Dissolution Of Ca Research Articles

Dealloying of Cu-Mg-Ca Alloys

The chemical dealloying of Cu-Mg-Ca alloys in free corrosion conditions was investigated for different alloy compositions and different leaching solutions. For some of the precursor alloys, a continuous, pure fcc copper with nanoporous structure can be obtained by dealloying in 0.04 M H2SO4 solution. Superficial nanoporous copper structures with extremely fine porous size were also obtained by dealloying in pure water and 0.1 M NaOH solutions. The dealloying of both amorphous and partially crystalline alloys was investigated obtaining bi-phase nanoporous/crystal composites with microstructures depending on the precursor alloy state. The fast dissolution of Mg and Ca makes the Cu-Mg-Ca system an ideal candidate for obtaining nanoporous copper structures with different properties as a function of different factors such as the alloy composition, the quenching process, and leaching conditions.

The temperature-dependent action of sugar in the retardation and strength improvement of Ca(OH)2-Na2CO3-activated fly ash systems through calcium complexation

This study reports the temperature-dependent strength improvement and retardation in Ca(OH)2-Na2CO3-activated fly ash binders with sugar. Without sugar, the system exhibited rapid stiffening due to the calcite formation. The addition of sugar clearly removed the false set; however, at room temperature, it retarded strength development because the calcium complexation of sugar inhibits the dissolved calcium ions from participating in calcite and C-S-H formation. However, at 90 °C, the use of sugar significantly improved the compressive strength by increasing the (1) degree of dissolution of fly ash and Ca(OH)2, (2) C-S-H formation, and (3) reduction of overall pore size and volume.

Erosive and cariogenic potential of various pediatric liquid medicaments on primary tooth enamel: A SEM study.

Oral pediatric liquid medications (PLMs) are commonly used in children who suffer from chronic diseases. The physicochemical parameters of PLMs can have a deleterious effect on tooth structure. The purpose of the present study was to investigate the erosive and cariogenic effect of widespread PLMs on the surface roughness and structure of primary tooth enamel. The erosive potential of 8 common PLMs used in Egypt was assessed by measuring their inherent pH, using a digital pH electrode meter. The total sugar content was measured according to the Fehling method. The erosive effect of each liquid medicine on the enamel surface of primary teeth was assessed using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) microanalysis for calcium (Ca) and phosphorus (P) content. Most PLMs revealed an acidic nature, with pH values ranging between 3.47 and 6.92. About 93.8% of analgesics had pH values ≤5.5, critical for enamel demineralization, whereas most antitussives and 1 antibiotic (Augmentin®) had pH values ≥6.2. Sucrose was present in all the samples studied. The SEM analysis revealed observable differences in the tooth enamel in the experimental groups, with different degrees of surface roughness and erosion. The current results suggest that the pH, sugar content and Ca dissolution ability of PLMs can significantly influence erosion in primary tooth enamel.

Study on the hydro-chemistry process after mixing between water and rocks

Abstract The chemical evolution of groundwater has received close attention from hydro-geologists. Northwest China largely consists of arid and semi-arid regions, where surface water and groundwater frequently exchange with each other, and where the mixing and water–rock interactions significantly affect the direction of water quality evolution. Based on experimental simulation, this paper investigates the interactions among the Yellow River water, groundwater and rocks in Yinchuan. The study found that when groundwater is mixed with the Yellow River water, the Yellow River water has a certain dilution effect on the hydro-chemical composition of groundwater; however, this effect is not simply diluted by proportion for no reaction between irons, but a portion of calcium, sulfur, and carbonate form precipitates. After mixing of the Yellow River water, groundwater and rocks, the pH increased, and the carbon dioxide system reached equilibrium again. In addition, CO32− was produced. While Na+ increase was mainly due to dissolution, SO42− decrease was because of precipitation. The precipitation or dissolution of Ca2+, Mg2+, and CO32− mainly depended on the mixing ratio between groundwater and river water, which suggested the reversible behavior of the dissolution-precipitation of carbonate minerals.

