Application of microbubble air flotation to harvest Microcystis sp. from agriculture wastewater: The regulation and mechanisms.

The harvesting of microalgae is the main bottleneck of its large-scale biomass production, and seeking an efficient, green, and low-cost microalgae harvesting technology is one of the urgent problems to be solved. Microbubble air flotation has been proven to be an effective measure, but the mechanisms of microbubbles-algal cell attachment are still unclear. In this study, microbubble air flotation was used as a harvesting method for Microcystis cultured in agricultural wastewater. The process mechanism of microbubble air flotation harvesting microalgae in wastewater was fully revealed from three aspects (the design of bubble formation, the adhesion law, and the recovery rate of microalgae under different working conditions). The results show that the length of the release pipe is the main factor affecting the proportion of microbubbles with a particle size of less than 50 µm. In the process of adhesion, when the particle size of microbubbles is 0.6-1.7 times the size of Microcystis, the adhesion efficiency of microbubbles to Microcystis is the highest. Under the conditions of pressure 0.45 MPa, gas-liquid ratio 5%, and release pipe length 100 cm, the harvesting performance of Microcystis was the best. Microbubble air flotation has better harvesting performance (63.5%, collection rate) of Microcystis with higher density. By understanding the mechanism of microbubble flotation, the technical parameters of microbubble flotation for harvesting energy microalgae are optimized to provide support for the development of efficient and low-cost devices and equipment for collecting microalgae.

Exploring the potential of the halotolerant bacterial strain Bacillus subtilis LN8B as an ecofriendly sulfide collector for seawater flotation.

AIM: To assess the effectiveness of Bacillus subtilis strain LN8B as a biocollector for recovering pyrite (Py) and chalcopyrite (CPy) in both seawater (Sw) and deionized water (Dw), and to explore the underlying adhesion mechanism in these bioflotation experiments. MATERIALS AND METHODS: The bioflotation test utilized B. subtilis strain LN8B as the biocollector through microflotation experiments. Additionally, frother methyl isobutyl carbinol (MIBC) and conventional collector potassium amyl xanthate (PAX) were introduced in some experiments. The zeta potential (ZP) and Fourier-transform infrared spectroscopy (FTIR) was employed to explore the adhesion mechanism of Py and CPy interacting with the biocollector in Sw and Dw. The adaptability of the B. subtilis strain to different water types and salinities was assessed through growth curves measuring optical density. Finally, antibiotic susceptibility tests were conducted to evaluate potential risks of the biocollector. RESULTS: Superior outcomes were observed in Sw where Py and CPy recovery was ∼39.3% ± 7.7% and 41.1% ± 5.8%, respectively, without microorganisms' presence. However, B. subtilis LN8B potentiate Py and CPy recovery, reaching 72.8% ± 4.9% and 84.6% ± 1.5%, respectively. When MIBC was added, only the Py recovery was improved (89.4% ± 3.6%), depicting an adverse effect for CPy (81.8% ± 1.1%). ZP measurements indicated increased mineral surface hydrophobicity when Py and CPy interacted with the biocollector in both Sw and Dw. FTIR revealed the presence of protein-related amide peaks, highlighting the hydrophobic nature of the bacterium. The adaptability of this strain to diverse water types and salinities was assessed, demonstrating remarkable growth versatility. Antibiotic susceptibility tests indicated that B. subtilis LN8B was susceptible to 23 of the 25 antibiotics examined, suggesting it poses minimal environmental risks. CONCLUSIONS: The study substantiates the biotechnological promise of B. subtilis strain LN8B as an efficient sulfide collector for promoting cleaner mineral production. This effectiveness is attributed to its ability to induce mineral surface hydrophobicity, a result of the distinct characteristics of proteins within its cell wall.

Constructing 3D flower-like S-scheme N-Bi2O2CO3/g-C3N4 heterojunction with enhanced photocatalytic performance.

