Calcium Ions In Solution Research Articles

Catalytic efficiency of copper nanoparticles modified silica-alginate hydrogel nanocomposite towards reduction of water pollutants and H2 generation

In the present study, a viscous solution of sodium alginate polymer (Alg) containing dispersed silica (Si) was prepared for the fabrication of hydrogel beads. It was added dropwise into a divalent calcium (Ca+2) ions solution which convert each drop into a hydrogel bead i.e, Si@AlgBD. In the next step, the outer surface of the Si@AlgBDs were modified with five different types of metal. As a result, it gives five types of metal coated M+n/Si@AlgBDs catalyst. These coated M+n [M+n = Ag+, Ni+2, Fe+3, Co+2, and Cu+2] were converted into zero-valent metal nanoparticles (MNPs) [M0 = Ag0, Ni0, Fe0, Co0, and Cu0] by NaBH4, which act as a strong reducing agent. Firstly, all catalysts were analyzed for the reduction of 4-NP to 4-AP to check out the efficiency of catalysts. Among which the reduction rate was higher for Cu0/Si@AlgBDs catalyst and was chosen for further study. Secondly, the Cu0/Si@AlgBDs catalyst was examined for the decolorization of 2-nitrophenol (2-NP), 2,6-dinitrophenol (2,6-DNP), methyl orange (MO), congo red (CR), and acridine orange (ArO). Additionally, its catalytic reduction was analyzed for the reduction of 4-NP to 4-AP in different quality of water sources. The highest reduction rate of 6.207 × 10−1 and 8.619 × 10−1 min−1 was calculated for CR and 4-NP, respectively. Beside its catalytic reduction, the same catalyst was evaluated for the generation of H2 gas from NaBH4 through methanolysis. Where, the lowest Ea energy of 25.9 kJ/mol was calculated at room temperature. In both experimental procedures i.e, catalytic reduction and H2 production, different parameters, such as, catalyst dosage, different amount of the NaBH4, initial concentration of the 4-NP, and temperature effect for the H2 production were studied in detail. Similarly, the hydrogel beads were characterized by SEM, EDX, and ICP-OES to identify and find out the successful incorporation of MNPs on Si@AlgBDs. Finally, the recyclability of the catalyst was also investigated.

Valorization of tannery solid wastes for sustainable enzyme induced carbonate precipitation process

Biocementation via enzyme induced carbonate precipitation (EICP) is an emerging ground improvement technique that utilizes urease for calcium carbonate precipitation. Usage of expensive laboratory grade chemicals in EICP hinders its implementation at field level applications. In this study, the feasibility of utilizing solid wastes generated from leather industry was investigated for EICP process. Initially, the proteinaceous fleshing waste was used as nitrogen source for production of an extracellular urease from Arthrobacter creatinolyticus MTCC 5604 followed by its subsequent use in EICP with suspended solids of tannery lime liquor, as alternative calcium source. The calcium ion solution was prepared by treating suspended solids of lime liquor with 1 N HCl. The EICP was optimum with 1000 U of urease, 1.0 M urea and 1.0 M CaCl2.2H2O for test tube experiments. Sand solidification experiments under optimal conditions with five times addition of cementation solution yielded a maximum unconfined compressive strength (UCS) of 810 kPa with laboratory grade CaCl2.2H2O and 780 kPa with calcium from lime liquor. The crystalline phases and morphology of the CaCO3 precipitate were analyzed by XRD, FTIR and SEM-EDX. The results showed the formation of more stable calcite in EICP with calcium obtained from lime liquor, while calcite and vaterite polymorphs were obtained with CaCl2.2H2O. Utilization of fleshing waste and lime liquor in EICP could reduce the pollution load and sludge formation that are generated during the pre-tanning operations of leather manufacturing. The results indicated the viability of process to achieve cost effective and sustainable biocementation for large scale applications.

Aptamer/Hydroxyapatite-Functionalized Titanium Substrate Promotes Implant Osseointegration via Recruiting Mesenchymal Stem Cells.

