Solution Chemistry Analysis Research Articles

Evaluation of Cyanide Leaching Behavior of Typical Associated Copper Minerals in Gold Concentrates Based on Solution Chemistry and Interfacial Physicochemical Properties Analysis

Evaluation of Cyanide Leaching Behavior of Typical Associated Copper Minerals in Gold Concentrates Based on Solution Chemistry and Interfacial Physicochemical Properties Analysis

Mechanism of polyaspartic acid as acid-base regulation depressant in reverse flotation separation of molybdenite and talc

The separation of talc and molybdenite through flotation has become a significant issue. The current inorganic and organic depressants demonstrate inadequate selectivity and limited efficacy in both positive flotation and reverse flotation of molybdenite. In this study, the utilization of the highly efficient green agent polyaspartic acid (PASP) as a molybdenite depressant was explored to investigate its pH-dependent acid-base depression mechanism. In the case of pH 4.0, molybdenite exhibited effective depression, talc was floated, PASP was desorbed at pH 10.0, and molybdenite was activated. In this study, the impact of electrostatic force on the adsorption process of PASP and examined the mechanism of PASP on molybdenite surface were studied by means of micro-flotation experiments, zeta potential measurements, analysis of solution chemistry, Fourier Transform Infrared Spectrometer (FT-IR) analysis, Ultraviolet–visible spectroscopy (UV–Vis) study, and X-ray photoelectron spectroscopy (XPS) detections. PASP produced chemisorption through the coordination of O or N atoms lone pair electrons with Mo2+ on the molybdenite surface. In this process, electrostatic repulsion determines whether the mineral can come into contact with PASP.

Thiacalix[4]arene Etching of an Anisotropic Cu70H22 Intermediate for Accessing Robust Modularly Assembled Copper Nanoclusters.

Atom-precise metal nanoclusters (NCs) with large bulk (nuclearity >60) are important species for insight into the embryonic phase of metal nanoparticles and their top-down etching synthesis. Herein, we report a metastable rod-shaped 70-nuclei copper-hydride NC, [Cl@Cu70H22(PhC≡C)29(CF3COO)16]2+ (Cu70), with Cl- as the template, in which the Cl@Cu59 kernel adopts a distinctive metal packing mode along the bipolar direction, and the protective ligand shell exhibits corresponding site differentiation. In terms of metal nuclearity, Cu70 is the largest alkynyl-stabilized Cu-hydride cluster to date. As a typical highly active intermediate, Cu70 could undergo a transformation into a series of robust modularly assembled Cu clusters (B-type Cu8, A-A-type Cu22, A-B-type Cu23, and A-B-A-type Cu38) upon etching by p-tert-butylthiacalix[4]arene (H4TC4A), which could not be achieved by "one-pot" synthetic methods. Notably, the patterns of A and B blocks in the Cu NCs could be effectively modulated by employing appropriate counterions and blockers, and the modular assembly mechanism was illustrated through comprehensive solution chemistry analysis using HR-ESI-MS. Furthermore, catalytic investigations reveal that Cu38 could serve as a highly efficient catalyst for the cycloaddition of propargylic amines with CO2 under mild conditions. This work not only enriched the family of high-nuclear copper-hydride NCs but also provided new insights into the growth mechanism of metal NCs.

Deciphering polymer degradation chemistry via integrating new database construction into suspect screening analysis.

Water-soluble synthetic polymers and their environmental degradation products are overlooked but important industrial pollutants in wastewater. However, the detection of degradation products is limited to bulk solution chemistry and molecular-level analysis remains unreachable. In this work, we assessed the feasibility of current suspect screening and nontarget workflow using liquid chromatography-high resolution mass spectrometry (LC-HRMS) to elucidate molecular level information about polyacrylamide (PAM) and its degraded products by free radicals. Radical chain scission of PAM (10 kDa) using heat-activated persulfate was conducted to simulate hydraulic fracturing conditions in the deep subsurface. We found that the current workflows in the commercial software generated predicted formulae with low accuracy, due to limited capability of peak picking and formula prediction for high mass and charge features. By modeling literature-reported degradation pathways, we constructed a degradation product database of over 463 000 unique formulae, which improved the accuracy of the predicted formula. For the matched features, the ratio of aldehyde/ketone terminating molecule abundance was found to increase over 24 h degradation time, suggesting increasing content of aldehydes by radical-induced oxidative chain scission of PAM. This is contradictory to previously proposed ratios of carbon-centered radical position on polymer backbone initiated by hydroxyl radicals. Using in silico fragmentation of MS1 features, we identified 11 structures with confidence levels 2b and 3 using their MS2 information. This is the first attempt to resolve complex polymer degradation chemistry using HRMS that can advance our ability to detect water-soluble polymer pollutants and their transformation products in environmental samples.

