Selective Depression Research Articles

Performance Analysis of Thiocarbonohydrazide as a Novel Selective Depressant for Chalcopyrite in Molybdenite-Chalcopyrite Separation

A novel surfactant, thiocarbonohydrazide (TCH), was synthesized and tested for the first time as a selective chalcopyrite depressant in Cu-Mo separation. Its adsorption mechanisms on chalcopyrite were studied by flotation tests, zeta potential, FTIR, XPS and ToF-SIMS measurements. FTIR and zeta potential analyses suggested that there was a strong chemisorption reaction between TCH and chalcopyrite, resulting in the formation of TCH–copper complexes. XPS and ToF-SIMS measurements further confirmed the chemisorption of TCH onto the chalcopyrite surface and showed that this chemisorption reaction is due to its S and N atoms, which form five-membered chelating rings by releasing H ions.

Use of ZnSO4 and SDD mixture as sphalerite depressant in copper flotation

The depression performance and mechanism of the zinc sulfate (ZnSO4) and sodium dimethyl dithiocarbamate (SDD) combined depressant with butyl xanthate (BX) as collector in a mixed Cu-Zn sulfide floation system were fully investigated using micro-flotation experiments, zeta-potential determination, and local electrochemical impedance spectroscopy (LEIS) analysis. The micro-flotation experimental results indicated that the combined depressant has a significant selective depression effect on sphalerite but has slight effect on chalcopyrite. The depression performance of the combined depressant strictly depends on the dosage of ZnSO4 + SDD and flotation pH. However, excessive SDD is detrimental to chalcopyrite flotation. The optimum conditions for flotation separation of chalcopyrite from the Cu-Zn sulfide were as follows: combined depressant dosage of 10−4 mol/L (ZnSO4: SDD = 3:1), BX dosage of 10−5 mol/L, and flotation pH of 10. Under such conditions, a copper concentrate assaying 30.21% Cu with 86.79% recovery was achieved from the Cu-Zn sulfide flotation system, and this concentrate had a very low Zn grade of 4.20% with 5.48% recovery. Both the zeta-potential and LEIS results confirmed that the presence of the combined depressant can significantly prevent the adsorption of BX onto the sphalerite surface, especially for an alkaline pH range of 9–12; however, the adsorption of BX onto the chalcopyrite surface is not affected. The LEIS provides a powerful tool for observing the adsorption of flotation reagents on mineral surface.

Utilization of sodium humate as selective depressants for calcite on the flotation of scheelite

ABSTRACTThe flotation separation of scheelite from calcite using sodium humate (SH) as a potential depressant has been studied through micro-flotation experiments, zeta potential and Fourier transform infrared (FT-IR) spectra measurements. The flotation results indicate SH exhibited selective depression effect on calcite in the presence of sodium oleate, achieving the flotation separation of scheelite from calcite. Zeta potential results indicate that SH strongly absorbed on calcite surface but negligibly on scheelite surface, which prevents the adsorption of sodium oleate on calcite surface. The FT-IR results also show that SH can be adsorb on the surface of calcite. Results shown a higher Ca density on the calcite than on scheelite surface, and that calcite can accommodate the interaction of SH.

Selective Attachment of Leptospirillum ferrooxidans for Separation of Chalcopyrite and Pyrite through Bio-Flotation

The replacement of depressants used in sulfide mineral beneficiation, with bacteria and their metabolites, promises to reduce the environmental impact left by the mining industry. In this study, the attachment of Leptospirillum ferrooxidans, L.f, to chalcopyrite and pyrite was investigated through Scanning Electron Microscopy (SEM). The impact of selective attachment, bacterial growth conditions, and extracellular polymeric substances (EPS) was investigated through bio-flotation. L.f exhibits selective attachment to pyrite between 0 h and 168 h exposure via an indirect contact mechanism. Separation of chalcopyrite from pyrite was achieved through exposing the minerals for 72 h with an L.f culture grown on either HH media, chalcopyrite, or pyrite. The results produced 80.4, 43.4, and 47.4% recovery of chalcopyrite, respectively. However, EPS supernatant extracted from L.f grown on chalcopyrite, conditioned for 48 h, provided the best separation efficiency by the selective depression of pyrite resulting in 95.8% Cu recovery. Polysaccharide-rich EPS selectively attaches to pyrite within 48 h, depressing its floatability and ensuring successful separation with a PIPX collector.

