Flotation Mechanisms of Boron Minerals

Abstract

The development of reagent strategies for the flotation of boron minerals requires an understanding of flotation chemistry of reagent/mineral interactions. The floatability of a typical boron mineral, colemanite, was investigated in a microflotation cell by using anionic and cationic surfactants as collectors and tannic acid as a depressant. The results obtained with zeta potential measurements together with flotation tests reveal that colemanite is floatable with both anionic and cationic surfactants at its natural pH of 9.3. While the floatability of colemanite with anionic surfactants decreases with increasing pH, that with a cationic surfactant exhibits a maximum at pH 10.2, indicating the major role of electrostatic interactions in the system.     

Dissolution of colemanite in (NH<Subscript>4</Subscript>)2SO<Subscript>4</Subscript> solutions

Turkey is the country having the richest boron ores in the world, and colemanite, tincal and ulexite are the ores being mined mostly in Turkey. These ores are used in the production of various boron compounds of which the production methods are generally patented. Colemanite ore also is reacted with sulfuric acid to product boric acid. Produced by this method, boric acid contains various impurities which reduce the market value and are difficult to remove. This study investigated the reaction between colemanite and ammonium sulfate as an alternative method to produce boric acid. Particle size, ammonium sulfate concentration, solid to liquid ratio and reaction temperature were chosen as parameters. In results, the conversion rate was increased by decreasing particle size and solid to liquid ratio, by increasing ammonium sulfate concentration and temperature. A semi-empirical model with 40.46 kJmol⁻¹ activation energy representing this process was found as follows: 1−(1−X)^1/3=2.12×10²·C^1.38·R^−0.75·(S/L)^−0.44·e^−4866/T·t^0.61.     

The Separation of Collectors Used as Coprecipitants of Trace Elements in Seawater by Adsorption Colloid Flotation

Abstract

Nine surfactants are screened for their ability to float six collectors, which have been used to coprecipitate trace metallic species in seawater, to the surface of seawater by adsorption colloid flotation as a function of pH.     

Determination of Optimal Conditions for Retention of Sulfur Dioxide by Waste Ulexite Ore in an Aqueous Medium

The main aim of this study was to remove sulfur dioxide (SO₂), which is one of the most significant air pollutants emitted from thermal power stations, using waste ulexite ore, which cannot be recycled industrially and poses a risk for the environment. In experiments conducted at atmospheric pressure in an aqueous environment, the optimization of holding SO₂ with waste ulexite ore has been investigated comprehensively and determined how much SO₂ could be retained in solid waste. The Taguchi method was used to determine the optimal conditions, and the effectiveness of the parameters was identified by variance analysis. The selected parameters and their ranges were defined as temperature (293–333?K), solid to liquid ratio (0.4–0.6?g?mL^?1), particle size (150–600?µm), time (10–30?min), pH (5.5–7.5), and stirring speed (350–800?rpm). The optimal conditions for these parameters were determined to be 333?K, 0.45?g?mL^?1, ?250?µm, 15?min, pH 6, and 350?rpm, respectively. Among all the parameters, temperature and pH were found to be the most effective. The results of the study revealed that SO₂ can be retained in solid waste with calcium content of the boron minerals as CaSO₃?·?0.5H₂O and nearly whole B₂O₃ in the waste ulexite passes into solution. Under the optimum conditions, 86% of B₂O₃ passed into the solution and 75.2?L SO₂ was retained by 1?kg waste ulexite ore. Thus, both B₂O₃ recovery and SO₂ removal were materialized, while waste ulexite ore was evaluated and removed, simultaneously.     

Extraction of boric acid from colemanite mineral by supercritical carbon dioxide

The use of H₂SO₄ in boric acid production from colemanite mineral has several problems, related to product impurities, corrosion and environmental discharge limits. To overcome these problems and to increase extraction efficiency of boric acid, heterogeneous reaction between colemanite and CO₂ dissolved in H₂O was studied at and above supercritical CO₂ conditions. Supercritical conditions enhanced the extraction efficiency of boric acid from colemanite mineral, with 96.9% boric acid extraction efficiency being obtained from CO₂–colemanite reaction at 60 °C, for 2 h of reaction time for particles in the range of +20–40 μm. A powder crystallized from filtrate of reaction was determined as H₃BO₃ and the solid formed at the end of reaction was characterized mostly as CaCO₃ according to FTIR, XRD, TGA and SEM analyses. The use of supercritical CO₂ as a leaching agent in colemanite does not only produce boric acid but also helps to reduce the amount of CO₂ in the atmosphere. Based on these facts, supercritical CO₂ as extractant makes this process green and sustainable for recovering boric acid from boron minerals.     

