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Article

Enhanced Recovery of an Arsenopyrite-Type Gold Ore: Flotation Surface Chemistry and Kinetics of Blended Collector W8 with ADD

by
Qingqing Xing
1,2,
Fei Li
1,2,*,
Pingtian Ming
1,2,3 and
Zhen Wang
4,*
1
The Sixth Geological Exploration Institute of Qinghai Province, Xining 810029, China
2
Qinghai Engineering Research Center for Gold Mineral Resource Development Dressing and Metallurgy Pilot Plant, Dulan Jin Hui Mining Limited Corporation, Haixi Zhou 816100, China
3
School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100089, China
4
School of Environment and Resource, Southwest University of Science and Technology, Mianyang 621010, China
*
Authors to whom correspondence should be addressed.
Colloids Interfaces 2025, 9(6), 76; https://doi.org/10.3390/colloids9060076
Submission received: 8 October 2025 / Revised: 9 November 2025 / Accepted: 18 November 2025 / Published: 22 November 2025
(This article belongs to the Special Issue State of the Art of Colloid and Interface Science in Asia)
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Versions Notes

Abstract

This study investigated the flotation performance of W8, a blended xanthate collector containing ethyl, butyl, propyl, and amyl xanthates, combined with ammonium dibutyl dithiophosphate (ADD) for treating low-grade arsenopyrite-type gold ore from Golmud, Qinghai. Real ore flotation tests demonstrated the superior efficacy of the W8 + ADD system, achieving 84.06% gold recovery with 0.34 g/t tailings, outperforming conventional sodium amyl xanthate (SAX) + ADD and sodium propyl xanthate (SPX) + ADD systems. Systematic studies on pure arsenopyrite revealed a significant synergistic effect in the mixed SPX-SAX system (1:4 ratio), representative of W8 composition. At pH 9, the mixed collector achieved 73.5% recovery, substantially higher than individual SPX (37.5%) or SAX (45.8%). This enhanced performance was attributed to improved surface hydrophobicity (contact angle 47.68° vs. 36.92° for SAX), greater adsorption density (4.97 × 10−7 mol/g under depressant conditions), and extensive formation of molecular aggregates observed via AFM, which increased surface roughness to 28.95 nm. Flotation kinetics further confirmed the advantage of W8 + ADD, which reached 72.1% cumulative recovery in 420 s, exceeding both mixed SPX/SAX (69.5%) and single SAX (65.5%) systems. The synergistic interaction among different xanthate components in W8 enables efficient recovery of gold from this refractory ore.

1. Introduction

Gold is a strategic metal with unique properties and extensive applications [1,2]. With the rapid growth in domestic gold demand and the current resource landscape in China, the exploitation of low-grade and associated/disseminated gold deposits has become an inevitable necessity. Among the proven gold reserves in China, associated gold accounts for 30% of the total reserves [3,4]. Taking the Wulonggou Gold Mine in Dulan County, Qinghai Province as an example, it is a representative gold deposit of this type in the Qaidam Basin. The mining area consists of three independent ore sections, covering a total area of 2.12 square kilometers, with a total resource reserve of 120.81 tons and an estimated potential economic value exceeding 10 billion American dollars. The majority of China’s associated gold deposits are arsenopyrite-type, primarily distributed in the northwestern region. These are low-grade polysulfide gold ores characterized by fine dissemination of gold-bearing minerals, often associated with clay minerals such as sericite, chlorite, and kaolinite; sulfides with poor floatability like arsenopyrite serve as the primary gold-bearing minerals, making these ores typically complex and refractory [5,6].
The efficient flotation of refractory minerals imposes higher demands on the performance of flotation reagents, particularly collectors. The development of high-performance collectors that combine strong collecting power with high selectivity remains a key research focus and challenge in the flotation field [7]. Two main strategies are currently pursued: first, the molecular design of novel collectors [8]. For instance, by introducing heteroatoms or heterocyclic groups into traditional xanthate molecules, the strength and nature of interactions between functional groups and surface-active atoms on minerals can be modulated to balance selectivity and collecting capacity, thereby enabling the design of new, highly effective collectors [9]. Second, the blended use of existing collectors [10]. In cases of complex mineral intergrowth, a single collector often fails to achieve satisfactory separation. However, the combination of reagents according to certain principles can produce unexpected synergistic effects—commonly referred to as synergism. Compared to single reagents, blended reagent systems can improve flotation efficiency, increase concentrate grade, reduce reagent consumption, or optimize the flotation environment [11,12].
For instance, the use of a mixed collector system comprising octyl hydroxamic acid (OHA) and sodium dodecyl sulfonate (SDS) enhanced columbite recovery while reducing operational costs [13]. To address the issue of high reagent costs at a copper smelting slag processing plant, Wang Zitao et al. conducted experimental studies with various collectors. Their results demonstrated that a combined collector system of Z-200 and butyl xanthate provided superior performance, optimizing metallurgical performance while simultaneously reducing reagent consumption [14]. In a case study conducted by Bradshaw, synergies between thiol collectors during pyrite flotation at pH 4 were reported. Potassium butyl xanthate and a dithiocarbamate collector were evaluated both as individual collectors and as components of a blended collector system. Batch flotation tests assessed the impact of the mixed collector on overall flotation performance by measuring sulfur recovery and grade, water recovery, and flotation kinetics. The results indicated that the use of the collector mixture enhanced the bubble-particle collection efficiency [15].
W8 is a blended xanthate collector comprising ethyl, butyl, propyl, and amyl xanthates. In this study, it was applied to the flotation of a gold ore from Golmud, Qinghai, where arsenopyrite serves as the primary gold-bearing mineral [16]. At present, under the collector system composed of amyl xanthate and butylamine black drug used on site, the recovery rate of gold concentrate is not good. Preliminary tests revealed that W8 outperformed pure amyl xanthate, even when both were used in combination with ammonium dibutyl dithiophosphate. Building on previous findings by other researchers, the enhanced mechanism of W8 was systematically investigated through a series of methods including micro-flotation tests on pure minerals, contact angle measurements, adsorption density analysis, surface morphology characterization, and flotation kinetics studies.

