Flotation separation of quartz from collophane using an amine collector and its adsorption mechanisms

Rice husk valorization into sustainable Ni@TiO2/biochar nanocomposite for highly selective Pb (II) ions removal from an aqueous media

Herein, we successfully prepared sustainable nanocomposites from agriculture waste (rice husk)-derived biochar precursor, and followed by nickel-doped, base-treated titanium dioxide nanomaterials loading for efficient lead (Pb²⁺) removal from aqueous media. By varying the loading contents of active materials, the optimized sample (Ni_0.01@Na-TiO₂/BC) possessed an efficient Pb²⁺ adsorption capability of 122.3 mg g^-1 under the under optimum adsorption parameters, which is attributable to its specific surface area (138.09 m² g^-1) and excess functional sites. Kinetic and Isothermal examination illustrated that Pb²⁺ adsorption phenomena was well followed through pseudo 2nd order and Langmuir models. In addition, superior Pb²⁺ ions adsorption selectivity was recorded by optimized sample in a multi-metallic system over other existing ion (such as Cd²⁺, Mg²⁺, Ca²⁺, Cu²⁺, and Zn²⁺). Desorption experiments has been performed by using desorbing agent that demonstrates the good regeneration ability of sample. Hence, these findings provide new insight for the biowaste management by converting them into innovative adsorbents for commercial scale environmental remediation.

Adsorption Mechanism of Amidoxime Collector on the Flotation of Lepidolite: Experiment and DFT Calculation

Lepidolite is an important mineral resource of lithium. With the increase in awareness of low-carbon and green travel, the demand for lithium has increased dramatically. Therefore, how to increase the output of lithium has to turn into high precedence. In this paper, amidoxime (DPA) was synthesized and used for the efficient collection of lepidolite. Dodecylamine (DA), a commonly used collector of lepidolite ore, was used for comparison. The collecting performances of DA and DPA for lepidolite were studied by the micro-flotation experiment, and the adsorption mechanism of DPA on lepidolite was verified by contact angle, zeta potential tests, FTIR spectra, and density functional theory (DFT) calculations. The results of flotation experiments showed that at the same collector dosage (3 × 10^-4 mol/L), the recovery of lepidolite could reach 90%, while the recovery of lepidolite with DA was only 52.5%, and to achieve the maximum recovery of DA (77.5%), only half of the DPA was added. The contact angle test results showed that DPA could effectively improve the hydrophobicity of lepidolite than DA. FTIR spectra and zeta potential tests suggested that DPA molecules were adsorbed on the lepidolite surface by electrostatic attraction. DFT calculations revealed that DPA reacted with the nucleophilic reagent (lepidolite) by the reactive site of the -CH₂NH(CH₂)₂C(NOH)N⁺H₃ group and more easily absorbed on the surface of lepidolite than DA. Therefore, our new finding will provide an important prospect for the sustainable development and utilization of lithium resources.

Flotation purification of waste high-silica phosphogypsum

High-silica phosphogypsum (PG) is a kind of industrial by-product with great utilization potential. However, it is difficult to reuse PG directly due to the related gangue minerals (e.g., SiO₂), and thus efficient purification is required to allow its further applications. Herein, a typical high-silica phosphogypsum waste was purified by a new "reverse-direct flotation" method. The organic matters and fine slimes were removed by reverse flotation, and then, the silica impurity was removed by direct flotation. Via the closed-circuit flotation process, the whiteness of the PG concentrate is improved from 33.23 to 63.42, and the purity of gypsum in the PG concentrate increases from 83.90% to 96.70%, with a gypsum recovery of 85%. Additionally, the content of SiO₂ is significantly reduced from 11.11% to 0.07%. In-depth investigations suggest that the difference in the floatability of gypsum and quartz is prominently intensified by flotation reagents at pH = 2-2.5, and thus leads to good desilication performance. Further characteristics of the PG concentrate prove that impurities have been well removed, and the PG concentrate meets the requirement of related standards for gypsum building materials. The flotation method reported here paves the way for the purification of high-silica phosphogypsum, which can be extended to the purification and value-added reutilization of other industrial solid wastes.