Flotation of monazite in the presence of calcite part II: Enhanced separation performance using sodium silicate and EDTA

Selective depression of calcite in a monazite-calcite flotation system was systematically studied using micro-flotation and electrokinetic tests as well as X-ray photoelectron spectroscopy (XPS) characterization and solution chemistry calculations. Monazite was found to be depressed by both sodium silicate and sodium hexametaphosphate when calcium ions appeared in solution. It was hypothesized that co-adsorption of calcium species (CaHCO3+ and CaCO3(aq)) and Si(OH)4 as well as SiO(OH)3- via hydrogen bonding formed a compact layer over the monazite surface, thereby reducing octanohydroxamic acid adsorption by steric hindrance. The use of citric acid or EDTA formed soluble chelates (e.g. CaCit− and CaEdta2−) with the calcium ions which negated the flotation suppression effect. An XPS study indicated that both EDTA and citric acid chemically adsorbed on the monazite surface, while the adsorption on the calcite surface was achieved mainly through hydrogen bonding. EDTA was more effective than citric acid due to two reasons: (i) citric acid itself presented stronger depression effects and (ii) citric acid has weaker chelating properties for calcium. Using 2.5 × 10−4 M octanohydroxamic acid, 0.05 g/L sodium silicate and 6 × 10−5 M EDTA, monazite recovery of more than 90% was achieved while recovering only 20% of the calcite.

Selective flotation of scheelite from calcite using calcium lignosulphonate as depressant

In this work, calcium lignosulphonate (CLS) was introduced as a novel flotation depressant for separation of scheelite from calcite. Sodium oleate (NaOl) acted as collector for scheelite. The flotation results showed that CLS had strong depressant effect on calcite flotation while exhibited little influence on scheelite flotation. Scheelite can be separated efficiently from scheelite-calcite mixed binary minerals in pH range of 7–11, when CLS was added prior to NaOl. The selective depressant effect of CLS on calcite was analyzed through interactions between the CLS micelles and mineral particles at water/particle interface.

Effect of Fe(II) as assistant depressant on flotation separation of scheelite from calcite

The preparation of high-grade schleelite concentrates from calcite containing ores despite significant research progress remains an important commercial challenge. In this study, Fe(II) was selected as an assistant depressant and combined with sodium silicate (SS) to improve the flotation separation of scheelite from calcite. Micro-flotation experiments of the individual minerals and artificially mixed minerals using oleic acid as a collector were conducted to evaluate the selective depression effect of the SS/Fe(II) depressant (the mixture of SS and Fe(II)). The results showed that the depressant mixture had a better selective depression effect on calcite than SS alone, and the optimum mass ratio of SS to ferrous sulphate was 4:1. Flotation tests using ore from a commercial mine showed that a concentrate with a WO3 grade of more than 62% and recovery greater than 89% could be achieved using SS/Fe(II) as the depressant. The depression mechanism of the SS/Fe(II) was investigated in detail using zeta potential measurements and X-ray photoelectron spectroscopy. The results showed that silicate species are more likely to adsorb on the surface of calcite and produce a selective depression effect. The improved depression effect could be attributed to the Fe(II), which not only increased the adsorption of the silicate species on the calcite surface, but also improved the formation of polymeric silicate species.