2. Materials and Methods

2.1. Materials and Reagents

The raw ore samples were collected from the Wulonggou mining area in Golmud City, Qinghai Province. The element composition is shown in Table 1. The gold ore assayed 2.16 g/t, a submarginal grade that remains economically viable for extraction under current technological and economic conditions [17]. Chemical analysis revealed a composition of 62.25% SiO2 and 13.37% Al2O3, indicating a high content of quartz and silicate/aluminosilicate minerals, which constitute the primary acidic gangue. Gold is mainly encapsulated in carrier minerals in a micro-submicroscopic state, accounting for more than 70% (with the remaining less than 30% distributed in other minerals): approximately 39.11% of the gold is encapsulated in arsenopyrite, 11.01% in pyrite, and 1.69% in pyrrhotite. Furthermore, the elevated concentrations of arsenic and carbon categorize this ore as refractory, presenting significant challenges for conventional cyanidation. The focus of this study is not on the gangue minerals, but on the efficient flotation of the gold-bearing mineral, arsenopyrite.
Pure minerals of arsenopyrite were obtained from Beijing Shuiyuan Shanchang mineral specimen Co., LTD. (Beijing, China). The samples were dry-ground using a jar mill with porcelain balls and subsequently classified by sieving through screens with apertures of 0.045 and 0.026 mm, respectively. The −0.045 + 0.026 mm fraction was reserved for micro-flotation tests, adsorption studies and contact angle measurements. This is a relatively common method for mineral sample processing [18]. Laser particle size analysis was conducted on the samples obtained through sieving, and the resulting curves are shown in Figure 1. It is obvious that the particle size of the samples is indeed within the expected range. The phase purity of arsenopyrite was verified by X-ray diffraction (XRD; X’Pert PRO, PANalytical B.V., Almelo, The Netherlands) to obtain the spectrum (Figure 2).
Analytically pure hydrochloric acid and sodium carbonate Na2CO3 were used as the pH regulators. Analytically pure terpilenol (C10H18O (4-methyl-2-pentanol)) was used as the frother. Copper sulfate (CuSO4), sodium amyl xanthate (SAX, C5H11OCSSNa), sodium propyl xanthate (SPX, C3H7OCSSNa), and Ammonium dibutyl dithiophosphate (ADD,(C4H9O)2PSSNH4), were also analytical reagent grade and used as the collector. The above analytically pure reagents were bought from Sinopharm Group (Beijing, China).

2.2. Flotation Tests

2.2.1. Flotation of the Real Ore

The open circuit flow sheet for collector comparison with one roughing and one scavenging is shown in Figure 2. A total of 500 g of raw ore was ground to −0.074 mm size fractions accounting for 78% in a laboratory conical ball mill and placed into the 1.5 L flotation cell (XFD-type flotation apparatus), and the flotation cell was filled with water to prepare a pulp with the solid concentration of approximately 40 w.%. The slurry pH was regulated using Na2CO3 solution; CuSO4 was used as the activator of Au-bearing sulfide minerals; SWUST-D01 (polysaccharide) was employed as the depressant; SAX + ADD or W8 + ADD was used as the collector; and 2# oil (industrial products of terpineol) was used as the frother. The condition time for each step and the reagent dosage are shown in Figure 3. After finishing the roughing operation, the scavenging was conducted with lower reagent dosage. The floated fraction of roughing was the concentrate, and that of scavenging was the middlings; the product remaining in the flotation cell was the tailings. The final concentrate, middlings, and tailings were filtered, dried, weighed, and analyzed for Au.

2.2.2. Flotation of Pure Mineral

Micro-flotation tests on pure minerals were performed using a 40 mL flotation cell. In each test, 2.0 g of the mineral sample was charged into the cell containing 35 mL of distilled water and agitated at 1920 r/min for 2 min. The pH was then adjusted to the desired value using HCl or Na2CO3 as regulators. Following pH conditioning, the activator was introduced, followed by the collector, with each reagent addition succeeded by 3 min of conditioning. Subsequently, terpinenol was added and the pulp was agitated for another 2 min prior to the 5-min flotation process. Both the floated and non-floated products were collected, separately filtered, dried, and weighed. The flotation recovery was calculated based on the dry weights of the concentrates and tailings. All tests were conducted in triplicate under identical conditions, and the average recovery was reported, with the deviation among replicates maintained within 3%.
For the flotation kinetics study, a single dose of reagents was added initially, followed by the collection of froth products in six timed intervals: the first two at 30 s each, the next two at 60 s each, and the final two at 120 s each.

2.3. Contact Angle

To determine the wettability of the arsenopyrite surface, a contact angle measurement apparatus was employed in this study. First, mineral tablets of the arsenopyrite powder were prepared, and then treated with various collectors. Subsequently, these treated bulk samples were air-dried naturally at room temperature to ensure the consistency of surface conditions. For the contact angle measurement, the sessile drop method was adopted to determine the contact angle of the processed thin tablets.