The hydrothermal treated Zn-incorporated titania based microarc oxidation coating: Surface characteristics, apatite-inducing ability and antibacterial ability

To improve the bioactivity and antibacterial ability of Zn-incorporated microarc oxidation (MAO-Zn) coating, the MAO-Zn coating was modified by hydrothermal treatment with deionized water (MAO-Zn-HT-0) and 5 mol/L NH3·H2O solution (MAO-Zn-HT-5). The hydrothermal treatment had a significantly effect on the structure, element and phase compositions of MAO-Zn coating. The hydrothermal treated MAO-Zn coatings remained the rough porous structure. Meanwhile, there were some TiO2 or CaTiO3 particles formed on the MAO-Zn-HT-0 and MAO-Zn-HT-5 coatings. Moreover, due to the dissolution of Ca and P elements and the enrichment of Zn element, the content of Zn element on the hydrothermal treated MAO-Zn coating surface was greatly increased. In addition, the Zn element existed in the amorphous ZnO after hydrothermal treatment. The release behavior of Zn element in the hydrothermal treated MAO-Zn coating exhibited slow, stable and continued. Compared to MAO-Zn coating, the MAO-Zn-HT-5 coating showed excellent apatite-inducing ability due to the formation of CaTiO3 and Ti-OH. Likewise, the antibacterial rates of the MAO-Zn-HT-0 coatings for E. coli and S. aureus were significantly improved due to the increase of Zn element on the MAO-Zn-HT-0 coating surfaces. Thus, the hydrothermal treatment was an effective method to improve the bioactivity and antibacterial ability of MAO-Zn coating.

Influence of triethanolamine on reactivity of hydrated matrix in sodium silicate self-healing system and the mechanism

A suitable binding agent proposed in literatures or patents is sodium silicate, which achieves self-healing by formation of calcium silicate hydrate (C-S-H) in cracks. We systematically investigated the influences of triethanolamine (TEA) on the stimulated C-S-H, sodium silicate/hydrated cement and real self-healing system. Results suggest that TEA addition induces the C-S-H to arrange in order and forms sponge-like structure. In sodium silicate/hydrated cement sample, the morphology of C-S-H is simultaneously affected by the heterogeneous nucleation and restriction effect of hydrated cement particles, and the reticulate structure is observed. It is believed that the formation of TEA-Ca2+ facilitated the dissolution of solid Ca from hydration products, hence increases the chemical reactivity of hydrated cement matrix and the actual binding ability is improved due to the increment of high density C-S-H. Finally, the improved performance of self-healed area was demonstrated by optical microscope, SEM and Raman analysis, meanwhile the promotion in micromechanical properties of C-S-H was studied by AFM.

Nanoemulsion synthesis of carbonated hydroxyapatite nanopowders: Effect of variant CO32−/PO43− molar ratios on phase, morphology, and bioactivity

Bone is a composite material containing carbonated hydroxyapatite (CHA) nanocrystallite and protein matrix. Low-temperature synthesis and assessment of the in vitro response of CHA nanopowders were conducted. Samples of CHA nanopowders were considered for their phase system, chemical compound, and reactions in a simulated body fluid (SBF). The crystallite size and phase for the CO32−/PO43− molar ratios of 0.67 and 1.00 were examined through X-ray diffraction (XRD). Chemical distinctiveness was analyzed by Fourier transform infrared (FTIR) spectroscopy. The compositions of the as-synthesized powders were quantified by X-ray fluorescence, and the carbon contents were estimated by carbon hydrogen nitrogen analysis. The morphology and textural properties were examined by field-emission scanning electron microscopy, transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) analysis. In vitro study was conducted in SBF medium, and the pH was intermittently recorded. Then, the dissolution of Ca2+ and PO43− in SBF was quantified by inductively coupled plasma optical emission spectroscopy. The outcomes of XRD and FTIR confirmed that pure single-phase B-type CHA without any secondary phase was formed. CHA.67 showed a crystallite size of (Scherrer) 22.7 nm, particle size by TEM (PTEM) of 24.87, and BET (PSBET) of 26.48 nm. Meanwhile, CHA1.00 achieved a crystallite and particle size of (Scherrer) 4.67, PTEM of 6.50, and PSBET of 13.23 nm. Results indicated that increasing the CO32−/PO43− molar ratio decreases the crystallite size and increases the amount of CO32−. Thus, we concluded that the nanoemulsion-synthesized CHA exhibits a crystallite size and chemistry comparable to those of biological hard tissue.