Enhanced Nesquehonite Formation and Stability in the Presence of Dissolved Silica.

One possible carbon dioxide sequestration strategy is via the carbonation of dissolved Mg2+ obtained through olivine ((Mg,Fe)2SiO4) dissolution. However, silica is also produced during the breakdown of olivine. This component may have a detrimental effect on the yield of Mg-carbonate as Mg2+ incorporation into complex Mg silicate phases would limit CO2 uptake by this system. Yet this potential competition is currently not considered. Here, we use crystal growth experiments at temperatures applicable for potential coastal applications to test the effect of silica on the formation of the hydrated Mg-carbonate phase nesquehonite (MgCO3·3H2O). Solution chemistry analysis coupled with phase identification demonstrates that the presence of silica in the solution can actually assist the formation of nesquehonite and increase its yield by as much as 60 times. Our findings suggest that the presence of silica changes interfacial stabilities, lowering the energetic barrier for nesquehonite nucleation. In addition, in situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) transformation experiments demonstrated that nesquehonite precipitating in a solution containing a high concentration of dissolved silica exhibits enhanced stability against its transformation into hydromagnesite. These findings will help to better constrain what we expect for applications of olivine during carbon remediation strategies as well as assist yields for industrial applications that use Mg-based cement as building materials to facilitate a CO2-neutral or negative footprint.

The enhanced flotation separation of magnesite and dolomite by introducing chelating reagent EDTA

In pulp environment, due to the migration and transformation of dissolved calcium ions, the surface properties of magnesite and dolomite tend to become similar, which in turn leads to difficulties in their flotation separation. In this paper, the chelating reagent EDTA is introduced to eliminate the adverse influence of calcium species and to restore the selectivity of magnesite-dolomite separation using sodium hexametaphosphate (SHMP) as depressant. Flotation experiments demonstrate that, in the presence of ethylenediaminetetraacetic acid (EDTA), the flotation recovery of magnesite increased by 22.14 % compared to using only the depressant SHMP. Zeta potential experiments combined with solution chemistry analysis indicate that the negatively charged hydrolysis species of EDTA can form soluble and stable chelates with positively charged Ca2+ and Ca(OH)+ species, effectively preventing the adsorption and transformation of calcium ions on the magnesite surface. Adsorption measurements directly confirm from a macroscopic perspective that the addition of EDTA reduces the adsorption of the depressant SHMP on the magnesite surface. X-ray photoelectron spectroscopy (XPS) measurements further confirm the phenomenon of calcium ion migration and transformation from the surface of magnesite to dolomite at the microscale, as well as the adsorption mechanisms of EDTA and SHMP on the surfaces of both minerals. Based on the experimental and analytical results, a flotation separation model of the system is established.

New insight into enhancing sulfurization of azurite with ethylenediamine and its response to xanthate adsorption

Organic amine salt is an efficient sulfurization accelerator for copper oxide minerals. In fact, its underlying function mechanism is scarce. In this study, the evolution of sulfurized products of azurite under ethylenediamine (EDA) regulation and its response to the xanthate adsorption and surface hydrophobicity were investigated. ToF-SIMS, ICP-OES, XPS and total nitrogen analyses showed that pretreatment with EDA promoted the additional formation of copper sulfide products on azurite, and the sulfurization efficiency increased by 17%. The solution chemistry and transition state search analyses revealed that EDA changed the sulfurization reaction pathway by the formation of copper ethylenediamine ion (Cu(en)n2+, n = 1, 2) resulting in the increase of the reaction energy barrier from 55.12 kcal/mol to 197.83 kcal/mol. Therefore, the deposition rate of copper sulfide on azurite was slowed down, thus creating stable solution environment for the dense adhesion of products, which was observed by FESEM. The increasing copper sulfide products created favorable conditions for the stable adsorption of SBX on azurite, ultimately improving the surface hydrophobicity of azurite. These results may provide a deeper understanding for EDA promoting the sulfurization of copper oxide minerals.

