Dissolution Of Ca Research Articles

Investigating the active phase of Ca-based glycerol polymerization catalysts: On the importance of calcium glycerolate

Ca-based catalysts are of strong interest for glycerol polymerization reaction due to their high catalytic performances, their wide availability and the absence of any toxicity. In the present study, we investigated the active phase of CaO, Ca(OH)2, CaCO3 and calcium diglyceroxide used as catalysts for this reaction. The solids were analyzed by XRD, solid-state 13C-NMR and TGA-DSC. XRD evidenced the presence of calcium glycerolate in the spent catalysts when CaO, Ca(OH)2 and calcium diglyceroxide were used as starting materials. This was corroborated by the TGA-DSC results. Further, the SS NMR results showed that the as-formed calcium glycerolate is a mixture of linear Ca(C3H7O3) and cyclic-branched Ca(C3H6O3). Moreover, the recycled catalyst issued, e.g., from CaO was more efficient that the initial catalyst with a glycerol conversion of 47 % (vs. 22 % initially for CaO) and a 70 % (vs. 55 %) selectivity to polyglycerols higher than tetraglycerol at 245 °C after 4 h in the presence of 3.5 mol.% of catalyst. As the main outcome, we have shown that Ca-glycerolate is the actual solid active phase, which is formed in situ from CaO and Ca(OH)2 playing the role of catalyst precursors. A mechanism involving the dissolution of CaO and Ca(OH)2, the formation of Ca-glycerolate and its precipitation followed by crystallization, supported by characterization studies, is proposed.

Synthesis and Characterization of Mesoporous Mg- and Sr-Doped Nanoparticles for Moxifloxacin Drug Delivery in Promising Tissue Engineering Applications.

Mesoporous silica-based nanoparticles (MSNs) are considered promising drug carriers because of their ordered pore structure, which permits high drug loading and release capacity. The dissolution of Si and Ca from MSNs can trigger osteogenic differentiation of stem cells towards extracellular matrix calcification, while Mg and Sr constitute key elements of bone biology and metabolism. The aim of this study was the synthesis and characterization of sol–gel-derived MSNs co-doped with Ca, Mg and Sr. Their physico-chemical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence spectroscopy (XRF), Brunauer Emmett Teller and Brunauer Joyner Halenda (BET/BJH), dynamic light scattering (DLS) and ζ-potential measurements. Moxifloxacin loading and release profiles were assessed with high performance liquid chromatography (HPLC) cell viability on human periodontal ligament fibroblasts and their hemolytic activity in contact with human red blood cells (RBCs) at various concentrations were also investigated. Doped MSNs generally retained their textural characteristics, while different compositions affected particle size, hemolytic activity and moxifloxacin loading/release profiles. All co-doped MSNs revealed the formation of hydroxycarbonate apatite on their surface after immersion in simulated body fluid (SBF) and promoted mitochondrial activity and cell proliferation.

Migration characteristics of heavy metals in the weathering process of exposed argillaceous sandstone in a mercury-thallium mining area

Lanmuchang mercury-thallium mine, a typical polymetallic mine is located in southwestern Guizhou, China, is the most serious and typical area resulted from multi-metal contamination (Tl, Hg, As, and Sb). After the mercury-thallium mining, a large area of surrounding rocks such as argillaceous sandstone with high contents of Tl, Hg, As, and Sb is exposed to air. Weathering caused the argillaceous sandstone to form different weathering layers, including the grey-black external layer, the brown-yellow middle layer and the gray-white inner layer, and the external layer was enriched with higher heavy metals. However, the reason of heavy metal migration and transformation in argillaceous sandstone caused by weathering is unclear. The objective of this paper was to investigate the migration, transformation and release characteristics of Tl, Hg, As, and Sb in argillaceous sandstone during the weathering. The results indicated that weathering not only promoted an acidic oxidation environment in argillaceous sandstone, but also increased its specific surface area, pore volume and hydrophilicity, which are beneficial to the permeability of oxygen and etching liquids during the process of weathering and leaching. Meanwhile, weathering led to the transformation or decomposition of hydrophilic groups, such as -OH and -C˭O in the grey-black external layer of argillaceous sandstone, resulting in the further release of heavy metals bound to these groups. The concentration of Tl, Hg, As, and Sb in the leaching solution of argillaceous sandstone represented a positive correlation with that of Fe, Ca, Mg at different levels, indicating that Tl, Hg, As, and Sb were released with the dissolution of Fe, Ca and Mg during weathering and leaching. In summary, these results indicated that weathering caused the dissolution and migration of heavy metals in the argillaceous sandstone. Tl, Hg, As, and Sb migrated from the grey-white inner layer to the grey-black external layer and partially adsorbed by free alumina (Ald), jarosite and Ca-bearing minerals, showing enrichment phenomena, partially released into the environment, causing environmental pollution.

