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The grinding process plays a crucial role in the floatability of mineral. The present study proposes a scheme to assist in the flotation separation of galena and pyrite by optimizing the choice of grinding media. The effects of grinding media (cast iron balls, steel balls containing 18% chromium, and steel balls containing 12% chromium) on the pulp properties and hydrophilicity of galena and pyrite were evaluated using grinding tests, micro-flotation tests, X-ray photoelectron spectroscopy, and adsorption capacity analyses. The results showed significant differences in the pH, potential, and dissolved oxygen content of the galena or pyrite pulp with different grinding media, resulting in significant differences in the flotation behavior of galena and pyrite. The use of cast iron balls in the grinding process was more favorable for the flotation separation of galena and pyrite. The pyrite surfaces adsorbed less butyl xanthate when cast iron balls were used as grinding media due to the presence of more hydrophilic hydroxyl iron. Therefore, cast iron balls as grinding media are favorable for broadening the surface hydrophilic differences between galena and pyrite. [ABSTRACT FROM AUTHOR]

The recovery of scheelite from calcium-bearing carbonate ores by foam flotation is challenging due to its low separation efficiency. This study investigated the effect of pentasodium diethylenetriaminepentaacetate (PD) on the surface properties of scheelite and fluorite. For this purpose, we performed micro-flotation tests and carried out zeta potential measurements, as well as Fourier transform infrared (FT-IR) and X-ray photoelectron (XPS) spectroscopic measurements, in order to analyze the surface properties of these minerals. The addition of PD as a novel depressor significantly improved the effect of fluorite and sodium oleate (NaOl) on the flotation-based scheelite recovery and separation from fluorite. PD was spontaneously adsorbed onto fluorite through electrostatic and chemical adsorption. By contrast, PD did not appear on the scheelite because of the reaction conditions, surface site, and steric hindrance. X-ray photoelectron spectroscopy measurements and a solution chemistry analysis were used for the determination of the PD-selective adsorption mechanism and key factors derived from multi-layer adsorption onto fluorite, which completely hindered that of NaOl. [ABSTRACT FROM AUTHOR]

Lead(II)–benzohydroxamic acid (Pb–BHA) complex collectors perform well with respect to scheelite flotation, and, due to their structure, they are widely used for industrial purposes. This paper examines the controversial issue of whether "O, O" five-membered ring or "N, O" four-membered ring complexes are formed when BHA coordinates with Pb ions, with their structure being comprehensively studied from the aspect of colloid and interface science. The configurations of Pb–BHA complexes are examined in a solution and on a mineral surface with experimental and computational methods. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) revealed that the five-membered ring is the dominant form of Pb–BHA complexes in a solution, whereas four-membered ring complexes are the stronger electron acceptor of the two. Moreover, XPS and time-of-flight secondary ion mass spectrometry (TOF-SIMS) confirmed that the four-membered ring complexes are stable with respect to being adsorbed on the scheelite surface. Therefore, although the four-membered ring is not as stable as the five-membered ring in a solution, it offers advantages with respect to adsorption on an electron-rich mineral surface during short-flotation processes. [ABSTRACT FROM AUTHOR]

Apatite (Ca10(PO4)6F2) is the most important phosphate mineral, and flotation is the main beneficiation method to separate apatite from its major gangue mineral calcite (CaCO3). Till date, fatty acids and their salts have been widely used as collectors in the apatite/calcite flotation separation due to their low cost and strong collecting ability, but their selectivity is limited. Therefore, screening or designing a selective collector becomes the key to the efficient separation. In this work, an attempt was made to utilize benzohydroxamic acid (BHA) as the collector for the selective separation of apatite from calcite without any depressant. The single and mixed binary mineral flotation experimental results prove the excellent selectivity of BHA in the apatite/calcite flotation separation. Zeta potential measurement results indicate a greater affinity of BHA on the apatite surface than calcite, which is also confirmed by the higher adsorption energy of BHA on the apatite surface based on the first-principle density functional theory calculations. The X-ray photoelectron spectroscopy analysis shows that the selective chemisorption of BHA on apatite over calcite is due to the stronger reactivity and the higher density of Ca2+ ion on the apatite surface than calcite. This work shows that surfactants of hydroxamic acid type can be an ideal collector for phosphate mineral flotation. [ABSTRACT FROM AUTHOR]