Mineral processing wastewater contains a lot of organic matter and heavy metal ions, and poor self-degradation ability makes it a key treatment object in environmental treatment. Photocatalysis is a promising technology to efficiently mineralize refractory contaminants from wastewater. In this work, 3D flower-like S-scheme N-Bi2O2CO3/g-C3N4 heterostructures were successfully constructed by hydrothermal method with the auxiliary of ionic liquids. The photocatalytic experiments show that the catalytic activity of heterojunction photocatalysts was significantly higher than that of bare g-C3N4 and N-Bi2O2CO3 for the degradation of two pollutants. NBOC/CN-2 shows the highest photocatalytic performance, and the degradation efficiency of sodium isobutyl xanthate (SIBX) on NBOC/CN-2 is 1.85 and 3 times that of bare g-C3N4 and Bi2O2CO3, respectively. The degradation efficiency of m-Cresol on NBOC/CN-2 is 8.34 and 6.93 times that of bare g-C3N4 and N-Bi2O2CO3, respectively. This significantly enhanced photocatalytic activity is attributed to the formation of flower-like heterojunctions, which can greatly increase the specific surface area and facilitate the separation and migration of photogenerated carriers. Total organic carbon (TOC) experiment proves that the two pollutants are effectively mineralized under the action of the prepared photocatalyst. The degradation path of m-Cresol degradation products was inferred based on the ion fragments. The capture experiment and Nitro-blue tetrazolium (NBT)-•O2- measurement show that superoxide radical plays a major role in photocatalytic degradation. The outstanding stability of the prepared flower-like heterojunction samples was examined by cyclic experiments. The S-scheme charge transfer mechanism has been proposed to explain the boosted activity of the flower-like heterojunction photocatalyst. This work provides a new idea for the design of efficient and stable g-C3N4-based photocatalyst for the photocatalytic degradation of refractory wastewater.

Recovering ancient parasites from Andean herbivores: test of the Mini-FLOTAC technique in archaeological samples.

The optimization of techniques for recovering parasitic remains is key in paleoparasitology. The Mini-FLOTAC technique (MF) is based on passive flotation and is used for diagnosis of parasites and was never tested on ancient samples. Our objective was to assess the effectiveness of MF in paleoparasitology, aiming at improving the techniques for the recovery of parasitic remains in order to upgrade the interpretative potential of the paleoparasitological evidence. Three techniques were tested: MF, spontaneous sedimentation (SS), and centrifugation-sucrose flotation (CF) testing camelid and goat coprolites. Statistical tests were performed with the R software. Our result displayed that, in the case of SAC samples, MF recovered less number of parasitic species than SS, but obtained a greater number of positive samples for protozoa. For goat samples, MF recovered a higher number of positive samples and parasitic species than SS, added that it was the technique that recovered a greater number of parasite structures. Therefore, results vary according to the zoological origin of the samples and the parasitic species recorded. We suggest starting using MF on ancient samples as a complementary method to those traditionally used in paleoparasitology. It is important to highlight that MF was a simple and faster way. The incorporation of reliable quantitative techniques opens the door to a new way of analyzing archaeological remains, deepening the study of the parasite-host relationships and its evolution through time with an epidemiological approach. Although further studies are needed, our results suggest the complementarity of these techniques in future paleoparasitological studies.

Deep Ensemble Learning-Based Sensor for Flotation Froth Image Recognition.

Froth flotation is a widespread and important method for mineral separation, significantly influencing the purity and quality of extracted minerals. Traditionally, workers need to control chemical dosages by observing the visual characteristics of flotation froth, but this requires considerable experience and operational skills. This paper designs a deep ensemble learning-based sensor for flotation froth image recognition to monitor actual flotation froth working conditions, so as to assist operators in facilitating chemical dosage adjustments and achieve the industrial goals of promoting concentrate grade and mineral recovery. In our approach, training and validation data on flotation froth images are partitioned in K-fold cross validation, and deep neural network (DNN) based learners are generated through pre-trained DNN models in image-enhanced training data, in order to improve their generalization and robustness. Then, a membership function utilizing the performance information of the DNN-based learners during the validation is proposed to improve the recognition accuracy of the DNN-based learners. Subsequently, a technique for order preference by similarity to an ideal solution (TOPSIS) based on the F1 score is proposed to select the most probable working condition of flotation froth images through a decision matrix composed of the DNN-based learners' predictions via a membership function, which is adopted to optimize the combination process of deep ensemble learning. The effectiveness and superiority of the designed sensor are verified in a real industrial gold-antimony froth flotation application.