The chemical behaviour of chlorine in silicate melts

We have performed experiments at 0.5–2 GPa and 1200–1500 °C to investigate the dissolution behaviour of chlorine in silicate melts. The experiments were performed with chlorine fugacities controlled by mixtures of Ag, AgCl and AgI and oxygen fugacity buffered at C-CO-CO2 (CCO) and Re-ReO2. The results demonstrate that the initial chlorine dissolution mechanism involves the replacement of O2− in the silicate melt by two dissociated Cl− ions according to the reaction:Cl2 + [O2−]melt = 2[Cl−]melt + 0.5O2.The same dissolution mechanism applies to hydrous, fluid-saturated basalt at 100–200 MPa/1050 °C. Experiments using both an Fe-free haplobasaltic composition (An50Di28Fo22) and an Icelandic basalt followed the predicted dependence of Cl concentration on f(Cl2)0.5 and f(O2)0.25. This Henrian behaviour extends from 0 to at least 2.6 wt% Cl dissolved in the haplobasaltic composition, 1.6 wt% Cl in anhydrous basalt and ∼1.5 wt% Cl in fluid-saturated basalt. Deviations from Henry’s Law behaviour at higher concentrations are consistent with progressive association of Cl− ions. In the Henry’s Law region Cl concentration in the An50Di28Fo22 composition is given by (wt%):logClmelt=1.20632-94040PT-0.25logfO2+0.5logfCl2P is in GPa, T in kelvin, values in brackets are 1 standard error, and f(Cl2) and f(O2) refer to standard states of pure gas at 0.1 MPa and the temperature of interest. For the natural anhydrous basalt we obtain:logClmelt=0.98464-93070PT-0.25logfO2+0.5logfCl2By considering the P-T dependences of the Cl contents of melts we find that the concentrations observed in nature are extremely stable in basalt to very low pressures. Basalts containing the typical concentration range of 0.05–0.5 wt% Cl should, for example, only begin to degas their chlorine significantly, as HCl, at pressures in the range 0–5 MPa. Data on hydrous, fluid-saturated basalt at 100–200 MPa are, when corrected for dissolution of Ca, Na and K in the fluid, broadly consistent with our results for anhydrous basalt.Finally, we use recently evaluated thermodynamic data for sodalite (Na4Al3Si3O12Cl) to calculate the conditions under which this phase would stabilise in trachytes and phonolites. We find that the appearance of sodalite as a liquidus phase reflects a combination of low liquidus temperature and high Na2O activity rather than unusually high chlorine fugacity.

Laser Conditioning: A Preferred Option Over Conventional Acid Etching for Orthodontic Bonding

Aim: To evaluate the demineralization resistance and the shear bond strength of enamel surfaces after erbium, chromium: yttrium–scandium–gallium-garnet (Er,Cr:YSGG) laser etching (2 W/15 Hz, 2 W/25 Hz) and to compare them with conventional acid etching for orthodontic bonding. Materials and Methods: A total of 60 extracted human premolars with intact enamel surface were used for this study. Demineralization Resistance was estimated using ion-coupled plasma atomic emission spectrometer (ICP-AES). Shear bond strength was evaluated using Universal Testing Machine—Instron. Results: Statistically significant difference ( P < .001) was found in the concentration of dissolved calcium (Ca) and phosphorus (P), with the highest mean Ca and P in the acid-etched group, followed by 2 W/15 Hz laser-etched group and least with 2 W/25 Hz laser-etched group. Maximum bond strength was found in the acid-etched group (12.06 MPa), followed by the 2 W/25 Hz laser-etched group (9.01 MPa) and 2 W/15 Hz laser-etched group (8.39 MPa). The differences were statistically significant. Conclusions: Laser conditioning of enamel surface revealed significant demineralization resistance with a minimal dissolution of Ca and P ions in the demineralizing solution. Moreover, optimum bond strength was obtained similar to that of acid etching; hence, Er,Cr:YSGG laser conditioning of enamel surface is preferred over the conventional phosphoric acid etching for orthodontic bonding.