Synthesis and Physico-Chemical Characterization of Different Mesoporous Bioactive Glass Nanopowders: in-vitro SBF Activity and Cytotoxicity

ABSTRACTMesoporous bioactive glass (MBG) nanopowders from SiO2-CaO-P2O5 system have been prepared by three different variations using different structure directing agents: (1) through wet chemical method (MBWC650) using non-ionic surfactant, PEG; (2) using Pluronic P123, another non-ionic surfactant via hydrothermal process (MBHM650); and (3) using ionic surfactant CTAB, via wet chemical process (MBCTAB650). Comparative study of phase, morphology and textural properties of all M BG nanopowders were accomplished by different characterization techniques. Specific surface area of powders was found to be 52.2, 169.3 and 473.2 m2.g–1 for MBWC650, MBHM650 and MBCTAB650, respectively. Kinetic SBF immersion study was carried out to examine hydroxyapatite forming ability of the powders. Supernatant analyses showed high dissolution of Ca2+ and PO43– ions in MBCTAB650 while MBHM650 showed initial level of HAp formation ability over its surface in contrast with MBWC650. Other characterizations confirmed formation of Ca-P over MBG nanopowders. Cell viability of 117% for MBWC650, 90% for MBHM650 and 89% for MBCTAB650 after seven days were noted. MBHM650 and MBWC650 could be suitable candidate as dental/orthopedic bone filler material whereas high surface area of MBCTAB650 powder can be useful for delivering pharmaceutical agents in-vitro / in-vivo.

Hydrochemistry of the meltwater streams on Fildes Peninsula, King George Island, Antarctica

King George Island, situated in the South Shetland Islands archipelago, is one of the most visited sites in Antarctica. Antarctica attracts much attention because it is one of the most sensitive areas under the influence of global warming. To understand its hydrochemistry characteristics, we collected various types of water samples, including samples from streams, meltwaters, ground waters, snow and ice from around the Great Wall Station, Fildes Peninsula, King George Island, from January to February, 2015. Major ions, alkalinities, silicate, pH, dissolved oxygen, temperature, and electric conductivities were measured. Several approaches were applied to identify processes that affect the hydrochemistry on Fildes Peninsula, including ternary diagrams, principal components analysis and cluster analysis. Our data suggest that atmospheric seasalt deposition is the main factor controlling the hydrochemistry on Fildes Peninsula. After atmospheric influences were corrected for seasalt, we defined the weathering of local rocks to be another important factor on the Peninsula’s hydrochemistry. Processes such as Ca dissolution from the Ca-bearing basalt, Si loss through secondary mineralization and biological uptake influence the chemical composition of runoffs on the peninsula. Cluster analysis identified 4 groups of streams based on their hydrochemical features, which reflect their original weathering characters under icecap and the combined effects with melt snow, biological activity and the anthropogenic input.