Molecular Design and Spodumene Flotation-A Review.

Spodumene flotation stands as the most commonly used method to concentrate lithium minerals. However, it faces significant challenges related to low collector recoveries and similarity in the surface characteristics of the minerals, which make the effective separation of this valuable mineral difficult. For this reason, numerous researchers have conducted studies to address and confront this problem. In this work, an exhaustive bibliographic search was carried out using keywords and search queries, and the results were structured in three sections according to temporal, methodological, and thematic criteria. The first section covers the period from 1950 to 2004, focusing on experimental tests. The second section covers from 2004 to the present and focuses on flotation tests and measurement analysis. Simultaneously, the third section spans from 2011 to the present and is based on molecular dynamics simulations. Topics covered include spodumene surface properties, the influence of metal ions, pre-treatment techniques, and the use of collectors. Ultimately, molecular dynamics simulations are positioned as a tool that accurately represents experimental phenomena. In this context, specialized software such as Materials Studio or Gromacs prove to be reliable instruments that allow a detailed study of mineral surfaces and other elements to be carried out, which justifies their consideration for future research in this scientific field.

Valorization of pyrolysis oils recycled from waste car tires as potential collector in coal flotation: Production, characterization, and collecting mechanism.

The present research study investigates the performance of pyrolysis oils recycled from waste tires as a collector in coal flotation. Three different types of pyrolysis oils (namely, POT1, POT2, and POT3) were produced through a two-step pressure pyrolysis method followed by an oil rolling process. The characteristics of POTs were adjusted using various oil-modifying additives such as mineral salts and organic solvents. The chemical structure of POTs was explored by employing necessary instrumental analysis techniques, including microwave-assisted acid digestion (MAD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), Fourier-transform infrared spectroscopy (FT-IR), and gas chromatography-mass spectrometry (GC-MS). The collecting performance of POTs in coal flotation was evaluated using an experimental design based on Response Surface Methodology (RSM), considering the ash content and yield of the final concentrate. The effect of the type and dosage of POTs was evaluated in conjunction with other important operating variables, including the dosage of frother, dosage of depressant, and the type of coal. Results of POTs characterization revealed that the pyrolysis oils were a complex composition of light and heavy hydrocarbon molecules, including naphthalene, biphenyl, acenaphthylene, fluorene, and pyrene. Statistical analysis of experimental results showed that among different POTs, POT1 exhibited remarkable superiority, achieving not only a 15% higher coal recovery but also a 12% lower ash content. The outstanding performance of POT1 was attributed to its unique composition, which includes a concentrated presence of carbon chains within the optimal range for efficient flotation. Additionally, the FT-IR spectra of POT1 reveal specific functional groups, including aromatic and aliphatic compounds, greatly enhancing its interaction with coal surfaces, as confirmed by contact angle measurement. This research provides valuable insights into the specific carbon chains and functional groups that contribute to the effectiveness of POT as a collector, facilitating the optimization of coal flotation processes and underscoring the environmental advantages of employing pyrolysis oils as sustainable alternatives in the mining industry.

A Review of Ultrasonic Treatment in Mineral Flotation: Mechanism and Recent Development.

Ultrasonic treatment has been widely used in the mineral flotation process due to its advantages in terms of operational simplicity, no secondary pollutant formation, and safety. Currently, many studies have reported the effect of ultrasonic treatment on mineral flotation and shown excellent flotation performance. In this review, the ultrasonic mechanisms are classified into three types: the transient cavitation effect, stable cavitation effect, and acoustic radiation force effect. The effect of the main ultrasonic parameters, including ultrasonic power and ultrasonic frequency, on mineral flotation are discussed. This review highlights the uses of the application of ultrasonic treatment in minerals (such as the cleaning effect, ultrasonic corrosion, and desulfuration), flotation agents (such as dispersion and emulsification and change in properties and microstructure of pharmaceutical solution), and slurry (such formation of microbubbles and coalescence). Additionally, this review discusses the challenges and prospects of using ultrasonic approaches for mineral flotation. The findings demonstrate that the application of the ultrasonic effect yields diverse impacts on flotation, thereby enabling the regulation of flotation behavior through various treatment methods to enhance flotation indices and achieve the desired objectives.

