Presence Of Sodium Hexametaphosphate Research Articles

Experimental and theoretical investigations into the surface chemical properties and separation of serpentine from quartz using xanthomonas campestris as a selective flocculant

Separation of fine serpentine (SPT) from quartz (QZ) both of d80 close to 20 µm using an eco-friendly microbial exo-polysaccharide, xanthomonas campestris (XCT), as a selective flocculant for SPT was conducted experimentally and substantiated theoretically. The adsorption of XCT onto SPT was observed to decrease with increase in pH, whereas that of QZ was nearly nil beyond pH 2.1. Zeta potential of SPT in presence of XCT decreased with increase in pH further attesting to the adsorption and anionicity of XCT. The FTIR studies confirmed the interaction of XCT with SPT in presence of sodium hexametaphosphate. The nature of intermolecular interactions present in complexes formed on SPT surface was revealed by quantum theory of atoms in molecules to be non-covalent. The electron density difference plot conducted on formed complexes indicated that electrons drifted from XCT to the surface of SPT. Selective flocculation SPT-QZ (1:1) mixture conducted at pH 6 and pH 7.5 in presence of 4 mg/L and 2 mg/L of sodium hexametaphosphate coupled with 100 mg/L of XCT yielded separation efficiency and selectivity ratio of 96.5 % and 71.2, respectively, after three desliming stages. Therefore, XCT is a potential selective flocculant for serpentine.

Bulk fluidity and apparent wall slip of deflocculated kaolin suspensions

The influence of different electrolytes on the apparent wall slip (AWS) of aqueous kaolin suspensions is studied experimentally. The fluidity and AWS characteristics of purely aqueous and deflocculated kaolin suspensions are measured by gap-dependent rotational viscometry using unconventional cone–cone geometry. The applied sensors are made of different materials: stainless steel (smooth and sandblasted), titanium, and duralumin (with an anodized surface). Both the quality of the sensor surface and the presence of electrolytes strongly influence the observed AWS behavior. In the case of a purely aqueous 40% kaolin suspension, positive AWS (depleted layer formation) is measured on the stainless steel and titanium sensors, while negative AWS (stagnant layer formation) is observed on the anodized duralumin sensor. In the case of fully deflocculated suspensions, Newtonian flow behavior is observed with almost no measurable AWS effects. In the case of partially deflocculated suspensions, the type of deflocculant becomes important. While the presence of Na2CO3 or NaOH does not qualitatively change the AWS trends and only slightly increases them, the presence of SHMP (sodium hexametaphosphate) leads to positive AWS on anodized duralumin. However, the addition of NaCMC (sodium salt of carboxymethylcellulose) induces negative AWS on all the surfaces studied.

A novel pH-responsive flocculant for efficient separation and recovery of Cu and Mo from secondary resources via selective flocculation-flotation

A novel pH-responsive flocculant, P(AM-DEA-DPL) (PADD), was first used for efficient separation and recovery of Cu and Mo from secondary resources via selective flocculation-flotation. The selective flocculation behavior, flocculation-flotation and deflocculation of fine molybdenite, chalcopyrite and quartz were researched by single and artificial mixed ore. Moreover, fourier transform infrared (FTIR) spectroscopy, zeta potential, contact angle and fluorescence microscope were utilized to reveal the flocculation and deflocculation mechanism. The results showed that PADD had an excellent selective flocculation of fine molybdenite and chalcopyrite particles in the presence of sodium hexametaphosphate (SHMP), which originated from the bridging molecular chains, electrostatic adsorption and hydrophobic interaction among PADD and the fine hydrophobic particles. Moreover, the floated flocs obtained from the artificial mixed ore of fine molybdenite, chalcopyrite and quartz could be well dissociated to small size particles when the slurry pH was adjusted to 6.0, resulting from the enhanced deprotonation effect and electronegativity of PADD. It would facilitate the further separation of molybdenite and chalcopyrite from the mixed concentrate via flotation. Therefore, PADD hold a broad application prospect with the efficiently recovering and further separating molybdenite and chalcopyrite from secondary resources containing Cu and Mo.

Silver nanoparticles affect wheat (Triticum aestivum L.) germination, seedling blight and yield.

