查看更多>>摘要：? 2022 Elsevier LtdEfficiently utilizing nickel sulfide ores containing multiple magnesium silicate gangue minerals through flotation is difficult. Therefore, in this study, we investigated the flotation behavior and discussed the mechanism of a refractory nickel sulfide ore with multiple MgO gangue minerals. The synergistic mechanism of acidified water glass (AWG) and carboxymethyl cellulose (CMC) in the flotation of the nickel sulfide ore was studied through flotation tests, zeta potential measurements, adsorption capacity tests, Fourier transform infrared ray (FTIR) spectroscopy, and observation under a microscope. The results showed that the addition of AWG could change the electrical properties on the surface of serpentine, weaken the heterogeneous aggregation of serpentine and talc, and increase the selective adsorption of CMC on the talc surface. The actual ore flotation test was conducted with the synergistic effect of AWG and CMC. In the practical flotation test of the ore, the concentration of MgO in the concentrate, compared with the original process with CMC alone, was reduced from 9.62% to lesser than 5.92%, with the combined synergistic action of acidified sodium silicate and CMC acting as the depressant. Simultaneously, the grade and recovery of Ni from the Ni-mixed concentrate remained unchanged, and the inhibiting effect of the magnesium-bearing gangue minerals improved.
查看更多>>摘要：? 2022 Elsevier LtdEnrichment of medium–low grade phosphate ore is very important for phosphorus chemical industry. This paper proposes a new enrichment method of medium–low grade phosphate ore with high silicon content via nitric acid leaching, separation and re-precipitation in sequence. The nitric acid leaching and the precipitation of the leaching solution were investigated and the P2O5 recovery reached 99.82%. The phosphorus in the leaching solution was re-precipitated in the form of phosphate after two stages of mineralization by using calcium carbonate slurry (CaCO3) and lime slurry (CaO) respectively. The effects of pH, reaction time, stirring speed, and temperature on the P2O5 recovery were methodically studied. Taguchi experiment and analysis of variance (ANOVA) showed that the pH and temperature of the reaction had the most significant effects on the P2O5 recovery. The parameters of the first mineralization were determined as follows: pH of 1.6, reaction time of 1 h, stirring speed of 300 rpm and reaction temperature of 45 °C. The P2O5 recovery could reach 99.04% in the total enrichment process after the second mineralization while the pH reached 3.8. The product was precipitated in the form of calcium hydrogen phosphate dihydrate and the P2O5 grade reached 38.24%.
查看更多>>摘要：? 2022 Elsevier LtdCarbon is a common gangue, often associated with base metal ores. The hydrophobicity of carbon causes interaction with air-bubbles during flotation, and results in carbon contamination of concentrate and grade reduction of base metals. Therefore, selective separation of carbon is important during froth flotation processing. Native and modified starch have been recommended to depress carbon during flotation, however neither the mechanism of interaction nor the efficiency of carbon depression by different forms of starch is currently clear. Using two sets of oxidized starches (native wheat starch oxidized by 2, 5 and 10% concentration of either H2O2 or NaOCl at pH 4) and comparing them with dextrin and native wheat starch (NWS), the mechanism of depression of graphite (a carbon exemplar) was investigated through adsorption isotherm and micro-flotation experiments as a function of starch functional group content, molecular size distribution and surface coverage estimation. Efficiency of depression of graphite by oxidized starches was favoured by a high proportion of substituted -C = O compared to –COOH groups. Increasing proportion of –COOH beyond a threshold negatively impacted on depression of graphite. Dextrin had an intermediate efficiency to depress graphite whereas NWS was poor at low dosage range but with high dosage showed good depression. A low estimated surface coverage (<22%) by different starch polymers was enough to cause effective depression of graphite. The data are consistent with depression of graphite by starches being guided by a hydrophobic interaction mechanism. The results also demonstrate that controlled oxidation modification can be used to tailor-make starch for graphite (carbon) depression.
查看更多>>摘要：? 2022 Elsevier LtdThe flotation separation of fluorite and calcite poses a long-standing challenge in the mineral processing industry because of their similar physicochemical characteristics. In this study, the effects of Cu2+ and soluble starch (SS) in the separation of fluorite from calcite by flotation, and the mechanisms behind these effects, were investigated using micro-flotation experiments, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), time of flight secondary ion mass spectrometry (ToF-SIMS) and density functional theory (DFT). The micro-flotation experiments show that the combination of Cu2+ and SS exhibits a stronger selective depression effect on calcite than that produced by SS alone; in contrast, the effect on fluorite flotation is relatively small. The XPS, FT-IR and ToF-SIMS analyses show that Cu2+ can react with SS to form a Cu–SS complex, which has better selectivity, resulting in the difference in flotation performance between fluorite and calcite. DFT results show that the SS and the Cu-SS complex form different chemical bonds during their interactions with the mineral surfaces: Ca–O bond and H–F bonds are formed when SS interacts with the fluorite surface, and Ca–O and hydrogen bonds are formed when SS interacts with the calcite surface. A Ca–Cu bond is formed when the Cu–SS complex interacts with the fluorite surface, but both Cu–O and Ca–Cu bonds are formed when the Cu–SS complex interacts with the calcite surface. This causes differences in adsorption energy. The adsorption energies of the interactions between SS or Cu–SS complex and the surfaces of fluorite and calcite are ranked as: calcite + Cu–SS complex > calcite + SS > fluorite + SS > fluorite + Cu–SS complex.