Endowing bone regeneration materials with both stem cell recruitment and osteoinduction properties is a key factor in promoting osseointegration of titanium (Ti) implants. In this study, Apt19s-grafted oxidized hyaluronic acid (OHA) was deposited onto a protein-mediated biomineralization hydroxyapatite (HAp) coating of Ti. HAp was achieved by the treatment of lysozyme and tris(2-carboxyethyl) phosphonate mixture and then soaked in calcium ion (Ca2+) solution to obtain functional Ti substrate (Ti/HAp/OHA-Apt). In vitro studies confirmed that Ti/HAp/OHA-Apt could effectively maintain the sustained release of Apt19s from Ti for 7 days. The released Apt19s significantly enhanced the migration of bone marrow mesenchymal stem cells (MSCs), which was reflected by the experiment of transwell assay, wound healing, and zymogram detection. Compared with pure Ti, Ti/HAp/OHA-Apt was able to adjust the adsorption of functional proteins at the Ti-based interface to expose their active sites, which significantly increased the expression of adhesion-associated proteins (vinculin and tensin) in MSCs to promote their adhesion on Ti-based interface. In vitro cell experiments of alkaline phosphatase activity staining, mineralization detection, and expression of osteogenesis-related genes showed that Ti/HAp/OHA-Apt significantly enhanced the osteogenic differentiation ability of MSCs, which may be highly related to the porous structure of hydroxyapatite on Ti interface. In vivo test of Micro-CT, H&E staining, and histochemical staining further confirmed that Ti/HAp/OHA-Apt was able to promote MSC recruitment at the peri-implant interface to form new bone. This work provides a new approach to develop functional Ti-based materials for bone defect repair.

Effect of calcium ions on the freeze-drying survival of probiotic encapsulated in sodium alginate

Alginate-based encapsulation of probiotics is a well-recognized method. Crosslinking of the hydrogel occurs by ions and the most commonly used ion is calcium. However, dramatic reduction of viable probiotics during freeze-drying of ion-crosslinked alginate hydrogel is often reported, although this loss is often overlooked or taken for granted. In the present work, the role of calcium in this critical loss of activity was examined. Compared with sodium alginate, it was found that the freeze-drying survival of Lactobacillus rhamnosus GG (LGG) encapsulated in calcium alginate was at least 0.6 log/CFU lower or completely lost. The loss of survival in calcium alginate was mainly in the drying process, which was positively correlated with the increase of calcium ions concentration. Calcium ion solution modeling exhibited significant survival loss at calcium above 1.5 M and the survival loss was proportional to the contact period between LGG and calcium. Under the same ionic strength, three common ions (sodium, potassium, and magnesium) caused a lower loss of LGG survival compared with calcium, indicating that the osmotic pressure effect is not the main reason for LGG damage by calcium. Transmission electron microscopy combined with ultra-thin section technology was used to observe the damage of calcium ions to LGG. The destruction of cell wall/membrane integrity, metabolic activity suppression, and reduced intracellular calcium ion concentration were factors in the loss of probiotic viability. This study provides new insights into the selection and design of alginate-based probiotic encapsulation. • LGG freeze-drying survival was higher in sodium than calcium alginate. • The LGG survival loss in calcium alginate was mainly in the drying process. • The survival loss was positively correlated with the increased calcium concentration. • The osmotic pressure effect was not the main reason for the LGG damage. • Calcium caused cell wall/membrane and intracellular homeostasis damage.

Influence of Electrostatic Field on Mixed Aqueous Solution of Calcium and Ferrous Ions: Insights from Molecular Dynamics Simulations

In order to investigate the anti-scaling and anti-corrosion characteristics of an electrostatic anti-fouling system in the application process, the influence of an electrostatic field (EF) on the structure and dynamics of hydrated Ca2+ and hydrated Fe2+ in a mixed aqueous system was studied through the calculation and analysis of the radial distribution function (RDF), self-diffusion coefficients, viscosity, and hydrogen bond structure by using molecular dynamics simulation. The study results show that the EF can decrease the radius of the first water shell of hydrated Ca2+ but increase that of Fe2+, which will reduce the possibility of forming calcite. The EF can make water molecules and Fe2+ more active, which can hinder iron release and thus decrease iron corrosion products. In addition, the EF can enhance the hydrogen structure of water molecules in the aqueous solution.

Paired Simulations and Experimental Investigations into the Calcium-Dependent Conformation of Albumin.