Impact of acid surface pretreatment on the flotation of ilmenite and titanaugite and its functional mechanism

The effect of acid surface pretreatment on the flotation behaviors of ilmenite and titanaugite was investigated with BHA collector and Pb2+ activator. The flotation recovery of ilmenite improved from 62.56% to 84.68% at pH 8.0 after pretreated with H2SO4 solution, while that of titanaugite decreased from 35.73% to 0.54%. The results of SEM and ICP analysis showed that the dissolution of Fe, Ca, and Mg elements on titanaugite surfaces was greater than those of ilmenite in the acid solution, especially Fe element. XPS analysis indicated that after the acid surface pretreatment, Ti became a new active site reacted with BHA and the main active sites for ilmenite changed from Fe, Mg, and Ca to Ti and Fe, while the Fe active site disappeared for titanaugite. These changes in the active sites increased the floatability of ilmenite and reduced the floatability of titanaugite.

The characteristics and formation mechanism of the dark rim in alkali-activated slag

This paper presents comprehensive investigation on the microstructure and micromechanical properties of the hydration products in alkali-activated slag by adopting the coupled techniques of nanoindentation, optical microscopy, backscattering electron (BSE) imaging and energy dispersive X-ray spectroscopy (EDS), aiming to provide insight into the formation mechanism of the dark rim in AAS. It is found that the dark rim is primarily comprised of a mixture of Mg-Al layered double hydroxide (LDH) and C-A-S-H gel, and the existence of this LDH phase contributes to the relatively high hardness and elastic modulus of the dark rim. The dark rim is in-situ formed in the outer layer of GGBFS. The dissolution and diffusion of Ca and Si in the outer layer of GGBFS results in a lower average atomic number in the dark rim region, contributing to its relatively lower grey level. Based on the experimental results, the formation mechanism of the dark rim is discussed in this investigation.

Fixed bed column studies for decontamination of acidic mineral effluent using porous fly ash-basic oxygen furnace slag based geopolymers

This paper presents column studies conducted to evaluate and assess the potential use of Fly Ash (FA). Basic Oxygen Furnace Slag (BOFS) based geopolymers to remove metals, sulphates and acidity from Acid Mine Drainage (AMD). Geopolymers were prepared using NaOH, Fly ash (FA) was used as source of silica additive to supplement BOFS. The blending ratio was fixed to 10% FA and the S/L ratio was kept 20%. The H2O2 was used as a blowing agent to increase the porosity of the FA/BOFS based geopolymer at four different percentages (1.5%, 1%, 0.5% and 0%). The four different geopolymers with distinct porosities were employed in different columns respectively. It was found that over 99% removal efficiency of metals and sulphates was achieved in the first 60 days of column studies. The dissolution of Ca(OH)2 was the main constituent responsible for the removal of acidity in AMD. Characterization revealed that precipitation was the main mechanism for removal of metals. Gypsum was the main byproduct formed with precipitated metals presented by goethite, spertite and manganite.

Experimental study on permeability enhancement of coal seam with high mineral content by acid fracturing

ABSTRACT The permeability enhancement is the key to increase the efficiency of gas drainage from low-permeability coal seam. In this paper, the acid fracturing technology is proposed to solve the problem of low permeability of coal seam with high mineral content. The self-developed coal-rock acid fracturing experimental system is used to study the whole process of coal fracturing under different stress conditions and the permeability of coal specimens with varying permeability enhancing methods. The surface characteristics and mineral content of coal specimens before and after acid fracturing were tested by SEM and XRF technologies. The test results show that the effect of coal permeability enhancement by acidizing fracturing is mainly dominated by initial permeability, mineral content, and stress environment. The higher initial permeability, soluble mineral content, and in situ stress difference will lead to greater enhancement of coal permeability after acid fracturing. The fracturing induced fractures extend along the direction of maximum principal stress. Acidification causes the dissolution of Ca and Mg minerals in coal specimens, which provides the priority of fractures for further extension. Therefore, acid fracturing in coal seam is the result of the joint action of hydraulic fracturing (dominant) and acidizing (auxiliary). In this study, acid fracturing increases the permeability of coal specimens by 26.5–28.3 times.