查看更多>>摘要：? 2022 Elsevier LtdLauryl glucoside (LG) was used for the first time as an impurity removal agent in ionic rare earth leaching solution to strengthen the removal of impurity metal ions and avoid the loss of rare earth effectively. Compared with ammonium bicarbonate (NH4HCO3), LG can ensure the high efficiency of impurity removal while avoiding ammonia nitrogen pollution. The impurity removal test showed that 91.03 ± 0.1% aluminum ion (Al3+) removal rate, 92.53 ± 0.2% iron ion (Fe3+) removal rate, and 23.27 ± 1.3% rare earth (Re3+) loss rate could be obtained when NH4HCO3 was used to adjust the pH value of leaching solution to 5.4. But the 99.09 ± 1.9% Al3+, 93.13 ± 1.3% Fe3+ removal rates, 5.33 ± 0.9% rare earth loss rate could be obtained by using LG as impurity remover. Infrared spectroscopy and solution chemical calculation showed that NH4HCO3 reacted with impurity metal ions to form Al(OH)3 precipitate, and a large amount of carbonate rare earth was formed. However, when LG was used as impurity remover, LG reacted with impurity metal ions to form a new Al-O band and no absorption peak related to rare earth ions that was found in the infrared spectrum. Density functional theory (DFT) calculation showed that at pH 5.4, the interaction intensity between LG and Al(OH)3 was largest, and rare earth ions did not interact with it. As the pH value of the leaching solution gradually exceeds 5.2, the free rare earth ions changed into the form of rare earth hydroxide. It caused the interaction between LG and rare earth elements to increase, resulting in the loss of rare earth. In addition, LG, as a green surfactant derived from renewable plant raw materials, could degrade naturally without causing environmental pollution. Therefore, using LG as an impurity remover can have a good application prospect in strengthening the impurity removal of ionic rare earth leaching solution.
查看更多>>摘要：? 2022 Elsevier LtdFlotation separation of apatite from calcite is difficult due to their same activate calcium atoms on the surface. To address this issue, amino trimethylene phosphonic acid (ATMP) was introduced to separate apatite and calcite in this research. The microflotation results showed that NaOl had an excellent collecting ability to apatite and calcite. Meanwhile, the tests also found that ATMP had a strong depression ability to calcite, but it hardly influenced the apatite floatability. The artificial mixed minerals flotation results confirmed that ATMP could be used as a depressant to separate apatite and calcite in the presence of NaOl. Zeta potential measurements illustrated that the addition of ATMP prevented the NaOl adsorption onto the calcite surface, while it hardly affected the interaction of NaOl with the apatite surface. Solution chemistry calculation of ATMP was conducted to reveal the main species of ATMP, while XPS analysis further indicated the strong chemisorption of ATMP onto calcite rather than apatite. Hence, the selective depression ability of ATMP was attributed to the electrostatic repulsion and steric resistance for the apatite surface and the stable adsorption structure at the calcite surface.
查看更多>>摘要：? 2022 Elsevier LtdThe efficient flotation separation of apatite and calcite is an intricate problem due to their similar physicochemical properties. The selection and utilization of selective depressant is the key to address this obstacle. In this study, sodium alginate (NaAl) was introduced as a selective inhibitor in the flotation separation of apatite from calcite with sodium oleate (NaOL) as collector. The inhibitory performance of NaAl on these two minerals was investigated via flotation tests. The depressing mechanism of NaAl was studied through zeta potential analysis, adsorption capacity tests, Fourier transform infrared spectroscopy (FTIR) measurements and X-ray photoelectron spectroscopy (XPS) analysis. Flotation results indicated that NaAl demonstrated strong inhibitory impact on the calcite flotation, whereas it presented little influence on the apatite flotation in the pH range of 9–12. A concentrate with P2O5 grade and recovery of 34.32% and 82.27% respectively was obtained in the bench-scale flotation experiment. Zeta potential analysis demonstrated that NaAl strongly affected the following NaOL adsorption onto the calcite surface, whereas it showed little influence on apatite. Adsorption test showed that NaAl absorbed on both these two mineral surfaces, whilst the adsorption amount on the calcite surface was significantly higher than that on the apatite surface. FTIR and XPS analyses further confirmed that NaAl adsorbed on the apatite surface through weak physical adsorption, while it chemically adhered on calcite in the form of calcium carboxyl which greatly prohibited the subsequent adhesion of NaOL on calcite. As a consequence, the calcite floatability was greatly depressed by NaAl and the selective flotation separation of apatite from calcite was realized.
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