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The selective flotation separation of gypsum and quartz in phosphogypsum (PG) is an urgent problem that is very important for the high‐value utilization of PG. In the work, dodecyl amine hydrochloride (DH) was introduced as a collector for the selective flotation separation of gypsum and quartz. The flotation property and selective mechanism of DH on the surface of gypsum and quartz were researched by single mineral flotation experiments, Fourier transform attenuated total reflection infrared spectroscopy analyzer, zeta potential analyzer, X‐ray photoelectron spectrum, molecular dynamic (MD) simulation, etc. Additionally, H+ was introduced into the mineral‐water system simulated by MD to take into account the effect of acidic conditions on the adsorption of DH. The pre‐adsorption of H+ on the quartz surface under strongly acidic conditions hindered the electrostatic force adsorption of DH on the quartz surface. Furthermore, DH was adopted as a collector in the direct flotation recovery of gypsum from PG, and the gypsum concentrates with productivity of 69.85%, CaSO4·2H2O content of 96.33%, and whiteness of 55.00% were obtained. The SiO2 content in the gypsum concentrate decreased from 9.08% to 0.616%. It suggested that DH could serve as a promising collector in the selective separation of gypsum and quartz in PG via flotation. [ABSTRACT FROM AUTHOR]

This paper presents the development of an environmentally friendly, small molecular depressant citrus pectin for improving the recovery of cassiterite resources. Citrus pectin extracted from citrus peel was utilized as the depressant, and it demonstrated significant potential in separating calcite from cassiterite in micro-flotation tests. The molecular weight of the citrus pectin extracted in this paper decreased from 11,485,412 Da to 32,959 Da compared to commercial pectin, resulting in the depressant efficiency of the reagent. The results of a zeta potential and adsorption test indicated that citrus pectin had less and weaker adsorption on the cassiterite surface and could be replaced with NaOL. The chemical adsorption process of citrus pectin on the surface of calcite was determined through FTIR spectroscopy analysis. XPS analysis results indicated that the interaction between the carboxyl groups of citrus pectin and calcium atoms enables adsorption to occur. The AFM revealed that citrus pectin displayed a uniform and dense pattern of point-like adsorption on the surface of calcite. Micro-flotation experiments showed that cassiterite recovery of 80% can be obtained at a citrus pectin dosage of 10 mg/L. Citrus pectin has the advantages of being low-cost, highly selective, and environmentally suitable, making it a promising alternative to conventional reagents. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation (EO) has received widespread attention as a green and non-polluting oxidation treatment. In this paper, we used EO to pretreat pyrite and molybdenite, and then flotation was adopted to separate them. The flotation behavior of the pyrite and molybdenite was studied by micro-flotation tests, and the mechanism for the flotation separation of them was explored via XPS, zeta potential, water contact angle and electrochemistry, etc. The flotation results showed that the floatability of pyrite declined sharply after EO treatment, while that of molybdenite was not affected. In the flotation experiments of artificially mixed ores with various mass ratios, the recoveries of pyrite and molybdenite in the concentrates varied considerably. The mechanism analysis showed that pyrite had a drastic decrease in floatability due to the generation of hydrophilic products of Fe(OH) 3 , FeOOH and Fe 2 (SO 4) 3 covered on its surface in the EO process. Additionally, the oxidation products further hindered the adsorption of the collector of sodium butylxanthate on the pyrite surface. However, the generated MoO 4 2- and SO 4 2- of molybdenite were rapidly dissolved in the pulp during the EO process, allowing its original surface and floatability to be maintained. Therefore, EO pretreatment could generate a great variance in surface properties of pyrite and molybdenite, resulting in an efficient separation of pyrite and molybdenite via subsequent flotation. The work provided a green and environmentally-friendly alternative method to achieve efficient separation of pyrite and molybdenite. [Display omitted] • Efficient separation of pyrite and molybdenite was achieved via electrochemical oxidation pretreatment and flotation. • Both pyrite and molybdenite was mainly oxidized by hydroxyl radicals generated in the process of electrochemical oxidation. • After electrochemical oxidation, pyrite surface became hydrophilic, concurrently reducing the adsorption of collectors. [ABSTRACT FROM AUTHOR]