Activation Mechanism of Fe2+ in Pyrrhotite Flotation: Microflotation and DFT Calculations.

In industrial manufacturing, pyrrhotite(Fe1-xS), once depressed, is commonly activated for flotation. However, the replacement of CuSO4 is necessary due to the need for exact control over the dosage during the activation of pyrrhotite, which can pose challenges in industrial settings. This research introduces the use of FeSO4 for the first time to efficiently activate pyrrhotite. The impact of two different activators on pyrrhotite was examined through microflotation experiments and density functional theory (DFT) calculations. Microflotation experiments confirmed that as the CuSO4 dosage increased from 0 to 8 × 10-4 mol/L, the recovery of pyrrhotite initially increased slightly from 71.27% to 87.65% but then sharply decreased to 16.47%. Conversely, when the FeSO4 dosage was increased from 0 to 8 × 10-4 mol/L, pyrrhotite's recovery rose from 71.27% to 82.37%. These results indicate a higher sensitivity of CuSO4 to dosage variations, suggesting that minor alterations in dosage can significantly impact its efficacy under certain experimental conditions. In contrast, FeSO4 might demonstrate reduced sensitivity to changes in dosage, leading to more consistent performance. Fe ions can chemically adsorb onto the surface of pyrrhotite (001), creating a stable chemical bond, thereby markedly activating pyrrhotite. The addition of butyl xanthate (BX), coupled with the action of Fe2+ on activated pyrrhotite, results in the formation of four Fe-S bonds on Fe2+. The proximity of their atomic distances contributes to the development of a stable double-chelate structure. The S 3p orbital on BX hybridizes with the Fe 3d orbital on pyrrhotite, but the hybrid effect of Fe2+ activation is stronger than that of nonactivation. In addition, the Fe-S bond formed by the addition of activated Fe2+ has a higher Mulliken population, more charge overlap, and stronger covalent bonds. Therefore, Fe2+ is an excellent, efficient, and stable pyrrhotite activator.

Influence of Different Types of Surfactants on the Flotation of Natural Quartz by Dodecylamine.

The synergistic effect among flotation agents is why combined flotation agents exhibit superior performance compared to single flotation agents. This research investigates the influence of three surfactants with different charges of polar groups, sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and octanol, combined with dodecylamine (DDA), on quartz flotation. Through the implementation of flotation tests, bubble-particle adhesion induction time testing, gas-liquid two-phase foam properties testing, and surface tension testing, it is revealed that substituting part of the DDA with these surfactants can either enhance or at least maintain the quartz recovery, affect the adhesion induction time, reduce the surface tension of the flotation system, and change the foaming performance and foam stability, depending on their mole ratio in the combined collector. Compared to DDA alone, combining CTAB or OCT with DDA can significantly increase quartz recovery, while SDS with DDA only yields an approximate recovery. Combining SDS or OCT with DDA can reduce the foam stability, while CTAB with DDA enhances the foam stability. The effect of the combination of surfactants and DDA on the adhesion induction time of quartz grains of different sizes with bubbles is the same; furthermore, there is a negative correlation between the adhesion induction time and the recovery, while the foaming properties and stability of foam are positively correlated with the recovery.

Efficient Flotation Separation of Ilmenite and Olivine in a Weak Alkaline Pulp Using a Ternary Combination Collector Centered around Al3.

Due to the similar physical and chemical properties of ilmenite and olivine, separating them is challenging. The flotation process, with the use of collectors, is an effective method. In this study, a ternary collector consisting of aluminum ion (III), benzohydroxamic acid (BHA), and sodium oleate (NaOL) was prepared for the flotation separation of ilmenite and olivine. Through micro-flotation experiments, molecular dynamics simulation (MD), density functional theory (DFT), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis, the synergistic effect between the components of the ternary collector and the adsorption configuration on the surface of ilmenite was investigated. The results revealed that at pH = 8, Al (III), BHA, and NaOL could coordinate and adsorb effectively on the surface of ilmenite, enhancing its floatability for separation from olivine. The adsorption configuration differed from previous reports, showing a co-adsorption of multiple forms on the surface of ilmenite.