Pyrite depression in copper ore flotation often requires large doses of inorganic depressants that lead to high toxicity, high costs, and low selectivity. Thus, this study offers a novel pyrite depressant, polyglutamic acid (PGA), in the selective flotation of chalcopyrite with xanthate as a collector. The flotation and adsorption mechanism on chalcopyrite and pyrite were systematically studied using a series of flotation tests, zeta potential measurements, adsorption analysis, infrared spectral (IR) analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The addition of PGA depressed the flotation of pyrite more strongly than chalcopyrite in the wide pH range of 8–12. In the presence of PGA, selective separation between the two minerals was achieved at pH 9, and the recovery of chalcopyrite was over 85% and that of pyrite was less than 20%. All of the surface analysis techniques indicated that PGA interacted differently with the two minerals and the surface of pyrite adsorbed a much greater amount of PGA than that of chalcopyrite. Prior addition of PGA significantly reduced the adsorption of the collector on the pyrite surface and thus depressed its flotation. However, the significant adsorption of the collector and its oxidation to dixanthogen on the chalcopyrite surface caused its improved flotation even in the presence of PGA. Therefore, PGA, which is a non-hazardous, biodegradable, and renewable reagent, could be used as an alternative pyrite depressant in Cu–Fe conventional flotation circuits. • PGA achieves improved selective separation of chalcopyrite (Clp) and pyrite (Pyr). • Polyglutamic acid (PGA) is a nontoxic and degradable depressant of Pyr flotation. • Clp adsorbs much greater amount of xanthate than Pyr in the presence of PGA. • PGA could be an alternative depressant in Cu–Fe conventional flotation circuits. [ABSTRACT FROM AUTHOR]

Highlights • TCSS achieves improved selective separation of chalcopyrite (Clp) from pyrite (Py). • Tricarboxylate sodium starch (TCSS) is a biodegradable depressant of Py flotation. • Clp adsorbs more xanthate collector than Py in the presence of TCSS depressant. Abstract In the flotation of copper sulfides, pyrite is often activated by Cu2+ ions dissolved from copper-bearing minerals in alkaline media (pH ˃ 9), which results in pyrite entering the copper concentrate. To reduce the floatability of pyrite, we designed a novel functionally modified biopolymer, tricarboxylate sodium starch (TCSS), that showed superior depression selectivity towards pyrite in low pH solutions when employed in Cu–Fe flotation separation in the presence of sodium butyl xanthate (SBX) as a collector. TCSS depressed the floatability of pyrite more strongly than that of chalcopyrite in single mineral flotation in the pH range 4–6. The most selective separation was achieved at pH ∼ 6; the recovery of Cu in the concentrate was over 77%, and the grade was improved to 24.50% compared to the initial feed grade of 12.50%. Surface characterization analyses, including zeta potential, X-ray photoelectron spectroscopy (XPS) analysis, and Fourier transform infrared (FTIR) spectroscopy, confirmed the different degrees of interaction of TCSS with the two minerals. TCSS was adsorbed on the pyrite surface, possibly via a chemisorption mechanism, as reflected in the FTIR and XPS analyses. The adsorption of TCSS passivated the pyrite surface, which inhibited the adsorption and oxidation of the collector. On the other hand, the adsorption and oxidation of the collector on chalcopyrite surface were effective even in the presence of TCSS, attesting to the weak interactions between chalcopyrite and TCSS. [ABSTRACT FROM AUTHOR]