The micro-floatation of an amorphous graphite sample was conducted using a Hallimond tube with various droplet sizes of emulsified kerosene as collector. The results showed that the experimental recovery of the sample and the kinetic constants (both k and ϵ∞) obtained from the four kinetics models all increased with the decrease of the droplet size. These may be attributed to the fact that the smaller and greater the specific surface area of the droplets, the more easy it is for them to collide with, adhere to, and spread on the sample particles, and then render the particles more hydrophobic. The stronger hydrophobic of particles was better beneficial to the adhesion probability and force between them and the bubbles, which made more amorphous graphite particles floated in the floatation process. In addition, the extended Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was applied to study the interaction between the sample particles and the emulsified kerosene droplets. The results indicated that the hydrophobic attractions played a dominant role in the combined effect of collision and attachment between the sample particles and the droplets. [ABSTRACT FROM PUBLISHER]

[Display omitted] • Once reverse flotation and direct flotation was adopted to purify PG. • Gypsum concentrate reached the first grade national standard of PG in China. • KH had a well selectivity of impurities via hydrogen bond and dehydration condensation. • DH exhibited superior selectivity of gypsum via electrostatic attraction. A simple and efficient approach of high-speed stirring scrubbing, reverse flotation and direct flotation was adopted to the purification of phosphogypsum (PG), and KH and dodecylamine hydrochloride (DH) were first used as the collectors of reverse and direct flotation, respectively. X-ray diffractometer (XRD), thermal gravimetric analyser (TGA), X-ray photoelectron spectrometry (XPS), and Fourier transform infrared spectroscopy (FT-IR) were used to characterise the samples and analyse the mechanism. KH selectively reactes with organic matter, slime, quartz and pyrite via hydrogen bond and dehydration condensation between the –OH in silanol hydrolyzed by KH and –OH on the surface of quartz and pyrite, and –COOH in the organic matter. Furthermore, the direct flotation collector of DH exhibited superior selectivity of gypsum via electrostatic attraction, and increased the whiteness and purity of the gypsum concentrate to 69.2% and 97.24%, respectively, and the soluble phosphorus and fluorine contents decreased to 0.046% and 0.024%, respectively. The gypsum concentrate reached the first-grade national standard of PG in China (GB/T 23456-2018). Therefore, this study provided a new approach for the purification of PG, which has an important guiding significance for the resource utilisation of PG. [ABSTRACT FROM AUTHOR]

Collectors commonly have synergetic effects in ores flotation. In this work, a waste engine oil (WEO) was introduced as a collector to an ilmenite flotation system with sodium oleate (NaOL). The results show that the floatability of ilmenite was significantly improved by using WEO and NaOL as a combined collector. The recovery of ilmenite was enhanced from 71.26% (only NaOL) to 93.89% (WEO/NaOL combined collector) at the pH of 6.72. The optimum molar ratio of NaOL to WEO was about 2.08 to 1. The WEO and NaOL also have synergetic effects for the collection of ilmenite, because to obtain the ilmenite recovery of 53.96%, the dosage of 45 mg/L NaOL is equal to 38.56 mg/L WEO/NaOL combined collector (30 mg/L NaOL + 8.56 mg/L WEO). In other words, 15 mg/L of NaOL can be replaced by 8.56 mg/L of WEO. It is an effective way to reduce the dosage of the collector and reuse WEO. Therefore, it is a highly valuable and environmentally friendly approach for WEO reuse. WEO mainly consists of oxygen functional groups, aromatics, and long-chain hydrocarbons, especially for the RCONH2 and RCOOH, thereby forming a strong interaction on the ilmenite surface. The adsorption mechanism of waste engine oil and sodium oleate on the ilmenite surface is mainly contributed by chemical adsorption. Therefore, WEO exhibits superior synergistic power with NaOL as a combined collector. Herein, this work provided an effective collector for ilmenite flotation and a feasible approach for reducing NaOL dosage and recycling WEO. [ABSTRACT FROM AUTHOR]