Gas-tight proton-conducting Nd2 − xCaxZr2O7 − δ (x = 0, 0.05) ceramics

Gas-tight Nd2 − xCaxZr2O7 − δ (x = 0, 0.05) pyrochlore materials have been prepared via mechanical activation of Nd2O3, ZrO2, and CaO, followed by single-step sintering of green compacts at 1600 °C for 3 or 10 h. Their structure has been studied using Rietveld refinement of X-ray diffraction data; their microstructure has been examined by scanning electron microscopy, and their conductivity has been determined by impedance spectroscopy in dry and wet air. In addition, we have assessed the effect of prolonged hydration on the proton conductivity of the Nd2 − xCaxZr2O7 − δ (x = 0, 0.05) pyrochlores. According to the Rietveld refinement results, Ca cations are incorporated into both Nd- and Zr- sub-lattice in Nd2 − xCaxZr2O7 − δ (x = 0.05) synthesized at 1600 °C, and most of the Ca cations reside on the Zr sites. The 500 °C proton conductivity of Nd2Zr2O7 is 5 × 10−6 S/cm (~ 1 × 10−5 S/cm at 600 °C) and that of Nd2 − xCaxZr2O7 − δ (x = 0.05) is 7 × 10−5 S/cm (~ 2.5 × 10−4 S/cm at 600 °C). Prolonged (5 months) immersion in water at room temperature has been shown to reduce the proton conductivity of Nd2 − xCaxZr2O7 − δ (x = 0, 0.05), which is attributable to partial dissolution of Nd and Ca. CaO and, to a considerably lesser extent, Nd2O3 segregation on polished and thermally etched (1450 °C) sections of the ceramics has been demonstrated. We attribute both effects to the high diffusion mobility of Ca2+ and Nd3+ cations, due to the basicity of their oxides in ambient air and water.

Selective flotation and adsorption of ilmenite from titanaugite by a novel method: Ultrasonic treatment

Herein, a novel method of ultrasonic treatment for selectively recovering ilmenite from titanaugite was investigated via systematic mineral flotation tests along with dissolution texts, microcalorimetry, scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) analyses. Flotation tests indicate that ultrasonic treatment promotes the ilmenite floatability but depresses titanaugite floatability. When ultrasonic time and power are 5 min and 500 W, selectivity of ilmenite from titanaugite can be enhanced. Dissolution tests show that ultrasound can strengthen the dissolution of Ca and Mg but has little effect on Fe species. Microcalorimetric measurements confirm that ultrasonic-treated ilmenite is more prone to release heat than titanaugite. SEM images reveal that the surface roughness of the titanaugite is greater than that of the ilmenite, indicating that the particle collision of titanaugite is greater than ilmenite. XPS indicates that NaOL adsorption on ultrasonic-treated ilmenite surfaces is greater than that for titanaugite.

Effect of sodium pyrophosphate on the flotation separation of calcite from apatite

In this study, the separation of calcite and apatite was achieved by the depressant sodium pyrophosphate (SPP). Microflotation results showed that when using 20 mg/l sodium oleate (NaOL) as the collector, apatite could be significantly depressed by 120 mg/l SPP, and calcite remained floatable at pH 6.5–9.3. Relatively more Ca2+ was selectively dissolved from the surface of apatite by pyrophosphate, and the dissolution of calcium on the surface of calcite was inhibited. For calcite, the dissolution of Ca2+ decreased first but then increased with increasing SPP dose, and the adsorption amount of SPP illustrated an opposite tendency. With respect to apatite, the dissolution of Ca2+ was similar to that of calcite, but pyrophosphate failed to adsorb onto apatite. The solution chemistry of pyrophosphate at different pH values and in the presence of Ca2+ was discussed. The XPS results revealed that both SPP and NaOL could be adsorbed on the surface of calcite, while NaOL was rarely adsorbed on the surface of apatite. Moreover, the Ca/P ratio of apatite decreased after adding SPP. Zeta potential measurements showed that NaOL could still be adsorbed on the negatively charged calcite surface by chemical adsorption with surface calcium. Regarding apatite, the adsorption of NaOL was hindered by the decrease of active calcium sites and negative surface charge. The differences in polyphosphate concentration and pH should be responsible for the divergent existing theories of the interaction of polyphosphate and calcium minerals.