Selective fabrication of hydrophilic BiOCl deposition layer on bismuthinite surface for efficient molybdenite/bismuthinite separation

Molybdenite and bismuthinite are valuable components arising from Mo–Bi sulfide ore, and their recoveries are considerably limited by separation efficiency. Herein, calcium hypochlorite (Ca(ClO)2) was first introduced as bismuth depressant for efficient separation of molybdenite and bismuthinite, and its depression mechanisms were investigated through a series of analytical techniques supplemented with solution chemistry and thermodynamic calculations. Flotation results showed that Ca(ClO)2 had a stronger depressing ability than conventional depressant sodium sulfide and exhibited superior selectivity for bismuthinite against molybdenite. At pH around 8.0, the high-selective separation of Mo–Bi bulk concentrate was realized, where more than 96% of molybdenite was recovered and over 98% of bismuthinite was depressed. Solution chemistry and thermodynamic analysis indicated that the bismuthinite surface was preferentially oxidized by Ca(ClO)2 to SO2- 4 and Bi3+. The former dissolved into solution and existed as stable ions, whereas the Bi3+ further interacted with Cl− and was hydrolyzed as BiOCl precipitates. Surface analysis demonstrated that the deposition of BiOCl on the bismuthinite surface not only made its surface rougher but also enhanced its surface hydrophilicity. In comparison, the surface of molybdenite was slightly oxidized and it remained hydrophobic as confirmed from scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and contact angle results. The difference in surface characteristics resulted in the selective adsorption of collector on the surface of molybdenite rather than that of bismuthinite, thus improving the floatability of molybdenite and drastically deteriorating the floatability of bismuthinite. This work suggests that Ca(ClO)2 could be a promising depressant for bismuthinite in the flotation separation of Mo–Bi sulfide ore.

Effect of dissolved unavoidable ions (Fe3+) from iron-containing gangue minerals on dispersion behavior of zinc oxide ore

With the decrease in zinc mineral resources, the secondary resource utilization of zinc tailings has attracted more attention all over the world. However, zinc oxide tailings contain many soluble minerals (limonite, pyrite), resulting in many metal ions interacting with the mineral surface. The effect of unavoidable ions (Fe3+) has become one of the challenges for the efficient separation and recovery of fine zinc oxide. Therefore, it is necessary to identify the effect of Fe3+ on the dispersion behavior of zinc oxide in order to improve the sorting efficiency and effective recycle of secondary resources. This study investigated the effect of Fe3+ on the dispersion behavior of fine smithsonite (zinc oxide). The turbidity experimental results showed that the turbidity of smithsonite was well dispersed in the deionized water, and decreased continuously with the addition of Fe3+. The smithsonite dispersion behavior was damaged by 5 × 10−4 mol/L Fe3+ from pH = 4 to 12. The results of zeta potential showed that the isoelectric point of smithsonite shifted positively from pH = 7.5 to 9.5. X-ray photoelectron spectroscopy (XPS) and solution chemistry analysis indicated that smithsonite was subjected to the action of Fe3+ to generate metal hydroxyl complexes or precipitates. The inter-particle interaction potential barrier of smithsonite at pH = 4 and 10 was 5.745 × 10−19 J and 2.31 × 10−19 J by calculations of DLVO theory, respectively. However, the potential energy of inter-particle interaction between smithsonite particles was less than zero in the presence of Fe3+, which indicated that the presence of iron ions disrupts the dispersion behavior of smithsonite. This study could provide theoretical guidance for the efficient recovery of secondary zinc resources from zinc oxide tailings.