Feasibility of Producing Pellet Grade Concentrate by Beneficiation of Iron Ore Slime in India

Abstract

Beneficiation of low grade iron ore slime from Chitradurga, India was studied with a view to produce pellet grade fines. The slime sample had a feed grade of 49.86% total Fe, 7.93% Al₂O₃, and 10.19% SiO₂. Kaolinite and quartz was found to be the main gangue minerals and they formed porous and friable oxide and hydroxide of iron. Over 54% of the materials in the slime were less than 20 micron and this size fraction contained higher percentage of gangue minerals. Liberation of free gangue minerals was observed to be substantial in all size classes. Beneficiation studies indicated that excellent rejection of silica and alumina could be obtained through physical separation. The low grade slime could be enriched to 66.36% Fe with 1.75% silica, and 1.44% alumina.     

Effect of mineral geology, mineral size and settling time on selective dispersion and separation process for recovering iron value from iron ultra fines

The dispersion study was conducted on ultra fines of iron ore collected from two locations, Joda and Noamundi slime ponds in the states of Orissa and Jharkhand (India) respectively using sodium hexametaphosphate as a dispersing agent. The Joda slime has been separated into two parts by using hydro cyclone to identify the effect of particle size on selective dispersion and separation of iron ore slimes. Among the gangue minerals present in the slimes, zeolite is more selective towards separation through dispersion process. Under a particular settling condition, a high grade concentrate containing 67.9 wt.% Fe, 1.2 wt.% Al₂O₃ and 1.25 wt.% SiO₂ with 58% iron recovery is achievable using off grade iron ultra fines containing 57.8 wt.% Fe, 7.55 wt.% Al₂O₃ and 7.15 wt.% SiO₂.The efficiency of selective dispersion process strongly depends on mineral geology and particle size. The iron ore ultra fines collected from the Joda slime pond have better selectivity towards dispersion resulting in better separation of gangue minerals in comparison to iron ore ultra fines collected from Noamundi slime pond. This can be attributed to better liberation of Joda slime and difference in nature of the mineral content in Noamundi slime.     

Kinetic Investigation of Reaction Between Colemanite Ore and Methanol

In the field of industry, it is very important that boron compounds are produced from boron ores. The aim of this study was to investigate the dissolution kinetics with carbon dioxide of colemanite in methanol medium in a pressure reactor and to derive an alternative process for producing boron compounds. Reaction temperature, stirring speed, solid/liquid ratio, pressure, and particle size were selected as parameters for the dissolution rate of colemanite. It was found that the dissolution rate increased with increase in pressure and reaction temperature, and with decrease in particle size and solid/liquid ratio. No effect of stirring speed was observed on conversion. The dissolution kinetics of colemanite were examined using both heterogeneous and homogeneous reaction models, and it was determined that the reaction rate can be described by a second-order pseudo-homogeneous reaction model. The activation energy was found to be 51.4 kJ/mol.     

Dissolution kinetics of ulexite in acetic acid solutions

Ulexite is an important boron mineral used for the production of boron compounds. The aims of this study are to examine the dissolution kinetics of ulexite in acetic acid solutions, and to present an alternative process to produce boric acid. In order to investigate the dissolution kinetics of ulexite in acetic acid solutions, the concentration of solution, reaction temperature, solid-to-liquid ratio, and particle size were selected as experimental parameters. It was determined that the dissolution rate of ulexite increased with increasing solution concentration and temperature and decreasing particle size and solid-to-liquid ratio. The activation energy of the process was found to be 55.8 kJ/mol.     

Utilization of borogypsum as set retarder in Portland cement production

Boron ores are used in the production of various boron compounds such as boric acid, borax and boron oxide. Boric acid is produced by reacting colemanite(2CaO·3B₂O₃·5H₂O) with sulphuric acid and a large quantity of borogypsum is formed during this production. This waste causes various environmental problems when discharged directly to the environment. Portland cement is the most important material in the building industry. This material is produced by adding about 3-5% gypsum (CaSO₄·2H₂O) to clinker as a set retarder. The aim of this study was to stabilize borogypsum, and to produce cements by adding borogypsum instead of natural gypsum to clinker. Concrete using cement produced with borogypsum was tested to find the mechanical properties and the test values were compared with those of concrete from cement with natural gypsum. Compressive strength of concrete from cement produced with borogypsum was found to be higher than that of natural gypsum. Also, the setting time of cement with borogypsum was longer than that of the Portland cement.     

