Search

In this study, selective adsorption mechanism of zinc ions on the surfaces of galena and sphalerite in the flotation separation of Pb-Zn was comprehensively explored by flotation tests, Zeta potential measurements, Fourier transform interferometric radiometer (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) analysis, and density functional theory (DFT) calculations. Microflotation test showed that the use of ZnSO4 in alkaline pulp could selectively separate galena from sphalerite better than that without ZnSO4. Zeta potential test results showed that ZnSO4 could significantly increase the Zeta potential of sphalerite under alkaline conditions, but had little effect on galena. The results of FTIR test showed that xanthan characteristic peak appeared in xanthate-treated galena at pH = 10, while sphalerite treated with xanthate did not. XPS and DFT calculation results showed that sphalerite had stronger adsorption capacity for hydroxyl ions than galena. DFT calculation further confirmed that Zn(OH)2 could be adsorbed on the surface of hydroxylated sphalerite instead of hydroxylated galena and formed a new interface microstructure of sphalerite (Znsurf-O-Zn-O-H), resulting in the inhibition of sphalerite. This paper further deepened the selective adsorption mechanism of zinc ions on the surface of sphalerite in the flotation separation of Pb-Zn under alkaline conditions. [ABSTRACT FROM AUTHOR]

When copper ores containing pyrite are crushed and ground, many unavoidable Fe3+ ions will be produced and enter the flotation process. At present, the adsorption mechanism of Fe3+ on chalcopyrite and pyrite surfaces is not clear. Here, the adsorption behaviors of Fe3+ on the surfaces of chalcopyrite and pyrite were systematically investigated by micro-flotation tests, infrared spectra studies, X-ray photoelectron spectroscopy analysis (XPS), first-principles density functional theory calculations and theoretical analysis of the coordination field. The micro-flotation tests showed that the recovery rate of pyrite reduced with the growth of pH, but the recovery rate of chalcopyrite was basically unchanged. The infrared spectra analysis revealed that the intensities of the characteristic xanthate peaks of the C=S and C-O-C groups in the Fe3+-treated pyrite surface changed more noticeably than those of the xanthate peaks of the Fe3+-treated chalcopyrite. XPS showed that Fe (OH)3 was more easily and spontaneously adsorbed on pyrite than chalcopyrite surfaces. First-principles DFT calculations and electronic structure analysis further showed that pyrite had a stronger adsorption of Fe (OH)3 than chalcopyrite. This work sheds new light on the adsorption mechanism of Fe3+ on the surfaces of chalcopyrite and pyrite during flotation. [ABSTRACT FROM AUTHOR]

Sulfidization xanthate flotation remains the most promising method for the beneficiation of malachite. In this study, L-arginine (LA) was first used to modify the malachite surface and improve the efficiency of sulfidization flotation. The performance of LA was evaluated by the flotation experiments. The mechanism of interaction between LA and the malachite surface was investigated by adsorption experiments, zeta potential measurements, scanning electron microscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) analysis. Flotation experiments showed that LA had a significantly promoting effect on malachite sulfidization flotation. Adsorption experiments and SEM-EDS results indicated that LA improved the adsorption of S (II) species into the malachite surface and promoted the formation of sulfides. This finding was further confirmed by the XPS analysis. The XPS measurements results determined that S (II) species reacted with Cu (II) on the malachite surface and form polysulfides, adding LA promoted the reaction. The zeta potential measurements showed that LA increased the positive electrical properties of the mineral surface, which was conducive to S (II) species adsorption and the sulfidization reaction. This work sheds new light on the development of sulfidization activation. [ABSTRACT FROM AUTHOR]