Serum albumin is the most abundant protein in blood plasma, and it is involved in multiple biological processes. Serum albumin has recently been adapted for improving biomaterial integration with bone tissue, and studies have shown the importance of this protein in bone repair and regeneration. However, the mechanism of action is not yet clear. In stark contrast, other studies have demonstrated that albumin blocks cell adhesion to surfaces, which is seen as a limitation to its bone healing role. These apparent contradictions suggest that the conformation of albumin facilitates its bioactivity, leading to enhanced bone repair. Serum albumin is known to play a major role in maintaining the calcium ion concentration in blood plasma. Due to the prevalence of calcium at bone repair and regeneration sites, it has been hypothesized that calcium binding to serum albumin triggers a conformational change, leading to bioactivity. In the current study, molecular modeling approaches including molecular docking, atomic molecular dynamics (MD) simulation, and coarse-grained MD simulation were used to test this hypothesis by investigating the conformational changes induced in bovine serum albumin by interaction with calcium ions. The computational results were qualitatively validated with experimental Fourier-transform infrared spectroscopy analysis. We find that free calcium ions in solution transiently bind with the three major loops in albumin, triggering a conformational change where N-terminal and C-terminal domains separate from each other in a partial unfolding process. The separation distance between these domains was found to correlate with the calcium ion concentration. The experimental data support the simulation results showing that albumin has enhanced conformational heterogeneity upon exposure to intermediate levels of calcium, without any significant secondary structure changes.

Cleaning high ash coal waste from coking coal via froth flotation method

In this work, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and laser particle size methods were employed. The surface of the particle obtained from the cyclonic-static microbubble flotation column (FCSMC) concentrate was coated with numerous small particles when compared to the clean coal collected from the Denver flotation cell. Even though the mass recovery of FCMSC concentrate (51.13%) was approximately twice the mass yield of Denver flotation cell concentrate (26.66%), the ash content in FCSMC concentrate (33.07%) was higher than that of the Denver flotation cell concentrate (14.88%). This result can be attributed to the advantages of FCSMC in small coal particle flotation, and this resulted in the misplacement of coarser particles with lower ash content in the tailing. The highest mass recovery of 0.250–0.500 mm in magnesium ion solution was 95.39%, which was slightly high than that (92.84%) in calcium ion solution. However, the concentrate ash content with 0.250–0.500 mm coarse size fraction in magnesium ion solution was 11.41%, which was higher than that (11.14%) in calcium ion solution. Flotation performances of different size fractions in rougher-cleaner flowsheet indicated that flotation responses in calcium ion solution were better than that in magnesium solution.

Bone-Adhesive Hydrogels Based on Dual Crosslinked Poly(2-oxazoline)s.

The development of bone glues based on bone-adhesive hydrogels to allow for facile bone fracture fixation remains a major challenge. Herein, dual crosslinked hydrogels that combine tunable stiffness, ductility, and self-healing capacity are successfully synthesized. The resulting double network hydrogel is formed by chemical crosslinking of N-hydroxysuccinimide-functionalized poly(2-oxazoline)s(POx-NHS)"?> with amine-functionalized poly(2-oxazoline)s, and physical crosslinking of alendronate-functionalized poly(2-oxazoline)s (POx-Ale) with calcium ions in solution. The use of an excess of alendronate-functionalized POx-Ale polymers also ensures affinity toward calcium cations in the mineral phase of bone, thereby rendering these hydrogels adhesive to bone. The mechanical and bone-adhesive properties of these novel hydrogels are superior to commercially available fibrin sealants. Moreover, hydrogels retain their bone-adhesive properties under wet conditions. Although the dual crosslinked hydrogels swell considerably, they are stable upon immersion in phosphate-buffered saline (up to 12 d) and even in ethylenediaminetetraacetic acid solution. The enhanced mechanical and bone-adhesive properties of these hydrogels, as well as their in vitro stability, indicate that they have much application potential as bone-adhesive glues.