The flotation chemistry between pyrite and isomeric xanthates (butyl xanthate and isobutyl xanthate) was investigated by means of adsorption experiments, surface tension tests, and molecular dynamic simulations in this work. The flotation chemical results were confirmed and further interpreted by quantum chemical calculations. The experiment results demonstrated that the isobutyl xanthate exhibited superior adsorption capacity and surface activity than those of butyl xanthate in flotation chemistry. In addition, molecular dynamic simulations were simultaneously performed in constant number, constant volume and temperature (NVT), and constant number, constant volume, and pressure (NPT) ensemble, indicating that the NPT ensemble was more suitable to the flotation system and the isobutyl xanthate was easier to be adsorbed on pyrite surface compared with butyl xanthate during an appropriate range of concentrations. Furthermore, the quantum chemical calculations elucidated that the isobutyl xanthate presented higher reactivity than that of the corresponding butyl xanthate based on the frontier molecular orbital theory of chemical reactivity, which was consistent with experimental and simulation results obtained. This work can provide theoretical guidance for an in-depth study of the flotation chemistry of pyrite with isomeric xanthates. [ABSTRACT FROM AUTHOR]

Schematic for selectively recovery of Cu(II) with AMID@GO as nano collector via ion flotation. [Display omitted] • 1,3-Diamino-1,2,3-trioximido-propane (AMID) was firstly used as chelation group for GO modification. • AMID functionalized GO (AMID@GO) was an efficient nano collector for Cu(II) recovery by ion flotation. • AMID@GO exhibited a better Cu(II) recovery and selectivity performance than GO. • AMID@GO showed a good recycling and regeneration property. In this work, amidoxime functionalized graphene oxide (AMID@GO) was prepared with 1,3-diamino-1,2,3-trioximido-propane as chelation group and used as nano collector for enhancing and selectively recovering Cu(II) from wastewater via ion flotation. AMID@GO was characterized by scanning electron microscope/energy dispersive X-ray detector (SEM/EDX), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Effects of pH, contact time, AMID@GO and hexadecyl trimethyl ammonium bromide (HTAB) concentration, and aeration rate on Cu(II) recovery and the turbidity of the residual solution were examined systematically. The experimental results showed that as compared with GO, the adsorption capacity and selectivity of AMID@GO for Cu(II) was greatly improved. Almost 99.26% of Cu(II) could be recovered with selectivity coefficient of 54.161, 73.430, 50.365 and 21.630 for Cu(II)/M(II) (M = Co, Ni, Zn and Cd, respectively). Moreover, the relative Cu(II) recovery maintained over 90.45% after five flotation- desorption cycles, indicating AMID@GO could be reused as nano collector in ion flotation. In addition, density functional theory (DFT) calculation suggested that AMID@GO had a stronger affinity to Cu(II) originated from both O and N from oximido contributed to the stable configuration of AMID@GO@Cu(II) complexes, endowing it possessed a higher selectivity coefficient for Cu(II). [ABSTRACT FROM AUTHOR]

• A novel hydroximic acid collector was synthesized and applied in ilmenite flotation. • NaTNA exhibited superior collectability and selectivity to ilmenite flotation compared to NaOL. • NaTNA could chemisorption on the ilmenite surface. • Adsorption layer of NaTNA on the ilmenite surface was much greater than forsterite. Sodium trans -2-nonene hydroxamate (NaTNA), a derivative of hydroxamic acid, was successfully synthesized as an effective collector for the flotation separation of ilmenite and forsterite. Micro-flotation results showed that NaTNA exhibits a superior flotation performance for ilmenite compared to sodium oleate. To elucidate the flotation process, the zeta potential, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to analyze the interaction between the reagents and mineral surfaces. The results indicated that NaTNA was strongly adsorbed on the ilmenite (Ti and Fe active sites) surface by chelation but weakly adsorbed on the forsterite surface through electrostatic attraction. Quartz crystal microbalance with dissipation results suggested that a slim NaTNA layer with an adsorption density of 112.50 ng/cm2 was detected on the forsterite surface, whereas a significantly thicker NaTNA layer with an adsorption density of 4415.00 ng/cm2 was detected on ilmenite. Moreover, a molecular dynamics simulation was employed to investigate the adsorption mechanism of NaTNA on ilmenite and forsterite, revealing that the O‐O distance (2.746 Å) in TiO 4 2- sufficiently matched with the O‐O distance (2.723 Å) of NaTNA. This facilitated bond formation between the reagents and ilmenite. Overall, NaTNA is a promising collector for ilmenite flotation, exhibiting excellent collection ability and selectivity. [ABSTRACT FROM AUTHOR]