2.4. Adsorption Measurements

The adsorption density of xanthate on arsenopyrite was determined by measuring the absorbance at the characteristic wavelength of 301 nm using a UV-3100 spectrophotometer. In a typical procedure, a 2.0 g sample of the −0.045 + 0.026 mm fraction was pulped with 40 mL of distilled water, followed by the addition of specified reagents. The slurry was agitated for 15 min and subsequently centrifuged for 10 min at 4500 rpm using a high-speed refrigerated centrifuge (S-1-150s, HONGHUAYIQI Co., Ltd., Cangzhou, China). The absorbance of the resulting supernatant was then measured. The residual xanthate concentration was determined by referring to a pre-established calibration curve (Figure 4). Finally, the amount of xanthate adsorbed on the mineral surface was calculated based on the difference between the initial and equilibrium concentrations [19].

2.5. Atomic Force Microscopy Observation

The surface morphology of arsenopyrite before and after collector adsorption was characterized in situ using atomic force microscopy (AFM; Dimension Icon, Bruker Nano Inc., USA). Sample preparation involved sequential wet polishing with 600-, 800-, 1000-, 1200-, 1500-, 2000-, and 2500-mesh abrasive papers, followed by final polishing with diamond suspensions of 3 μm, 1 μm, and 0.2 μm particle sizes [20]. After being immersed in the respective collector solutions for 6 h, the polished sections were thoroughly rinsed with deionized water, dried under a gentle nitrogen stream, and subsequently examined by AFM. Imaging was conducted under ambient conditions using ScanAsyst mode for topographical analysis and force modulation mode for mechanical property mapping, with antimony (n)-doped silicon cantilevers (TESPA-V2, Bruker, Billerica, MA, USA).

3. Results and Discussion

3.1. Real Ore Flotation

The separation indicators of a certain gold ore in Golmud under three reagent systems were comparatively studied, and the results are shown in Table 2. In the production plant of a Golmud gold mine, the combined collector system of SAX and ADD was employed. When applied to the experimental flowsheet, this system achieved a high gold concentrate grade of 14.10 g/t, along with a recovery of 81.94%, while reducing the gold content in the tailings to 0.37 g/t. These results are considered satisfactory. For comparison, when SPX was used to replace SAX at the same dosage, forming an SPX + ADD collector system, the resulting gold recovery and concentrate grade were 81.27% and 13.4 g/t, respectively. Both of these key indicators were lower than those obtained with the SAX + ADD system. Obviously, this is related to the longer chain length of the hydrocarbons in SAX [21].
When the novel collector W8 was substituted for SAX, the new W8 + ADD system yielded the best overall performance: a gold recovery of 84.06% and a concentrate grade of 13.30 g/t, with the gold content in tailings further reduced to 0.34 g/t. Given that recovery is generally of greater practical significance than grade during the roughing and scavenging stages, the W8 + ADD collector system clearly delivered the most favorable outcomes [22]. It demonstrates the superior flotation performance of W8 + ADD for this specific gold ore compared to the collector system currently used in the plant.

3.2. Micro Flotation of Pure Mineral

The novel collector W8 has a complex composition, being a mixture of several xanthates and dithiophosphates in specific proportions. To simplify the experimental system and more directly reveal the physicochemical mechanism underlying the synergistic effects of reagent blending, this study investigates the flotation behavior and interfacial interactions of arsenopyrite using a mixed propyl/amyl xanthate collector system. The results are shown in Figure 5.
When used individually, SAX generally demonstrated better collecting power than SPX. Both collectors reached their maximum flotation efficiency at a dosage of 6 × 10−5 mol/L. Further increasing the dosage did not significantly improve the recovery of arsenopyrite, which is likely attributed to the approach of monolayer adsorption saturation on the mineral surface at higher concentrations [23]. Beyond this point, the incremental increase in adsorption density decreases sharply.
When SPX and SAX were used in combination (Mixed, mass ratio 1:1), a noticeable improvement in recovery was observed. That is, replacing part of the long-chain SAX with short-chain SPX resulted in better flotation performance than using SAX alone. This finding contrasts with the conventional understanding that longer-chain collectors typically exhibit superior performance when used individually and instead indicates a synergistic interaction between short-chain SPX and long-chain SAX in the mixed system, enhancing the flotation recovery of arsenopyrite [24].
Figure 6 illustrates the relationship between pulp pH and the flotation recovery of arsenopyrite in different xanthate systems. Overall, the flotation recovery of arsenopyrite decreased with increasing pulp pH across all reagent systems. However, at any given pH value, the mixed collector system consistently yielded significantly higher recovery compared to individual collectors. For instance, under weakly alkaline conditions (pH ≈ 9), the recoveries achieved with SPX, SAX, and the mixed system were 37.5%, 45.8%, and 73.5%, respectively, indicating a pronounced enhancement in flotation performance with the mixed collectors.
Furthermore, it can be observed that when the pH exceeded the neutral range, the flotation recovery of arsenopyrite declined rapidly in single-collector systems. In contrast, with the mixed collector system, the recovery remained relatively stable from the neutral pH range up to around pH 9. This suggests that the mixed collectors not only enhance the adsorption capacity on the arsenopyrite surface but also exhibit stronger adaptability to pH variations compared to individual collector systems.