The potential use of green mussel (Perna Viridis) shells for synthetic calcium carbonate polymorphs in biomaterials

Green mussel shells contain a high content of calcium that can be potentially used for starting biomaterials. A powder processing and subsequent calcination-dissolution-precipitation (CDP) technique for recycling the shells into the value-added of precipitated calcium carbonates (PCC) is presented in this paper. In the experimental study, the received green mussel shells were initially washed and ground and followed by heat treatment at different temperatures in an electric furnace. PCC product was precipitated from the blended solution of calcium and carbonate ions derived from the heat-treated ground powder. The precipitating solids were then investigated via XRD, SEM-EDX, and FTIR methods. The XRD Rietveld method confirmed that the raw green mussels were rich in crystalline aragonite, which could be recycled into vaterite and calcite in the PCC product. The current study demonstrated that the green mussel shells are technically possible for the starting materials in biomedical applications.

Effect of calcium ion on the morphology structure and compression elasticity of muscle fibers from honeybee abdomen

Muscle contraction activated by calcium ion is the key to reveal that honeybee abdomen can achieve various physiological activities through flexible exercises and contributes to a powerful mechanical function of muscle fibers. To investigate the stimulating effect of calcium ion on muscle fibers of honeybee abdomen, atomic force microscopy was used to measure the morphology structure and mechanical properties of muscle fibers from honeybee abdomen in different calcium ion solutions. The periodic morphology structure of muscle fibers stimulated by different calcium ion concentration changed greatly, and the sarcomere length contracted from 6.53 μm to 4.29 μm as the calcium ion concentration increased from 0.11 mM to 10 mM. The mechanical measurement showed that the elastic modulus of Z-line reached the maximum, followed by M-line, overlap zone and I-band in sequence at the same calcium ion concentration, and was approximately 3.636, 2.450, 2.284, 2.748 times that of I-band from 0.11 mM to 10 mM calcium ion concentration. Combining the experimental analysis, the calcium ion threshold range was obtained based on the response surface method. This work adequately elucidates biological structure and biomechanics of muscle fibers from honeybee abdomen and could provide reference for other similar muscle system.

Effect of pH level and calcination on the production of calcium phosphates by acidic route of wet precipitation

Multiphasic calcium phosphate powders were synthesized by the acidic route, using lactic acid as a chelating agent that allows the production of a stable and rich solution of calcium and phosphate ions at room temperature. After pH adjusting, without varying the concentrations of precursor solution, XRD and FTIR analyses showed different CaP phases before and after heat treatment at 1000 °C. At pH 5, brushite plate-like particles were produced, while at higher pH levels (7 to 12) nano-hydroxyapatite particles were formed. After the calcination process, partial and total decomposition of hydroxyapatite in the β-TCP phase was explained by XRF analysis due to the calcium-deficient hydroxyapatite of synthesized samples at pH 7 and 10. This work presents an important method to synthesize any desired CaP phase compositions by varying the pH level and subsequently performing heat treatment, which has a direct effect on morphology, crystallinity, and formation of different CaP powders.

Dual Functional Alginate‐Polyethylene Polyamine Composite Aerogel Toward Sensing and Extracting Copper Ions in Water

AbstractIn this study, a new type of sodium alginate‐polyethylene polyamine composite aerogel (Alg‐PEMA) was synthesized to detect and remove excess copper ions (Cu2+) in water. First, a classic acylation reaction was used to graft polyethylene polyamine onto alginate, which was then gelatinized in a calcium ion solution and vacuum freeze‐dried to prepare the final Alg‐PEMA adsorbent. Experimental results showed that the as‐prepared Alg‐PEMA can remove 99.2 % of Cu2+ (0.1 mM) in water, and the maximum adsorption capacity for Cu2+ is 46.78 mg/g. Alg‐PEMA can also be used for qualitative colorimetric detection of Cu2+ in aqueous solution. The detection limit for Cu2+ is as low as 0.64 mg/L, which is lower than the WHO standard for drinking water Cu2+ content (2.0 mg/L). Its green and safe raw materials, simple desorption and regeneration process, and stable detection and adsorption performance indicate that the Alg‐PEMA adsorbent has broad application prospects in the treatment of Cu2+‐containing wastewater.