Effect of drying, composting and subsequent impurity removal by sieving on the properties of digestates from municipal organic waste

The application of organic soil amendments is a common measure to prevent structural degradation of agricultural soils and to maintain and improve long-term soil fertility. Solid residues from anaerobic digestion of municipal organic waste (MOW) are rich in nutrients and organic matter and have a promising potential to be used as soil amendment. However, no study has related amendment properties of MOW digestate of one origin to different treatment procedures. We therefore investigated the impact of drying, composting and sieving on final digestate properties and specifically nutrient availability and heavy metal and carbon elution.Samples were provided by a semi-industrial two-stage biogas plant with dry fermentation of MOW. Results confirm that in comparison to drying, composting of MOW digestates leads to a significant increase of K, P, Mg, Ca, Cd and Cr in the digestates. Sieving of composted digestates showed that heavy metals are not evenly distributed and that heavy metal concentration in the digestate increases with decreasing mesh sizes (highest concentrations in the fractions <1 mm). Although the element concentration is higher in composted batches, the water-extractability of nutrients, heavy metals and carbon is significantly lower from composted over dried digestates. A significant correlation was found between the dissolution of Zn, Ni, Ca and Mg and pH of eluate as well as dissolved organic carbon (DOC) release (R > 0.7, p<0.05). Results confirm that the extent of carbon elution depends on the degradation rate of digestates. DOC may therefore be a good measure to evaluate digestate stability and to decide on treatment measures.

Chemical interactions between a calcium aluminate glaze and molten stainless steel containing alumina inclusions

High calcium or corundum refractories are the main materials in ladle linings used in the refining of stainless steel, and a calcium aluminate glaze layer is usually formed on the surface of these linings during the smelting process. Chemical reactivity experiments between the calcium aluminate glaze layer and molten steel with different alumina inclusions distributions were carried out to study the effect of calcium aluminate ladle glaze on alloy composition and alumina inclusions in stainless steel. A certain amount of alumina inclusions produced by Al deoxidation merged and grew larger in molten steel during smelting. The inclusions also consume a considerable amount of Cr in steel to form a solid solution. Furthermore, the glaze endured erosion in the initial stages because of the dissolution of Ca. The glaze preferentially absorbed smaller particles of the inclusions to reduce the content of alumina inclusions and the consumption of Cr in molten steel, and CaAl4O7/CaAl12O19 with a high melting point was generated in the glaze gradually because of the effect of the absorption.

Corrosion study of resorbable Ca60Mg15Zn25 bulk metallic glasses in physiological fluids

The corrosion activity of amorphous plates of Ca60Mg15Zn25 alloy was investigated. The biocompatible elements were selected for the alloy composition. The electrochemical corrosion and immersion tests were carried out in a multi-electrolyte fluid and Ringer's solution. Better corrosion behavior was observed for the samples tested in a multi-electrolyte fluid despite the active dissolution of Ca and Mg in Ringer's solution. The experimental results indicated that reducing concentration of NaCl from 8.6g/dm3 for Ringer's solution to 5.75g/dm3 caused the decrease of the corrosion rate. The volume of the hydrogen evolved after 480min in Ringer's solution (40.1ml/cm2) was higher in comparison with that obtained in a multi-electrolyte fluid (24.4ml/cm2). The values of open-circuit potential (EOCP) for the Ca60Mg15Zn25 glass after 1h incubation in Ringer's solution and a multi-electrolyte fluid were determined to be −1553 and −1536mV vs. a saturated calomel electrode (SCE). The electrochemical measurements indicated a shift of the corrosion current density (jcorr) from 1062 μA/cm2 for the sample tested in Ringer's solution to 788 μA/cm2 for the specimen immersed in a multi-electrolyte fluid. The corrosion products analysis was conducted by using the X-ray photoelectron spectroscopy (XPS). The corrosion products were identified to be CaCO3, Mg(OH)2, CaO, MgO and ZnO. The mechanism of corrosion process was proposed and described based on the microscopic observations. The X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) also indicated that Ca(OH)2, CaCO3, Zn(OH)2 and Ca(Zn(OH)3)2·2H2O mainly formed on the surface of the studied alloy.