Iron ore production using a new Gemini surfactant at 273 K

Herein we present the use of a Gemini surfactant and reverse froth flotation to efficiently separate magnetite from quartz and produce iron ore at 273 K. This surfactant achieved an obviously superior flotation performance (TFe recovery increased by 48.18%), and the dosage of the Gemini surfactant was three times less than that of a conventional monomeric surfactant. Our findings are expected to serve as a general guide to design a new and excellent collector for high-efficiency mineral flotation and to lead to an efficient and clean development of mineral resources.

Effects of Al(III) Ions at Magnetite Flotation from Quartz by Dodecylamine Al(III)

The flotation separation of magnetite and quartz is a long-term challenge for the beneficiation industry. For high-quartz magnetite, conventional flotation shows poor separation effect, resulting in the waste of resources and low flotation efficiency. In this paper, dodecylamine acts as a collector and Al(III) ions in water act as a depressant to selectively separate magnetite and quartz at high alkalinity. The experimental results are analyzed by a micro-flotation experiment, solution chemical calculation, zeta potential, contact angle measurement, and Fourier transform infrared spectroscopy (FTIR). The results of micro-flotation experiments showed that Al(III) ions in water inhibited magnetite more strongly than quartz. The calculation results of solution stoichiometry and zeta potential showed that the phase formed by Al(III) ions on the surface of magnetite and quartz are mainly Al(OH)3(s), which covers the surface of magnetite and quartz, The contact angle measurement results showed that with the addition of Al(III) ions, the contact angle of magnetite varies significantly than that of quartz, and the floatability of magnetite is lower than that of quartz. The FT-IR results further indicated that the addition of Al(III) ions could hinder the adsorption of dodecylamine on the magnetite surface. Meanwhile, the addition of Al(III) ions has no obvious effect on the adsorption of dodecylamine on the quartz surface.

Co-oxidative removal of arsenite and tetracycline based on a heterogeneous Fenton-like reaction using iron nanoparticles-impregnated biochar

A highly efficient, eco-friendly and relatively low-cost catalyst is necessary to tackle bottlenecks in the treatment of industrial wastewater laden with heavy metals and antibiotic such as livestock farm and biogas liquids. This study investigated co-oxidative removal of arsenite (As(III)) and tetracycline (TC) by iron nanoparticles (Fe NP)-impregnated carbons based on heterogeneous Fenton-like reactions. The composites included Fe NP@biochar (BC), Fe NP@hydrochar (HC), and Fe NP@HC-derived pyrolysis char (HDPC). The functions of N and S atoms and the loading mass of the Fe NP in the Fe NP@BC in heterogeneous Fenton-like reactions were studied. To sustain its cost-effectiveness, the spent Fe NP@BC was regenerated using NaOH. Among the composites, the Fe NP@BC achieved an almost complete removal of As(III) and TC under optimized conditions (1.0 g/L of dose; 10 mM H₂O₂; pH 6; 4 h of reaction; As(III): 50 μM; TC: 50 μM). The co-oxidative removal of As(III) and TC by the Fe NP@ BC was controlled by the synergistic interactions between the Fe NPs and the active N and S sites of the BC for generating reactive oxygen species (ROS). After four consecutive regeneration cycles, about 61 and 95% of As(III) and TC removal were attained. This implies that the spent carbocatalyst still has reasonable catalytic activities for reuse. Overall, this suggests that adding technological values to unused biochar as a carbocatalyst like Fe NP@BC was promising for co-oxidative removal of As(III) and TC from contaminated water.

The pH dependent surface charging and points of zero charge. IX. Update

of the points of zero charge (PZC) and isoelectric points (IEP) of various materials published in the recent literature and of older results overlooked in the previous compilations. The roles of experimental conditions, especially of the temperature, of the nature and concentration of supporting electrolyte, and of the type of apparatus are emphasized. The newest results are compared with the zero points reported in previous reviews. Most recent studies were carried out with materials whose pH dependent surface charging is already well-documented, and the newest results are consistent with the older literature. Isoelectric points of Gd(OH)₃, Sm(OH)₃, and TeO₂ have been reported for the first time in the recent literature.