Glycine Surfactants Derived from Dodecenyl Succinic Anhydride

We report the synthesis and properties of two surfactants with a novel head group based on glycine. A monocarboxylic surfactant N-glycine methyl ester (2-dodecen-1-yl succinamic acid) (I) was prepared by ring opening of an n-alkyl succinic anhydride. Hydrolysis of the ester functionality yields a dicarboxylic acid II. The sodium salts of I and II were effective surfactants at neutral pH giving a low minimum surface tension (<30 mN m⁻¹ at 20 °C). At high pH (~12) the surface activity of both surfactants is reduced compared to neutral pH, indicating that at neutral pH an ‘acid soap’ is formed. The pK _a of the acid form of the surfactants was determined. Addition of calcium ions reduced the CMC of II but did not reduce the surface tension above the CMC. The resistance of II to calcium ion precipitation was measured at pH 7.     

The effect of heat treatment on colemanite processing: a ceramics application

Boron oxide (B₂O₃), water content, particle size, and specific surface area are important parameters in colemanite (2CaO3B₂O₃5H₂O) in the production of glasses especially of E-glass, boron carbide (B₄C) and borides (CaB₆, LaB₆, SiB₆, LiB₆, MgB₂, TiB₂, and TaB₂ etc.) which are used in ceramics applications. Calcination, a thermal treatment method, is known to affect these parameters significantly. In this study, differential thermal analysis (DTA)-TG, X-ray diffraction (XRD), SEM, BET and chemical analysis were performed on Turkish colemanites before and after calcination. The results are compared in order to elucidate the influence of calcination on processing. An application in the ceramic industry for the production of CaB₆ is demonstrated. Results indicate that the raw colemanite could be processed through calcination in the temperature range of 400 and 600 °C without milling. Calcination is shown to have a significant impact on colemanite similar to that of the milling process. As a result, colemanite was upgraded to ∼58 wt.% B₂O₃ for <250 μm yielding a specific surface area of 2.8 m²/g. This is higher than that of milled colemanite. Because of the crystal water of colemanite, CaB₆ is not produced from uncalcined colemanite, but easily produced from colemanite calcined at 600 °C.     

Comparative Study of Selective Separation of Magnesium from Brine and Seawater

Abstract

A highly selective, sensitive, and inexpensive procedure for the separation of magnesium from brine and seawaters is proposed. The method is based on the separation of the harmful major constituent (calcium) of saline water. This is achieved by floating both calcium and magnesium as their oleates at the pH of saline water (7.5–8.5) to avoid the effect of NaCl on the precipitation of Ca as CaSO₄. The float is dissolved in HNO₃/methanol, precipitated as CaSO₄, and the mother liquor is refloated as pure magnesium oleate. This purity is confirmed by infrared measurements.     

Radiometric study of the adsorption of chromate ions in anionic flotation of barite and celestite minerals

An investigation of the optimum conditions for concentrating barite and celestite ores was carried out by floating the gangue minerals (calcite and quartz) with sodium oleate while depressing BaSO₄ or SrSO₄ with CrO₄^2? ions. The isotope dilution technique was applied to determine the adsorption of CrO₄^2? ions tagged with ⁵¹Cr on high grade barite and celestite minerals at different pH values in the presence and absence of sodium oleate. Flotation of synthetic ores of barite and celestite was carried out at pH 10, whereby effective selectivity between float and nonfloat minerals could be achieved.     

Elimination of boron and lithium coexisting in geothermal water by adsorption-membrane filtration hybrid process

Direct release of geothermal waters to the environment may cause some damages to some plants because they contain toxic species such as boron, arsenic, fluoride etc. along with valuable minerals including lithium. In this study, a hybrid process combining adsorption and membrane filtration was used to separate boron and lithium simultaneously from geothermal water. According to the results obtained, separation efficiencies for lithium and boron from geothermal water were 100% and 83% using boron selective ion exchange resin Dowex XUS-43594.00 and lithium selective λ-MnO₂ adsorbent, respectively. The kinetic data of lithium and boron adsorption have been evaluated using pseudo-first order and pseudo-second-order kinetic models.     