This study presents a highly selective reagent system that utilizes sodium hexametaphosphate (SHMP) to improve the separation of scheelite from calcite and fluorite using an anionic–nonionic collector. The recoveries of calcite and fluorite decreased to 20% as the SHMP dose exceeded 6 × 10−6 mol/L, whereas that of scheelite remained at 85%. The interaction mechanisms of minerals with SHMP were investigated through equilibrium speciation, Zeta potential, Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy analyses. SHMP exists as hydrogen phosphate anion in the aqueous solution with a pH of 7–12. Moreover, it may be adsorbed intensively on the positively charged surfaces of calcite and fluorite via electrostatic force or chelation with calcium ion to impede further adsorption of the assembled collector. By comparison, the adsorption of SHMP is feeble on the scheelite surface because of its negative charge. The roughing grade of low-grade scheelite ore is substantially improved from 0.74% to 1.65% compared with that in the contrast test in the absence of SHMP. [ABSTRACT FROM AUTHOR]

The influences of long-term static interaction between flotation reagents and minerals on mineral surface properties and their flotation behaviors were investigated in this work. Single mineral results showed that when the static interaction time between flotation reagents and minerals increased from 0 to 8 days, there were no significant differences in the recovery of fluorite (ranging from 77.50% to 74.50%), while the recovery of calcite dramatically decreased from 97.17% to 41.13%. The collector adsorption results indicated that after the long-term static interaction between the collector and minerals, adsorption and desorption of collector on the minerals occurred, and the adsorption amount of collector on fluorite and calcite varied from 0.396 mg/g to 0.421 mg/g, and from 0.444 mg/g to 0.404 mg/g, respectively. The contact angles of fluorite and calcite decreased from 134.3° and 105.0° for 0 days to 109.7° and 52.5° for 8 days, respectively, which demonstrated that the fluorite had a higher hydrophobicity than that of calcite after 8 days of static interaction between the minerals and collector. The Fourier transform infrared spectroscopy (FTIR) analysis showed that there were chemisorptions between the collector and the surfaces of the fluorite and calcite. Meanwhile, the X-ray photoelectron spectroscopy (XPS) results further elucidated that the amount of C=O from the oleic acid (OA) molecule for calcite treated for 8 days was less than for that treated for 0 days. In addition, the flotation results of the tailings from Jiangxi containing fluorite and calcite, indicated that the grade and recovery of fluorite increased from 87.18% and 40.99% for 0 days to 93.00% and 46.01% for 8 days, respectively, indicating that the separation of fluorite from calcite could be achieved via increasing the long-term static interaction between the flotation reagents and minerals. [ABSTRACT FROM AUTHOR]

Selective adsorption of tannic acid (TA) on calcite surfaces and the implications of this process for the separation of fluorite ore were studied by microflotation tests, surface adsorption experiments, zeta potential measurements, UV–vis analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The microflotation tests indicated that TA, when added before sodium oleate (NaOl), could selectively depress calcite from fluorite at pH 7. Surface adsorption experiments revealed that TA hinders the interaction of NaOl with calcite. The zeta potential of calcite became more negative with TA than with NaOl. However, the characteristic features of TA adsorption were not observed on fluorite, suggesting that the dominant adsorption sites are dissimilar on the fluorite and calcite surfaces in the pulp. UV–vis spectroscopy, XPS, and solution chemistry analysis were utilized to obtain a better understanding of the mechanism for selective adsorption of TA as well as the key factors determined by the Ca 2+ and Ca(OH) + components on the mineral surfaces. A possible adsorption mechanism along with an adsorption mode is proposed for the surface interaction between TA and calcite. [ABSTRACT FROM AUTHOR]