Lead ions (lead nitrate) were introduced to modify the surface properties of tungsten minerals, effectively improving the floatability, with benzohydroxamic acid (BHA) serving as the collector. Flotation tests indicated that Pb-BHA complexes were the active species responsible for flotation of the tungsten minerals. The developed Pb-BHA complexes and the novel flotation process effectively increased the recovery of scheelite and wolframite, simplified the technological process, and led to reduced costs. Fourier transform infrared spectra data showed the presence of adsorbed Pb-BHA complexes on the surface of the minerals. The characteristic peaks of BHA shifted by a considerable extent, indicating that chemical adsorption plays an important role in the flotation process. Zeta potential results confirmed physical adsorption of the positively charged Pb-BHA complexes on the mineral surfaces. The synergistic effect between chemical and physical adsorption facilitated the maximum flotation recovery of scheelite and wolframite. [ABSTRACT FROM AUTHOR]

In this study, salicylhydroxamic acid (SHA), which exhibits superior flotation performance to conventional collector benzohydroxamic acid (BHA), was first introduced in ilmenite flotation. The addition of lead(II) can significantly increase the recovery of ilmenite using SHA as collector. Thus, the adsorption mechanism of SHA on lead(II)-activated ilmenite surface was systematically studied using micro-flotation tests, adsorption analysis, zeta potential measurements, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Micro-flotation results revealed that SHA had stronger collecting ability than BHA, and ilmenite floatability could be activated by lead ions with either SHA or BHA as collector. Ilmenite showed good floatability at pH 6–8 (over 90% recovery) in the presence of Pb2+ and SHA. In such conditions, the main lead species of Pb(OH)+ and Pb2+ acted as active sites and caused positive surface potential shifts, thereby increasing the adsorbed amounts of negatively charged SHA on the surface of the mineral. FTIR and XPS analyses suggested that the lead species was chemically adsorbed on the surface of ilmenite to form active sites chelated by SHA. Moreover, the free lead ions in solution might form the Pb–SHA complexes to adsorb on the mineral surface, thereby increasing the floatability of ilmenite. [ABSTRACT FROM AUTHOR]

• The paper introduced a new composite depressant. • Invested the effect of the mineral particle size on the flotation recovery. • Galena can be effectively inhibited by using a composite depressant. • Revealed the mechanism of composite depressant depress galena. In this study, the inhibitory effect of a composite depressant consisting of sodium sulfite and sodium lignosulfonate mixed at a molar ratio of 5:1 on Cu–Pb flotation separation was analyzed. The results of the mineral flotation tests show that both chalcopyrite and galena are floatable in a pH range of 6–12 and the composite depressant has a stronger inhibitory effect on galena than that of single inhibitors. The particle-size analyses of the concentrates and tailings show that it is difficult to inhibit the floatability of fine-grained galena using a single depressant, but the composite depressant can effectively deteriorate its floatability. The results obtained from zeta potential measurements and SEM reveal that the zeta potential of galena becomes more negative after a composite depressant is added because of the greater adsorption of sulfite and lignosulfonate ions on the surface of the galena. The XPS results show that sodium sulfite chemically reacts with the surface of galena and that hydrogen bonds are the main driving force of the adsorption of sodium lignosulfonate onto the surface of galena. The use of a combination of sodium sulfite and sodium lignosulfonate increases their adsorption onto the surface of fine-grained galena. [ABSTRACT FROM AUTHOR]

The flotation separation of scheelite from calcite is problematic, where sodium silicate modified by polyvalent metal ions has shown some advantages for selective depression. In this study, an Al-Na2SiO3 polymer was used as the depressant for the flotation separation of scheelite from calcite using a lead complex of benzohydroxamic acid (Pb-BHA) as the collector. Furthermore, a number of measurements were conducted to investigate the structure of the Al-Na2SiO3 polymer and its adsorption behavior with Pb-BHA complexes on the mineral surface. Flotation experiments indicated that the Al-Na2SiO3 polymer shows good selectivity for the flotation separation of scheelite from calcite at pH 8, where the optimum ratio of sodium silicate to aluminum sulfate was 2:1. Fourier-Transform Infrared (FTIR) and solution chemical analyses revealed that aluminum hydroxide complexes and the hydroxy moiety of silicic acid are able to self-assemble via condensation affording an Al-Na2SiO3 polymer, i.e., a composite aluminosilicate polymer. The zeta potential measurements and adsorption capacity measurements indicated that, upon adsorption of the Al-Na2SiO3 polymer and Pb-BHA complexes on the mineral surface, the Al-Na2SiO3 polymer had less influence on the adsorption of Pb-BHA complexes on the scheelite surface, while the opposite was true for calcite. Therefore, more Pb-BHA complexes and fewer Al-Na2SiO3 polymers were deposited on the scheelite surface, while fewer Pb-BHA complexes and more Al-Na2SiO3 polymers were adsorbed on the calcite surface. The selective separation of scheelite from calcite was attributed to the cooperative selectivity of the Pb-BHA complexes and Al-Na2SiO3 polymer. [ABSTRACT FROM AUTHOR]