Synergism of mixed cationic collectors in the flotation of quartz unveiled by AFM, solution chemistry and quantum chemical calculations

The considerable increase in worldwide demand for iron ore requires more studies for efficiency of silicate gangue flotation. New reagents and synergistic mixtures have been pursued to tackle this technological problem. Although there are several studies of collector mixtures in the literature, very few were dedicated to mixtures of cationic collectors. To fill such gap, the interaction between ethermonoamine (M) and etherdiamine (D) was evaluated using bench flotation tests with a typical Brazilian iron ore, solution chemistry analysis and density functional theory calculations (DFT) for the first time in literature. The combined use of these collectors in the proportion 3 D: 1 M, w/w, at pH 10.5, provided the best recovery and selectivity, showing synergism. The iron recovery was 83.9% with a rougher concentrate presenting an iron and silica content of 64.0% and 4.6%, respectively. Differences in the pKa values of primary and secondary amino groups point to minimization of electrostatic repulsion between adsorbed collectors. Interaction free energy values indicate that the complexes M(0)-D(+) (−8.29 kcal/mol), D(0)-D(+) (−7.74 kcal/mol) and M(+)-D(0) (−8.66 kcal/mol) are the most thermodynamically favored and, therefore, confirm the experimental results and explain the nature of the favorability, which is related to the reorganization of the collectors in order to minimize ether-ether and cation-cation repulsion and maximize ether-amine or amine–amine neighbors, especially when the amino group is protonated.

Desorption of cadmium from Fe[tbnd]Cd and recycle of Fe0: Experimental and mechanism study

Zero valent iron (Fe0) has been proven to be a highly efficient adsorption material for cadmium in wastewater. However, how to deal with Fe0 after cadmium adsorption, restricts its industrialization. In this paper, we attempted to desorb cadmium from the post-adsorption material (FeCd) through ammoniacal leaching and recycle the Fe0. Desorption experiments, Infrared and SEM-EDS results showed leaching with (NH4)2SO4 and NH3·H2O can effectively desorb cadmium from FeCd. Based on Ultraviolet spectrum, solution chemistry and quantum chemical analysis, cadmium on FeCd can combine with free ammonia and form Cd-NH3 complexes. Then the complexes are transferred into the leached solution, achieving the desorption of cadmium. Subsequently, cadmium in leached solution was precipitated into Cd(OH)2, a high-grade cadmium product. Finally, the cadmium adsorption capability of regenerated Fe0 was roughly investigated, and the results showed that it has a better capability for cadmium adsorption than initial Fe0, which further guaranteed the recycle of Fe0.

Aggregation process of fine hematite particles suspension using xanthan gum in the presence of Fe(III)

Aggregation is an economical and widely existing method to in hematite mineral processing. In order to achieve the aggregation of hematite particles, high-efficiency agents are required. In this work, the xanthan gum (XG) and Fe3+ were used to explore its aggregation effect on the fine hematite particles. The settling and adsorption experiments were conducted on hematite with XG in the absence and presence of Fe3+. The results show that it is difficult to settle hematite with XG alone, and XG exhibits excellent performance with the mass ratio of 2/1 (XG/ FeCl3) at pH 2–10 in the presence of Fe3+. Zeta potential measurements, Fourier transform infrared (FTIR), Microscope and X-ray photoelectron spectroscopy (XPS) analyses were performed to detect the underlying mechanism. The zeta potential, solution chemistry and FTIR analyses results show that the co-adsorption of XG, Fe(OH)2+, Fe(OH)2+ and Fe3+ is found on hematite surface through specific and electrostatic adsorption, respectively, and the hematite surface is also covered by Fe(OH)3(s) precipitation turned by Fe3+. XPS spectral investigations and microscope observations provide evidence in support of coordination interaction between ferric ions active sites and XG. In addition, the aggregation model of fine hematite particles suspension using XG in the presence of Fe3+ was drawn.

Study on the Influence of Metal Ions on the Dispersion of Fine Calcium Gangue Minerals.

