Adsorption Of Ca Research Articles

Modulation of the magnetic, electronic, and optical behaviors of WS2 after metals adsorption: A first-principles study

The electronic, magnetic, and optical absorption properties of partial metal adsorbed WS2 systems were calculated by using the first-principles approach. The optimal adsorption sites corresponding to each metal adsorption on the WS2 system are diverse. The Pt-, Mg-, and Zn-WS2 systems are non-magnetic semiconductors, and the Ag-, Au-, Cr-, Fe-, Mn-, Mo-, Nb-, Ni-, and Ti-WS2 systems appear magnetic semiconductors. Whereas the Ca-, Li-, and Na-WS2 systems exhibit magnetic metal properties. The Ca- and Nb-WS2 systems have a significant red-shift tendency in the ultraviolet region. In particular, the adsorption of Ca and Nb enhance the absorption of WS2 in the ultraviolet region. The Nb-WS2 system has a strong absorption peak intensity that reached 1.09◊105 cm−1 at 448.3 nm. Therefore, metal adsorbed WS2 systems will be helpful for the studying of nano-spintronics and photovoltaics devices.

Reuse of mine and ore washing wastewater in scheelite flotation process to save freshwater: Lab to industrial scale

This paper describes an economical and eco-friendly technology that utilises carbide slag to treat mine and ore washing wastewater (MOW) and reuses the treated wastewater in a scheelite flotation circuit. The results of systematic bench-scale and industrial-scale experiments indicate that the wastewater reuse process can reliably improve the WO3 grade with negligible effect on the recovery of scheelite. At the Yuanjing processing plant, the WO3 enrichment ratio improved from 17.4 to 23.6 and the recovery was maintained at approximately 79.2 % when recycled wastewater was used. The fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses consistently implied that the interaction between the collector of sodium oleate and scheelite in the recycled wastewater was stronger than that in plant water. Specifically, the adsorption of Ca2+ on the scheelite surface and the formation of colloidal complexes by Ca2+ and oleate ions were responsible for the superior selectivity, while the gangue minerals such as quartz were effectively depressed by the depressant of water glass. Consequently, the treated MOW could be a suitable alternative to reduce freshwater consumption in mining areas, which is of great significance for the mining and mineral processing industries.

Probing the interaction of calcium and magnesium ions on scheelite surface by atomic force microscopy

The presence of Ca2+/ Mg2+ could affect the surface potential of minerals during the flotation process. Still, the adsorption mechanism of these ions on specific crystal planes has yet to be fully understood. The surface potential of the scheelite (112) and (001) surfaces, under the effect of Ca2+/Mg2+ at pH 8 and 11, were determined by fitting force curve using the Derjaguin−Landau−Verwey−Overbeek (DLVO) model. It was found that increasing the Ca2+/Mg2+ concentration caused the surface potential of the (112) surface to be less negative at pH 8 and 11. The charge reversal occurred when Mg2+ concentration was only 1 mM at pH 11, indicating that MgOH+ was firmly adsorbed on the scheelite (112) surface, which is ascribed as the specific adsorption. While the (001) surface is inert regarding the adsorption of Ca2+/ Mg2+ at pH 8 and 11. The fitted potential indicated that the (001) surface was slightly affected by the increased Ca2+/ Mg2+ concentration. The understanding of adsorption mechanisms on different crystal planes may be helpful to rational design of the flotation process for scheelite.

Electronic and optical properties of Be, Ca, Ba and Eu adsorbed on β-Si3N4 (2 0 0) surface based on first-principles calculations

In this work, we have calculated the geometric structure, as well as the electronic and optical properties of Be, Ca, Ba, and Eu adsorption systems by first-principles calculations based on density functional theory. First, the adsorption energy was calculated to verify the stability of the optimized adsorption systems. In addition, the PBE and PBE-TS functions are used for comparison the calculations of Be and Ca adsorption systems. Secondly, the band gap variation of the adsorption system was analyzed by the density of states, and the charge transfer and the properties of chemical bonding properties were investigated by the charge density difference and the Mulliken population. Finally, the optical properties of the adsorbed β-Si3N4 (2 0 0) surface were investigated in terms of the dielectric function, absorption spectrum, and reflection spectrum. The lower adsorption energies indicate the superior structural stability of these adsorption systems and the negative adsorption energy of the Eu adsorption system is characteristic of chemisorption. It also exhibits semi-metallic properties and enhances the absorption of visible light. The static dielectric function of these systems decreased after adsorption. The peaks of the absorption and reflection spectra are red-shifted.