The effects of partially replacing amine collectors by a commercial frother in a reverse cationic hematite flotation

Iron ore froth flotation has recently been used to obtain pure minerals due to the depletion of high-grade deposits. Amine collectors have often been used in cationic reverse iron ore flotation to achieve the separation with quartz impurities. The main problem associated with these collectors is related to the control of frothing properties and the high cost of amine reagents. In this paper, we report the benefits of partial replacement of amine collectors with a frother in reverse cationic flotation of hematite. Surface tension and batch flotation experimental results indicated for the first time that replacing Flotigam EDA, an etheramine collector by more than 10% improved the flotation performance in both grade and recovery of hematite. It was also noted mild hematite entrainments for lower frother dosages whilst reagents cost estimation indicated profitability per ton of iron recovered. At higher frother dosage however, higher quartz recoveries were observed as a result of entrainment which led to satisfactory results in terms of iron grade in the sink, but results showed higher costs of reagents than when collector was used alone. From observed results, it was concluded that partially replacing amine collector by a frother does improve the performance of the flotation globally regardless of pronounced entrainment that was mainly due the mineralogy of the ore with notable amounts of locked particles in the lower sizes. Finally, it would be useful to investigate these findings with alternative reagents and on minerals with different mineralogical properties.

Review of the Main Factors Affecting the Flotation of Phosphate Ores

The way to successfully upgrade a phosphate ore is based on the full understanding of its mineralogy, minerals surface properties, minerals distribution and liberation. The conception of a treatment process consists of choosing the proper operations with an adequate succession depending on the ore properties. Usually, froth flotation takes place in phosphate enrichment processes, since it is cheap, convenient, and well developed. Nevertheless, it is a complex technique as it depends on the mineral’s superficial properties in aqueous solutions. Aspects such as wettability, surface charge, zeta potential, and the solubility of minerals play a basic role in defining the flotation conditions. These aspects range from the reagents type and dosage to the pH of the pulp. Other variables namely particles size, froth stability, and bubbles size play critical roles during the treatment, as well. The overall aim is to control the selectivity and recovery of the process. The following review is an attempt to add to previous works gathering phosphate froth flotation data. In that sense, the relevant parameters of phosphate ores flotation are discussed while focusing on apatite, calcite, dolomite, and quartz as main constituent minerals.

Laboratory Testing of Scheelite Flotation from Raw Ore in Sangdong Mine for Process Development

Tungsten is an essential metal for the manufacture of special alloys, which is in constant demand due to the development of the industry. The recovery of scheelite from undeveloped tungsten ore in South Korea was investigated to improve the flotation performance for high grade and recovery of concentrate. To investigate the interaction between the flotation reagents and the minerals, the adsorption experiments of oleic acid as a collector on Ca-bearing minerals, such as scheelite, calcite, and fluorite were carried out. This reaction was confirmed chemical adsorption by analysis of zeta potential and FTIR analysis. The batch test was performed using a raw ore to enhance the grade and recovery of the scheelite concentrate. It was obtained at the optimal conditions for high WO3 grade and recovery of scheelite concentrate by using a simple process. In particular, the sodium carbonate used as a pH modifier was investigated to increase scheelite flotation performance by supporting the selective depression of Ca-bearing gangue minerals. Furthermore, a locked cycle test (LCT) was carried out based on batch test results for the design of a continuous pilot plant.

Controlling the Pore Size and Connectivity of Alumina-Particle-Stabilized Foams Using Sodium Dodecyl Sulfate: Role of Surfactant Concentration

Herein, alumina foams were prepared from particle-stabilized foams, fabricated by direct foaming methods, that varied according to the concentration of sodium dodecyl sulfate (SDS). To confirm the formation mechanism of pore structures in alumina ceramic foams with varying SDS concentrations, the adsorption density, contact angle, ζ-potential, and surface tension of the alumina particles dispersed in SDS were analyzed. Additionally, model analysis was performed to confirm the interaction between alumina and air bubbles by applying the extended Derjaguin-Landau-Verwey-Overbeek model. The attachment of alumina particles to bubble surfaces at different SDS concentrations affected the pore structure of the ceramic foams; this confirmed that the attachment was significantly affected by the electrostatic interaction energy rather than hydrophobic interaction. Therefore, the pore size and connectivity of alumina foams could be controlled by varying the electrostatic interaction energy between alumina particles and air bubbles, which is determined by the SDS concentration.