3.3. Contact Angle Measurement

Measuring the contact angle is a widely used method to assess changes in surface wettability [25]. A smaller contact angle indicates better wettability (i.e., poorer hydrophobicity), while a larger angle indicates poorer wettability (i.e., better hydrophobicity). The flotation process relies heavily on the wettability of specific mineral surfaces in the pulp. For instance, the adsorption of collectors onto valuable mineral surfaces inevitably reduces their wettability, whereas the interaction of depressants with gangue minerals increases it [26]. Thus, contact angle measurements performed on arsenopyrite—a characteristic gold-bearing mineral in this ore—before and after reagent treatment, help clarify the performance of the reagents.
Figure 7 presents the contact angle results for arsenopyrite before and after interaction with the reagent. In this study, contact angles were measured on pressed powder pellets of arsenopyrite, which explains the difference from values reported in the literature for natural arsenopyrite surfaces. Nevertheless, the comparison of contact angles before and after reagent treatment effectively reveals the reagents’ impact and their effect on mineral surface hydrophilicity/hydrophobicity [27].
Figure 7a shows the arsenopyrite surface without any reagent treatment. Figure 7b–d show the surfaces after treatment with the collector SPX, SAX, and the mixed-xanthate system, respectively.
As shown in the figures, the contact angle on the untreated arsenopyrite surface is 17.98°, a relatively low value indicating its naturally hydrophilic. After treatment with SPX, the contact angle increases significantly to 33.54°, demonstrating that this collector substantially enhances the hydrophobicity of the arsenopyrite surface. Treatment with SAX results in a further increase in the contact angle to 36.92°, indicating its stronger ability to impart hydrophobicity compared to SPX. This observation aligns with the literature reports that longer-chain xanthate collectors generally exhibit greater collecting power and hydrophobization capability [28].
Notably, after treatment with the mixed-xanthate system, the contact angle reaches 47.68°, the highest value observed. This suggests that the mixed collector system has a stronger hydrophobizing effect on the arsenopyrite surface than SAX alone.
It is particularly noteworthy that, at the same concentration, the proportion of the long-chain component (SAX) in the mixed system is lower than that in the single-xanthate system. This finding further supports the existence of a synergistic interaction between the long-chain SAX and the short-chain SPX in the mixed system, producing a combined effect greater than the sum of its parts.
The contact angle results are consistent with the flotation test data, explaining the flotation behavior of pure arsenopyrite from the perspective of surface hydrophobicity changes. This alignment also corresponds well with the improved gold recovery observed in the plant following the adoption of the new collector W8.

3.4. Adsorption Amounts of Collector

Measuring the adsorption density of reagents on mineral surfaces can explain why certain collectors can float minerals previously considered refractory, or why specific modifiers render normally floatable minerals difficult to concentrate. Understanding reagent adsorption helps optimize the flotation process, improving both efficiency and recovery. For instance, by adjusting reagent type, concentration, and dosage, the floatability of target minerals can be better controlled, thereby enhancing overall separation performance [29].
Figure 8 shows the relationship between xanthate collector dosage and its adsorption density on arsenopyrite surfaces. The results clearly indicate that under identical concentration conditions, the adsorption density of SAX is higher than that of SPX. This suggests that the stronger collecting power of the longer-chain SAX is attributable not only to a more robust interaction between its molecules and the active sites on the mineral surface but also to a greater number of molecules adsorbed [30].
In the mixed collector system, the total adsorption density of xanthate molecules per gram of mineral was found to be higher than that in any single-collector system. This is noteworthy given that the proportion of the long-chain component (SAX) in the mixture is lower than its dosage in the single SAX system. This observation strongly indicates a mutually enhanced adsorption, or a synergistic effect, between the different collector molecules in the mixed propyl/amyl xanthate system. The resulting increase in overall adsorption density on the arsenopyrite surface provides a plausible explanation for the superior flotation performance observed in the single-mineral flotation tests.
Figure 9 illustrates the relationship between the adsorption density of xanthate collectors on arsenopyrite surfaces and the dosage of the inhibitor EMY-515 (polysaccharide). These results clearly demonstrate that the depressant significantly influences the adsorption density across all three collector systems.
At a depressant dosage of 100 mg/L, the adsorption densities for the SPX, SAX, and mixed collector systems were measured at 0.74 × 10−7 mol/g, 1.46 × 10−7 mol/g, and 4.97 × 10−7 mol/g, respectively. In contrast, the corresponding values in the absence of the depressant were 7.24 × 10−7 mol/g, 7.59 × 10−7 mol/g, and 7.94 × 10−7 mol/g. Notably, the mixed collector system exhibited a relatively smaller reduction in adsorption density under the influence of the depressant. This indicates that the mixed-xanthate system possesses better adaptability to the plant-used depressant EMY-515, effectively mitigating its suppressive effect on collector adsorption. As a result, the negative impact of the depressant on the floatability of arsenopyrite—the primary gold-bearing mineral—is minimized, which is of significant importance for achieving efficient separation between valuable and gangue minerals.

3.5. Surface Topography Measurement

AFM has been employed to investigate the adsorption morphology and mechanisms of collectors on mineral surfaces, thereby providing microscopic insights into how reagents influence reagent adsorption [31].
Figure 10a shows the surface morphology of arsenopyrite after adsorption of the long-chain xanthate collector SAX. Certain regions exhibit pronounced protrusions due to the adsorption of collector molecular aggregates, while multiple smaller raised features are also distributed across the surface. The maximum surface height reaches 114 nm, with a surface roughness of 5.87 nm, indicating multi-site adsorption of the collector in the form of molecular aggregates [32].
Figure 10b presents the surface topography of arsenopyrite treated with the mixed SPX/SAX collector system. It can be observed that large areas of the surface are covered with prominent protrusions resulting from the adsorption of collector aggregates. The maximum height measured is 105 nm, and these features are widely distributed across the surface, accompanied by a significantly higher roughness of 28.95 nm. This suggests a greater number of adsorbed molecular aggregates in the mixed system [33]. Notably, since the proportion of the long-chain amyl xanthate in the mixed system was lower than that in the single-collector system, the abundant aggregate adsorption observed demonstrates a markedly enhanced adsorption capability of the mixed propyl/amyl xanthate system over individual collectors.