Selective depression of titanaugite in the ilmenite flotation with carboxymethyl starch

In order to intensify the flotation separation of ilmenite from titanaugite, surface modification of mineral particles was carried out using carboxymethyl starch (CMS) by microflotation experiments, zeta potential measurements, Fourier transform infrared (FTIR) and atomic force microscopy (AFM) analysis. Microflotation results showed that CMS was a selective depressant, and it effectively enhanced the floatability difference between ilmenite and titanaugite in the pH range from 6.0 to 10.0. As it was revealed by the zeta potential, FTIR and AFM analysis, the CMS adsorption occurred onto mineral surfaces through chemisorption and hydrogen bonding, while CMS exhibited a stronger interaction with titanaugite than ilmenite. After that, the CMS adsorption impeded the adsorption of sodium oleate collector on titanaugite surfaces, giving rise to a concomitant decrease in the floatability of titanaugite. These findings exhibit great potential for CMS application in the selective flotation of ilmenite.

Selective flotation separation of molybdenite and talc by humic substances

Humic acid (HA) has been studied as a potential selective depressant for molybdenite in the flotation separation of molybdenite and talc in this paper. In the single mineral flotation tests, HA has shown good depression ability to molybdenite over the entire pH range tested from pH 3–11, while the floatability of talc was only affected by HA under strong acidic condition (pH 3). In the mixed minerals flotation, HA can effectively depress the flotation of molybdenite while not affecting the flotation of talc under strong alkaline condition (pH 11). Contact angle measurements have proved that the hydrophobicity of both talc and molybdenite decreases after treatment by HA, however, the contact angles of treated talc are still higher than molybdenite. Equilibrium adsorption studies indicate that HA has a much higher adsorption density on molybdenite than on talc. The preferential adsorption of HA on molybdenite was further confirmed by diffusion reflectance infrared Fourier transform spectroscopy (DRIFTS) and atomic force microscopy (AFM) imaging. All of the experimental results suggest that humic acids can be employed as a selective depressant for molybdenite during the flotation separation of molybdenite and talc under alkaline conditions, and the higher adsorption density of HA on molybdenite over talc is the primary reason for the selective separation.

Selective adsorption of benzhydroxamic acid on fluorite rendering selective separation of fluorite/calcite

Fluorite, a chief source of fluorine in the nature, usually coexists with calcite mineral in ore deposits. Worldwide, flotation techniques with a selective collector and/or a selective depressant are commonly preferred for the separation of fluorite from calcite. In the present study, an attempt was made to use benzhydroxamic acid (BHA) as a collector for the selective separation of fluorite from calcite without using any depressant. Results obtained from the flotation experiments for single mineral and mixed binary minerals revealed that the BHA has a good selective collecting ability for the fluorite when 50mg/L of BHA was used at pH of 9. The results from the zeta potential and X-ray photoelectron spectroscopy (XPS) indicated that the BHA easily chemisorbs onto the fluorite as compared to calcite. Crystal chemistry calculations showed the larger Ca density and the higher Ca activity on fluorite surface mainly account for the selective adsorption of BHA on fluorite, leading to the selective separation of fluorite from calcite. Moreover, a stronger hydrogen bonding with BHA and the weaker electrostatic repulsion with BHA− also contribute to the stronger interaction of BHA species with fluorite surface.

The effect of changes in pH on the depression of talc by chitosan and the associated mechanisms

The depression effect of chitosan on talc as well as the associated mechanisms were investigated at different pH values. The flotation results showed that chitosan is a useful depressant for talc flotation and that its depression effect is independent of pH. The adsorption mechanisms of chitosan were different at pH3 and 9. X-ray photoelectron spectroscopy analysis indicated that at pH3 and pH9, the chitosan adsorbed on talc surfaces through physical interactions. At pH3, the adsorption changed the zeta potential of the talc from negative to positive and the adsorption was achieved via hydrogen bonding interaction. At pH9, in addition to adsorption due to hydrogen bonding, the water-insoluble chitosan also deposited on the talc surfaces and shifted the slip surface of the electric double layer outward, thus making the surface potential of the talc gradually approach zero. The adsorbed chitosan could be washed away from the surface. This phenomenon occurred more easily at pH3, because the deposited chitosan dissolved and entered the aqueous phase again. Flotation separation tests on the mineral mixtures indicated that the chitosan could only be used as a selective depressant for chalcopyrite and talc separation at pH3.