[Display omitted] • Found that NH 4 + eliminated the inhibitory effect of Cu2+ on sulfidization. • Found that NH 4 + worked with Cu2+ to further promote sulfidization. • Reveal the mechanism of action between NH 4 + and Cu2+. • Reveal the effects of Cu2+ and Cu(NH 3) 4 2+ on surface sulfidization. Ammonium sulfate [(NH 4) 2 SO 4 ] is an effective activator of malachite sulfidization flotation. In this work, we explored the effects of ammonium ion (NH 4 +) and copper ion (Cu2+) on malachite sulfidization flotation and investigated the underlying mechanism. Flotation experiments demonstrated that NH 4 + can not only eliminate the negative effects of Cu2+, but also work together with Cu2+ to further promote malachite sulfidization flotation in a certain concentration range. Zeta potential, SEM-EDS, and X-ray photoelectron spectroscopy analysis results indicated that the single Cu2+ weakened the oxidation of S (II) species on the malachite surface and reduced the formation of sulfides. In the presence of NH 4 +, Cu2+ did not inhibit the formation of sulfides on malachite surface but worked with NH 4 + to promote it. Aqueous speciation calculation and adsorption test revealed that NH 4 + and Cu2+ interacted to form Cu (II)–NH 3 complexes, which reacts with S (II) species to form a copper sulfide substance that is more easily adsorbed on the malachite surface than the copper sulfide colloid formed by the reaction between Cu2+ and S (II) species. This leads to the improvement of surface sulfidization. [ABSTRACT FROM AUTHOR]

• Collector OL is less competitive than hydroxyl on the mineral surfaces. • Better selectivity of Ca(II) to the hydroxylated quartz than that of goethite. • Better selectivity of SHM to the hydroxylated goethite than that of quartz. • OL can be effectively adsorbed on hydroxylated quartz in the presence of Ca(II). This paper mainly investigates the role of hydroxyl on the desilication of goethite by anionic reverse flotation. Accordingly, micro-flotation experiments suggested that the activation effect of Ca(II) on quartz was obviously better than that of goethite in the high alkaline sodium oleate (OL) system.. Furthermore, the Zeta potential also confirmed that the selectivity of Ca(II) ions on quartz surface was better than that on goethite surface. Solution chemical analysis revealed that the dominant species of activator Ca(II) and collector OL were Ca2+ and OL−, respectively. Fourier transform infrared (FT-IR) spectroscopy suggested that OL− could not form an effective adsorption on mineral surfaces in the absence of Ca2+, while OL - had a strong chemisorption in the presence of Ca2+. Density functional theory (DFT) calculations demonstrated that the successful floating of quartz involves three surface modifications, namely the surface hydroxylation, the adsorption of Ca2+ on the hydroxylated surface, and the adsorption of OL− on the Ca2+-activated surface. In this process, hydroxylation is the prerequisite for the subsequent adsorption of Ca2+ and OL−. Besides, the selective adsorption of sodium humate (SHM) causes the flocculation and inhibition of goethite, which also plays a key role in the desilication of goethite. [ABSTRACT FROM AUTHOR]