3.6. Flotation Kinetics Results

Therefore, the various analytical techniques employed in this mechanistic study collectively and consistently demonstrate a distinct synergistic effect in the mixed-xanthate systems compared to single-xanthate systems. The results obtained from these different methods are highly coherent and mutually reinforcing, and they provide a clear explanation for the phenomena observed in single-mineral flotation tests. These findings offer a robust interpretation for the improved flotation recovery achieved in the plant using the new reagent W8, which is formulated as a blend of several xanthate-based collectors.
The flotation kinetics is also an important aspect of flotation research [34]. In actual production, it was also observed that the W8 flotation reagent, when combined with ADD, provides a significant advantage in flotation rate over the conventional amyl xanthate + ADD collector system (greater amount of froth in roughing stage). To further investigate this, the present study subsequently examined the flotation rates of a single SAX system, a Mixed (SPX + SAX, 1:4) system, and a Mixed + ADD system—the latter was prepared by combining the aforementioned Mixed collectors with ADD at a 1:1 ratio, based on the previously established interfacial chemistry findings.
The flotation kinetics of arsenopyrite in different collector systems are summarized in Table 3. The corresponding flotation rate curves, relating concentrate recovery to flotation time, are subsequently plotted in Figure 11 based on the data presented in the table.
Figure 11a illustrates the relationship between the instantaneous recovery of arsenopyrite and flotation time under different collector systems. As shown, during the first three froth collections, the instantaneous recovery achieved with the Mixed + ADD system consistently ranked the highest, following the order: Mixed + ADD > Mixed > SAX. Beyond 120 s, the instantaneous recovery of the Mixed + ADD system decreased notably, which can be attributed to the rapid recovery of most floatable valuable minerals within the initial two minutes. This observation clearly demonstrates the flotation rate advantage of the Mixed + ADD collector system [35].
Figure 11b presents the cumulative recovery of arsenopyrite as a function of flotation time for the different collector systems. It is evident that the cumulative recovery obtained with the Mixed + ADD system is the highest at each time point, maintaining the same order: Mixed + ADD > Mixed > SAX. Within the total flotation time of 420 s, the Mixed + ADD system also achieved the highest final cumulative recovery. Moreover, the trend observed in the later stage of the kinetics curve suggests that the Mixed + ADD system has the potential to achieve a greater ultimate recovery even at extended flotation times.
These results indicate that the Mixed + ADD system—new collector system based on W8—not only exhibits superior collecting power compared to the mixed xanthate (Mixed) and single SAX systems—but also demonstrates a significant advantage in flotation kinetics [36]. The favorable flotation kinetics performance of W8 is of great practical importance for the flash flotation and rapid recovery of gold-bearing minerals in industrial operations, and it has been preliminarily elucidated through these tests.

4. Conclusions

(I) W8 + ADD exhibits superior performance in flotation of Golmud’s low-grade arsenopyrite-type gold ore. It achieves 84.06% gold recovery and 0.34 g/t tailing gold, outperforming SPX + ADD and SAX + ADD, effectively addressing the ore’s challenges of flotation.
(II) A distinct synergism exists between SPX and SAX (1:4 mass ratio) in W8. This synergism boosts arsenopyrite recovery (73.5% at pH 9, vs. 37.5% for SPX and 45.8% for SAX) and enhances depressant resistance: under 100 mg/L depressant, the mixed system maintains 4.97 × 10−7 mol/g adsorption, much higher than single collectors.
(III) SPX–SAX system (1:4, representative of W8) significantly modifies arsenopyrite’s surface properties: it increases the contact angle to 47.68° to strengthen hydrophobicity, and forms extensive adsorption aggregates, raising surface roughness to 28.95 nm (vs. 5.87 nm for SAX), which improves bubble-particle attachment stability.
(IV) (SPX–SAX) + ADD has a notable kinetic advantage, achieving 72.1% cumulative arsenopyrite recovery in 420 s (vs. 69.5% for mixed SPX/SAX). This suits industrial flash flotation, promoting rapid gold-bearing mineral recovery and enhancing production efficiency.

Author Contributions

Conceptualization, F.L. and Z.W.; methodology, Z.W.; validation, Q.X. and P.M.; investigation, Q.X.; resources, Z.W.; writing—original draft preparation, Q.X.; writing—review and editing, Z.W.; supervision, P.M.; funding acquisition, Z.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Sichuan Science and Technology Program of China (Nos. 2024YFHZ0243), the National Natural Science Foundation of China (No. 52474301), and the key program of the National Key Research and Development Program (No. 2023YFE0104100).