Environmental Compatibility of Lightweight Aggregates from Mine Tailings and Industrial Byproducts

A lightweight aggregate was produced by sintering the mixture of gold mine tailings, red mud, and limestone at 1150 °C. The physical (i.e., skid resistance, abrasion resistance, and bond strength) and environmental (i.e., leachability) feasibility of this aggregate was assessed to consider its potential use as a construction material for bicycle lanes. The skid resistance (British pendulum number of 71) and bond strength (1.5 N·mm−2) of the aggregate were found to be appropriate for this use. However, the abrasion loss value of the aggregate was found to be 290 mg, which exceeds the limit of Korean Standard KS F 281 (200 mg). Heavy metals were found to not leach from the aggregate in various leaching tests. These include Korean (Korea Standard Method for Solid Waste), American (Toxic Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP)), and European (BS EN 12457-1) leaching tests, despite the raw materials containing significant amounts of Pb, As, and F. However, leachate extracted from the aggregate exhibited an aquatic toxicity to Daphnia magna of 13.94 TU24hr and 14.25 TU48hr, most likely due to a high pH and Ca concentration originating from the free CaO present in the aggregate. The data suggests that the physical properties of the reconstructed aggregate are appropriate for use in bicycle lane construction, however the dissolution of Ca and the pH level of the leachate need to be controlled to protect aquatic ecosystems.

Hydrochemical assessment of environmental status of surface and ground water in mine areas in South Korea: Emphasis on geochemical behaviors of metals and sulfate in ground water

In this study, hydrochemistry of ground and surface water collected around six metalliferous mines and one coal mine in South Korea was investigated to evaluate the status of mining-related impact and pollution. Groundwater system under the mine impact shows varying degrees of immobilization and retardation of heavy metals during the flow. SO42− is shown to be the most reliable indicator of the mining impact on groundwater, as it reflects the degree of initial sulfide oxidation even after subsequent removal of metals; SO42− is also less prone to sorption, precipitation, and geochemical reduction. A good correlation between the concentrations of SO42− and the sum of Ca and Mg is observed, indicating that SO42− represents the degree of dissolution of Ca- and Mg-bearing carbonates and silicates (i.e., neutralization of acidic water to circumneutral pH) by generated H+ that is proportional to SO42−. The higher Zn/Cd ratios of ores and water than those of tailings and precipitates indicate a more preferential immobilization of Cd, and this ratio also reflects the inherent composition of each ore. The modified HPI (Heavy Metal Pollution Index) consisting of the measured concentrations and respective environmental standards of Fe, Mn, Al, Zn, Pb, Cd, Cu, As, and SO42− is suggested as MPI (Mine Pollution Index) to overall reliably evaluate the status of mining-related water pollution. The plot of SO42− versus MPI is very effective to identify the contaminated mine water and its evolution, including the source and the pathways consisting of immobilization (precipitation, sorption) and dilution of contaminants in groundwater system. This study shows that a careful examination of the relationship between MPI and SO42− can be very useful to identify diverse geochemical processes occurring in groundwater affected by mine drainage.

Waste glass as partial mineral precursor in alkali-activated slag/fly ash system

The feasibility of a waste glass powder residue (GP) from glass recycling as partial mineral precursor to produce alkali-activated materials is investigated. GP served as powder coal fly ash (PCFA) replacement within a reference system composed of 50% PCFA and 50% ground granulated blast furnace slag (GGBS). Compared with PCFA, GP was better involved in the alkali activation process by having a higher silica and Ca dissolution. Furthermore, increasing GP replacement up to 30% prolonged the induction period, facilitated the gel formation and yielded a 35% higher 28-day compressive strength. These observations are similar to the effect of using both sodium hydroxide and sodium silicate as alkali activator in alkali-activated slag/fly ash systems. A higher polymerization of the gel network was also observed. Microstructure analysis indicated that the main reaction product is a calcium silicate hydrate type gel substituted with Al and Na (C-(N)-A-S-H type gel).This work largely contributes to the understanding of the reactivity and potential of GP and promotes its practical utilization as a mineral precursor in the production of alkaline cements.