In this study, the calcium gangue material calcite (-10 μm) was used to investigate the effects of different kinds of metal ions and dosages on the dispersion behavior of calcite. The test results showed that the dispersion behavior of calcite was poor under strongly alkaline conditions without the addition of metal ions, and the reason for that was calcite dissolved ions. The degree of influence of different metal ions on calcite dispersion behavior was Fe3+ > Mg2+ > Na+. The three metal ion dosage tests showed that the dispersion behavior of calcite became poorer with the increase of metal ion dosage. This mainly showed that with the increase of Na+ dosage, the trend of the dispersion behavior of calcite was not obvious, but with the increase of Fe3+ and Mg2+ dosage, the trend of calcite dispersion behavior changed more. The dispersion behavior of calcite was devastated by 5 × 10-4 mol/L Fe3+ at pH = 4-12. The different mechanisms of the three metal ions were identified by zeta potential, solution chemistry, and XPS analysis. Na+ only changed the zeta potential value of the calcite surface, which acted as a compressed electric double layer. However, the formation of metal hydroxide species or metal hydroxide surface precipitation due to the adsorption of Fe3+ and Mg2+ on the mineral surface resulted in the change of the dispersion behavior of calcite.

Enhanced alite dissolution by CAH10 addition

The influence of varying Al addition in the form of CAH10 on the hydration of alite was studied to gain further insights into the alite hydration mechanisms in the presence of increased Al concentration in pore solution. Therefore, pure alite and mixtures of alite and CAH10 were investigated by means of isothermal heat flow calorimetry, XRD and pore solution chemistry analysis. The two occurring hydration events can be attributed to the precipitation of two different silicate-bearing hydrate phases, C2ASH8 and C-(A)-S-H. In this case, the consumption and removal of Al in pore solution initiated the change to C-(A)-S-H-forming hydration. Furthermore, the formation of C2ASH8 and the alite reaction rate and reaction were directly influenced by the amount of Al provided by CAH10 addition, leading to an alite reaction turnover of up to 68–86 % within 48 h.

Effect of calcium ions on surface properties of chalcopyrite and arsenopyrite and its response to flotation separation under low-alkalinity conditions

Herein, the effect of calcium ions on surface properties of chalcopyrite and arsenopyrite and its response to flotation separation under low-alkalinity conditions were investigated by flotation tests, zeta potential measurements, solution chemistry analysis, XPS tests, and DFT calculations. The flotation test results showed that calcium ions can selectively decrease the arsenopyrite floatability. The analysis results of zeta potential and solution chemistry showed that the positively charged Ca2+ and Ca(OH)+ were adsorbed on the chalcopyrite and arsenopyrite surfaces, and more adsorption of which on the arsenopyrite surface was found. Furthermore, the pre-adsorption of calcium ions greatly hindered the collector adsorption on the arsenopyrite surface while did not hinder that on the chalcopyrite surface. The XPS test results further demonstrated that CaOH+ was covered on the arsenopyrite surface via interaction with the Fe atom and S atom. Moreover, DFT calculation results revealed that the Ca-S bond can form on the chalcopyrite surface while the Fe-O bond cannot form. However, the Fe-O bond and Ca-S bond were both formed on the arsenopyrite surface, and the formed Ca-S bonds on the chalcopyrite surface were weaker than that on the arsenopyrite surface. Thus, a more hydrophilic surface of arsenopyrite was generated, which decreased its floatability.

Selective flotation separation of smithsonite from dolomite by using sodium hexametaphosphate as a depressant

In this study, a depressant sodium hexametaphosphate (SHMP) was introduced for the flotation separation of smithsonite from dolomite using mixed benzohydroxamic acid (BHA) and sodium oleate (NaOL) as the collectors. Micro-flotation experiments were conducted to investigate the flotation behavior of smithsonite and dolomite in the absence and presence of SHMP. Furthermore, the depression mechanism of the SHMP was unraveled by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) analysis, and flotation solution chemistry. The flotation results showed that the recovery of dolomite decreased from 26.63% to 2.25% when the addition of SHMP in the flotation system increased from 0 to 50 g/t, while the smithsonite recovery exhibited a slight increase from 91.05% to 93.10%, which improved the separation effect greatly. FTIR measurements and XPS analysis revealed that the SHMP was chemically adsorbed on the dolomite surface in the form of hydrophilic complexes with Ca2+ and Mg2+, thus depressing adsorption of the mixed BHA/NaOL. Flotation solution chemistry analysis suggested that Zn2+ could form ZnCO3 on the surface of the dolomite leading to the transformation of the dolomite surface to the smithsonite surface. And SHMP could form hydrophilic complexes with Ca and Mg sites on the dolomite surface, thus depressing the adsorption of BHA/NaOL on the transformed dolomite surface.