The aim of the study was to evaluate the effect of two types of negatively charged quasi-spherical silver nanoparticles (AgNPs) at concentrations of 10, 20 and 30mgL-1 and silver ions at a concentration of 30mgL-1 on the growth, selected physiological aspects and yielding of wheat (Triticum aestivum L.) cv. Tybalt, and on plant resistance to seedling blight. Seed germination, α-amylase activity in seeds, morphology and infestation of seedlings by pathogens were assessed in a hydroponic treatment. Growth rate, PSII efficiency, heading and yield of the same plants were then analysed in pot culture. Results showed that the AgNPs and silver ions had a negative effect on roots, but reduced seedling blight and improved leaf area compared to the control. In addition, the AgNPs reduced with sodium borohydride in the presence of trisodium citrate at concentrations of 10 and 20mgL-1 stimulated germination, α-amylase activity and shoot length, which was not observed in the case of silver ions and the AgNPs reduced with sodium hypophosphite in the presence of sodium hexametaphosphate. In a pot experiment, the AgNPs improved plant growth, PSII efficiency, accelerated heading and increased yield-related parameters compared with the control. Results revealed the interaction strength in the following order: TCSB-AgNPs>SHSH-AgNPs>silver ions. TCSB-AgNPs in the lowest concentration had the most favourable effect, indicating their great potential for use in improving wheat cultivation.

Selective flotation separation of smithsonite from dolomite by using sodium hexametaphosphate as a depressant

In this study, a depressant sodium hexametaphosphate (SHMP) was introduced for the flotation separation of smithsonite from dolomite using mixed benzohydroxamic acid (BHA) and sodium oleate (NaOL) as the collectors. Micro-flotation experiments were conducted to investigate the flotation behavior of smithsonite and dolomite in the absence and presence of SHMP. Furthermore, the depression mechanism of the SHMP was unraveled by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) analysis, and flotation solution chemistry. The flotation results showed that the recovery of dolomite decreased from 26.63% to 2.25% when the addition of SHMP in the flotation system increased from 0 to 50 g/t, while the smithsonite recovery exhibited a slight increase from 91.05% to 93.10%, which improved the separation effect greatly. FTIR measurements and XPS analysis revealed that the SHMP was chemically adsorbed on the dolomite surface in the form of hydrophilic complexes with Ca2+ and Mg2+, thus depressing adsorption of the mixed BHA/NaOL. Flotation solution chemistry analysis suggested that Zn2+ could form ZnCO3 on the surface of the dolomite leading to the transformation of the dolomite surface to the smithsonite surface. And SHMP could form hydrophilic complexes with Ca and Mg sites on the dolomite surface, thus depressing the adsorption of BHA/NaOL on the transformed dolomite surface.

Improvement of the protective properties of the nanocomposite polypyrrole-Zinc oxide coating on mild steel by adding the dispersant sodium hexametaphosphate

This work reports on the use of the sodium hexametaphosphate (SHMP) surfactant for the dispersion of ZnO nanoparticles in the PPy polymer matrix for the production of the composite PPy-ZnO as an anticorrosive coating on mild steel. The coatings of PPy, PPy-ZnO and PPy-ZnO-SHMP were electrodeposited by cyclic voltammetry (CV) method. The anticorrosion behavior of all the coatings was studied in a 3.5% NaCl solution medium at room temperature. The performance of all the coatings was evaluated using polarization measurements, electrochemical impedance spectroscopy (EIS) and chronopotentiometry at open circuit potential (OCP). It was found that the presence of SHMP during synthesis resulted in a more homogeneous and compact coating in which the ZnO nanoparticles were more evenly distributed among the PPy particles. Furthermore the coating PPy-ZnO-SHMP exhibited higher corrosion resistance and provided better barrier properties compared to pure PPy and PPy-ZnO coatings.