间歇式泡沫分离法回收海水中硼的研究

采用间歇式泡沫分离法研究了海水中硼的回收工艺。主要考察了表面活性剂种类及用量、溶液pH、气体流量等因素对海水中硼的分离性能的影响。实验结果表明：十二烷基三甲基氯化铵（DTAC）、十四烷基三甲基氯化铵（TTAC）、十六烷基三甲基氯化铵（CTAC）以及十八烷基三甲基氯化铵（OTAC） 4种表面活性剂中CTAC对海水中硼的分离效果最好;随溶液pH的增加,硼的回收率和富集比均先增大后减小;随CTAC用量的增加,硼的回收率逐渐增大并趋于稳定,而富集比先增大后减小;随气体流量的增加,硼的回收率先增大后减小,而富集比则逐渐减小。在实验条件范围内,当CTAC质量浓度为0.2 g/L、溶液pH为9、气体流量为200 mL/min时,硼的回收率达到90%,富集比达到8。     

SOLVENT-IN-PULP EXTRACTION OF BORON FROM SLURRIES

ABSTRACT

Solvent-in-pulp extraction of boron from various slurries has been studied. Extraction of boron from synthetic slurries of quartz, bentonite and from natural plant-end-slurry from Kirka/Turkey with 2-ethyl-1,3-hexanediol (EHD), 2-cloro-4-(1,1, 3,3-tetramethyl-butyl)-6-methylol-phenol (CTMP) and 1:1 mixture of the two is considered here.

The results show that, under the pulse conditions used, phase separation appeared acceptably sharp and the level of clarity is acceptable regardless of pH. The transmittance evidently decreased with increase in pH but did not drop below about 75%. However, some solid and water were transferred and the organic layers were slightly turbid in decreasing order CTMP>CTMP/EHD>EHD but the phase clarity is reduced by solids in the order quartz>bentonite>water.

Combining the data of observed turbidities on extraction with the transmittance measurements of the organic phase rough estimates of solids transferred may be made. For example, in the case of extraction from bentonite slurry at pH 9 the % solids in the organic phase are 0.4, 0.3 and 0.1 for CTMP, CTMP/EHD and EHD respectively, assuming that the solids content of the aqueous phase is 50,000 gm^-3. Values are of course lower at lower pH. For quartz slurries the corresponding figures are; 0.3, 0.2 and 0.05.     

Folate Functionalized Boron Nitride Nanotubes and their Selective Uptake by Glioblastoma Multiforme Cells: Implications for their Use as Boron Carriers in Clinical Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) is increasingly being used in the treatment of several aggressive cancers, including cerebral glioblastoma multiforme. The main requirement for this therapy is selective targeting of tumor cells by sufficient quantities of ¹⁰B atoms required for their capture/irradiation with low-energy thermal neutrons. The low content of boron targeting species in glioblastoma multiforme accounts for the difficulty in selective targeting of this very malignant cerebral tumor by this radiation modality. In the present study, we have used for the first time boron nitride nanotubes as carriers of boron atoms to overcome this problem and enhance the selective targeting and ablative efficacy of BNCT for these tumors. Following their dispersion in aqueous solution by noncovalent coating with biocompatible poly-l-lysine solutions, boron nitride nanotubes were functionalized with a fluorescent probe (quantum dots) to enable their tracking and with folic acid as selective tumor targeting ligand. Initial in vitro studies have confirmed substantive and selective uptake of these nanovectors by glioblastoma multiforme cells, an observation which confirms their potential clinical application for BNCT therapy for these malignant cerebral tumors.     

The Solvent Extraction of Boron with Synthesized Aliphatic 1,3‐Diols: Stripping and Extraction Behavior of Boron by 2,2,5‐Trimethyl‐1,3‐hexanediol

Abstract

A variety of aliphatic 1,3‐diols (4a–c, 5a–c, 6a–c) was synthesized from β‐hydroxy carbonyl compounds (1–3) for potential use in the solvent extraction of boron. Primary‐secondary and primary‐tertiary alcohol structures of 1,3‐diols substituted with isopropyl, isobutyl, and isopentyl groups have been demonstrated to be very efficient for the solvent extraction of boric acid from aqueous solutions. The extraction ability of 2,2,5‐trimethyl‐1,3‐hexanediol (5b) was investigated as a function of 5b concentration, solution pH, solvent properties, and stripping conditions. Extraction efficiency increased with increasing concentration of 5b, and the best extraction of boron (96.8%) was found to be at an equilibrium pH of 2 with 0.5 M of 5b. Chloroform, toluene, chlorobenzene, 2‐octanol, and n‐amyl alcohol were found to be suitable solvents for the solvent extraction of boron. The boron complex can be recovered from the organic phase by treatment with an aqueous solution of sodium hydroxide. The highest ratio (96.7%) of boron was recovered by 0.1 M of sodium hydroxide solution.