Investigation of the Flotation Separation of Scheelite from Fluorite with a Novel Chelating Agent: Pentasodium Diethylenetriaminepentaacetate

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.

Adsorption of octanohydroxamic acid at fluorite surface in presence of calcite species

The surface properties of fluorite are often affected by dissolved gangue species (e.g., calcite) during the flotation process. Microflotation testing with and without the addition of calcite supernatant was conducted using octanohydroxamic acid (OHA) as the collector. The results revealed that dissolved calcite species significantly affected the flotation behavior of fluorite. Fourier transform infrared spectra confirmed that the decrease in flotation recovery was linked to lower OHA adsorption. Solution chemistry analysis indicated that CaCO3 and Ca2+ from the calcite supernatant were the most favorably adsorbed species, and X-ray photoelectron spectroscopy analysis confirmed the surface adsorption of calcite species. Density functional theory simulations provided a detailed analysis of the multidentate adsorption configuration of OHA, which was the most favorable for adsorption on the fluorite surface. The adsorption energy calculation showed that the calcite dissolved species were more stably adsorbed on the fluorite surface than OHA. The pre-adsorption of calcite dissolved species hindered the adsorption of OHA due to electrostatic repulsion.

Improving the bonding capacity of recycled concrete aggregate by creating a reactive shell with aqueous carbonation

Recycling end-of-life concrete back to construction industry in the form of aggregate has been a preferential solution to deal with the huge quantities of waste concrete. However, the recycled concrete aggregate (RCA) contains residual cement paste which adversely affects its properties and the resulting new concrete. Based on previous literature, enhancing the ITZ is one of the significant principles to improve the performance of the new concrete. Therefore, in this study, an innovative aqueous carbonation (AC) method was employed to treat modelled RCA, aiming at modifying the surface of the RCA to improve its bonding ability with new mortar and revealing the mechanism. Subsequently, AC was also applied to real RCA to validate its structural changes were compatible with the modelled RCA. Multi-scale investigations including thermogravimetric analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy line scanning, nanoindentation, solution chemistry analysis, etc. were conducted to characterize the structural changes and the reaction kinetics. The experimental results showed that the surface layers of RCA were significantly modified after AC. A shell-core structure was formed, which included, starting from the outermost region of the RCA, a calcite coating, a silica-rich layer, a partially decalcified layer, and an uncarbonated matrix. The surface modification significantly improved the frictional and tensile bonding strength of RCA with the new mortar by triggering physicochemical changes to the interface. Generally, AC can be considered as an efficient approach for improving the bonding capacity of RCA and therefore promoting the recycling of waste concrete.

Selective adsorption mechanism of dodecylamine on the hydrated surface of hematite and quartz

• The hydration structure of quartz and hematite were considered in the calculations. • DDA and CCS are physically adsorbed on the hydrated surface of quartz and hematite. • The selectivity of dodecylamine to quartz is better than that of hematite. • The selectivity of starch to hematite is better than that of quartz. Flotation is one of the most effective methods to selectively separate refractory hematite from quartz. However, the separation mechanism of the hydrophilic minerals of hematite and quartz is still poor understood. In this work, the selective adsorption behaviors of the representative collector dodecylamine (DDA) and depressant causticized cassava starch (CCS) on the hydrated surface of quartz and hematite were systematically investigated based on experimental and computational methods. Accordingly, microflotation results showed that the TFE grade could be significantly improved by increasing the dosage of DDA appropriately, but it had a negative effect on the concentrate recovery, however, with the increase of CCS dosage, concentrate recovery could be improved, but TFE grade could be reduced to a certain extent. Solution-chemistry analysis indicated that the positively charged RNH 3 + was the main component of DDA at pH 7. Because the Zeta potential of quartz is more negative than that of hematite, DDA can be selectively adsorbed on the quartz surface by electrostatic attraction. The DFT calculations showed that the adsorption (inhibition) of starch fragments on the hydrated surface of hematite was stronger than that of quartz, while the collector RNH 3 + had a better selective adsorption interaction with the starch-modified hydrated surface of quartz, resulting in the selective separation of quartz from hematite. This work shed new light on the selective adsorption mechanism of flotation reagents on the hydrated surface of oxide minerals.