• CO 2 significantly improved the flotation recovery of pyrite. • CO 2 effectively eliminated hydrophilic compounds from pyrite surface. • Xanthate oxidation to form dixanthogen was the dominant anodic process. • Pilot-scale experiments of pyrite flotation with CO 2 were successfully conducted. Activation flotation of lime-depressed pyrite by sulfuric acid (H 2 SO 4) is usually accompanied by safety hazards and environmental pollution. Exploring eco-friendly, economical and effective activator to replace H 2 SO 4 holds great significance for the sustainable development of mining industry. In this study, carbon dioxide (CO 2) as a potential activator was applied in activation flotation of lime-depressed pyrite. Micro-flotation experiments results showed CO 2 significantly improved the floatability of pyrite, and a maximum recovery of 93.94% was achieved under optimal operating conditions. The activation mechanism was investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results indicated the depression of pyrite by lime was attributed to the formation of iron oxide/hydroxide species and calcium film, and CO 2 effectively eliminated these hydrophilic compounds from the surface of pyrite, thus promoted the adsorption of xanthate onto the pyrite surface. Moreover, the anodic oxidation of xanthate on pyrite and the influence of CO 2 on this process were investigated by cyclic voltammetry measurements. It was found that xanthate oxidation to form dixanthogen was more likely to occur in the presence of CO 2 , and this reaction replaced pyrite surface oxidation as the dominant anodic process. Finally, pilot-scale experiments were successfully conducted and the recovery of pyrite reached 93.18%, surpassing the ore dressing index of using H 2 SO 4 as activator in actual production at the same period. Moreover, the concentration of sulfate ions in mineral processing wastewater was significantly reduced, and the annual cost of activator can be saved by 0.52 million RMB. The new process of activation flotation pyrite with CO 2 has prospects for large-scale application in terms of activation performance, cost-effectiveness and environmental impact. [ABSTRACT FROM AUTHOR]

Laurionite (PbOHCl) was the highly hazardous lead bearing waste in iron ore sintering dust and sulfidization flotation was a feasible and promising process for its enrichment. The flotation behavior and surface feature of Laurionite were first examined in this study. PbS films forming on the surface of PbOHCl greatly enhanced its floatability. Moderate dosage of Na 2 S was a significant parameter for the successful flotation of laurionite. • The flotation behavior and surface feature of Laurionite were first examined. • PbS films forming on the surface of PbOHCl greatly enhanced its floatability. • The mechanism of laurionite sulfidization flotation was first studied in detail. • Results shed light on the flotation recovery of laurionite in iron sintering dust. Laurionite is the main highly hazardous lead bearing waste in iron ore sintering dust due to its poor stability and high content, while its flotability and flotation separation have not been adequately investigated. In this study, the flotation behavior of laurionite and its interaction with Na 2 S were investigated in detail to find an economic and promising way for the separation of lead from sintering dust. The flotability and sulfidization flotation of laurionite were examined by micro-flotation experiments, zeta potential measurement, Fourier transform infrared spectroscopy (FT-IR) analysis and X-ray photoelectron spectroscopy (XPS) studies and solution chemistry calculation. The micro-flotation experiments results indicated that Na 2 S would improve the flotability of laurionite within a moderate dosage, otherwise decrease its float. The negativity of zeta potential observably increased when adding an appreciate amount of Na 2 S prior to NaBX, indicating a better adsorption of BX− on mineral surface, which would increase the flotation recovery. To figure out the mechanism behind that, the laurionite surface was analyzed by XPS, which found the formation of PbS films after adding Na 2 S. The FT-IR analysis showed the BX− absorbance on laurionite significantly decreased after treating with high concentration of Na 2 S. Moreover, the solution chemistry calculations demonstrated that the proper dosage of Na 2 S could enhance the flotation of laurionite by reduce free lead ion in solution and covered some part of lead mineral surface, which sharply reduced the demand of collectors in flotation. However, the excess S2− would inhibited the adsorption of BX− on laurionite surface since the formation Pb(BX) 2 was weaker than PbS. These results did not only expose that the addition of appropriate amount of Na 2 S could enhance laurionite's sulfidization flotation, but also provide an effective way to separate laurionite from iron ore sintering dust. [ABSTRACT FROM AUTHOR]