To improve the floatability of tungsten minerals, lead ions (lead nitrate) were used to modify the surface properties of the minerals and benzohydroxamic acid (BHA) was used as a collector in the flotation system. Pb 2+ -BHA complexes are inevitably present in this process and the role of it is unclear. This investigation is going to describe a new approach and the mechanism of catalyzing BHA adsorption onto scheelite by lead ions. Chemical speciation, zeta potential, FTIR, and XPS studies were conducted to establish the important role of lead ions. Indeed, Pb 2+ -BHA complexes were shown to be the active species responsible for flotation. The speciation and zeta potential results showed the presence of the adsorbed Pb 2+ -BHA complexes on the scheelite. The XPS results for atomic composition and binding energies confirmed Pb 2+ -BHA species adsorbed on the scheelite surface, which contributed to more adsorption of BHA. The new method would increase the recovery of scheelite, simplify the flowsheet and reduce the processing cost. [ABSTRACT FROM AUTHOR]

Pb 2+ ions are commonly used as the activator in the flotation of cassiterite. However, lead pollution of surface water has attracted more concern and attention. In this study, the effect of Fe 3+ ions as an activator on the flotation performance of cassiterite using benzohydroxamic acid (BHA) as the collector was investigated by the micro-flotation tests. The results of the flotation experiments showed that the addition of Fe 3+ ions significantly increased the recovery of cassiterite in the presence of BHA collector. In the BHA flotation of cassiterite, there was a direct relationship between the recovery of cassiterite and the adsorption amount of BHA on the cassiterite surface. The adsorption mechanism of BHA on un-activated and Fe-activated cassiterite surfaces was studied by the adsorption experiments, zeta potential measurements, and X-ray photoelectron spectroscopy (XPS) analysis. The results of the adsorption and zeta potential experiments indicated that the adsorption amount of BHA on the cassiterite surface increased significantly in the presence of Fe 3+ ions. The XPS analysis also revealed that terminal hydroxyl group oxygen atoms of the cassiterite surface were the dominant reactive sites for Fe 3+ ion adsorption. Furthermore, BHA anions can react with Fe atoms adsorbed on the cassiterite surface to form Fe-BHA complexes, thus improving the hydrophobicity of the cassiterite surface. [ABSTRACT FROM AUTHOR]

The adsorption behaviors and the activation mechanism of calcium ions (Ca 2+ ) on sericite surface have been investigated by Zeta potential measurements, Fourier transform infrared spectroscopy (FT-IR), Micro–flotation tests and First principle calculations. Zeta potential tests results show that the sericite surface potential increases due to the adsorption of calcium ions on the surface. Micro-flotation tests demonstrate that sericite recovery remarkably rise by 10% due to the calcium ions activation on sericite surface. However, the characteristic adsorption bands of calcium oleate do not appear in the FT-IR spectrum, suggesting that oleate ions just physically adsorb on the sericite surface. The first principle calculations based on the density functional theory (DFT) further reveals the microscopic adsorption mechanism of calcium ions on the sericite surface before and after hydration. [ABSTRACT FROM AUTHOR]