Indirect Measurement of the Amounts of Casein Phosphopeptides Added to Dangmyon (Starch Vermicelli or Glass Noodle) as a Calcium-Absorption Enhancer

Industrial-scale Ca-fortified Dangmyon was manufactured with added casein phosphopeptides (CPP) to increase Ca adsorption in the intestine. Very low P content in eggshell Ca (egg Ca) and Dangmyon could make it possible to indirectly measure CPP content in Dangmyon. Partitions of the whole P present in Dangmyon were made into sweet potato, egg Ca, and CPP. The CPP content was obtained by multiplying CPP per P by the amount of P partitioned into CPP. It was found that 88.46% of CPP was obtained. However, when milk Ca, which was much higher in P, was added to fortify Dangmyon with CPP, it was found that the CPP content was either under- or over-estimated. Care must be taken when a much higher content of P as a Ca source is selected using this method. It was discovered that the added Ca and CPP were retained after cooking at boiling temperature; therefore, Dangmyon could be an excellent Ca and CPP carrier for humans.

Evaluation of the role perfect and defect boron nitride monolayer in calcium ion batteries as a anode

In present work, anode materials of pristine boron nitride (BN) and its Stone-Wales defect (SW-BN) nanosheets have been studied for calcium ion batteries (CIBs), which include related cell voltage and theoretical capacity attributes, structural geometry variations, and Ca diffusion. Compared with the BN monolayer, Stone-Wales BN has superior conductivity as well as Ca adsorption properties. The more rapid mobility of Ca ion in SW-BN two-dimensional nanosheet is proved by lower diffusion barriers values (0.11 eV). Moreover, SW-BN has a proper open-circuit voltage (OCV) range to be employed as anode materials. The Highest theoretical capacity value of SW-BN could attain to 1162.66 mAh/g, which is about triple more than pristine BN (345 mAh/g). Therefore, anodes constructed by SW-BN nanosheets can be an appropriate option for CIBs.

Surface properties of ceramic waste powder and its effect on the rheology, hydration and strength development of cement paste

To reduce carbon emissions and environmental impacts, ceramic waste powder (CWP) can be used to replace part of the cement in concrete. To understand the mechanisms of the influence of CWP on the properties (i.e. rheology, hydration and strength) of cement-based materials, a zeta potential test with different Ca2+ concentrations was conducted. It was found that CWP has a similar absorption for Ca2+ as cement and quartz particles, which is directly related to its surface chemical properties. The adsorption of Ca2+ on the particle surface affects the formation of C–S–H and the rheology of the cement paste. Based on the similarity in surface chemistry, it is elucidated that the effect of CWP on the rheology and early-age hydration of cement paste is attributed to its size or shape, not the surface chemical properties. In addition to strength measurement, the effect of CWP on the strength of cement paste was investigated by crack characterization and fracture surface observation. The results demonstrated that as hydration proceeded the interface strength between CWP and hydrates increased, and the chemical reaction of CWP became apparent. It also showed that CWP is an inert filler similar to quartz particles at early age. Nevertheless, at late age the pozzolanic reaction becomes obvious and improves the strength development of the cement paste.