• Petrov's process is complex, costly and difficult to control. • Scheelite was selectively separated from fluorite using Pb-BHA complexes. • Adsorption mechanism of Pb-BHA complexes was studied. • A simplified flotation process was developed. • New process is beneficial to improving the recovery and water treatment. It is difficult to separate scheelite especially from fluorite with fatty acid collectors because the adsorption mechanism of these collectors occurs through chemisorption of the oleate ion onto the mineral surface. A simplified flotation process using Pb-BHA complexes was developed to replace the energy-inefficient Petrov's process of using a fatty acid, increasing the recovery of scheelite and reducing the cost. The relationship between surface chemical properties (crystal chemistry, solubility, and Zeta potential) of minerals and flotation by using a fatty acid or Pb-BHA complexes was studied in detail to provide new insights into the selective separation mechanism. The results indicate that the scheelite surface exposes more O atoms than Ca and that they are negatively charged due to the anisometric dissolution of Ca and WO 4 , which provides the possibility for separation using selective interfacial reaction. The Fourier Transform infrared spectroscopy (FTIR) and Zeta potential results indicate that both chemical and electrostatic adsorption play an important role in the adsorption of Pb-BHA complexes on the scheelite surface. The X-ray photoelectron spectroscopy (XPS) results of the atomic composition and binding energies confirmed the presence of the adsorbed Pb-BHA complexes and that Pb, O and Ca may be the active adsorption sites. Therefore, scheelite was able to be collected by forming either a Ca-O-Pb-collector or W-O-Pb-collector (BHA). However, fluorite was only able to be collected by a fatty acid collector and colloidal [H 2 SiO 3 ] n −, and a high temperature was needed improve the selective desorption of the adsorbed fatty acid collector by forming Ca-[H 2 SiO 3 ] n − on the fluorite surface, resulting in serious problems in industry. However, the Pb-BHA complexes significantly contribute to improving the recovery of scheelite minerals, simplifying the flotation process, and circulation of the residual reagents and water. [ABSTRACT FROM AUTHOR]

A selective organic depressant was investigated to promote the separation of scheelite from calcite and fluorite. 1-Hydroxyethylidene-1, 1-diphosphonicacid (HEDP) could efficiently reduce the recoveries of calcite and fluorite to less than 20%, while that of scheelite remained above 85%. The selective interaction mechanism was demonstrated via Zeta potential and X-ray photoelectron spectroscopy (XPS) analyses. The conceivable adsorption models of reagents on mineral surfaces were constructed to explain their adsorption mechanism. HEDP exhibited an excellent ability to selectively depress calcite and fluorite attributed to the intense adsorption on their surfaces, whereas its adsorption on scheelite surface was feeble. The technology feasibility of using HEDP to improve the scheelite flotation performance was verified through laboratory and industrial tests. The roughing grade was dramatically improved from 1.22% to 1.68%, and the product grade was enhanced from 24.66% to 28.26% with a noteworthy improvement of cleaning recovery by 6.93%, which would produce a considerable economic benefit. [ABSTRACT FROM AUTHOR]

The dissolved components of calcium-bearing gangue minerals will adsorb onto the celestite surface, which increases the difficulty of the flotation separation of celestite from fluorite and calcite. Single mineral and artificial mineral flotation experiments show that EDTA exhibits an excellent selective inhibition effect towards celestite and calcium-bearing minerals. Surface dissolution experiments reveal that EDTA can strongly inhibit the dissolution of calcium ions on the fluorite surface, thus reducing the influence of dissolved calcium ions on celestite flotation. Zeta potential experiments and adsorption experiments demonstrate that the amount of depressant EDTA adsorbed on the fluorite surface is greater than that on the celestite surface, which is contrary to the adsorption amount of collector sodium dodecyl sulfate (SDS) on the fluorite and celestite surfaces. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses further reveal that, through chelating with calcium ions, EDTA can change the chemical surroundings of elements on the fluorite surface, while the chelation is not evident on the celestite surface. Based on the experimental and analytical results above, a possible model for the flotation separation process is created. Unlabelled Image • EDTA can selective inhibit the flotation of celestite and calcium bearing minerals. • EDTA can strongly inhibit the dissolution of calcium ions on the fluorite surface. • The adsorption of EDTA on the fluorite surface is greater than that of celestite. • EDTA can be adsorbed by chelating with calcium ions on the fluorite surface. [ABSTRACT FROM AUTHOR]