Hydrolysis kinetic study of CaAlSiN3:Eu2+ red phosphor with both water immersion test and first-principles calculation

At present, most high-power white Light-emitting diode and laser diode (LED&LD) package is usually constructed by a blue LED&LD chip with a Cerium doped Yttrium Aluminum Garnet (YAG:Ce3+) yellow phosphor, but its color rendering performance is severely challenged due to the lack of red light emission spectrum. The CaAlSiN3:Eu2+ red phosphor can effectively improve the color quality of traditional yellow phosphor converted white LED&LDs(pc-wLED&LDs), however, it is often susceptible to degradation under high temperature and high humidity environments, which will directly affect the color quality of pc-wLED&LDs. In this study, a series of water immersion tests on CaAlSiN3:Eu2+ red phosphor are used to quantitatively study its hydrolysis reaction kinetics. Then, the degradations of its photoluminescence and photothermal performances are evaluated by characterizing the crystal structure, micromorphology and chemical element composition. Finally, an atomic level hydrolysis reaction mechanism of CaAlSiN3:Eu2+ red phosphor is investigated by using the first-principles density functional theory (DFT) calculation. The results show that: (1) By modelling the in-situ monitored electrical conductivity of CaAlSiN3:Eu2+ red phosphor water solution with a first-order reaction function, the calculated hydrolysis reaction rate satisfies the Arrhenius relationship and the reaction activation energy is estimated as 49.19 kJ/mol; (2) The increased self-heating effect of CaAlSiN3:Eu2+ red phosphor after water immersion test attribute to its drastic drop of light emission efficiency; (3) The hydrolysis reaction mechanism of CaAlSiN3:Eu2+ red phosphor is confirmed, which sequentially results in the dissolution of Ca2+ and OH−, the crash of host lattice and the accumulation of reaction residues.

Replacing Petrov's process with atmospheric flotation using Pb-BHA complexes for separating scheelite from fluorite

It is difficult to separate scheelite especially from fluorite with fatty acid collectors because the adsorption mechanism of these collectors occurs through chemisorption of the oleate ion onto the mineral surface. A simplified flotation process using Pb-BHA complexes was developed to replace the energy-inefficient Petrov’s process of using a fatty acid, increasing the recovery of scheelite and reducing the cost. The relationship between surface chemical properties (crystal chemistry, solubility, and Zeta potential) of minerals and flotation by using a fatty acid or Pb-BHA complexes was studied in detail to provide new insights into the selective separation mechanism. The results indicate that the scheelite surface exposes more O atoms than Ca and that they are negatively charged due to the anisometric dissolution of Ca and WO4, which provides the possibility for separation using selective interfacial reaction. The Fourier Transform infrared spectroscopy (FTIR) and Zeta potential results indicate that both chemical and electrostatic adsorption play an important role in the adsorption of Pb-BHA complexes on the scheelite surface. The X-ray photoelectron spectroscopy (XPS) results of the atomic composition and binding energies confirmed the presence of the adsorbed Pb-BHA complexes and that Pb, O and Ca may be the active adsorption sites. Therefore, scheelite was able to be collected by forming either a Ca-O-Pb-collector or W-O-Pb-collector (BHA). However, fluorite was only able to be collected by a fatty acid collector and colloidal [H2SiO3]n−, and a high temperature was needed improve the selective desorption of the adsorbed fatty acid collector by forming Ca-[H2SiO3]n− on the fluorite surface, resulting in serious problems in industry. However, the Pb-BHA complexes significantly contribute to improving the recovery of scheelite minerals, simplifying the flotation process, and circulation of the residual reagents and water.