Thermodynamic and kinetic studies of heavy metal adsorption by modified nano-zeolite

ABSTRACT In this study, for the first time, nano-sized clinoptilolite zeolite produced by a dry planetary ball mill in the presence of sodium hexametaphosphate was employed to remove heavy metals. Results represented that the concentration of adsorbed ions on nano-zeolite increases with increasing pH, initial concentration of metals, and temperature. The maximum adsorption efficiency for Ni2+, Cd2+, and Cu2+ was found to be 74.20%, 97.60%, and 99.50% at a pH of 7.5 and 60°C, respectively. The adsorption of Ni2+, Cd2+ and Cu2+ on nano-zeolite increased from 44.40% to 74.20 %, 76.4% to 97.60%, and 94.30% to 99.50% by enhancing temperature from 20 to 60 °C. Furthermore, Gibbs’s free energy obtained from thermodynamic evaluations depicted that adsorptions had spontaneous behavior. According to Langmuir models, the maximum capacity (qm) of Ni2+, Cu2+, and Cd2+using nano-zeolite was found to be 17.79, 17.92, and 18.32 mg/g. Adsorption isotherms showed that results fitted better on the Langmuir model for Ni2+and Cu2+ and the Freundlich model for Cd+2 because the correlation coefficients (R2) were 0.99 for them. Finally, the pseudo-second-order kinetic model was selected to interpret the experimental data.

Structuring of acidic oil-in-water emulsions by controlled aggregation of nanofibrillated egg white protein in the aqueous phase using sodium hexametaphosphate

This study investigated the mechanism behind the structuring of acidic oil-in-water emulsions made with native and nanofibrillated egg white proteins (EWP) in the presence of sodium hexametaphosphate (SHMP). Oil-in-water emulsions containing 10–70% oil content were prepared from EWP suspensions and treated with 0–500 ppm SHMP. Whereas 70% oil-in-water emulsions with both native and nanofibrillated EWP in the absence of SHMP showed a paste-like texture, the emulsions with a lower oil content (10–50% oil) had a more liquid consistency and quickly separated into two layers. No structuring effect was observed for the emulsions made with native EWP with 10–50% oil contents, however, the addition of SHMP significantly increased the creaming stability and the rheological properties of the nanofibrillated EWP emulsions containing 10–50% oil. Microstructural data suggested that nanofibrillated EWP could form a well crosslinked network in the aqueous phase of the emulsions through ion bridges with SHMP oligo anions. It resulted in the fabrication of reduced-fat emulsions with 10–50% oil content with a similar or stronger texture than that of high-fat emulsions with 70% oil content. This research provided insight into the crosslinking of nanofibrillated EWP by SHMP as a viable food grade cross-linker in designing structured acidic O/W emulsions.

Study on Dispersion of TiO2 Nanopowder in Aqueous Solution via Near Supercritical Fluids.

In this study, we investigated the effects of near supercritical carbon dioxide (SCCO2) parameters, including pressure, temperature, and saturation time on titanium dioxide (TiO2) nanopowder dispersion in water-containing sodium hexametaphosphate (SHMP). The stability and morphology of TiO2 particles dispersed in an aqueous solution were examined using a zeta potential instrument, dynamic light scattering, and transmission electron microscopy. As shown in the results, of particular interest, it was found that near SCCO2’s pressure and saturation time had the strongest impact on TiO2 dispersion in water-containing SHMP. This finding indicated that TiO2’s secondary average particle size was significantly reduced with an increase in near SCCO2’s pressure and saturation time. Additionally, in the presence of SHMP, the zeta potential of the as-prepared dispersion solution reached −53.7 mV because of production of the larger negative static charge repulsion force (resulting from SHMP dissociation) on the TiO2 particle surface. The secondary average size was 127 ± 68 nm, indicating good stability of TiO2 dispersed in water containing an inorganic dispersant.

Effect of phosphate additives on the hydration process of magnesium silicate cements

The role of phosphate additives on the hydration process of magnesium silicate cement pastes was investigated through a multi-technique approach. A MgO/SiO2 mixture was hydrated for 28 days either in the absence or in the presence of sodium hexametaphosphate, trimetaphosphate or orthophosphate. Information on the kinetics of the hydration reaction was acquired by monitoring the free water index by means of differential scanning calorimetry, while the hydration products were thoroughly investigated by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and 29Si solid-state nuclear magnetic resonance spectroscopy. The overall results provide new insight into the effect of phosphates on the hydration reaction and on the structure of magnesium silicate hydrate cements. All additives showed a plasticizing effect and promoted the formation of the binding phase magnesium silicate hydrate (M–S–H), without significantly altering its structure. Sodium orthophosphate was found to be by far the best-performing additive, even better than sodium hexametaphosphate, which is commonly used in these cementitious formulations. For the first time, 31P solid-state NMR investigation allowed orthophosphate ion to be identified as the effective species.