• The flotation separation of fluorite from calcite and celestite was realized. • The optimum conditions for flotation separation were found. • The selective depression mechanism of the mixed depressant Al 2 (SO 4) 3 -AWG was discussed. To cope with the increase of sulfate gangue minerals in fluorite ores, flotation separation of fluorite from calcite and celestite using Al 2 (SO 4) 3 and acidified water glass (AWG) as mixture depressants was studied in this paper. The flotation separation performance and underlying mechanism were studied by flotation experiments, zeta potential measurements, microcalorimetric analysis, adsorption measurements, and X-ray photoelectron spectroscopy (XPS). The flotation results show that under optimum conditions, the inhibition effect of AWG on celestite is more remarkable with the assistance of Al 2 (SO 4) 3 , but has no obvious effect on the flotation of fluorite. Zeta potential measurements show that both positively charged Al species and negatively charged Si species are adsorbed on the surface of the minerals. Microcalorimetric analysis confirms that the interaction between Al 2 (SO 4) 3 and celestite is more intense than that of calcite and fluorite, while AWG is more likely to be adsorbed on the calcite surface. Adsorption measurements reVeal that there is competitive adsorption between the depressant and collector and that the adsorption of the depressant AWG prevents the collector NaOL from adsorbing on the surface of the minerals. The XPS results show that Al species and Si species are chemically adsorbed on the surface of the minerals and change the chemical surroundings of the elements on the mineral surface. Moreover, compared with fluorite, Al species can more clearly enhance the adsorption of Si species on the celestite surface. [ABSTRACT FROM AUTHOR]

Abstract Herein, we employed a range of instrumental techniques to investigate the performance of l -cysteine as a biodegradable and selective depressant in the flotation separation of molybdenite (MoS 2) from galena (PbS), demonstrating that this amino acid exhibited a superior depressing efficiency toward PbS and enabled the separation of the above minerals under alkaline conditions. In the presence of l -cysteine, the zeta potentials of PbS shifted to more negative values, which was indicative of chemisorption. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy measurements indicated that the above chemisorption involved the formation of a five-membered chelate ring via coordination of Pb by S (–SH) and N (–NH 2) atoms, as was further confirmed by time-of-flight secondary ion mass spectrometry measurements. Moreover, the detection of l -cysteine dimer on the surface of PbS was ascribed to the occurrence of oxidation processes. The predicted adsorption modes suggested an appreciable extent of surface interaction between l -cysteine and PbS, whereas density functional theory calculations demonstrated that the interaction between l -cysteine and the PbS (100) slab corresponds to both physical and chemical adsorption. Highlights • PbS was separated from MoS 2 by flotation using l -cysteine as a depressant. • The surface of l -cysteine-treated PbS was examined by a number of techniques. • l -Cysteine was found to coordinate Pb ions via NH 2 and SH groups. • l -Cysteine was concluded to be an excellent alternative to inorganic depressants. [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]

Plenty of respirable sintering dust are generated in ironmaking process and part of this hazardous particle easily escaped from electrostatic precipitators, becoming Particulate Matter 10. Previous studies are usually focused on the comprehensive recovery of this dust, however, its wetting, which was an essential procedure in many industrial processes, has long been a challenge due to its strongly hydrophobic property. The current study investigated the origin of its hydrophobicity through wettability tests, dynamic contact angle analysis, Fourier transform infrared spectrophotometer and X-ray photoelectron spectroscopy, with the goal of enhancing its wettability. The results revealed for the first time that the hydrophobicity of respirable sintering dust was attributed to a hydrophobic shell consisting of organics with n -alkyl chains and/or aromatic groups and bonding by hydrophilic functional groups. Further, results of response surface methodology with central composite design and dynamic contact angle analysis demonstrated that increasing agitation strength, such as stirring speed and time, can improve the wettability of respirable sintering dust, while the largest wettable ratio of 95.3% was obtained by stirring with 0.2% Triton X-100. Eventually, a possible wetting mechanism was mainly concluded as nonionic surfactants adsorbing with the hydrophobic shell on respirable sintering dust surface via its hydrophobic tail and leaving its hydrophilic head groups exposed to water, achieving sufficiently and efficiently wetting. The adsorption experiments and surface analysis results implied that the adsorption process for Triton X-100 onto respirable sintering dust is favorable and governed by physisorption. This study provides an effective method on the wetting of respirable sintering dust, which is essential for its treatment such as dust control and hydrometallurgy. [ABSTRACT FROM AUTHOR]