Sorption of calcium by chitosan hydrogel: Kinetics and equilibrium

One of the major applications of chitosan is based on its ability to bind ions. In essence, the presence of active hydroxyl groups (-OH) and amino groups (-NH2), chitosan coordinates easily e.g. with transition metal ions, meanwhile it has a weak adsorption properties towards to alkaline earth metals. In this paper, a batch adsorption system was applied to study the adsorption of Ca(II) ions from aqueous solution by thermosensitive chitosan hydrogels. Due to the presence of sodium β-glycerophosphate (β-GP) in the sol structure, chitosan salts respond with phase transition and obtain thermosensitive properties, including changes in sorption abilities. Experimental research (the maximum adsorption capacity obtained 1.157 g g−1) and theoretical investigation on sorption of calcium in range of concentrations of CaCl2 solution, has been studied. Equilibria were described by Langmuir, Freundlich, Toth, Redlich-Peterson, Dubinin-Radushkevich, Radke-Praushnitz, Fritz-S, Langmuir-Freundlich, Marczewski-Jaroniec, Bi-Langmuir isotherm equations. Whereas, to describe sorption kinetics an original model was proposed, which combine chemical reaction on sorbent surface and intraparticle diffusion. The process of sorption was described by two parameters: diffusion coefficient DAB = 2.967·10−9 m2 s−1 and surface process rate constant kv = 9.129·10−5 s−1.

Flotation separation of smithsonite from calcite with guar gum as depressant

Naturally, smithsonite and calcite have similar surface physico-chemical properties so as similar floatability, hence their separation via flotation has always been one of the difficult problems in mineral processing industry. To solve this dilemma, efficient flotation reagents which could expand the difference in surface properties could be a good bailout. In this study, guar gum was successfully employed as depressant for calcite during the smithsonite flotation, and its function mechanism were studied by micro flotation, and X-ray photoelectron spectroscopy (XPS) analysis, Fourier transform infrared (FT-IR) analysis, and Zeta potential measurement. The result of micro flotation showed that using guar gum as a depressant can effectively separate smithsonite from calcite by flotation; the analysis results of XPS, FT-IR, and Zeta potential measurements showed that the adsorption behavior of Guar gum on calcite and smithsonite was significantly different. Guar gum selectively adsorbed on the calcite surface and formed strong Ca-O chemical bond via phosphate group and hydroxide radical, which reduced the number of Ca adsorption sites on the calcite surface and thus hindered the interaction between sodium oleate and calcite surface, realizing the effective flotation separation of smithsonite from calcite.

PEMBUATAN KARBON AKTIF DARI LIMBAH SABUT PINANG ASAL PULAU TIMOR SEBAGAI BIOSORBEN LOGAM Ca DAN Mg DALAM AIR TANAH

The production of activated carbon from areca nut waste as a biosorbent for Ca and Mg in groundwater has been done. This research aimed to determine the ash content, water content, and iodine number of activated carbons from areca nut waste and determine the optimum contact time and adsorption capacity for the adsorption of Ca and Mg in groundwater. Activated carbon making is done by carbonation and activation. The activator used was H2SO4 1,5 M with a soaking time of 24 hours. The adsorption process is carried out in batches with variations in contact time. The results showed that the activated carbon from areca nuts waste had an ash content of 14,97%, water content of 7,17%, iodine number of 1,079.19 mg/g, and the FTIR characterization results showed that activated carbon has the functional groups OH, CH, CO, C≡C, C=C and C=O. The optimum time condition for the adsorption of areca fiber-activated carbon to calcium and magnesium in groundwater is at a contact time of 90 minutes with an adsorption capacity of 2.1196 mg/g for Ca and 0.7540 mg/g for Mg .

Binding of Cu(Ⅱ) and Zn(Ⅱ) in Portland cement immobilization systems: Effect of C-A-S-H composition

In this study, statistical EDS point analysis was conducted to understand the binding mechanisms of Cu2+ and Zn2+ in Portland cement immobilization systems based on their correlation with compositions of Al incorporated into calcium silicate hydrate (C-A-S-H). Cu2+ and Zn2+ significantly retarded early hydration and strength development within the first day but exerted an accelerating effect at later ages. The uptake of Cu2+ by C-A-S-H occurs through two types of binding forms, which are dominated by the adsorption of Cu2+ on the Al sites of substituted bridging silicate tetrahedra and on deprotonated silanol group sites. These binding forms result in competitive adsorption between Cu2+ and Ca2+. Zn2+ is primarily bound to the outer-product C-A-S-H. Zn anion species were adsorbed on the positively charged sites of the C-A-S-H surface, which were generated from the adsorption of Ca2+. Consequently, the uptake of Zn exhibits a noncompetitive relationship with Ca2+ and increased with Ca content in C-A-S-H.