The flotation separation of scheelite from calcite and fluorite using dextran sulfate sodium as depressant

This paper introduced dextran sulfate sodium, a medical intermediate rich in sulfate group, as a potential depressant for calcite and fluorite in scheelite flotation. The flotation behaviors of scheelite, calcite and fluorite under different pulp pH with dextran sulfate sodium acting as depressant and sodium oleate acting as collector were studied through micro-flotation tests. The results showed that when sodium oleate was used alone, the three minerals floated well and were difficult to separate. Dextran sulfate sodium exhibited a selective depressant effect on calcite and fluorite flotation when it was added before sodium oleate. Using dextran sulfate sodium as depressant could achieve the preferential flotation separation of scheelite from calcite and fluorite by control of pulp pH at 7.0. The selective depressant effect of dextran sulfate sodium on calcite and fluorite was explored through surface analyses including zeta potential measurements, contact angle measurements and FTIR studies on mineral samples treated with dextran sulfate sodium and/or sodium oleate. On the basis of the surface analyses, a selective adsorption model of dextran sulfate sodium on calcite and fluorite was proposed.

The effect of sodium alginate on the flotation separation of scheelite from calcite and fluorite

In this paper, the effect of sodium alginate on the flotation separation of scheelite from calcite and fluorite using sodium oleate as collector was investigated. Flotation results showed that sodium alginate could selectively depress the flotation of calcite and fluorite in pH range of 7–12 when it was added before sodium oleate. The selective depressant effect of sodium alginate was studied using zeta potential measurements, contact angle measurements and FTIR. The zeta potential measurements results showed that sodium alginate exhibited little influence on the surface charge of scheelite but had remarkable effect on that of calcite and fluorite. The results of contact angle measurements indicated that sodium alginate could produce selective, non-recoverable decrease in surface hydrophobicity of calcite and fluorite. The FTIR studies demonstrated the chemical absorption of sodium alginate on calcite and fluorite surface and no form of adsorption on scheelite surface.

Effects of sodium carbonate and calcium chloride on calcite depression in cationic flotation of pyrolusite

Abstract In the cationic flotation of pyrolusite using dodecyl ammine (DDA), the depressive effect of sodium carbonate and calcium chloride on the calcite mineral was investigated systematically through flotation experiments, FTIR analysis, contact angle measurements and zeta potential tests. The microflotation experiments showed that both depressant agents decrease the flotation recovery of calcite significantly. In addition, sodium carbonate acts as activator agent for pyrolusite, and increases its floatability. The flotation experiments and contact angle measurements indicated that the selective depression effect of sodium carbonate on the calcite mineral is more than that of calcium chloride. As evidenced by zeta potential and FT-IR analysis, sodium carbonate decreases the negative charges on the surface of calcite mineral and subsequently reduces the adsorption of DDA collector through electrostatic forces. At a pH of 7.5, using 2000 g/t DDA and 1500 g/t sodium carbonate, a pyrolusite concentrate containing almost 40% MnO with 71.5% recovery is achieved by carrying out the ore flotation experiments on the tabling pre-concentrate.

Selective depression behavior of guar gum on talc-type scheelite flotation

The depression behavior and mechanism of guar gum on talc-type scheelite flotation were systematically investigated by flotation experiments, adsorption tests, zeta-potential measurements, and infrared spectroscopic analyses. The flotation results for monominerals, mixed minerals, and actual mineral samples indicated that guar gum exhibited much higher selective depression for talc than for scheelite. Bench-scale closed-circuit tests showed that a tungsten concentrate with a WO3 grade of 51.43% and a WO3 recovery of 76.18% was obtained. Adsorption tests, zeta-potential measurements, and infrared spectral analyses confirmed that guar gum absorbed more strongly onto the talc surface than onto the scheelite surface because of chemisorption between guar gum and talc. This chemisorption is responsible for the guar gum’s highly selective depression for talc and small depression for scheelite. The flotation results provide technical support for talc-type scheelite flotation.