The Features of Interaction of Collagen and Collagenase Molecules in the Presence of Chromium and Calcium Ions in Solutions by Dynamic Light Scattering

The Features of Interaction of Collagen and Collagenase Molecules in the Presence of Chromium and Calcium Ions in Solutions by Dynamic Light Scattering

Effect of precipitation mineralization reactions on convective dissolution ofCO2: An experimental study

When CO${}_{2}$ dissolves in a solution of calcium ions, a precipitation mineralization reaction can take place, producing solid calcium carbonate particles that sink to the bottom of the host phase. Convective motions present both above and below the reaction front favor the entrainment of CO${}_{2}$ toward the bottom, which is favorable for the security of carbon sequestration techniques. An experimental study of the influence of such a precipitation reaction on convective dissolution of CO${}_{2}$ is conducted.

Transcriptional and metabolite analysis reveal a shift in fruit quality in response to calcium chloride treatment on "Kyoho" grapevine.

'Kyoho' grapevine (Vitis vinifera) treated by calcium ions solution has been proved as an effective treatment to extend grape quality during storage to reduce disease, but its molecular mechanism was not clear yet. In the current work, grape berries were treated with different concentration of Calcium chloride (CaCl2) solution, and their effects on antioxidant enzyme activity and transcriptome and metabolome in fruit were investigated. CaCl2 treatments reduced weight loss and inhibited the decrement of flesh firmness. 80mM CaCl2 significantly increased the activity of antioxidant enzymes POD, SOD and CAT, which was the optimum experimental concentration. The study showed that the expression level of heat shock transcription factor and UBX which involved in endoplasmic reticulum stress and degradation pathway increased significantly. Moreover, the corresponding metabolites, such as heat shock protein and organic acid, also increased significantly. The misfolded proteins are transported to the cytosol for degradation, so that the preservation ability of grape is improved.

Experimental study on solidification of tailings by MICP under the regulation of organic matrix

Microbial grouting reinforcement technology can improve the strength of tailings to a certain extent, but there is still much room for improvement. To balance the adverse effects of the technology to cure the tailings, this paper introduced the mineralization technology of soft template into the microbial induced calcium carbonate precipitation (MICP), and carried out the experiments on microbial grouting to strengthen the tailings under the control of organic matrix. The results of aqueous solution test showed that the organic matrix can significantly regulate the structural characteristics of calcium carbonate. When the added organic matrix is egg white protein with a volume fraction of 20%, the contribution to the conversion rate of calcium ions in the reaction solution was the largest, and the concentration of calcium ions in the solution at 20 h is reduced by about 83.72% compared with the control group. In the solidification test of tailings, as the egg white concentration increased, the curing unevenness of the tailings was further aggravated. When the egg white volume fraction is 5%, the strength improvement effect of the tailings was the best and the dilatancy characteristic was the most significant. At the same time, the calcium carbonate produced are mostly large-sized calcite, and the corresponding formation amount, cohesive force and internal friction angle are 16.01%, 131.98 kPa and 42.7°, respectively. The study showed that mineralization technology of soft template can promote the MICP technology, which provides a new method for the reinforcement of tailings dam.

The effect of alginate composition on adsorption to calcium carbonate surfaces

Bacterial anchoring to limestone rocks is thought to occur by selective adsorption of biomolecules found in the extracellular matrix, such as polysaccharides. Here we study the adsorbed structure of a model matrix polysaccharide, sodium alginate, at the calcite/water interface using neutron reflection (NR). Sodium alginate was found to form highly hydrated layers extending up to 350 Å into solution at concentrations up to 2.5 ppm (the inflection point of the adsorption isotherm). The adsorption of alginate was driven by dissolution of the calcite surface through complexation of free calcium ions. This was shown using two alginates with differing ratios of sugar residues. Alginates with a higher proportion of guluronic acid (G) have a higher affinity for calcium ions and were found to cause the surface to dissolve to a greater extent and to adsorb more at the surface when compared to alginates with a higher proportion of mannuronic acid (M). Adding magnesium to the high G alginate solution reduced dissolution of the surface and the adsorbed amount. In this work, we have shown that polysaccharide adsorption to sparingly soluble calcite interfaces is closely related to polymer conformation and affinity for free calcium ions in solution.