Selective removal of Na+ by NaTi2(PO4)3-MWCNT composite hollow-fiber membrane electrode in capacitive deionization

In this study, NaTi2(PO4)3 (NTP) nanoparticles were incorporated into a carbon nanotube hollow-fiber (CHF) electrode for the selective removal of Na+ during the capacitive deionization (CDI) of salty water. Due to the Na+-selective electro-sorption of NTP nanoparticles, NTP-CHF achieved 1.5 ~2 times higher Na+ adsorption capacity than that of CHF only electrodes at a range of 1.7 mM~17.1 mM (100 mg L−1~1000 mg L−1) NaCl solution. Moreover NTP-CHF sustained the Na+ adsorption capacity even at the presence of Ca2+ ions, whereas the dramatic decrease in Na+ removal was observed in CHF with an increase of Ca2+ concentration. As the result, NTP-CHF can retain 52% of the initial Na+ removal capacity after three times of capture and release cycles at the presence of Ca2+, while CHF showed <10% of the initial Na+ removal capacity due to the irreversible adsorption of Ca2+ ions onto the MWCNT surface. Thus, the incorporation of NTP into the conductive carbon nanomaterial network can greatly improve both the adsorption capacity and selectivity of Na+ compared to the conventional carbon-based electrode during the CDI of salty water containing multivalent cations such as Ca2+.

How bulk and surface properties of sulfonated cation-exchange membranes response to their exposure to electric current during electrodialysis of a Ca2+ containing solution

Electrodialysis (ED) of calcium-containing solutions is a widely applied process in water treatment, dairy industry etc. The lower performance of ion-exchange membranes in these processes (in comparison, e.g. with ED of sodium-containing solutions) is known, but the reasons for this effect are still unclear. We study the behavior of two sulfonated cation-exchange membranes: a CMX (Astom, Japan) and a CJMC-5 (Hefei Chemjoy Polymer Materials, China). For both membranes, the bulk properties (conductivity, diffusion permeability, counterion permselectivity) change when the membrane is soaked in a 0.02 N CaCl 2 solution, but these changes are reversible: when the membranes are again equilibrated with a NaCl solution, the bulk properties restore and become the same as before. The exposure of the membranes to an overlimiting current does not affect the bulk properties. However, it is not the case for the properties controlled by the membrane surface. In particular, the length of the limiting current plateau of the current-voltage curve increases and electroconvection (visualized using Rhodamine 6G) decreases with increasing the time of the membrane exposure to overlimiting current in a CaCl 2 solution. The zeta potential is about −30 mV for a “fresh” membrane, and +40 mV after exposure of this membrane to an overlimiting current in a 0.02 N CaCl 2 solution; the both measurements were made in the same NaCl solution. The changes in surface-controlled properties appear to be irreversible. This effect is explained by specific adsorption of Ca 2+ ions on the surface of sulfonated membranes promoted by a strong electric field at the interface. This explanation is supported by simulations of the distribution of the electric potential and ion concentrations in the interfacial electrical double layer. • Two sulfonated cation-exchange membranes are studied. • Performances change after exposing the membranes to electric current in a CaCl 2 solution. • The change in bulk properties (conductivity, diffusion permeability) is reversible. • Changes in surface-controlled properties (e.g. zeta-potential) appear to be irreversible. • The effect is explained by specific adsorption of Ca 2+ enhanced by a strong electric field.

Reversible Adsorption of Polycarboxylates on Silica Fume in High pH, High Ionic Strength Environments for Control of Concrete Fluidity.

