Calcium Carbonate Surface Research Articles

Visualisation of surface coating distribution patterns on modified CaCO3

In this work, the surface modification of calcite-type calcium carbonate using the anionic surfactant sodium stearate was studied. The optimal amount of surfactant and its distribution on the surface of calcium carbonate is of great significance to the actual production. Various techniques were used to characterize these important parameters such as Fourier-transform infrared spectroscopy (FTIR), water contact angle measurements, Raman Mapping visualizationimaging, Raman depth profiling, thermogravimetric analysis (TGA), and atomic force microscopy (AFM). The results of the Fourier Transform Infrared (FTIR) suggest the formation of a coating on the surface of the modified calcium carbonate. Water contact angle measurements, Raman Mapping visualizationimaging, and TGA indicate that the optimal initial dosage of sodium stearate required to form a monolayer coating is about 2 wt%. Here, the hydrophilic heads of the sodium stearate are arranged vertically on the calcium carbonate surface forming the monolayer. As the concentration of sodium stearate increases, the hydrophobic tails of the sodium stearate or calcium stearate connect each other, forming bilayer or multilayer coatings. Furthermore, the surface coating on calcium carbonate originates from the edge vertices and gradually spreads towards the central region as the amount of sodium stearate increases until complete coverage is achieved. Raman depth profiling and AFM visualization results suggest that the thickness of the monolayer coating is approximately 5.25 nm.

Effects of xylan-modified precipitated calcium carbonate filler on the properties of paper

Abstract The use of mineral-based fillers tends to reduce the mechanical properties of paper, which can limit their application. The filler surface modification is a significant treatment to overcome this limitation. This research aims to offer a novel modified mineral-based filler to provide its industrial application. The surface of precipitated calcium carbonate (PCC) was modified with xylan (XS), which is a type of hemicellulose, a polysaccharide consisting mainly of xylose residues. It is used as a filler at different filler dosage levels in paper pulp. Modified PCC(MPCC) was characterized with Fourier transform infrared spectroscopy, Thermogravimetric analysis, X-ray photoelectron spectroscopy, X-ray diffraction and Field-emission scanning electron microscopy analyses. The analysis demonstrated that the MPCC filler surface was coated with XS successfully. The effect of PCC and MPCC-filled hand-sheet paper physical, chemical and optical properties were studied. The experimental results showed that the mechanical (tensile, burst, tear strength) and optical (brightness, opacity) of hand-sheet paper filled with MPCC were significantly improved compared with unmodified PCC-filled paper at the same ash content. The filler retention of PCC and MPCC fillers in paper was investigated, and the MPCC filler showed better filler retention properties in paper stock than the PCC filler.

The impact of seawater ions on urea decomposition and calcium carbonate precipitation in the MICP process

As an environmentally friendly biotechnology, the microbial induced calcium carbonate precipitation (MICP) provides a new approach to repair concrete cracks. Most existing studies focused on finding a suitable environment for bacteria to induce as much calcium carbonate as possible, but the effect of actual concrete service environment on the repair of concrete cracks was usually ignored. This work compared the repair quality of cracked specimens via MICP with the original Sporosarcina (Sp.) pasteurii strain and salt-tolerant Sp. pasteurii strain in the deionized water and simulated seawater. Then the adverse effects of seawater ions on the MICP process was investigated. The results showed that the permeability coefficient of repaired specimens was 175.7 % higher, and the bond strength between the calcium carbonate and concrete surface was lower in the simulated seawater as compared with the deionized water environment. The high concentration of sodium, chloride, magnesium, and sulfate ions in the seawater led to the decrease of the urea decomposition rate and calcium carbonate yield rate, which further induced the decreased super-saturation of calcium carbonate and the conversion of the calcium carbonate crystal form from calcite to vaterite. Besides, the salt-tolerant strain with a high salt adaptability showed a higher repair ability in the simulated seawater as compared with the original strain.

Synthesis of seawater-derived superhydrophobic calcium carbonate via CO2 mineralization by utilizing L-Arginine/L-Lysine oleate-based self-assembly structures