The Role of Fe(III) in Selective Adsorption of Pullulan on Calcite Surfaces: Experimental Investigation and Molecular Dynamics Simulation.

The floatability of fluorite and calcite exhibit similar properties, rendering their flotation separation challenging. Macromolecular polysaccharide reagents containing the polyhydroxyl group have shown broad promising application. The selectivity of polysaccharide is relatively low. In this study, the introduction of Fe3+ was employed to enhance the selective adsorption capacity of Pullulan polysaccharide towards fluorite and calcite minerals, thereby achieving effective flotation separation. Furthermore, the mechanism underlying intramolecular interactions was elucidated. The DFT calculation and XPS analysis revealed that the adsorption of Fe3+ on the calcite surface was more favorable, leading to the formation of a Ca-O-Fe structure. The MD simulation, XPS analysis, and Zeta potential analysis revealed that the Fe-OH groups on the surface of calcite reacted with the -OH groups in Pullulan and formed bonds, resulting in the formation of a Calcite-Fe-Pullulan structure. This facilitated the attachment of a significant number of Pullulan molecules to the calcite surface. The formation of a hydrophilic layer on the outer surface of calcite by Pullulan, in contrast to the absence of such layer on fluorite's surface, results in an increased disparity in surface floatability between these two minerals, thereby enhancing the efficiency of flotation separation.

Effect of Sulfuric Acid Corrosion on Flotation Performance of Calcite by Changing Surface Roughness.

Surface roughness is a crucial factor that affects the flotation performance of minerals. In this study, the effect of sulfuric acid corrosion on the surface roughness of calcite flotation was investigated through microflotation tests, scanning electron microscopy (SEM-EDS), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and contact angle analysis. Microflotation test results show that sulfuric acid treatment has a serious negative effect on the floatability of calcite. When the sulfuric acid dosage was 4 mL (3 mol/L), the flotation recovery of calcite was reduced to less than 19%. SEM-EDS and AFM results verified that the sulfuric acid treatment significantly changed the surface morphology of calcite, reduced the average surface roughness and surface area, and reduced the amount of active Ca2+ sites on the calcite surface. As characterized by FT-IR and contact angle analyses, the sulfuric acid treatment enhanced the hydrophilicity of the calcite surface and reduced the amount of sodium oleate adsorbed on the calcite surface. Consequently, sulfuric acid corrosion can reduce the average surface roughness of calcite and have a serious negative effect on the flotation performance of calcite.

Effect of Pre-Sulfidization on the Octadecyl Amine Adsorption on the Smithsonite Surface and Its Flotation.

The low-grade zinc oxide ore was sulfidized to increase the efficiency of flotation, but the effect of pre-sulfidization on the adsorption mechanism of octadecyl amine (ODA) on the smithsonite surface is currently unclear. In this study, the effect of pre-sulfidization on the adsorption mechanism of ODA and the flotation behavior was studied using smithsonite and pre-sulfidized smithsonite as the samples by zeta potential, contact angle measurement, total organic carbon analyzer (TOC), quartz microcrystalline balance (QCM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and micro-flotation tests. Micro-flotation tests showed that the pretreatment of sulfidization could improve the floatability of smithsonite. Zeta potential and contact angle measurements demonstrated that pre-sulfidization could favor the adsorption of ODA, which is further confirmed by the adsorption tests of ODA using TOC and QCM. Furthermore, FTIR and XPS analysis showed that pre-sulfidization changes the adsorption mode of ODA, changing it from physical adsorption to chemical adsorption. These results suggested that the favorable effect of pre-sulfidization on the adsorption of ODA and the flotation of smithsonite might provide important guidance for industrial application.

Utilization of Lead Nitrate to Enhance the Impact of Hydroxamic Acids on the Hydrophobic Aggregation and Flotation Behavior of Cassiterite.

