Presence Of Sodium Silicate Research Articles

Recovery of Phosphate Minerals from Plant Tailings Using Direct Froth Flotation

Wastes produced from the phosphate industry presents many challenges due to the high economic and environmental impacts involved with their disposal. However, the relative scarcity of high-grade phosphate ores has driven researchers to recover and recycle these valuable wastes (secondary sources). The goal of this study was to investigate the possibility of upgrading the P2O5 content in tailings produced from a phosphorous production plant using direct froth flotation. Characterization assays, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and mineral liberation analysis (MLA), were first conducted to identify the mineralogical and morphological characteristics of tailings samples and grain properties to better understand the behavior of the flotation feed. Flotation experiments were conducted using Denver D-12 in a 1-L flotation cell in the presence of sodium silicate (dispersant) and sodium oleate (collector). Several parameters, such as the solids content of the flotation pulp, pulp pH and flotation time, were investigated to optimize the recovery and grade of the concentrate products. Results obtained from this study indicated that the P2O5 content in plant tailings could be upgraded from 21.57% to 28.4% at >73% recovery.

Combination formation in the reinforcement of metakaolin geopolymers with quartz sand

Although quartz sand is widely used as filler material in construction, a few studies investigated the incorporation of quartz sand in geopolymers. To study the incorporation of quartz sand in the reinforcement of metakaolin geopolymer not only fills this gap, but also gives a clue on using non-calcinated aluminosilicates (e.g., mine tailings) in the synthesis of geopolymers. In the presence of sodium silicate, metakaolin geopolymers were synthesized with quartz sand of various size ranges as filler material. XRD, FTIR, SEM and NMR characterizations on the geopolymers indicate the dissolution, precipitation, and the formation of combination on quartz particles that associates them into the geopolymeric gel, so as to reinforce the mechanical strength of geopolymers. The compressive strength of metakaolin geopolymers with only silicate, silicate plus quartz sand and silicate plus rutile sand is 31.2, 52.2 and 41.5 MPa, respectively. In geopolymer with silicate and quartz sand, a decreasing Si/Al ratio as increasing distance from the quartz particle is observed through an energy dispersive X-ray (EDX) mapping. The SEM images and NMR spectra suggest that the formed combination is of several micrometers with main species of polysialates (-Si-O-) such as Q4(2Al), Q4(1Al).

Selective flotation of scheelite from calcite: A novel reagent scheme

Sodium oleate (NaOl) has been widely used as a collector for the scheelite flotation. However, low selectivity of NaOl and large amount of sodium silicate (SS) needed remain tough problems. In this study, octyl hydroxamic acid (HXMA-8) was used as an associate collector with NaOl in scheelite flotation. The flotation tests showed that a novel reagent scheme, i.e., a lower dosage of SS (300mg/L) and mixed collectors of HXMA-8+NaOl (total concentration 4.5×10−4mol/L, preferred mass ratio of 1:2) achieved the selective separation of scheelite from calcite. Zeta potential measurements indicated that the depressant, SS, adsorbed more strongly on calcite surface than on scheelite surface. HXMA-8 adsorbed significantly on scheelite surface either in the absence or presence of SS by chemical bonding between oxygens of HXMA-8 and surface metal ions. NaOl also adsorbed on both mineral surfaces by chemisorption, but the adsorption on calcite surface was influenced adversely by the presence of SS.

A functionalized hybrid silicate adsorbent derived from naturally abundant low-grade palygorskite clay for highly efficient removal of hazardous antibiotics

As promising eco-friendly materials, natural silicates have received great attention as abundant, low-cost, non-toxic, stable, and environmentally benign adsorbents. Inspired by the idea of “from nature, for nature”, a series of highly efficient hybrid silicate adsorbents were synthesized via a simple one-step hydrothermal process, using naturally abundant low-grade palygorskite (PAL) as the initial material in the presence of sodium silicate (SS), magnesium sulfate (MS), and monochloroacetic acid (MCA). As expected, the PAL crystal and the associated minerals were restructured as amorphous and multi-porous Mg, Al-silicates, while the active COOH groups were simultaneously introduced into the silicate to form a hybrid adsorbent with a specific surface area of 410.61m2/g (compared to 52.87m2/g for raw PAL). The hybrid silicate adsorbent showed excellent adsorption capabilities for the antibiotics chlortetracycline (CTC) (329.84mg/g) and oxytetracycline (OTC) (207.47mg/g), which were enhanced by 218.9% and 107.9%, respectively, in contrast to that of raw PAL. The adsorption of the hybrid adsorbent for CTC and OTC was pH-dependent, and the pH values of 3.56–7.82 (for CTC) and 3.45–7.57 (for OTC) favored the adsorption. The dynamic adsorption process was well described by a pseudo second-order model, which suggested that chemical adsorption was the prominent driving force. The thermodynamic adsorption pattern agreed well with the Redlich–Peterson model, revealing that the heterogeneous surface was the main adsorption site and that removal of antibiotics occurred mainly by multi-layer adsorption.