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

Authors Qingqing Xing, Fei Li and Pingtian Ming were employed by the company Dulan Jin Hui Mining Limited Corporation. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

  1. Zare, I.; Yaraki, M.T.; Speranza, G.; Najafabadi, A.H.; Shourangiz-Haghighi, A.; Nik, A.B.; Manshian, B.B.; Saraiva, C.; Soenen, S.J.; Kogan, M.J.; et al. Gold Nanostructures: Synthesis, Properties, and Neurological Applications. Chem. Soc. Rev. 2022, 51, 2601–2680. [Google Scholar] [CrossRef] [PubMed]
  2. Xolo, L.; Moleko-Boyce, P.; Makelane, H.; Faleni, N.; Tshentu, Z.R. Status of Recovery of Strategic Metals from Spent Secondary Products. Minerals 2021, 11, 673. [Google Scholar] [CrossRef]
  3. Özçelik, S.; Ekmekçi, Z. Surface Chemistry and Flotation of Gold-Bearing Pyrite. Minerals 2024, 14, 914. [Google Scholar] [CrossRef]
  4. Gorain, B. FLOT-ART: An Integrated Plant Optimization Tool for the Flotation of Copper and Copper–Gold Ores. Miner. Eng. 2024, 207, 108578. [Google Scholar] [CrossRef]
  5. Wang, Z.; Zou, D.; Zhao, K.; Chen, R.; Huang, X.; Wang, X. Reducing the Adhesion of Mica on Arsenopyrite Surface Using Sodium Phytate and the Application in Flotation Separation. Sep. Sci. Technol. 2022, 58, 835–847. [Google Scholar] [CrossRef]
  6. Xing, Q.; Ming, P.; Wang, X.; Li, F.; Wang, Z.; Zhao, K. Fenugreek Polysaccharide Gum as a Depressant in the Flotation Separation of Gold Ore with a High Content of Clay Minerals. Colloids Interfaces 2025, 9, 21. [Google Scholar] [CrossRef]
  7. Forson, P.; Skinner, W.; Asamoah, R. Investigating the Selective Flotation of Auriferous Arsenian Pyrite from Refractory Ores Using Thionocarbamate. Powder Technol. 2023, 426, 118649. [Google Scholar] [CrossRef]
  8. Liu, J.; Tao, Y.; Chang, T.; Ge, W.; Jiang, K.; Lv, L.; Zhu, Y.; Yuan, S. Study on Flotation Separation of Barite Fluorite by Citric Acid under New Collector System. Colloids Surfaces A Physicochem. Eng. Asp. 2024, 692, 134058. [Google Scholar] [CrossRef]
  9. Zhang, W.; Feng, Z.; Xu, S.; Gao, Z. Molecular Design and Performance Evaluation of Collectors for Sulfide Minerals: A Review. J. Nonferrous Met. 2025, 2, 68–86. [Google Scholar] [CrossRef]
  10. Rao, K.H.; Forssberg, K.S.E. Mixed Collector Systems in Flotation. Int. J. Miner. Process 1997, 51, 67–79. [Google Scholar] [CrossRef]
  11. Cao, Q.; Cheng, J.; Wen, S.; Li, C.; Bai, S.; Liu, D. A Mixed Collector System for Phosphate Flotation. Miner. Eng. 2015, 78, 114–121. [Google Scholar] [CrossRef]
  12. Lotter, N.; Bradshaw, D. The Formulation and Use of Mixed Collectors in Sulphide flotation. Miner. Eng. 2010, 23, 945–951. [Google Scholar] [CrossRef]
  13. Hu, Y.; Wang, J.; Qin, Q.; Cao, Z.; Lu, W.; Shi, J.; Wu, X.; Wang, P.; Sun, Y. Enhancing the Flotation of Columbite via the Synergistic Effect of Mixed Collectors. Miner. Eng. 2025, 225, 109235. [Google Scholar] [CrossRef]
  14. Wang, Z.; Yan, G.; Yang, L. Experimental Study and Production Practice for Reducing the Tailing Grade in a Copper Smelting Slag Concentrator. World Nonferrous Met. 2022, 31, 43–47. [Google Scholar] [CrossRef]
  15. Bradshaw, D.J.; Harris, P.J.; O’Connor, C.T. Synergistic Interactions between Reagents in Sulphide flotation. J. S. Afr. I. Min. Metall. 1998, 98, 189–193. Available online: https://journals.co.za/doi/abs/10.10520/AJA0038223X_2481 (accessed on 15 November 2025).
  16. Zhou, X.; Pan, T.; Ding, Q.-F.; Cheng, L.; Song, K.; Liu, F.; Gao, Y. Isotope Geochemistry of the Shenshuitan Gold Deposit within the Wulonggou Gold Field in the Eastern Kunlun Orogen, Northwest China: Implications for Metallogeny. Minerals 2022, 12, 339. [Google Scholar] [CrossRef]
  17. Zhang, W.; Yuan, Q.; Jia, S.; Li, Z.; Yin, X. Multi-Objective Optimization of Forth Flotation Process: An Application in Gold Ore. Sustainability 2021, 13, 8314. [Google Scholar] [CrossRef]
  18. Zhao, P.; Liu, W.; Liu, W.; Bao, L.; Shen, Y.; Butt, S.; Zhang, Y. Synthesis, Flotation Behavior, and Structure-Performance Relationship of Three Hydroxyl-Containing Cationic Collectors. Miner. Eng. 2025, 231, 109443. [Google Scholar] [CrossRef]
  19. Pan, Z.; Sun, X.; Wei, Q.; Jiao, F.; Qin, W. Impact of Serpentine Particle Coating on the Adsorption of Ethyl Xanthate on Pentlandite Surface in Flotation. Miner. Eng. 2024, 216, 108845. [Google Scholar] [CrossRef]
  20. Zhou, M.; Wang, Z.; Zhao, K.; Yao, C.; Chen, R.; Huang, X.; Safarov, S.S.; Kholov, K.I. Combined Collector Based on N-propyl-N-allyl-o-isobutyl Thiocarbamate Improving the Flotation of Pentlandite. Miner. Eng. 2025, 227. [Google Scholar] [CrossRef]
  21. Suo, X.; Yu, B.; Sha, J.; Gao, R.; Qi, M.; Huang, Y.; Peng, W.; Guo, X.; Wang, W.; Cao, Y.; et al. Flotation Separation of Quartz and Feldspar under Weak Alkaline Conditions Using Amine ether as a Novel Collector. Chem. Eng. Sci. 2025, 315, 121873. [Google Scholar] [CrossRef]