Lead nitrate (LN) is frequently employed as an activator in the flotation of cassiterite using hydroxamic acids as the collectors. This study investigated the effect of LN on the hydrophobic aggregation of cassiterite when benzohydroxamic acid (BHA), hexyl hydroxamate (HHA), and octyl hydroxamate (OHA) were used as the collectors through micro-flotation, focused beam reflectance measurement (FBRM) and a particle video microscope (PVM), zeta potential, and the extended DLVO theory. Micro-flotation tests confirmed that LN activated the flotation of cassiterite using the hydroxamic acids as collectors. Focused beam reflectance measurement (FBRM) and a particle video microscope (PVM) were used to capture in situ data on the changes in size distribution and morphology of cassiterite aggregates during stirring. The FBRM and PVM image results indicated that the addition of LN could promote the formation of hydrophobic aggregates of fine cassiterite, when BHA or HHA was used as the collector, and reduce the dosage of OHA needed to induce the formation of hydrophobic aggregates of cassiterite. The extended DLVO theory interaction energies indicated that the presence of LN could decrease the electrostatic interaction energies (Vedl) and increase the hydrophobic interaction energies (Vhy) between cassiterite particles, resulting in the disappearance of the high energy barriers that existed between the particles in the absence of LN. Thus, cassiterite particles could aggregate in the presence of LN when BHA, HHA, or a low concentration of OHA was used as the collector.

Enhancing Sulfidization and Flotation of Smithsonite Using Eco-Friendly Triethanolamine: Insights from Experimental and Simulation Studies.

Triethanolamine (TEA) is a promising eco-friendly alternative to inorganic ammonia for enhancing surface sulfidization and flotation recovery of smithsonite. Micro-flotation experiments revealed an enhancement in smithsonite recovery to 95.21% with TEA modification, comparable to the results obtained using ammonia. The mechanisms behind the ability of TEA to enhance the sulfidization process were investigated through surface analysis and molecular dynamics simulations. TEA modification increased the content of sulfidization products, the proportion of crucial S22- in adsorbed products, and the thickness and size of the sulfidization product layer. The complexation of TEA with Zn sites formed positively charged Zn-TEA complexes that adsorb onto the smithsonite surface. These complexes promoted negatively charged HS- adsorption, creating a multi-layered adsorption structure. Moreover, TEA modification reduced the total energy required for the sulfidization. These findings open up new possibilities for using eco-friendly reagents in mineral processing, highlighting the potential of TEA in green mineral processing practices.

The Development of Innovated Complex Process for Treatment of Old Flotation Tailings of Copper-Zinc Sulfide Ore.

The possibility of selective Cu and Zn leaching from the sample of old pyrite tailings, which is one of the most widespread types of solid waste forming during non-ferrous metal production, using sulfuric acid solutions and water was studied. It was shown that water leaching provided selective extraction of Cu and Zn and comparatively low iron ion extraction. At the same time, acid leaching provided the obtainment of pregnant solutions with high ferric ion concentration, which can be used for oxidative leaching of substandard copper concentrates. Water and acid leaching also provided increased Au recovery by cyanidation. The results suggest that acid leaching can be an effective approach for processing old flotation tailings, which allows the extraction of base metals from these wastes and treating flotation tailings for subsequent cyanidation. Effective flotation treatment methods should also provide environmental load reduction, which is caused by the long-term storage of metal-bearing wastes.

Unravelling the Flotation Performance of 1-Hydroxy-2-naphthyl hydroxamic Acid and Styrene Phosphonic Acid Collectors on Monazite Using Experiments and DFT Calculations.

The atomic-level structure and electronic properties of monazite were investigated using a first-principles method based on density functional theory (DFT). First, the geometric structure of monazite was optimized, followed by calculations of its Mulliken population, electron density, and density of states, which were subsequently analyzed. The findings of this analysis suggest that monazite is highly susceptible to cleavage along the {100} plane during crushing and grinding. When SPA was utilized as the collector, the recovery rate of monazite was higher than that when LF-P8 was used. The zeta potential and adsorption energy results indicated that the zeta potential after SPA adsorption tended towards negativity, and the adsorption energy was smaller, indicating that SPA exhibited stronger adsorption performance. LF-P8 was stably adsorbed on the monazite (100) surface via mononuclear double coordination. SPA was stably adsorbed on the surface of monazite (100) via binuclear double coordination. The results of this study provide valuable insights into the adsorption of monazite by commonly used flotation collectors. These findings are of substantial importance for future endeavors in designing flotation collectors capable of achieving selective monazite flotation.

