was synthesized and used as collector in the laboratory. The interactions between DMBI and pyrite with different adsorption time, solution pH, solution temperature and DMBI concentration were investigated in this work. Results show that the equilibrium adsorption time is 20 min, and the adsorption capacity decreases with increasing pH as well as temperature. With the increasing concentration, adsorption value increases and achieves the saturated adsorption. The adsorption of DMBI on pyrite is more consistent with Langmuir isothermal adsorption equation from 298.15 to 318.15 K. However, the adsorption is more fitted by the Freundlich isothermal adsorption equation at 288.15 K. Thermodynamic studies display that the adsorption of DMBI and pyrite is non-spontaneous and exothermic.

Physicochemical Problems of Mineral Processing; ISSN 2084-4735

The authors have developed a series of humic substances-based binders for iron ore pelletizing. This work was to gather information for the further industry application of humic substances-based binders in the field of iron ore oxidized pellets production. Pyrolysis of humic substances as the active fraction in the binders and its effects on fired hematite pellets was investigated in this study. Pyrolysis product of humic substances was focusing on four main gases (CO2, CO, H2and CxHy). The results demonstrated that effect of O2/N2atmosphere on weight loss of humic substances is obvious above 600 °C. Instantaneous concentration of gas products is increased with increasing pyrolysis temperature. Weight percentage of CO2 is increased obviously with increasing O2 concentration, while those of CO and H2 decreasing.

The extraction and recovery of Ti from Ti-enriched tailing with acid leaching and precipitate flotation, as one of the critical steps, was proposed for the stepwise utilization of red mud. The factors influencing acid leaching and precipitate flotation were examined by factorial design. The leaching thermodynamics, kinetics of Ti(4+), Al(3+) and Fe(3+), and the mechanism of selectively Fe(3+) removal using [Hbet][Tf2N] as precipitating reagent were discussed. The extracting of Ti(4+), Al(3+) and Fe(3+) in concentrated H2SO4 is controlled by diffusion reactions, depending mainly upon leaching time and temperature. The maximum extracting efficiency of Ti(4+) is approximately 92.3%, whereas Al(3+) and Fe(3+) leaching are respectively 75.8% and 84.2%. [Hbet][Tf2N], as a precipitating reagent, operates through a coordination mechanism in flotation. The pH value is the key factor influencing the flotation recovery of Ti(4+), whereas the dosage of precipitating reagent is that for Al(3+) recovery. The maximum flotation recovery of Ti(4+) is 92.7%, whereas the maximum Al(3+) recovery is 93.5%. The total recovery rate for extracting and recovering titanium is 85.5%. The liquor with Ti(4+) of 15.5g/L, Al(3+) of 30.4g/L and Fe(3+) of 0.48g/L was obtained for the following hydrolysis step in the integrated process for red mud utilisation.