Polycarboxylate-based superplasticizers are essential for production of ultrahigh-performance concrete (UHPC), facilitating particle dispersion through electrostatic repulsion and steric hindrance. This study examines for the first time the effect of changes in pH, ionic strength, and charge on the adsorption/desorption behavior of a polycarboxylate-based superplasticizer on silica fume in aqueous chemistries common in low-CO2 UHPC. Data from total organic carbon measurements, Fourier transform infrared and nuclear magnetic resonance spectroscopy, and zeta potential measurements reveal the silica surface chemistry and electrokinetic properties in simulated UHPC. Addition of divalent cations (Ca2+) results in polycarboxylate adsorption on silica fume via (i) adsorption of Ca2+ ions on the silica surface and a negative zeta potential of lower magnitude on the silica surface and (ii) reduction of polycarboxylate anionic charge density due to complexation with Ca2+ ions and counter-ion condensation. Addition of OH– ions results in polycarboxylate desorption via deprotonation of silanol groups and a negative zeta potential of greater magnitude on the silica surface. Simultaneous addition of both Ca2+ and OH– results in rapid polycarboxylate desorption via (i) formation of an electric double layer and negative zeta potential on the silica surface and (ii) an increase in polycarboxylate anionic charge density due to deprotonation of the carboxylate groups in the polymer backbone, complexation with Ca2+ ions, and counter-ion condensation. This provides an explanation for the remarkable fluidizing effect observed upon addition of small amounts (1.0 wt %) of a solid, powdered Ca source to fresh, low-CO2, UHPC, which exhibits significantly higher fresh state pH (>13) than those based on Portland cement (pH 11).

Review on the Application of Supplementary Cementitious Materials in Self-Compacting Concrete

For the sustainable development of construction materials, supplementary cementitious materials (SCMs) are commonly added to self-compacting concrete (SCC). This paper reviewed the application techniques and hydration mechanisms of SCMs in SCC. The impacts of SCMs on the microstructure and performance of SCC were also discussed. SCMs are used as a powder material to produce SCC by replacing 10% to 50% of cement. Hydration mechanisms include the pozzolanic reaction, alkaline activation, and adsorption effect. Moreover, the filling effect and dilution effect of some SCMs can refine the pore structure and decrease the temperature rise of concrete, respectively. Specifically, the spherical particles of fly ash can improve the fluidity of SCC, and the aluminum-containing mineral phase can enhance the resistance to chloride ion penetration. Silica fume will increase the water demand of the paste and promote its strength development (a replacement of 10% results in a 20% increase at 28 days). Ground-granulated blast furnace slag may reduce the early strength of SCC. The adsorption of Ca2+ by CaCO3 in limestone powder can accelerate the hydration of cement and promote its strength development.

Experimental investigation on chemical clogging mechanism of loose porous media in recharge process of groundwater heat pump

ABSTRACT Groundwater heat pumps (GWHP) are an efficient utilisation of shallow geothermal energy technology and of great significance in terms of promoting energy conservation and reducing emissions. However, recharge clogging has been a key problem restricting the continuous operation of GWHP. In this study, a simulation test device for sand column was designed with the aim of addressing chemical clogging induced by heat pump reinjection in a porous saline aquifer in the Huaibei Plain, China. The trend in the variation of the permeability coefficient was studied based on the detection of the sand sample composition, recharge water quality, and sand layer temperature, and the cause of formation was analysed using the saturation index (SI) and ion ratio method. The results indicated that the permeability coefficient in the sand column decreased exponentially, with a maximum and minimum decrease of 8.14% and 71.65% of the original coefficient, respectively, found in sections P2–P3 and P8–P9. Therefore, the clogging effect of the aquifer at approximately 200–400 mm from the recharge well was significant. Water–rock interactions predominantly involved the dissolution of halite, albite, chlorite, anhydrite, and dolomite and the precipitation of calcite, as well as the exchange adsorption of Ca2+ and Mg2+ to Na+, which were the key sources of ions during the water chemical evolution process. Finally, quartz was formed by the weathering and dissolution of aluminosilicate minerals such as albite, and particle migration and precipitation during the hydrodynamic disturbance were the primary causes of the front-end blockage of the column.