The Interaction between Iron Cyanide and Lead Ions in Pyrite Flotation.

Despite being a major cyanide species in the process water, it is unclear how iron cyanide influences pyritic gold ore flotation as well as how lead ions influence pyritic gold ore flotation in the presence of iron cyanide. This study aims at revealing the interaction of Fe(CN)63- and lead ions in pyrite flotation to investigate the strong depressing effect of Fe(CN)63- on pyritic gold ore flotation and the significant activating effect of lead ions on pyritic gold ore flotation in the presence of Fe(CN)63- using flotation, zeta potential measurement and surface analysis methods. The flotation results showed that upon 5 × 10-5 mol/L Fe(CN)63- addition, pyrite recovery drastically decreased from about 51.3% to 8.6%, while the subsequent addition of 9.5 × 10-4 mol/L lead ions significantly activated pyrite with the recovery increasing from 8.6% to 91%, which demonstrated that Fe(CN)63- strongly depressed pyrite flotation, while lead ions completely activated pyrite in the presence of Fe(CN)63-. Zeta potential measurement, surface analysis using Cryogenic X-ray photoelectron spectroscopy (Cryo-XPS) and electrochemical impedance spectroscopy (EIS) revealed that Fe(CN)63- depression was attributed to the chemical adsorption of Fe(CN)63- on iron sites of pyrite as Prussian Blue (Fe[Fe(CN)6]); however, this hydrophilic layer could be covered totally by lead ions which adsorbed on as lead hydroxide/oxide through electrostatic interactions, which resulted in the significant activation effect of lead ions. The results from this study will lead to improved flotation of gold associated with pyrite in gold flotation plants.

Experimental Study on Combined Microwave-Magnetic Separation-Flotation Coal Desulfurization.

In order to reduce the content of sulfur and ash in coal, improve the desulfurization and deashing rates, a combined experiment method of microwave magnetic separation-flotation was proposed for raw coal. The desulfurization and deashing rates of three experiment methods, namely, single magnetic separation, microwave magnetic separation, and microwave magnetic separation-flotation, were compared. Taking the microwave magnetic separation-flotation experiment method as the main line, the effects of the microwave irradiation time, microwave power, grinding time, magnetic field intensity, plate seam width, foaming agent dosage, collector dosage, and inhibitor dosage on desulfurization and deashing were discussed, and the mechanism of microwave irradiation on magnetic separation and flotation was revealed. The results show that under the conditions of a microwave irradiation time of 60 s, a microwave power of 80% of the rated power (800 W), a grinding time of 8 min, a plate seam width (the plate seam width of a magnetic separator sorting box) of 1 mm, a magnetic field intensity of 2.32 T, a foaming agent dosage of 90 g/t, a collector dosage of 2125 g/t, and an inhibitor dosage of 1500 g/t, the desulfurization and deashing effect is the best. The desulphurization rate is 76.51%, the sulfur removal rate of pyrite is 96.50%, and the deashing rate is 61.91%. Microwaves have the characteristic of selective heating, and the thermal conductivity of organic matter in coal is greater than that of mineral. Microwave irradiation can improve the reactivity of pyrite in coal, pyrolyze pyrite into high-magnetic pyrite, improve the magnetic properties, and improve the magnetic separation effect. Therefore, microwave irradiation plays a role in promoting magnetic separation. Through microwave irradiation, the positive and negative charges in coal molecules constantly vibrate and create friction under the action of an electric field force, and the thermal action generated by this vibration and friction process affects the structural changes in oxygen-containing functional groups in coal. With the increase in the irradiation time and power, the hydrophilic functional groups of -OH and -COOH decrease and the hydrophilicity decreases. Microwave heating evaporates the water in the pores of coal samples and weakens surface hydration. At the same time, microwave irradiation destroys the structure of coal and impurity minerals, produces cracks at the junction, increases the surface area of coal to a certain extent, enhances the hydrophobicity, and then improves the effect of flotation desulfurization and deashing. Therefore, after the microwave irradiation of raw coal, the magnetic separation effect is enhanced, and the flotation desulfurization effect is also enhanced.