  22. Chen, G.; Zhao, H.; Zhou, J.; Liu, Z.; Yang, H. Process Mineralogy Study and Flotation Testwork of a Complex Lead–Gold Rougher Concentrate. Minerals 2025, 15, 967. [Google Scholar] [CrossRef]
  23. Tamm, K.; Zadeh, Z.A.; Kuusik, R.; Kallas, J.; Yang, J.; Tõnsuaadu, K.; Trikkel, A. Effect of Flotation Time and Collector Dosage on Estonian Phosphorite Beneficiation. Minerals 2021, 11, 114. [Google Scholar] [CrossRef]
  24. Özün, S.; Ergen, G. Determination of Optimum Parameters for Flotation of Galena: Effect of Chain Length and Chain Structure of Xanthates on Flotation Recovery. ACS Omega 2019, 4, 1516–1524. [Google Scholar] [CrossRef] [PubMed]
  25. Kwok, D.Y.; Neumann, A.W. Contact Angle Measurement and Contact Angle Interpretation. Adv. Colloid Interfac. 1999, 8, 167–249. [Google Scholar] [CrossRef]
  26. Kruszelnicki, M.; Polowczyk, I.; Kowalczuk, P.B. Insight into the Influence of Surface Wettability on Flotation Properties of Solid Particles—Critical Contact Angle in Flotation. Powder Technol. 2023, 431, 119056. [Google Scholar] [CrossRef]
  27. Alghunaim, A.; Kirdponpattara, S.; Newby, B.-M.Z. Techniques for Determining Contact Angle and Wettability of Powders. Powder Technol. 2016, 287, 201–215. [Google Scholar] [CrossRef]
  28. de Medeiros, A.R.S.; Baltar, C.A.M. Importance of Collector Chain Length in Flotation of Fine Particles. Min. Eng. 2018, 122, 179–184. [Google Scholar] [CrossRef]
  29. Rao, K.H.; Forssberg, K.S.E. Mechanism of Fatty Acid Adsorption in Salt-type Mineral Flotation. Min. Eng. 1991, 4, 879–890. [Google Scholar] [CrossRef]
  30. Xie, Y.; Yin, W.; Yao, J.; Yin, X.; Liu, J.; Xue, F.; Tian, D. Flotation Behavior and Surface Adsorption Mechanism of a Novel Selective Inhibitor HDP in the Separation of Chalcopyrite and Talc Flotation. J. Mol. Liq. 2024, 398, 124206. [Google Scholar] [CrossRef]
  31. Monte, M.B.d.M.; Pimentel, D.A.; Albuquerque, M.D.d.F.d.; Neumann, R.; Silva, L.A.; Correia, J.C.; Uliana, A. Synergism of mixed cationic collectors in the flotation of quartz unveiled by AFM, solution chemistry and quantum chemical calculations. J. Mol. Liq. 2023, 376. [Google Scholar] [CrossRef]
  32. Zeng, H.; Sun, W.; Tang, H.; Jiang, F.; Wang, L. Surface Roughness and Its Role in Flotation Behavior, Wettability, and Bubble–Particle Interactions: A Systematic Review. Appl. Sci. 2025, 15, 4557. [Google Scholar] [CrossRef]
  33. Lu, Y.; Liu, D.; Cai, Y.; Gao, C.; Jia, Q.; Zhou, Y. AFM measurement of roughness, adhesive force and wettability in various rank coal samples from Qinshui and Junggar basin, China. Fuel 2022, 317, 123556. [Google Scholar] [CrossRef]
  34. Zhu, R.; Gu, G.; Chen, Z.; Wang, Y.; Song, S. A new collector for effectively increasing recovery in copper oxide ore-staged flotation. Minerals 2019, 9, 595. [Google Scholar] [CrossRef]
  35. Şimşek, S.; Kilinç, T.; Cebeci, Y.; Abbaker, A. Application of Flotation Kinetics Models to Chalcopyrite Flotation: Determination of Optimum Flotation Times. J. Dispers. Sci. Technol. 2024, 1–11. [Google Scholar] [CrossRef]
  36. Bahrami, A.; Kazemi, F.; Ghorbani, Y. Effect of Different Reagent Regime on the Kinetic Model and Recovery in Gilsonite Flota-Tion. J. Mater. Res. Technol. 2019, 8, 4498–4509. [Google Scholar] [CrossRef]
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Figure 1. The particle size distribution of the sieved arsenopyrite sample.
Figure 1. The particle size distribution of the sieved arsenopyrite sample.
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Figure 2. XRD patterns of arsenopyrite used in the tests.
Figure 2. XRD patterns of arsenopyrite used in the tests.
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Figure 3. Flow chart of open circuit flotation test for collector comparison.
Figure 3. Flow chart of open circuit flotation test for collector comparison.
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Figure 4. The standard curve of xanthate.
Figure 4. The standard curve of xanthate.
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Figure 5. The relationship between the flotation recovery of arsenopyrite (a) in different collector solution and the concentration of reagent (for the mixed system SAX: SPX = 1:1; pH 7), and (b) in a mixed collector system and the mixing ratio.
Figure 5. The relationship between the flotation recovery of arsenopyrite (a) in different collector solution and the concentration of reagent (for the mixed system SAX: SPX = 1:1; pH 7), and (b) in a mixed collector system and the mixing ratio.
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Figure 6. The relationship between the flotation recovery of arsenopyrite in different collector solution systems and the pH of the pulp (for the mixed system SAX-SPX = 4:1; C = 4×10−5 mol/L).