Benzohydroxamic acid-lead (BHA-Pb) complex reagent is a commonly used collector for the flotation of oxidized ores such as tungsten ore, cassiterite, and ilmenite, but the BHA-Pb complex remaining in the mineral processing wastewater (MPW) after flotation is economically and efficiently difficult to remove. At present, the treatment technology usually starts from the treatment of MPW at a wastewater treatment station. However, the treatment cost is inevitably high due to the huge amount of MPW. In this study, a new process of removing residual BHA-Pb complex reagent from MPW in one-step using metal ions combined with gangue minerals in tailings pulp was proposed. It started from tailings pulp treatment and taking tailings reservoir as the main reaction site. The basic issues related to the new process were mainly studied. The concentration of BHA was characterized using chemical oxygen demand (COD). The results show that when Ca2+, Fe3+, or Al3+ was added to the BHA-Pb solution, only Fe3+ could effectively remove the COD of the BHA-Pb solution, while Ca2+ and Al3+ could not. This is because the BHA-Pb complex can be preferentially transformed into the BHA-Fe complex, and the COD of the BHA-Fe complex solution is most easily removed. However, BHA-Fe complex systems have dark colors and are difficult to settle. When gangue minerals are added to the BHA-Fe complex system, gangue minerals can play the role of coarse particles carrying fine particles settling, which is helpful to the sedimentation of the BHA-Fe complex system. The transformation mechanism between BHA-Pb and BHA-Fe complexes was explained by the conditional stability constants and Gibbs free energy changes analysis. In addition, the sedimentation mechanism of the BHA-Fe complex system was analyzed by zeta potential and scanning electron microscope-energy dispersive spectrometer. This study provides a new idea for removing residual organic flotation reagents from MPW starting from tailings pulp treatment. • Compared with Ca2+ and Al3+, only Fe3+ can effectively remove COD from the BHA-Pb solution. • The BHA-Pb complex can be preferentially transformed into BHA-Fe complex. • The COD of the BHA-Fe complex solution is most easily removed. • Gangue minerals are helpful to the sedimentation of the BHA-Fe complex system. • Gangue minerals can play the role of coarse particles carrying fine particles to settle. [ABSTRACT FROM AUTHOR]

Reverse flotation desilication with anionic collector sodium oleate (OL) and activator Ca2+ is a common beneficiation method to purify hematite. Herein, the separation mechanism of hematite and quartz were systematically investigated by experiments and DFT calculations with the effect of surface hydroxylation fully considered. Flotation results showed that the success of anionic reverse flotation of hematite was inseparable from the activation of quartz by Ca2+. In addition, the use of sodium humate (HM), which selectively inhibited hematite, was also very critical. The Zeta potential revealed that the activator Ca2+ ions were highly selective for quartz and depression HM was highly selective for hematite. SEM clearly showed that Ca species were adsorbed on the quartz surface, which was confirmed as chemisorption by XPS. DFT calculations further confirmed that the adsorption of HM on the surface of hematite was more favorable than that of quartz, while Ca2+ on the surface of quartz was more favorable than that of hematite, and the chemisorbed Ca2+ ions on the quartz surface provided targeted reaction sites for the subsequent adsorption of OL, which enabled the activated quartz to overflow into the froth products, while the inhibited hematite to sink and concentrate in the flotation cell. [Display omitted] • Collector OL is less competitive than hydroxyl on the mineral surfaces. • Better selectivity of Ca(II) to the hydroxylated quartz than that of hematite. • Better selectivity of HM to the hydroxylated hematite than that of quartz. • OL can be effectively adsorbed on hydroxylated quartz in the presence of Ca(II). [ABSTRACT FROM AUTHOR]

The removal of residual organic flotation reagents from mineral processing wastewater (MPW) can be divided into two steps: the tailings pulp settles in the tailings reservoir, and the effluent from the reservoir is treated in a wastewater treatment station. To simplify the wastewater treatment process, this work explored the fundamental problems of removing residual sodium oleate (NaOl) from tailings wastewater by one step starting from tailings pulp treatment. The removal behavior and mechanism of NaOl from wastewater by metal ions combined with gangue minerals in the tailings pulp were studied. The concentration of NaOl was determined using chemical oxygen demand (COD). Results showed that the newly prepared 100 mg/L NaOl solution formed NaOl colloid after a period of time, and Fe3+ and Al3+ were more conducive to the COD removal of NaOl colloid than Ca2+. Moreover, metal ions and gangue minerals played a synergistic role in enhancing the COD removal of NaOl colloid. Mechanism analysis showed that the unit charge solubility of FeOl 3 or AlOl 3 was much lower than that of CaOl 2 , so Fe3+ or Al3+ was more likely to precipitate with NaOl than Ca2+. The addition of Fe3+ or Al3+ to NaOl colloid reduced the absolute value of the zeta potential of the suspended solids under suitable pH conditions, leading to colloid condensation. When metal ions and gangue minerals coexisted, gangue minerals adsorbed part of NaOl and played the role of coarse particles carrying fine particles to settle. This finding can be used to explain the synergistic effect of metal ions and gangue minerals. The study provides a new idea for the treatment of MPW and has great application prospect. [Display omitted] • Fe3+ and Al3+ were more conducive to the COD removal of NaOl colloid than Ca2+. • The unit charge solubility product of Fe(Ol) 3 and Al(Ol) 3 was much lower than that of Ca(Ol) 2. • Metal ions and gangue minerals played a synergistic role in enhancing COD removal. • Gangue minerals can play the role of coarse particles carrying fine particles to settle. [ABSTRACT FROM AUTHOR]