Sustainable Low-Concentration Arsenite [As(III)] Removal in Single and Multicomponent Systems Using Hybrid Iron Oxide-Biochar Nanocomposite Adsorbents-A Mechanistic Study

Rice and wheat husks were converted to biochars by slow pyrolysis (1 h) at 600 °C. Iron oxide rice husk hybrid biochar (RHIOB) and wheat husk hybrid biochar (WHIOB) were synthesized by copyrolysis of FeCl₃-impregnated rice or wheat husks at 600 °C. These hybrid sorbents were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), SEM-energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, physical parameter measurement system, and Brunauer-Emmett-Teller (BET) surface area techniques. Fe₃O₄ was the predominant iron oxide present with some Fe₂O₃. RHIOB and WHIOB rapidly chemisorbed As(III) from water (∼24% removal in first half an hour reaching up to ∼100% removal in 24 h) at surface Fe-OH functions forming monodentate ≡Fe-OAs(OH)₂ and bidentate (≡Fe-O)₂AsOH complexes. Optimum removal occurred in the pH 7.5-8.5 range for both RHIOB and WHIOB, but excellent removal occurred from pH 3 to 10. Batch kinetic studies at various initial adsorbate-adsorbent concentrations, temperatures, and contact times gave excellent pseudo-second-order model fits. Equilibrium data were fitted to different sorption isotherm models. Fits to isotherm models (based on R ² and χ²) on RHIOB and WHIOB followed the order: Redlich-Peterson > Toth > Sips = Koble-Corrigan > Langmuir > Freundlich = Radke-Prausnitz > Temkin and Sips = Koble-Corrigan > Toth > Redlich-Peterson > Langmuir > Temkin > Freundlich = Radke-Prausnitz, respectively. Maximum adsorption capacities, Q _RHIOB ⁰ = 96 μg/g and Q _WHIOB ⁰ = 111 μg/g, were obtained. No As(III) oxidation to As(V) was detected. Arsenic adsorption was endothermic. Particle diffusion was a rate-determining step at low (≤50 μg/L) concentrations, but film diffusion controls the rate at ≥100-200 μg/L. Binding interactions with RHIOB and WHIOB were established, and the mechanism was carefully discussed. RHIOB and WHIOB can successfully be used for As(III) removal in single and multicomponent systems with no significant decrease in adsorption capacity in the presence of interfering ions mainly Cl^-, HCO₃ ^-, NO₃ ^-, SO₄ ^2-, PO₄ ^3-, K⁺, Na⁺, Ca²⁺. Simultaneous As(III) desorption and regeneration of RHIOB and WHIOB was successfully achieved. A very nominal decrease in As(III) removal capacity in four consecutive cycles demonstrates the reusability of RHIOB and WHIOB. Furthermore, these sustainable composites had good sorption efficiencies and may be removed magnetically to avoid slow filtration.

Insight into the Influence of Surface Roughness on the Wettability of Apatite and Dolomite

Surface roughness has an important influence on the wettability of particles. This paper is an innovative exploration to control the surface wettability of apatite and dolomite from the perspective of roughness in the background of phosphate flotation. Roughness characteristics of apatite and dolomite particles and its effects on wettability were investigated with surface roughness, contact angle measurements, and SEM analysis. The relationship between surface energy and wettability of different roughness surfaces was also discussed. The results indicated that the influence of roughness on apatite and dolomite particles showed the same regularity, and wettability increased with the increasing roughness for hydrophilic surfaces, while the wettability decreased for hydrophobic surfaces. The influence of roughness on wettability can be well explained by Wenzel and Cassie models, and the surface energy of different rough surfaces had a strong correlation with their wettability. When sodium oleate was added after acid treatment, the apatite was hydrophilic, while the dolomite was hydrophobic; the difference in wettability between them became greater as surface roughness increased. Thus, it can be predicted that the selective separation of dolomite and apatite under acid reverse flotation conditions can be strengthened by increasing the mineral surface roughness during comminution.