Figure 6. The relationship between the flotation recovery of arsenopyrite in different collector solution systems and the pH of the pulp (for the mixed system SAX-SPX = 4:1; C = 4×10−5 mol/L).
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Figure 7. The surface contact angle of the arsenopyrite pressed powder after its action in (a) water, (b) SPX, (c) SAX, and (d) mixed solution (C = 4 × 10−5 mol/L; pH 7; for the mixed system SAX: SPX = 4:1).
Figure 7. The surface contact angle of the arsenopyrite pressed powder after its action in (a) water, (b) SPX, (c) SAX, and (d) mixed solution (C = 4 × 10−5 mol/L; pH 7; for the mixed system SAX: SPX = 4:1).
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Figure 8. Adsorbed amount of collector onto arsenopyrite as a function of dosage (C = 8 × 10−5 mol/L; pH 7; for the mixed system SAX-SPX = 4:1).
Figure 8. Adsorbed amount of collector onto arsenopyrite as a function of dosage (C = 8 × 10−5 mol/L; pH 7; for the mixed system SAX-SPX = 4:1).
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Figure 9. The relationship between the adsorption amount of collector on the surface of arsenopyrite and the dosage of the inhibitor (C = 8 × 10−5 mol/L; pH 7; for the mixed system SAX-SPX = 4:1).
Figure 9. The relationship between the adsorption amount of collector on the surface of arsenopyrite and the dosage of the inhibitor (C = 8 × 10−5 mol/L; pH 7; for the mixed system SAX-SPX = 4:1).
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Figure 10. Surface morphology image of arsenopyrite after (a) SAX and (b) mixed collector treatment.
Figure 10. Surface morphology image of arsenopyrite after (a) SAX and (b) mixed collector treatment.
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Figure 11. The relationship between the (a) individual recovery and (b) cumulative recovery of arsenopyrite and the flotation time under different collectors’ systems.
Figure 11. The relationship between the (a) individual recovery and (b) cumulative recovery of arsenopyrite and the flotation time under different collectors’ systems.
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Table 1. Chemical multi-element analysis results of the ore.
Table 1. Chemical multi-element analysis results of the ore.
ElementAu *Ag *SAsSiO2Al2O3CaO
Content/%2.161.542.010.2662.2513.373.52
ElementMgOCuZnNiCoTFeC
Content/%1.900.0080.0560.0070.0024.100.38
* Unit of Au/Ag content, g/t.
Table 2. Test results of collector comparison.
Table 2. Test results of collector comparison.
Type of Collector and the Dosage Selected for Roughing and Scavenging (g/t)ProductYield (%)Au Grade (g/t)Au Recovery (%)
SPX + ADD
(200 + 50)/(100 + 25)		Au Concentrate13.0513.4081.27
Middlings2.762.763.54
Tailings83.790.3915.19
Raw Ore99.602.16100.00
SAX + ADD
(200 + 50)/(100 + 25)		Au Concentrate13.0414.1081.94
Middlings3.722.644.38
Tailings82.940.3713.68
Raw Ore99.702.25100.00
W8 + ADD
(200 + 50)/(100 + 25)		Au Concentrate13.8813.3084.06
Middlings2.482.653.00
Tailings83.640.3412.94
Raw Ore100.002.20100.00
Table 3. Individual and cumulative recovery of arsenopyrite (C = 8 × 10−5 M).
Table 3. Individual and cumulative recovery of arsenopyrite (C = 8 × 10−5 M).
ProductRecovery/%
SAXMixedMixed + ADD
IndividualCumulativeIndividualCumulativeIndividualCumulative
Concentrate 123.423.424.524.528.128.1
Concentrate 221.544.922.246.726.554.6
Concentrate 37.452.38.755.410.965.5
Concentrate 47.159.47.362.71.867.3
Concentrate 53.362.74.266.92.870.1
Concentrate 62.865.52.669.5272.1
Tailings34.530.527.9
Total100100100
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Xing, Q.; Li, F.; Ming, P.; Wang, Z. Enhanced Recovery of an Arsenopyrite-Type Gold Ore: Flotation Surface Chemistry and Kinetics of Blended Collector W8 with ADD. Colloids Interfaces 2025, 9, 76. https://doi.org/10.3390/colloids9060076

AMA Style

Xing Q, Li F, Ming P, Wang Z. Enhanced Recovery of an Arsenopyrite-Type Gold Ore: Flotation Surface Chemistry and Kinetics of Blended Collector W8 with ADD. Colloids and Interfaces. 2025; 9(6):76. https://doi.org/10.3390/colloids9060076

Chicago/Turabian Style

Xing, Qingqing, Fei Li, Pingtian Ming, and Zhen Wang. 2025. "Enhanced Recovery of an Arsenopyrite-Type Gold Ore: Flotation Surface Chemistry and Kinetics of Blended Collector W8 with ADD" Colloids and Interfaces 9, no. 6: 76. https://doi.org/10.3390/colloids9060076

APA Style

Xing, Q., Li, F., Ming, P., & Wang, Z. (2025). Enhanced Recovery of an Arsenopyrite-Type Gold Ore: Flotation Surface Chemistry and Kinetics of Blended Collector W8 with ADD. Colloids and Interfaces, 9(6), 76. https://doi.org/10.3390/colloids9060076

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