Gallstone formation analysis using the particle appearance, the particle binding to calcium ions, and the cholesterol nucleation with time in supersaturated taurocholate–lecithin–calcium ion solutions

AbstractWe conducted a time‐dependent study of cholesterol (Ch) nucleation to investigate the effect of calcium ions in the moderate supersaturated bile. In taurocholate/lecithin (TC/L) bile at a TC to L ratio of 5.1, the presence of calcium ions enhanced the nucleation rate of Ch. Contrarily, we observed the delayed nucleation of Ch after ~30 days in TC/L bile at a ratio of 2.0, regardless of the calcium ions. From the physical chemistry standpoint, the cholesterol activity (ChAT) is believed to be the driving force for Ch nucleation together with the sufficient nucleation sites. Hence, the micellar formation models along with the binding of TC monomers to calcium ions interpreted the time‐dependent results. Furthermore, a quasielastic light–scattering technique detected the formation of micelles and vesicles. In conclusion, the presence of calcium ions in TC/L bile at a high ratio enhances the vesicle appearance for nucleation sites and the high ChAT values for fast nucleation rate of Ch. However, an increase in the L concentration (i.e., low ratio bile) plays a significant role in the prevention of Ch gallstone formation, compared to the decrease in calcium ion concentration.

Experimental investigation of Alfalfa natural surfactant and synergistic effects of Ca2+, Mg2+, and SO42− ions for EOR applications: Interfacial tension optimization, wettability alteration and imbibition studies

Fractured moderate oil-wet carbonate reservoirs are the main productive formations in the Middle East. The change in wettability state toward water wetness beside interfacial tension (IFT) reduction is one of the potential scenarios for more oil recovery process. Smart water and natural surfactant injection into the porous media will alter the rock wettability and reduce IFT which consequently results in more oil sweep from untouched pores. In this paper, a novel natural surfactant (Alfalfa species) is introduced for EOR applications. IFT and contact angle tests were carried out between the oil phase, rock surface, Alfalfa natural surfactant, and surfactant—ion hybrid aqueous solutions. The results of Alfalfa natural surfactant showed a 29.29 mN/m reduction of IFT (63.39% IFT optimization) at the concentration of 4 wt% as the critical micelle concentration (CMC). Also, after addition of Alfalfa the wettability of rock tends to be more water-wet from the initial oil-wet state by application of Alfalfa because of 86.84° reduction of contact angle (49.91% wettability alteration). Solutions of calcium, magnesium, and sulfate ions were prepared as modified synthetic seawater at CMC of Alfalfa natural surfactant to investigate their synergistic influences on intensifying the optimizations of IFT and wettability alteration as hybrid solutions. IFT measurements of the hybrids demonstrated that among mentioned ions calcium brings the best results as it showed good synergistic effects with mentioned non-ionic natural surfactant in advancing the optimization of IFT reduction from 63.39 (surfactant solution) to 71.0 (surfactant—ion hybrid solution) percent. Also, contact angle measurements of the hybrids demonstrated that calcium ions gain the best results and advance the contact angle optimization from 49.91 (surfactant solution) to 61.8 (surfactant—ion hybrid solution) percent. Therefore, the solution of 3 times Ca concentrated seawater + CMC of surfactant selected to conduct imbibition tests as a displacement experiment based on the hybrid results and the candidate solution caused a 19.2% increase in oil recovery factor regarding seawater flooding and a total oil recovery factor of 62%.

Novel hybrid materials based on alginate-boehmite-riboflavin for photogeneration of reactive oxygen species in aqueous media. Potential environmental implications

In this work, hybrid composites based on beads of alginate, boehmite and riboflavin-5′-phosphate dye (ALG-B-RP) were synthesized in order to obtain novel materials capable to generate reactive oxygen species (ROS). The synthesis was performed by adsorbing the dye RP on boehmite (B) and then alginate (ALG) was added forming a homogeneous suspension. This suspension was dripped on a solution of calcium ions resulting in the formation of bead-shaped yellow hydrogels. Beads with different RP content were synthesized. Confocal laser scanning microscope images indicate that the RP is homogeneously distributed in the ALG polymeric matrix. This microscopy, UV–Vis and fluorescence spectroscopies show that dye photophysical properties are not affected. Uptake oxygen experiments show that these beads have the ability to generate ROS, mainly singlet oxygen O2(1Δg). On top of that mentioned above, these materials are economical, environmentally friendly because are synthesized from non-toxic components and their synthesis does not generate waste and only use water as solvent. On the other hand, these beads are easy to handle and their ability to generate ROS making them promising for water remediation.