[Display omitted] • The adsorption of hydroxyl on Fe site are stronger than on Cu site for chalcopyrite. • The competitiveness of xanthate to Cu site are stronger than to Fe site under high pH. • The interaction of the pyrite surface with hydroxyl are stronger than with xanthate. The separation of chalcopyrite from pyrite is usually carried out under high alkaline conditions. However, the separation mechanism of chalcopyrite from pyrite under high alkaline conditions was still unclear. In this work, the effects of hydroxyl on the separation of chalcopyrite from pyrite were systematically investigated by flotation tests, Zeta potential measurements, adsorption studies, Fourier Transform Infrared Spectrometer (FTIR) analysis and density functional theory (DFT) calculations. Micro-flotation results showed that chalcopyrite could be separated from pyrite in high alkaline pulp. Furthermore, Zeta potential indicated that the adsorption of xanthate on the surface of pyrite was obviously weakened at pH = 12, while its on chalcopyrite surface had little change. Such results were confirmed by adsorption tests. The adsorption amount of sodium butyl xanthate (SBX) on chalcopyrite was much higher than pyrite at pH = 12. Besides, FTIR analysis demonstrated that the characteristic peaks (C=S, C–O–C) of SBX were observed for chalcopyrite, while no characteristic peak of SBX was found for pyrite. DFT calculation further confirmed that the competitiveness of xanthate on the surface Cu sites of chalcopyrite was stronger than on the surface Fe sites of pyrite. Hydroxyl ion can be effectively adsorbed on pyrite rather than chalcopyrite, owing to its stronger affinity with pyrite. [ABSTRACT FROM AUTHOR]

• L-cysteine could potentially become an efficient and low toxicity depressant in Cu-Mo separation; • The Cu-Mo flotation separation could be achieved by L-cysteine selective depressing chalcopyrite; • L-cysteine might adsorb on chalcopyrite to form a stable L-cysteine-Cu chelate compound. In this work, L-cysteine was introduced as an environmentally-efficient flotation reagent in the selective separation of molybdenite from chalcopyrite. Its flotation performance and adsorption mechanism onto chalcopyrite were also investigated by flotation experiment, zeta potential, FTIR spectra, Raman spectra, TOF-SIMS measurements and DFT calculations. The flotation results indicated that L-cysteine exhibited stronger depressing ability than the conventional chalcopyrite depressants of Na 2 S, NaHS and sodium thioglycolate, suggesting it could become a promising potential depressant in the selective flotation separation of molybdenite from chalcopyrite. The results of zeta potential, FTIR spectra, TOF-SIMS and Raman spectra measurements demonstrated that L-cysteine might chemisorb on the Cu atoms of chalcopyrite surface via -SH and –NH 2 groups to form a stable L-cysteine-Cu chelate compound. The DFT calculations further supported the experimental characterizations; the calculated adsorption reaction energy of L-cysteine with Cu in the (0 0 1) surface of chalcopyrite was much lower than that of L-cysteine with Fe, which implied that L-cysteine would prefer to adsorb onto the Cu site of chalcopyrite surface. [ABSTRACT FROM AUTHOR]