Pyrogallol, an eco-friendly derivative of tannic, was a potential substitute of toxic depressant used in bismuth-molybdenum (Bi–Mo) sulfide ore flotation. However, unclear depression mechanisms of pyrogallol on bismuth sulfides hindered its further application in the industry. In this work, the effect of pyrogallol on the flotation performance of bismuthinite was evaluated using flotation tests, and associated interaction mechanisms were investigated by using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. Micro-flotation tests showed that pyrogallol exhibited excellent depressing performance to bismuthinite in the whole pH range tested (2–12). In the presence of 300 g/t pyrogallol, over 95% of bismuthinite was effectively depressed in the real flotation process at pH around 9. FTIR and XPS results demonstrated that pyrogallol was chemisorbed on bismuthinite through the interactions among Bi atoms exposed on the bismuthinite surface and O−H groups in pyrogallol. The adsorption mechanism was further ascertained by DFT calculations, which revealed that the Bi–O–C single bond and the five-membered ring complex models were involved in the chemisorption of pyrogallol on bismuthinite surface. The work presented here not only provides new insights into the inhibition mechanisms of pyrogallol on bismuthinite but also provides theoretical support for the industrial application of pyrogallol. Image 1 • The floatability of bismuthinite decreases with increasing pH. • Pyrogallol exhibits excellent depression effect on bismuthinite flotation. • Bi sites in bismuthinite surface account for pyrogallic acid adsorption. • Pyrogallol chemisorbs on bismuthinite surface via the formation of Bi–O–C bonds. [ABSTRACT FROM AUTHOR]

• Pb2+ greatly improve spodumene floatability using BHA as collector. • Pb2+ cannot increase benzohydroxamic acid (BHA) adsorption amount on spodumene. • Pb2+ can change BHA structural arrangement at the spodumene-aqueous interface. In recent years, benzohydroxamic acid (BHA) has been widely used as a selective collector in the flotation of oxide minerals such as scheelite, wolframite, cassiterite and ilmenite despite its moderate collecting ability. Lead nitrate (Pb(NO 3) 2 , LN) is a commonly used activator for improving BHA flotation. According to the classical activation theory, the pre-adsorbed Pb2+ ion can increase the number of active site on oxide mineral surface, thus increasing the subsequent adsorption amount of BHA collector. In this study, BHA and LN were used, for the first time, in the flotation of spodumene, a valuable silicate and major source mineral for lithium battery materials. Interestingly, the adsorption test results show that the adsorption amount of BHA on spodumene surface was the same whether LN was added or not, while the micro-flotation test results show that the addition of LN helped increase the spodumene recovery from 0 to 80% using 120 mg/L BHA at pH 8. These results seem to be contradictory to the classical activation theory, yet by using density functional theory-based first-principle calculations, X-ray photoelectron spectroscopy and atomic force microscopy theoretically and experimentally, their underlying mechanism is therefore revealed. Those results show that in the absence of LN, a "flat" adsorption mode with the benzene ring of BHA parallel to the spodumene surface, is more inclined to a monodentate mode between O2− ion (attached to N) of BHA and surface Al3+ ion, leading to an adsorption energy of −113 kJ/mol. While with the presence of LN, a "vertical" adsorption mode with the benzene ring perpendicular to the spodumene surface, is favored in a bidentate mode between two O2− ions of BHA and Pb2+ ion of pre-adsorbed solvated Pb(OH)+ complex, leading to a much higher adsorption energy of −270 kJ/mol. Based on coordination chemistry analysis, differences in the adsorption mode and energy of BHA on Pb2+-activated and unactivated spodumene surfaces can be explained by differences in coordination number and bond dissociation energy. This study will provide valuable insights into the activation of Pb2+ ion in BHA flotation of valuable silicate minerals, and help to enrich understanding of activation mechanisms of metal ions in anionic collector flotation of minerals. [ABSTRACT FROM AUTHOR]