Core-shell structured mZVI/Ca(OH)2 particle: Morphology, aggregation and corrosion

A calcium hydroxide shell was coated onto the surface of micro-sized zero valent iron (mZVI) particles by hydrothermal approach in oversaturated Ca(OH)2 solution. The heterogeneous nucleation of nano-scale Ca(OH)2 particle on micro-scale spherical ZVI surface was clearly observed by scanning electronic microscope (SEM). The moderate solubility of Ca(OH)2 was demonstrated as the crucial factor in inducing slow nucleation rate and in facilitating the abundant growth of Ca(OH)2 nuclei on mZVI surface. The growth of shell thickness was found to obey the zero order kinetics with the rate constant at about 15nm/h. The Ca(OH)2 shell was demonstrated to be anticorrosive to protect reactive Fe0 from oxidation based on standard corrosion test. In addition, the instant aggregation process of mZVI within 120s was slowed down after Ca(OH)2 shell coating. The saturation magnetization of mZVI, measured by a vibrating sample magnetometer (VSM), was gradually diminished along with the shell formation with a 32% reduction after excluding the Fe0 content change effect. This indicated that Ca(OH)2 shell coating can partially eliminated particle-particle or cluster-cluster magnetic attraction force to enhance the dispersion stability and resultantly facilitate the transportation. The dissolution of Ca(OH)2 shell was greatly dependent on the pH value of the background water environment. The pH gradient change resulted from the Ca(OH)2 shell dissolution along mZVI particle transport was illustrated by a conceptual model.

Dissolution behavior of CaO-MgO-SiO2 -based multiphase bioceramic powders and effects of the released ions on osteogenesis.

In the present study, the dissolution behavior of the CaO-MgO-SiO2 -based multiphase bioceramic powders as well as the effects of released ions on osteogenesis was investigated. In the dissolution process, Ca, Mg, and Si ions could be dissolved out from the powders. The incorporation of Mg could slow down the degradation rate of the powders so that to reduce the local concentration of Ca and Si ions. In return, the dissolution of Ca and Si ions leading to the formation of a porous SiO2 -rich layer could enhance the readsorption of free Mg ions in solution and thus down-regulate the concentration of Mg ions. In addition, the released ions exhibited both positive and negative synergistic effects on osteogenesis with a concentration-dependent manner. Trace amount of released Si ions could stimulate cell proliferation and osteogenic differentiation in the presence of Ca and Mg ions. The optimal concentration of Ca-Mg-Si ion combination to promote osteogenesis was existed in the 1/4 diluted extract, whereas a slightly inhibitory effect on cell proliferation and ALP activity was observed in the 1/2 diluted extract with higher concentration of Ca and Si ions . All above results suggested that the ion dissolution behavior of the CaO-MgO-SiO2 -based multiphase bioceramic could be regulated via adjustment of the composition so that released ions could be maintained at an appropriate composite concentration to cooperatively regulate the osteogenesis. This research provided an experimental basis for further optimization and application of CaO-MgO-SiO2 -based multiphase bioceramics with controlled ion dissolution and excellent physicochemical and biological properties. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3159-3168, 2017.