Inhibition of CaCO3growth and synthesis of submicron particles by preferential adsorption of additive Ca2+ions on fresh precipitates

Method to inhibit CaCO3growth and synthesize submicron particles in a chemical precipitation process under ambient and high supersaturation conditions.

Mechanism of bacterial control of mineralisation gradient at the surface layer of cement-based materials

Cement-based composites reinforced with steel bars are the primary material in the construction of infrastructure. Their durability in the service environment is thus a crucial topic. The application of bio-mineralisation technology shows great prospects in improving the properties of cement-based materials (CBMs). In this study, the underlying mechanism was explored by investigating the effects of various factors on the mineralisation gradient at the surface layer of CBMs. Four factors were studied to investigate the process of bacterial action: the absorption of carbon dioxide from the air, the transformation of carbon dioxide into HCO3−, the adsorption of Ca2+ from the pore solution of CBMs and the formation of calcium carbonate in pores, which results in a decrease in porosity. The results of calcium carbonate content and porosity indicated that bacteria could regulate the mineralisation gradient at the surface of CBMs. Numerical calculations and experimental measurements were also conducted for further verification.

In vitro Evaluation of Surface Free Energy of Dentin after Treatment with Sodium Trimetaphosphate Associated or Not with Fluoride, Exposed or Not to Calcium

It has been stated that sodium trimetaphosphate (TMP) promotes a more anionic dentin surface inducing greater calcium (Ca) and phosphate precipitation. The aim of the present study was to evaluate in vitro the surface free energy (γ_s) of dentin after treatment with TMP associated or not with fluoride (F), exposed or not to Ca, as well as the adsorption of TMP, F, and Ca by dentin. Bovine dentin blocks (n = 12 blocks/group) were treated with solutions containing TMP at 0, 1, 3, or 9 (w/v) followed or not by the application of Ca. These solutions were or were not associated to 1,100 ppm F. F, Ca, and TMP were determined in the solutions before and after the treatment to calculate the adsorption by dentin. To analyze the γ_s of dentin, the apolar (γ_s^LW), and polar (γ_s^AB), components were determined by contact angle measurement. Data were submitted to 2-way ANOVA followed by the Student-Newman-Keuls test (p < 0.05). TMP reduces γ_s of dentin and increases electron donor sites (γ_s⁻). Higher values of γ_s⁻ led to higher adsorption of Ca (p < 0.001). The F/TMP association did not change γ_s or γ_s^LW and reduced the values of γ_s⁻, but the adsorption of Ca was higher. There was correlation between the adsorption of TMP and γ_s⁻ (Pearson’s r = 0.801; p < 0.001) and F (Pearson’s r = 0.871, p < 0.001). It is possible to conclude that TMP increased γ_s⁻ and Ca adsorption, and reduced γ_s. The association with F increased the adsorption of TMP without rising γ_s⁻; however, there was higher adsorption of Ca.

Application of a hybrid material formed by layered zinc hydroxide chloride modified with spiropyran in the adsorption of Ca2+ from water

The excess of metal ions in water is associated with drawbacks in industrial processes due to the precipitation of insoluble compounds in pipes and cooling systems. Therefore, investigating alternatives for the removal of ions is especially important and can be achieved with the use of adsorbing materials. In this paper, a novel hybrid material formed by zinc hydroxy chloride (ZHC) functionalized with molecules of the spiropyran class is presented as an alternative for the removal of calcium ions from water. Characterization techniques, including XRD, FTIR, and EDS allowed to identify the spiropyran molecules covering the surface of ZHC in the merocyanine form, forming active sites for calcium chemisorption. The material, described as ZHC/MC24, showed good adsorption capacities that reached 19 mg g−1 at pH 8.0. ZHC/MC24 presented a negatively charged surface, according to zeta potential analyses. Shifting the pH to alkaline values increased the negative potential, which reflected in greater calcium adsorptions. The isotherm investigation showed that the adsorption occurs in a monolayer process, and a first-order adsorption model was found to describe the process. Control tests performed with the ZHC without spiropyran showed low adsorption capacities, inferior to 2 mg g−1, evidencing the importance of the functionalization with spiropyran to the proposed application.