Graphene oxide is an outstanding nano collector for removing heavy metal ions from wastewater via ion flotation. In this current work, the mechanism for enhancing Cu(Ⅱ) removal via adjusting the oxidation degree of nano collector was first proposed when graphene oxide was selected as nano collector of ion flotation. A series of graphene oxide samples with various degrees of oxidation were prepared and characterized by zeta potential, fourier transform infrared spectroscopy, particle size measurement and water contact angle. Furthermore, the variations of initial solution pH, ionic strength, cetyl trimethyl ammonium bromide dosage and gas flowrate were studied systematically. The results showed that Cu(Ⅱ) removal could be enhanced by increasing the oxidation degree of nano collector (graphene oxide). On the one hand, more oxygenous functional groups were introduced when increasing the oxidation degree of graphene oxide, which gave rise to a higher Cu(Ⅱ) removal. On the other hand, graphene oxide with higher degree of oxidation were more easily to flocculate into bigger flocs, making it easier to collide with and attach to bubbles, thus achieving efficient separation with the aid of cetyl trimethyl ammonium bromide to enhance its affinity towards bubbles. Diagram of Cu(Ⅱ) removal via ion flotation with GO at different oxidation degrees served as nano collector. [Display omitted] • GO was an efficient nano collector for Cu(Ⅱ) removal by ion flotation. • Enhancing Cu(Ⅱ) removal by adjusting the oxidation degree of GO was firstly proposed. • Cu(Ⅱ) removal and mineralization efficiency were improved by oxidation degree of GO. • Higher oxidation degree of GO exhibited better recycling and regeneration property. [ABSTRACT FROM AUTHOR]

Synergetic cleaner disposal of coal gasification waste and waste engine oil is urgent, as the harmfulness to environment and lacks of clean and efficient technique. In this work, coal gasification fine slag was divided to two clean products without byproducts or wastes by flotation using waste engine oil as flotation collector, achieved the goals of " Carbons Recycle " and " Waste Disposal by Waste ". The waste engine oil improved the flotation property of the −0.5 mm fraction coal gasification fine slag, thereby a flotation concentrate with a loss-on ignition of 88.86 wt% and recovery of 92.13 wt% was produced at the waste engine oil dosage of 3 kg/t. The main components of waste engine oil were hydrocarbons, esters, and heteroatom-containing species, as confirmed by gas chromatography/mass spectrometry. The mechanism of flotation using waste engine oil as a collector for the coal gasification fine slag particles was examined via the measurement of contact angles and wrap angles. The qualified tailings (i.e. flotation tailings and +0.5 mm fraction coal gasification fine slag) with loss-on ignition of less than 5 wt% were also obtained to the standard for direct utilization in building materials. Economic evaluation indicates that the net profit would reach 12309.46 USD/h, with a coal gasification fine slag raw capacity of 400 t/h. This work demonstrates that the application of waste engine oil in coal gasification fine slag flotation is feasible, efficient, economical, and eco-friendly, and it has potential industrial application prospects. Image 1 • Synergetic cleaner disposal of CGFS and WEO was achieved without byproducts. • The loss-on ignition of +0.5 mm fraction CGFS and flotation tailings is < 5 wt%. • WEO increased the contact angles and wrap angles. • Loss-on ignition and recovery of flotation concentrate is 88.86 wt% and 92.13 wt%. [ABSTRACT FROM AUTHOR]

The effect of oxidation degree of graphene oxides (GO) on their removal from wastewater via froth flotation was studied in this work. Four types of GO samples with different oxidation degrees were synthesized and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), atomic force spectroscopy (AFM) et al. The effects of cetyl trimethyl ammonium bromide (CTAB) concentration, pH, stirring time on the removal of GO by froth flotation had been discussed. It was found that the addition of CTAB could improve surface hydrophobicity of GO, endowing GO to be easily separated by froth flotation. The removal was dependent on CTAB dosage, pH and stirring time. Moreover, the removal first increased and then decreased with the increasing oxidation degree of GO, and less kinetic energy input was needed to overcome the energy barrier between GO flocs with the increase of oxidation degree. The removal mechanism was proven to be electrostatic attraction, and the different contents of oxgenous-containing functional groups in GOs with various oxidation degrees played a vital role in their removal via froth flotation. Image 1 • Froth flotation is an efficient method for the removal of GO from wastewater. • Effect of oxidation degree on GO removal by froth flotation was first investigated. • Surface energy, zeta potential and sheet-size of GO varied with its oxidation degree. • Electrostatic interaction plays an important role in the removal. [ABSTRACT FROM AUTHOR]