Geochemical Characteristics of Dolomitic Phosphorite Containing Rare Earth Elements and Its Weathered Ore

In order to provide a good theoretical guidance for the development and utilization of weathered phosphorite resources, we investigated the geochemical and mineralogical characteristics of primary and weathered phosphorites. The analysis of trace elements showed that the primary ore has hydrothermal sedimentation effect in the later stage, the weathered ore has obvious residual enrichment and the phosphate ore belongs to clastic lithologic phosphate rock. In addition, through leaching test method, it was shown that rare earth elements are present in fluorapatite in the form of isomorphic substitution, and the proportion of rare earth elements adsorbed on clay and other minerals was likely to be between 2% and 3%. The light rare earth elements are relatively enriched in both primary and weathered phosphorite, and Ce and Eu have obvious negative anomalies. The primary phosphorite is a dolomitic phosphorite containing rare earth elements, which are naturally enriched by weathering, and its weathered ore has obvious residual enrichment, while the deposit was characterized by normal marine sedimentation and hydrothermal action.

Effect of ultrasound on bubble-particle interaction in quartz-amine flotation system

In this study, the effect of ultrasound (US) on the quartz-amine flotation system was investigated in detail by considering various surface chemistry techniques. The effect of ultrasound on particle size, shape factor, and surface roughness were characterized by using Brunauer-Emmett-Teller (BET) surface area measurements and scanning electron microscopy (SEM) analyses. The contact angle and bubble-particle attachment time, as well as adsorption density measurements was carried out to evaluate the effect of ultrasound on quartz surface wetting ability. In addition, atomic force microscopy (AFM) analyses were conducted, and finally micro-flotation studies were performed. As a result, it was found that the micro-flotation recovery at 2 × 10^-5 M dodecyl amine hydrochloride (DAH) concentration increased from 45.45% to 63.64% with 30 W ultrasonic application at conditioning step. However, the micro-flotation recovery decreased to 37.50% when the ultrasonic power increased to 150 W. The results showed some effect of ultrasound on particle size, particle shape, and surface roughness in some extent. The increase in the contact angle and the decrease in the bubble-particle attachment time were observed. A slightly high adsorption density was measured. All these show a positive effect of ultrasound on quartz flotation with amine as a collector.

Apatite enrichment by rare earth elements: A review of the effects of surface properties

Apatite subspecies depend on their halogen and hydroxyl content; chlorapatite, hydroxylapatite and fluorapatite, with additional substitution of other elements within the lattice such as rare earth elements (REE), sodium, strontium and manganese also possible. Rare earth elements are vital to green and emerging technologies, with demand set to outstrip supply. Apatite provides a possible future source of REE. Processing rare earth deposits is often complex, with surface behaviour having a significant effect on the optimization of a process flow sheet. The effect of enrichment of natural apatite and the doping of synthetic apatite on surface behaviour can be determined by measuring the zeta potential and the isoelectric point of the mineral. In this paper, we review zeta potential studies of natural and synthetic apatite to determine the effect of elemental enrichment on surface behaviour. Fifty three studies of natural apatite and forty four studies of synthetic apatite were reviewed. The isoelectric point of apatite varied from pH 1 to pH 8.7, with studies of apatite specified to be >90% pure reducing the variation to pH 3 to pH 6.5. Of the four studies of rare earth enriched apatite found, three had IEP values between pH 3 and pH 4. A study of synthetic apatite showing enrichment of between 1 and 10% by the REE europium does not affect surface behaviour. However, no studies were found that investigated the effect of common REE processing reagents on REE enriched apatite zeta potentials. Therefore, in addition to comparing previous studies we also therefore present new zeta potential measurements of apatite from a REE enriched deposit under water and common flotation collector conditions. The IEP value of this apatite under water conditions was at pH 3.6, shifting to <3.5 under both hydroxamic acid and betacol conditions. When compared to previous studies, the behaviour of REE enriched apatite under collector conditions is similar to non-REE apatite. This result could be important for future processing of apatite enriched with REE, and therefore global apatite and rare earth supply.

Biochar production and applications in soil fertility and carbon sequestration – a sustainable solution to crop-residue burning in India

A sustainable solution to crop residues burning by converting residues into biochars is provided.