Characterisation of polyphosphate coated aluminium-doped titania nanoparticles during milling

This paper investigates the characterisation of alumina-doped titania nanoparticles, milled under high-shear over time, in the presence of sodium hexametaphosphate (SHMP) dispersant. Transmission electron microscopy (TEM) indicated that prolonged milling times led to the formation of 10 nm particle fines which were electrostatically attracted to larger particles, where no change in the crystal structure was observed. Primary particle sizes measured by dynamic light scattering (DLS) and TEM were in agreement and showed no change in primary particle size (∼250 nm) with respect to milling time, however, there was a clear reduction in the magnitude of the slow mode decay associated to aggregates. The TiO2 was found to have an isoelectric point (iep) in the range of pH 3–4.5, where an increase in milling time led to a lower pHiep, indicative of an increase in SHMP coverage, which was further supported by an intensification in phosphorus content measured by X-ray fluorescence (XRF). Phosphorus content and zeta potential analysis before and after centrifugal washing showed that SHMP was partially removed or hydrolysed for the longer milled pigment samples, whereas no change was observed for shorter milled samples. Relaxation NMR was also performed, where enhanced relaxation rates at longer milling times were associated partially to increases in surface area and exposure of Al sites, as well as physicochemical changes to SHMP density and structure. It is thought that extended milling times may lead to hydrolysis or other structural changes of the dispersant from the high energy milling conditions, allowing easier removal after washing for longer milled pigments.

Magnetic separation of pentlandite from serpentine by selective magnetic coating

In this study, pentlandite was selectively separated from serpentine using magnetic coating technology by adjusting and optimizing pH, stirring speeds, magnetic field intensities, and dosages of sodium hexametaphosphate (SHMP) and sodium oleate (SO). A magnetic concentrate with Ni grade of 20.8% and Ni recovery of 80.5% was attained under the optimized operating conditions. Considering the above, the adsorption behaviors of SHMP and SO and the surface properties of minerals after the magnetic coating were studied by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that magnetite was preferentially coated on the pentlandite surfaces and sparingly coated on the serpentine surfaces in the presence of SHMP and SO. Furthermore, calculations by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory indicate that the preferential adsorption of magnetite on the pentlandite surfaces is due to the presence of a hydrophobic interaction between the magnetite and pentlandite, which is much stronger than the interaction between magnetite and serpentine.

Flotation studies of fluorite and barite with sodium petroleum sulfonate and sodium hexametaphosphate

The development of new collectors to separate fluorite from barite is urgently needed in mineral processing. In this study, the flotation behavior of fluorite and barite was studied using sodium petroleum sulfonate (SPS) as a collector with sodium hexametaphosphate (SHMP) as a depressant. The performance of reagents on minerals was interpreted by infrared spectroscopic analysis and zeta potential measurement. The flotation results showed that SPS performed well in a wide pH region (7–11) even at a low temperature (5°C), while the flotability of fluorite and barite were almost the same. At pH 11, the presence of SHMP obviously depressed fluorite rather than barite and SHMP exhibited good selective inhibition to fluorite. Fourier-transform infrared spectra and zeta potential results showed that: (1) SPS can adsorb on fluorite and barite surfaces and (2) SHMP had little effect on the adsorption of SPS on a barite surface, although it interfered with the adsorption of SPS on a fluorite surface through strong adsorption.