Solution Chemistry of Sodium Silicate and Implications for Pyrite Flotation

The solution chemistry of sodium silicate and implications for pyrite flotation have been studied. In addition to flotation and sedimentation tests, electrophoresis, inductively coupled plasma (ICP) tests, and X-ray photoelectron spectroscopy (XPS) have been used. The flotation and sedimentation results show that lizardite causes problems in the flotation of pyrite by adhering to the pyrite particles. Addition of the sodium silicate could make the mixed sample of pyrite and lizardite more disperse in the alkaline condition and significantly reduce the adverse effect of lizardite on the flotation of pyrite. ICP tests and XPS analysises show that sodium silicate can adsorb onto the lizardite surface and change the surface characteristic of lizardite. Sodium silicate mainly exists in the form of SiO(OH)3– in the pH range that sodium silicate can restore pyrite flotation recovery. The adsorption of SiO(OH)3– ions at the lizardite/solution interface overcompensates the positive charge on the lizardite particle and its ζ potential is rendered negative. The total interaction energy between lizardite and pyrite is changed from attractive energy to repulsive energy in the presence of sodium silicate, according to the calculation of the Derjaguin–Landau–Verwey–Overbeek theory.

Electrokinetic and rheological properties of highly concentrated kaolin dispersions: Influence of particle volume fraction and dispersant concentration

An industrial kaolin was selected and characterised. Different dispersions were prepared with solids volume fractions between ϕ = 0.20 and ϕ = 0.47 in the presence of sodium silicate (between X s = 0.075 mg dispersant/m 2 and X s = 0.225 mg dispersant/m 2), to determine the electrokinetic and rheological properties. The Fe, Ca, Mg, Na, and Si concentrations, pH, and electrical conductivity of the solutions increased after dispersant addition, X s, and/or the solids volume fraction, ϕ, was raised. Electrophoretic mobility, negative for all studied dispersions, became more negative after dispersant addition and less negative with increasing solids fraction. The dispersions with X s ≤ 0.075 mg dispersant/m 2 displayed plastic behaviour (in the shear flow test) and exhibited the characteristics of a gel (in the oscillatory test), owing to the extensive aggregation of the kaolinite particles. The dispersions with X s ≥ 0.105 mg dispersant/m 2 displayed shear-thinning behaviour (in the shear flow test) and viscoelastic fluid characteristics (in the oscillatory test). This behaviour is typical of dense dispersions of plate-shaped colloidal particles, which are well stabilised by electrostatic repulsion. The rheological properties of well-stabilised dispersions were analysed and readily interpreted by redefining the kaolin platelets as new effective hard particles, the thickness of the plate-like particle with its ionic double layer being considered as effective thickness. This enabled an effective volume fraction to be calculated that describes the combined effect of the solids volume fraction and the dispersant addition on dispersion rheological properties. The study showed that excluded volume interactions are essential to understanding the effect of ionic strength on the rheological properties of well-stabilised highly concentrated dispersions.

The structural bases of long-term anabiosis in non-spore-forming bacteria

Peculiarities of the structural organization in non-spore-forming bacteria associated with long-term anabiosis were revealed both in laboratory cultures and in natural populations isolated from 1–3-Myr-old Eastern Siberian permafrost and tundra soil. Different advanced methods were used, including (a) high-resolution electron microscopy; (b) simulation of in situ conditions in the laboratory by varying the composition of growth medium and cultivation conditions; (c) low-temperature fractionation to isolate and concentrate microbial cells from natural soils; (d) comparative morphological analysis of microbial cells in model cultures and natural soils (in situ). Under laboratory conditions, the intense formation of resting cells by representatives of various taxa of eubacteria and halophilic archaea occurred in 2–9-month-old cultures grown in carbon-, nitrogen-, or phosphorus-limited media, in starved cell suspensions in the presence of sodium silicate, or on soil agar. Among resting cells, we revealed cystlike forms having a complicated structure and common features. These included a thick capsule; a thickened and multiprofile cell wall; the presence of large intramembrane particles on PF- and EF-fracture surfaces; fine-grained or lumpy cytoplasm; and a condensed nucleoid. The general morphological properties, ultrastructural organization, physiological features of cystlike cells, and their ability to germinate under the appropriate conditions suggest the existence of constitutive dormancy in non-spore-forming bacteria. It was found that the majority of microorganisms in permafrost and tundra soil are cystlike cells, very similar to those in laboratory cultures. Anabiotic (resting) cystlike cells are responsible for the survival of non-spore-formers in extreme Earth habitats and may be regarded as possible analogs of extraterrestrial forms of microbial life.

Reverse Flotation of Magnesite by Dodecyl Phosphate from Dolomite in the Presence of Sodium Silicate

Magnesite and dolomite are two salt‐type minerals. They show similar flotation behavior due to the same crystal structure, similar chemical composition, and high solubility. It is difficult to achieve effective flotation of magnesite from dolomite in a single stage. The present study was performed to develop a new and better flotation scheme for magnesite from dolomite. The flotation tests show that there exists a significant difference in flotability between magnesite and dolomite when dodecyl phosphate synthesized with dodecanol, phosphorus oxychloride, and other chemicals is used as collector. Modifiers are necessary to improve flotation selectivity. It was found that sodium silicate selectively depressed magnesite at a pH of 4.5 to 7.5. The flotation mechanism was investigated by characterizing surface electrical properties and measuring the adsorption density of the reagents on magnesite and dolomite.