• Froth stability was positively related to solids concentration and NaOL dosage. • Froth viscosity was related negatively to solids concentration and NaOL dosage. • Froth stability was negatively associated with froth viscosity. • Increasing solids concentration or NaOL dosage significantly increased water holdup. Flotation froth plays a key role in determining overall flotation performance. It has been well known that froth transportation has a significant impact on froth performance. Froth transportation is related closely to froth stability and viscosity. Little work has yet been performed in terms of investigating the relationship between froth stability and viscosity to better predict froth performance. In this work, the correlation between froth stability and viscosity was experimentally studied, for the first time, by conducting flotation tests in a 5 cm diameter flotation column operated in a continuous mode. Pure silica of two different particle size distributions was used as the model material. Solids concentration in the feed and the dosage of sodium oleate (NaOL) were varied to change froth behaviors. A negative correlation between froth stability and froth viscosity was observed in this study. The underlying mechanisms were discussed. [ABSTRACT FROM AUTHOR]

Flotation separation of ilmenite and forsterite is challenging owing to their similar natural floatability. In this work, low-molecular-weight carboxylated starch (LMWCS) was prepared as a selective depressant for forsterite and ilmenite separation via flotation. Compared with conventional natural starch, LMWCS has stronger depression on forsterite flotation. X-ray photoelectron spectroscopy analysis confirmed that LMWCS was adsorbed onto the ilmenite surface via the formation of weak hydrogen bonds, whereas it adsorbed onto the forsterite surface via strong chemisorption. The adsorption layer density of LMWCS on the forsterite surface was higher than that on ilmenite according to atomic force microscopy and quartz crystal microbalance with dissipation analyses. Therefore, LMWCS is an effective and promising depressant for forsterite flotation. [Display omitted] • The LMWCS depressant was prepared and applied in ilmenite and forsterite flotation. • LMWCS exhibited a better selective depressing ability to forsterite than ilmenite. • LMWCS chemisorbed on the forsterite surface. • Adsorption density of LMWCS on the forsterite surface was much greater than ilmenite. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel hydroxamic acid collector was synthesized and applied in the flotation of ilmenite. • NaOLH exhibited superior separation performance of ilmenite than forsterite. • NaOLH performed chemisorption on ilmenite surface in form of chelates. • NaOLH formed the strongest affinity to Fe and Ti active sites. Collectors are important for mineral flotation. In this work, a novel hydroxamic acid collector, i.e. sodium oleate hydroxamate (NaOLH), was synthesised and applied for ilmenite flotation. The collector was designed by constructing an oleic acid chain and hydroxamic acid group into the collector's molecular structure, based on the flotation mechanism of ilmenite. Liquid chromatography/mass spectrometry and nuclear magnetic resonance spectroscopy were employed to identify the component and structure of NaOLH. Micro-flotation was performed to explore the flotation performance of NaOLH. The absorption mechanism was investigated by zeta potential, Fourier transforms infrared spectroscopy, and X-ray photoelectron spectroscopy. Results demonstrated that NaOLH had a stronger flotation performance than the conventional collector sodium oleate (NaOL). The NaOLH was adsorbed onto the surface of the ilmenite and forsterite, and the O and N atoms of NaOLH were mainly chemisorbed on ilmenite via Fe and Ti sites on the surface, whereas mainly reacted with Mg sites on the forsterite surface. The distribution of NaOLH and NaOL at the solid–liquid interface was studied by molecular dynamics simulation. Results showed that the adsorption capacity between NaOLH and ilmenite was stronger than that of NaOL. Taken together, results suggest that the NaOLH is a potentially novel and a promising collector for ilmenite flotation. [ABSTRACT FROM AUTHOR]