Drinking quality assessment of some groundwater sources along the stretch of Jhelum River in Kashmir Himalaya

The physicochemical properties and major ion chemistry of the groundwater sources from alluvial aquifers along the stretch (60 km) of Jhelum River in Kashmir Himalaya were determined in order to identify hydro-geochemical processes and their suitability for drinking purposes. The data depicted that calcium and bicarbonates were dominating among the cations and anions. The results indicate the trend of cation dominance as Ca2+ > Na+ > Mg2+ > K+, whereas anion dominance was in the order of HCO3 − > Cl− > SO4 2−. Ratio of calcium to magnesium indicated the dissolution of Ca2+ from CaCO3, which results in an increased levels of Ca2+ in the groundwater. Interpretation of Piper Trilinear plot understands the various geochemical processes affecting the groundwater quality and shows groundwater was dominated by Ca–HCO3 type. The pH was recorded in the slightly alkalinity range 7.2–7.8 and was showing positive correlation with HCO3 −. The chloro-alkaline indices revealed 86% of the sources exchange by a type of base-exchange reactions, rest by cation–anion exchange. Gibbs diagram revealed groundwater sources fall in the category of rock dominance. The concentration of the nitrogen compounds was in the progression of NO3–N > NH4–N > NO2–N, and the PO4 − fluctuated from 0.12 to 0.22 mg/L. Moreover, corrosivity ratio indicated that water from the majority of sources (71%) is safe to supply using pipes without any corrosive effects, while 29% of sources are corrosive in nature and need non-corrosive pipes for transporting and lifting of groundwater. The results revealed, groundwater samples were within permissible limits as prescribed by International and National standards, for drinking purposes. The State government and NGO’s can show their interest in utilizing such water resources to overcome the shortage of drinking water in a sustainable way for the daily consumption of the people living in the vicinity of Jhelum River.

Selective reverse flotation of apatite from dolomite in collophanite ore using saponified gutter oil fatty acid as a collector

Reverse flotation is an effective method for separating apatite from gangue minerals (such as dolomite) in collophanite ore. However, collophanite ore flotation using traditional fatty acid collectors is uneconomical because of the relatively high cost of the raw materials. In this work, saponified gutter oil fatty acid (GOFA) was used as the collector, and its effect on collophanite ore flotation and the mechanism of adsorption were studied. The results showed that Ca2+ is the active site for reaction with GOFA and initiates apatite flotation. The dissolution of Ca2+ from dolomite was found to be thermodynamically more favorable than that from apatite, and the relative abundance of Ca2+ enhanced the reaction of dolomite with GOFA. XPS analysis revealed that the interaction between GOFA and magnesium on the dolomite surface strengthened chemisorption. As magnesium is a major constituent of dolomite, but not of apatite, GOFA was selectively chemisorbed onto the dolomite surface. Closed-circuit reverse flotation tests using GOFA as the collector resulted in an excellent concentrate with 28.46wt% P2O5 and 0.65wt% MgO, corresponding to a P2O5 recovery of 87.2%. GOFA was demonstrated to exhibit outstanding selectivity for dolomite in the reverse flotation of collophanite ore. The use of GOFA as an environment-friendly, cost-effective, and selective collector is expected to provide new insights into low-cost collophanite ore flotation.

Effects of Experimental Parameters on the Extraction of Silica and Carbonation of Blast Furnace Slag at Atmospheric Pressure in Low-Concentration Acetic Acid

Blast furnace slag (BFS), a calcium-rich industrial byproduct, has been utilized since 2005 as a mineral carbonation feedstock for CO2 sequestration, producing calcium carbonate precipitates. In this study, the conditions for the dissolution of Ca and Si in acetic acid, and subsequent carbonation, were elaborated. For this purpose, the retardation of the polymerization of silicon was attempted by varying the concentration of acetic acid, temperature, and leaching time. An inductively coupled plasma (ICP) analysis revealed that both the Ca and Si dissolved completely within 30 min in 5% acetic acid at room temperature. This high dissolution value can be attributed to the fact that Ca was bound to O rather than to Si, as determined by X-ray photoelectron spectroscopy (XPS). The use of CO2-absorbed monoethanolamine enabled the complete carbonation of BFS at ambient conditions without the need for a pH swing. The presence of dissolved silica was found to affect the polymorphs of the precipitated CaCO3. We believe that this process offers a simple method for manipulating the composites of products obtained by mineral carbonation diminishing the leaching residues.