Childhood cumulative contextual risk and depression diagnosis among young adults: The mediating roles of adolescent alcohol use and perceived social support

This study examined associations between cumulative contextual risk in childhood and depression diagnosis in early adulthood, testing two adolescent mediating mechanisms, alcohol use and perceived social support from family and friends, while accounting for the stability of internalizing problems over time and examining possible gender moderation. Multiple group mediation analyses were conducted using parent- and adolescent-report as well as hospital records data from the Northern Finland Birth Cohort 1986 (N = 6963). Our analyses demonstrated that the association between cumulative contextual risk in childhood and depression diagnosis in adulthood is mediated by adolescent alcohol use and perceived social support both for boys and girls. The findings highlight potentially malleable mediating mechanisms associated with depression in vulnerable youth that could be targets in selective depression preventive interventions.

Flotation Separation of Scheelite from Fluorite Using Sodium Polyacrylate as Inhibitor

The depressing properties of sodium polyacrylate (PA-Na) for scheelite and fluorite were studied by micro-flotation tests, infrared spectroscopy (IR), zeta potentials, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The flotation results reveal that the selective depression effect of PA-Na is better than that of sodium silicate, and PA-Na can depress fluorite more effectively than scheelite. The flotation recovery of scheelite and fluorite keeps at about 75% and 10%, respectively, at the pulp pH 9.3~9.6 and PA-Na concentration from 30 to 50 mg/L. IR spectra results suggest that PA-Na has a chemical effect on the surface of scheelite and fluorite. The zeta potential of fluorite becomes more negative than that of scheelite after PA-Na addition. XPS analysis deduces the occurrence of chemisorption between PA-Na and mineral surfaces, and the chemisorption of PA-Na on fluorite is stronger than on scheelite. DFT demonstrates that the absolute value of the adsorption energy in the presence of PA-Na is larger on the fluorite {111} surface than on the scheelite {111} surface. Thus, fluorite is more readily depressed than scheelite, which remarkably matches the micro-flotation test results.

Active Vision: Dynamic Reformatting of Visual Information by the Saccade-Drift Cycle

Visual processing depends on rapid parsing of global features followed by analysis of fine detail. A new study suggests that this transformation is enabled by a cycle of saccades and fixational drifts, which reformat visual input to match the spatiotemporal sensitivity of fast and slow neuronal pathways.

Depressing behaviors and mechanism of disodium bis (carboxymethyl) trithiocarbonate on separation of chalcopyrite and molybdenite

This work focuses on the organic depressant, disodium bis(carboxymethyl) trithiocarbonate (DBT), as a selective depressant in copper-molybdenum sulfide flotation separation. Micro-flotation, Zeta potential, FTIR and XPS measurements were carried out to investigate the selective depression mechanism of DBT on chalcopyrite. Zeta potential and FTIR measurements revealed that DBT had higher affinity for chalcopyrite than molybdenite and the XPS results of chalcopyrite before and after treatment with DBT further proved that DBT adsorbed on chalcopyrite surface. The investigation indicates that the mechanism of DBT adsorbing on chalcopyrite is mainly physical adsorption. Locked circuit experiments were carried out and the results showed that DBT could be considered as a cleaner option in commercial Cu-Mo flotation separation circuits.

Synthesis of acetic acid-​[(hydrazinylthioxome​thyl)​thio]-sodium and its application on the flotation separation of molybdenite from galena

Abstract A novel organic compound acetic acid-​[(hydrazinylthioxome​thyl)​thio]-sodium was synthesized and characterized. The flotation performance and adsorption mechanism of AHS to galena were investigated by micro, bench flotation tests, UV spectra, zeta potential, FTIR and XPS measurements. The results demonstrated that AHS exhibited superior depressing power to galena and could be used as selective depressant for flotation separation of molybdenite from galena. The results of UV spectra, FTIR, zeta potential and XPS measurements demonstrated that AHS chemisorb on galena surface by forming five-membered cheat ring with releasing of H ions. Therefore, the possible adsorption mode of AHS on galena surface was recommended.