Influence of surface dissolution on sodium oleate adsorption on ilmenite and its gangue minerals by ultrasonic treatment

Selective separation of ilmenite from gangue minerals after ultrasonic preconditioning was studied in terms of surface dissolution. After preconditioning, ilmenite exhibited better single-mineral flotation capacity while titanaugite and olivine had lower recoveries. Significant separation could be obtained at pH 6.0 after ultrasonic treatment (500 W, 5 min). Zeta potentials of preconditioned titanaugite and olivine shifted positively compared to those of raw titanaugite and olivine treated with sodium oleate (NaOL), respectively. Meanwhile, the zeta potential of ilmenite was similar before and after NaOL adsorption. Mineral dissolution results indicate that ultrasonic preconditioning promotes the dissolution of Mg and Fe species but not the Ca species. The dissolution of Ca and Mg is much higher than that of Fe. According to solution chemistry calculation, Fe(OH)3 precipitate is dominant at pH greater than 2.5, and Ca2+, Mg2+, Fe2+, and Fe(OH)+ are dominant under acidic conditions. Microcalorimetric measurements demonstrate that the preconditioned ilmenite releases more heat during NaOL adsorption than titanaugite and olivine do. XPS results reveal that ultrasonic treatment facilitates the conversion of Fe2+ to Fe3+. After preconditioning, Fe species interacted with NaOL to promote the latter’s chemisorption on ilmenite and olivine, while Ca2+ was more likely to interact with NaOL on titanaugite.

CATION SELECTIVITY OF VERTISOLS

The effect of salinity and SAR on Gapon selectivity coefficient of two Vertisols , collected from Duhok Governorate in northern Iraq(Summel and Zakho) classified taxonomically as (fine clay-smectitic-calcareous-cracked soils), were studied in a laboratory experiment. Twenty solutions , including five TEC levels (5,10, 20, 50 and 100 mmolc.l-1 and four SAR levels 2.5, 5.0 ,10 and 25( mmol.l)0.5 were synthesized to equilibrate the soil samples using chloride salts of sodium and calcium, magnesium . SAR of equilibrium solution decreased compared to equilibrating solution especially at high SAR and low electrolyte solutions . At low salt concentrations , the dissolution of CaCO3 and Ca bearing minerals causes a decrease in SAR of the equilibrium solution but their effect becomes less at high electrolyte concentrations . Exchangeable sodium increased with increase in SAR and TEC . Irrecpective of TEC , NaX increased by about 2.8-fold and 0.8-fold and irrecpective of SAR , the increase was about 1.3-fold and 2.1-fold for Summel and Zakho sites respectively. An increase in ESP was observed when correction for anion exclusion was calculated especially at higher TEC level. All relationships between ESR and SAR were significant for each salinity level and when the treatments were handled as a composite data . The values of Gapon constant were in the range of (0.0057- 0.0259) and (0.0155- 0.0425)( mmol.l)-0.5 and Correction for anion exclusion caused an increase by about 18% and 11% for Summel and Zakho sites respectively compared to not corrected samples .

Evaluation of Nanofiltration Membrane Process for Smartwater Production in Carbonate Reservoirs From Deoiled Produced Water and Seawater

SummaryThis research focuses on membrane-separation efficiencies by adjusting the ionic composition of deoiled produced water (PW) and evaluates the possibility for smartwater production from PW for enhanced oil recovery (EOR) in carbonate reservoirs. Key characteristics of smartwater for carbonate reservoirs are increased concentrations of divalent ions and low concentrations of monovalent ions compared with seawater.In this research, PW was pretreated with media filters, which resulted in 96 to 98% oil removal. This deoiled PW was used as feed for nanofiltration (NF) membranes. Combinations of NF retentate with seawater as feed and NF permeate from PW were considered. PW NF permeate, mixed with seawater spiked with multivalent ions, sulfate (SO42−), or phosphate (PO43−), is expected to alter the wettability of oil reservoirs.NF-membrane performance was evaluated in terms of flux and the separation efficiencies of the key scaling ions calcium (Ca) and barium (Ba). The tested membranes removed 60% of Ca2+ and 53% of Ba2+, thereby reducing the scaling tendency. No membrane fouling was observed during the experiments.NF-treated PW was analyzed for solubility of calcium carbonate (CaCO3). The results showed no Ca dissolution, which could affect chalk-reservoir compaction. This research also reflects the use of nonprecipitating PO43− for smartwater production, simultaneously decreasing the Ba concentration and the scaling potential of PW. The results obtained conclude that spiking PO43− below 12 mM showed no indication of chalk dissolution during equilibration tests at room temperature. Experiments performed with 44 mM of PO43− resulted in calcium phosphate [Ca3(PO4)2] precipitation.A process scheme is proposed for smartwater production by ionic selection from seawater and PW at an operating pressure of 18 bar. Energy-consumption analysis for smartwater production before membrane treatment concluded NF to be economic over other desalination technologies. The power consumed by NF membranes for smartwater production at 18 bar is calculated at 0.88 kW·h/m3, whereas the power consumed is 51.22 and 103.52 kW·h/m3 for reverse osmosis (RO) and multistage flash distillation (MSF), respectively.