Reduction of silica from complex calcite ore for use in seawater magnesia production

The amenability of a calcite-bearing ore to the reduction of silica to below 0.2% by physical beneficiation was studied. The objective was to use the ore as a raw material for seawater magnesia production. The ore contains complex gangue minerals such as diopside, forsterite, phlogopite, clinohumite, graphite and quartz. These contribute to around 25% acid insolubles with 6% SiO2. Reverse-flotation studies using various cationic collectors with tannin as a depressant indicated the possibility of reducing the acid insolubles to around 5%. Direct flotation of calcite with anionic sodium oleate in the presence of sodium silicate and lactic acid as a depressant indicated the possibility of reducing the acid insolubles to below 3% and the SiO2 to from 0.2% to 0.3%. Lactic acid was found to be an effective depressant of the complex gangue minerals in the ore.

Estimation of the liberation size of graphite in a schistose rock and its response to beneficiation

Liberation size can be estimated using various techniques such as grain counting, frequency curves, X-ray intensity and the mesh of grind. The present investigation deals with the estimation of the liberation size of graphite flake contained in a schistose ore from Shivaganga, India. It was observed that the flakes are liberated at from 75 to 150 µm. The rougher flotation concentrate obtained after grinding the run-of-mine ore for 5 min contained 54% fixed carbon. This represented the first stage of liberation. After regrinding to <90 µm in the presence of sodium silicate and guar gum, a cleaner concentrate containing 82% fixed carbon was obtained.

A General Route to Labile Niobium and Tantalum d0 Monoimides. Discussion of Metal−Nitrogen Vibrational Modes

Reaction of TaCl5 with 2 equiv of an amine in the presence of sodium silicate and pyridine affords Ta(NR)Cl3(py)2 in good yield. Reaction of NbCl5 with ZnCl2 followed by addition of an amine RNH2 and pyridine affords M(NR)Cl3(dme) (dme is 1,2-dimethoxyethane). For niobium this reaction proceeds smoothly regardless of the amine but is ineffective with tantalum and alkyl amines. An alternative route involves reaction of TaCl5 with 3 equiv of RNH2 to form [RNH3]2[Ta(NR)Cl5], followed by reaction of this salt with ZnCl2 in the presence of dme. The molecular structure of Nb(NtBu)Cl3(dme) (formula C8H19Cl3NNbO2) was determined by X-ray crystallography (monoclinic space group Cc with a = 30.565(4) A, b = 7.2406(13) A, c = 13.915(2) A, β = 90.626(7)°, V = 3079.4(8) A3, Z = 8). The Nb−N bond length is 1.72 A with a Nb−N−C bond angle of 177° in a distorted octahedral structure. In order to characterize the M−N stretching frequencies in these compounds, IR data for each compound are compared with calculated stretchi...

Mechanism of oleate interaction on salt-type minerals, Part II. Adsorption and electrokinetic studies of apatite in the presence of sodium oleate and sodium metasilicate

The mechanism of oleate interaction on apatite is investigated through adsorption and electrokinetic studies. The adsorption density at monolayer coverage corresponds to a condensed state of surfactant molecule with a molecular area of 33 Å 2. The isotherm at pH 8 showed the monolayer coverage followed by the precipitation step of calcium oleate, whereas at pH values 9, 10 and 11, the isotherms showed bilayered structure of oleate on the surface before the precipitation step of calcium oleate. The vertical step characterizing calcium oleate precipitation after bilayer formation is found to be dependent on the solid/liquid ratio. The zeta-potentials correlate to the adsorption of oleate up to bilayer formation. The presence of sodium silicate has no influence on the adsorption of oleate.

Coalescence and froth collapse in the presence of fatty acid

Bubble coalescence and froth collapse occurred during carbonate/silicate separation tests in a flotation column using a commercial fatty acid. To study this a method of quantifying coalescence is developed using the change in gas holdup in the collection (pulp) zone of the flotation column and the calculated change in bubble diameter. Fatty acid (mainly oleic acid), in 3:1 ratio with lannagol emulsifier, caused significant coalescence. For example, 10 ppm of fatty acid added to 20 ppm of TEB (1,1,3-triethoxybutane), a frother, caused a 55% decrease in gas holdup (corresponding to a 50% increase in bubble diameter) and collapsed the froth completely. Higher concentrations of lannagol stabilized the froth, but failed to prevent bubble coalescence. Solids in the presence of sodium silicate, a dispersant, further enhanced coalescence and froth collapse. It is observed that there was no simple relationship between coalescence and froth collapse as a persistent froth could be maintained even with high coalescence. A mechanism of coalescence is proposed based on hydrophobic coating of the bubble causing water drainage.