Flotation separation of limonite from quartz with sodium oleate: effects of limonite dissolution and addition of sodium hexametaphosphate

ABSTRACT The utilisation of limonite ore is potentially important to China as the high quality iron resource, such as magnetite and hematite of high grade, are rapidly depleting, but many detrimental impurities, such quartz and calcite etc, are difficult to upgrade to make suitable concentrates for the blast furnace. The flotation behaviour of limonite, quartz and their mixture by using sodium oleate as collector were studied systematically in this paper. Single-mineral flotation tests showed that the flotation recovery of limonite was much higher than that of quartz in a broad range of pH. However, flotation tests for the mixture of limonite and quartz showed rather poor mineral separation efficiency with the flotation recovery of both minerals being high in froth products. The flotation separation efficiency of limonite from quartz was substantially improved by adding sodium hexametaphosphate (SHMP) as a depressant for quartz flotation. To elucidate these phenomena, the solution species calculation of limonite dissolution and the measurements of iron ions content were carried out. It was found that iron ions or its species released into the pulp from the dissolving of limonite could effectively activate the flotation of quartz but have little influence on the flotation of limonite. In the presence of SHMP, iron ions or its species lost their activating power on quartz flotation which caused by the chemical reaction between SHMP and iron ions or its species, and then removed iron ions or its species from quartz surface into the solution.

Reducing quartz entrainment in fine coal flotation by polyaluminum chloride

Flotation tests using artificial mixtures of clean coal and quartz were conducted with and without the presence of sodium hexametaphosphate (SHMP) to study the effect of polyaluminum chloride (PAC) on quartz entrainment in fine coal flotation. Comparisons of flotation results show that the degree of quartz entrainment was greatly reduced using a suitable amount (e.g., 20 mg/L) of PAC in the absence of SHMP, however, significant changes of PAC on quartz entrainment did not appear in the presence of SHMP. The possible mechanisms responsible for the reduced quartz entrainment using PAC in fine coal flotation were investigated by particle size distribution measurements, zeta potential measurements, and interaction force calculations. Analysis of particle size distribution results reveals that when SHMP was not added, quartz particles were selectively aggregated with the addition of 20 mg/L PAC and the aggregation of quartz or coal particles was negligible at a high PAC dosage (e.g., 50 mg/L). Meanwhile, the aggregation of quartz particles induced by PAC was eliminated with the presence of SHMP. The electrostatic double layer repulsive force between quartz particles was calculated using the Deyaguin-Landau-Verwey-Overbeek (DLVO) theory with incorporating the results of zeta potential measurements. At 20 mg/L of PAC, the negative surface charge of quartz particle was neutralized and the electrostatic double layer repulsive force between quartz particles reached the minimum. These findings might be reasons of the aggregation of quart particles and therefore reduce the quartz entrainment in fine coal flotation.

Effect of dispersants on dispersion stability of collophane and quartz fines in aqueous suspensions

ABSTRACTA stable dispersion of fine mineral particles in an aqueous system facilitated by dispersants is an essential prerequisite for their successful separation. We investigated the dispersion stability and mechanism of suspensions of aqueous collophane and quartz fines (10 µm) in the presence of sodium hexametaphosphate (SHMP), sodium silicate or sodium carbonate using the sedimentation balance method, zeta potential measurements, contact angle measurements, micro-flotation tests and theoretical calculation of Extended-DLVO (Derjaguin-Landau-Verwey-Overbeek). The results showed that three dispersants significantly enhanced the dispersion stability of collophane in the following descending order SHMP > sodium silicate > sodium carbonate. This is because they increased the zeta potential of collophane in the same order; meanwhile, the SHMP made the collophane more hydrophilic compared to two other dispersants. These results illustrated that the dispersion stability was attributed to electrostatic repulsion and hydration repulsion and that the hydration repulsion had a greater influence on the stability than electrostatic repulsion based on the calculation of Extended-DLVO. However, the quartz suspension always maintained a stable dispersion in the absence or presence of dispersants, since there was a higher zeta potential and stronger hydrophilicity for natural quartz. These provide a theoretical direction for the dispersion of fine-disseminated siliceous phosphorites and phosphate slimes in separations.