Hydrogeochemical and multivariate statistical appraisal of pollution sources in the groundwater of the lower Bhavani River basin in Tamil Nadu

ABSTRACTMultivariate statistical techniques have emerged as one of the most effective tools in hydrochemical characterization and the identification of pollution sources in groundwater. Hydrogeochemical data of the 36 wells in the Lower Bhavani River basin in Tamil Nadu are used in this study. Hierarchical cluster analysis(HCA) derived three major clusters, in which cluster 1 has high concentration of Ions (n = 14; avg TDS = 1259 mg/L), followed by cluster 2 (n = 13; avg TDS = 775 mg/L) and cluster 3 (n = 8; avg TDS = 357mg/L). The hydrochemical facies also agree with the cluster hydrochemistry with Na-Cl type (cluster 1), Ca-Mg-Cl (cluster 2), and Ca-HCO3 (cluster 3) showing the influences of anthropogenic and the natural (rock–water interaction related) geochemical patterns. Aqueous Speciation Modeling suggests that the undersaturated Halite (Na-Cl), Gypsum, and Anhydrate minerals in all three clusters, Indicating the possibility for the dissolution of Na, Ca, SO4, and Cl. As in HCA, Principle Component Analysis (PCA) also delivered three major components showing the impact of textile industries and agricultural fertilizers, leakage of sewages and the natural interaction of water with fluorite rich minerals. It is observed that both natural and anthropogenic processes are controlling the variations in the hydrochemical parameters and correlated with land use patterns.

Potential Pollution of Groundwater by Dissolution and Release of Contaminants due to Using Gangue for Backfilling

Large quantities of solid wastes, including gangue (waste rock) have been added to the goafs in China’s coal mines as backfill. In this study, the mineral and chemical compositions of gangue from the No. 12 coal mine of the Pingdingshan Coal Group were investigated to determine potential pollution concerns, and the behaviour of contaminants in the gangue, such as salts, alkali metals, and alkaline earth metals, was explored using static immersion tests. COMSOL Multiphysics was used to study contaminant migration. The concentration and diffusion distance of metal ions were found to increase over time; this was negatively correlated with gangue particle size. Acidic environments promoted the dissolution of Ca, Fe, Mn, Na, Zn, Pb, and Be, while in alkaline environments, Se dissolution was accelerated.

Using a geochemical method of dissolved and insoluble fractions to characterize surface snow melting and major element elution

ABSTRACTA geochemical method to characterize post-depositional melting and elution is demonstrated using inductively coupled plasma mass spectrometry to measure concentrations of dissolved and insoluble fractions of major crustal elements in snow samples collected from March 2006 to January 2010 at Urumqi Glacier No. 1, Tien Shan. Dust from these samples has compositional homogeneity, suggesting that dust has a stable dissolved fraction percentage (DFP, calculated as dissolved/(dissolved + insoluble)%). Calcium has the highest DFP (averaging 61.5 ± 19.4%), followed by Na (30.4 ± 19.6%), Mg (13.2 ± 9.8%), and K (7.9 ± 9.8%). Acid input can affect dissolution of Na and Ca. Taking DFP values of unmelted samples as the reference, the higher DFPs refer to strengthened dissolution from acid input, while the lower ones refer to elution. Based on the DFP difference between unmelted and eluted states, an elution sequence Ca > Na > Mg > K is obtained. Some details such as the beginning and the ending stages of elution can be found by DFP and acid input index, while using ion concentration is not capable of this. Our results reveal that acid input is an important mechanism for DFP changes, that the DFP index can provide an effective assessment of snow elution, and that this will aid in understanding low latitude ice cores.