Development of Magnesium-Silicate-Hydrate Cement by Pulverized Fuel Ash

Magnesium silicate hydrate (M-S-H) gel can be fabricated via the reaction of MgO with silica fume in the presence of sodium hexametaphosphate (Na-HMP). In this study, in effort to reduce the cost of the M-S-H gel system, pulverized fuel ash (PFA) was utilized as a silica source to replace silica fume. The influence of various PFA quantities on the compression strength and other properties of the M-S-H system were investigated via XRD, SEM, and TG-RTG analysis. Compressive strength was optimal when 35 wt% of silica fume was replaced. The hydration products were relatively more complex when PFA was used, containing hydrated calcium silicate, hydrated magnesium silicate, and carbonate gel, among other products. Magnesium carbonate participated in the hydration reaction process, which generated carbonated gel to form a grid structure and promoted the initial strength of the material. Taken together, the results showed that PFA can be feasibly and effectively used to form M-S-H gel cement systems at low cost.

Heavy metals adsorption by nanozeolites: effect of sodium hexametaphosphate

In this study, for the first time, sodium hexametaphosphate (SHMP) was used as a dispersant in the production of nanozeolites. In addition, the effect of SHMP on the adsorption of ion metals by nanozeolite was investigated. In order to characterize the prepared nanozeolite by a planetary mill, the scanning electron microscope (SEM) was used. The SEM photographs showed that the planetary mill could produce the nanoparticles of zeolites. Furthermore, according to the SEM and X-ray diffraction (XRD) results, the zeolite samples milled with SHMP have regular and fine particles in comparison with nanozeolites produced without SHMP. On the other hand, the nanozeolites produced with SHMP have high qualification. According to the size fraction results, in the presence of SHMP, less than 15 % (3 g) of the milled sample remained on the 20-micron sieve, while 70 % (14 g) of the milled sample without SHMP remained on the 20-micron sieve. Finally, a series of experiments was performed to study the effect of SHMP on the adsorption of nickel, cadmium and copper ions using nanoparticles of zeolite. As a result, the adsorption percentage of nickel and cadmium on nanozeolites pretreated by SHMP is higher for times less than 2 h and more than 6 h in comparison with nanozeolites not pretreated by SHMP. On the other hand, the effect of SHMP on the adsorption of copper by nanozeolite is not significant. This insignificant effect probably occurs due to the stronger interaction of Cu2+ and AlO4− than that of Cu2+ and SHMP.

Control of drying shrinkage in magnesium silicate hydrate (m-s-h) gel mortars

Magnesium silicate hydrate (M-S-H) gel can be formed by the reaction of MgO with amorphous silica in the presence of sodium hexametaphosphate (Na-HMP). Typical pastes contain 40% MgO and 60% SF and have a w/c ratio of 0.5, but these exhibit shrinkage cracking on drying. The shrinkage characteristics of M-S-H mortar samples containing different additions of sand have been studied using dilatometry. The drying shrinkage was found to decrease with increasing sand addition and to increase with increased water content. Mortars with 60wt.% sand addition and a w/c ratio of 0.5 had a drying shrinkage of 0.16% and did not show shrinkage cracking. A simple geometrical model based on particle packing is presented that explains the observed changes in drying shrinkage. Based on the geometrical model, the shrinkage of M-S-H mortar system can be reduced to zero when the volume fraction of sand in the mortar is about 0.77.

Amphoteric ion polymer as fluid loss additive for phosphoaluminate cement in the presence of sodium hexametaphosphate

The fluid loss of modified aluminate phosphate cement system with excellent CO2 resistant ability cannot meet the demand of cementing engineering and the conventional fluid loss additive lose effectiveness in this cement system. The aim of this paper is to reveal the failure mechanisms of the conventional fluid loss additive and develop one kind of amphoteric ion polymer to control the fluid loss. Results showed that massive of sodium hexametaphosphate exists in cement system limits the hydration and expansive degree of hydrophilic group of fluid loss additive and succeeds in the competition with fluid loss additive for adsorbing on the surface of cement particle. Using 2-acrylamido-2-methyl propane sulfonic acid, acrylamide, diallyl dimethyl ammonium chloride, and itaconic acid, a new fluid loss additive which has excellent ability to control fluid loss is synthesized by free radical aqueous solution copolymerization. The reducing fluid loss function of this kind of fluid loss additive is achieved by the cationic groups adsorbing on the surface of cement particle and anionic groups absorbing water to achieve hydration expansion to plug the flow passages between the cement particles. However, the dosage of this kind of fluid loss additive is limited by the negative retarding effect.