Superhydrophobic materials have been gaining popularity owing to their self-cleaning, anti-freezing, and anti-corrosion properties. This study presents an approach for the synthesis of superhydrophobic calcium carbonate via CO2 mineralization using carbon capture utilization (CCU) technology. By using biodegradable amino acids (L-arginine/L-lysine) and oleic acid, various biosurfactant self-assembly structures were formed as surface-modifying agents of calcium carbonate owing to the saponification and lyotropic phase transition. Moreover, calcium cations were recovered from salt-farm wastewater using pH-swing ion separation for sustainability and waste management. we presented various self-assembly structures depending on the ratio of amino acids to oleic acid, such as spherical micelles, liquid crystal nanoparticles, and vesicles for L-arginine oleate and spherical micelles, cylindrical micelles, and planar lamellar structures for L-lysine oleate. The synthesized calcium carbonates were 87.95 % purified scalenohedral calcite under micellar L-arginine oleate and 87.08 % purified spherical calcite under micellar L-lysine. Moreover, their surface areas were 28.85 m2/g for L-arginine and 13.46 m2/g for L-lysine. They were significantly improved and larger than that of commercial calcium carbonate (3.45 m2/g). In comparison, larger agglomerated calcite particles were produced under the other self-assembled structures. During mineralization, the amount of calcium oleate adsorbed on the surface of calcium carbonate played a crucial role in particle formation. Notably, superhydrophobic calcium carbonates were synthesized with a contact angle of 168.66° under spherical micelles of L-arginine oleate and 167.46° under spherical micelles of L-lysine oleate. The in-situ surface modification method utilizing biosurfactant self-assembled structures was expected to revitalize the carbon capture and utilization.

Preparation and Mechanism of Calcium Carbonate Whiskers from DoLOMITE Refined Solution

AbstractThe preparation of calcium carbonate whiskers by gas‐liquid contact method using low‐grade dolomite refining solution and CO2 as raw materials has attracted widespread attention. The effects of reaction temperature, Mg2+ concentration and pH value on the morphology, particle size, aspect ratio and crystal form of CaCO3（Calcium carbonate） whiskers are investigated in detail. SEM (Scanning Electron Microscope) and XRD (X‐ray powder diffraction) are combined to analyze the calcium carbonate whiskers. The results demonstrated that under the conditions such as 100 °C, Mg2+ concentration of 0.05 mol L−1 and pH value of 9.5, calcium carbonate whiskers with uniform distribution, aspect ratio of 15–20, and purity of 99.38% can be prepared. Through Material Studios simulation software and critical nucleation energy analysis, it is confirmed that the morphology of calcium carbonate whiskers emerged to be a long hexagonal prism. Mg2+ in the refined solution would adhere to the surface of calcium carbonate during carbonization, inhibit the formation of calcite phase, and promote the growth of face clusters connected by vertex angles between CaCO3 crystals. The initial pH condition determines the solubility of CO32− and the supersaturation of the solution, which in turn affected the formed calcium carbonate crystal form.

Preparation of PW@CaCO3 phase change microcapsules modified by ZnO nanoparticles with excellent photocatalytic and thermal properties

We utilized an in-situ polymerization method to dope zinc oxide (ZnO) nanoparticles onto the surface of the inorganic calcium carbonate (CaCO3) shell capable of encapsulating paraffin wax (PW) cores, and synthesized a novel bifunctional microcapsule, which can be applied to optical catalysis and thermal energy storage. The PW@CaCO3/ZnO microcapsules with the varying ZnO nanoparticles were successfully synthesized. The micromorphology, chemical components, thermal properties, and photocatalytic applications of microcapsules doped with various ZnO concentrations were investigated. The results indicated that the PW@CaCO3/0.03%ZnO (i.e., the mass ratio of ZnO to PW of 0.03 wt%) exhibited the greatest thermal storage effectiveness and capacity with regard to all the samples. Under exposure to a particular wavelength of ultraviolet light, the PW@CaCO3/ZnO microcapsules can degrade the methylene blue dye solution by photocatalysis. The photocatalytic effect of the dye solution with PW@CaCO3/1.50%ZnO was the best after 12 h of exposure to ultraviolet radiation, and the degradation rate reached 98.97 %. In the spheres of energy conservation and environmental preservation, the PW@CaCO3/ZnO microcapsules offer a wide range of potential applications.

Nano-modulators with the function of disrupting mitochondrial Ca2+ homeostasis and photothermal conversion for synergistic breast cancer therapy

Breast cancer treatment has been a global puzzle, and apoptosis strategies based on mitochondrial Ca2+ overload have attracted extensive attention. However, various limitations of current Ca2+ nanogenerators make it difficult to maintain effective Ca2+ overload concentrations. Here, we constructed a multimodal Ca2+ nano-modulator that, for the first time, combined photothermal therapy (PTT) and mitochondrial Ca2+ overload strategies to inhibit tumor development. By crosslinking sodium alginate (SA) on the surface of calcium carbonate (CaCO3) nanoparticles encapsulating with Cur and ICG, we prepared a synergistic Ca2+ nano-regulator SA/Cur@CaCO3-ICG (SCCI). In vitro studies have shown that SCCI further enhanced photostability while preserving the optical properties of ICG. After uptake by tumor cells, SCCI can reduce mitochondrial membrane potential and down-regulate ATP production by producing large amounts of Ca2+ at low pH. Near-infrared light radiation (NIR) laser irradiation made the tumor cells heat up sharply, which not only accelerated the decomposition of CaCO3, but also produced large amounts of reactive oxygen species (ROS) followed by cell apoptosis. In vivo studies have revealed that the Ca2+ nano-regulators had excellent targeting, biocompatibility, and anti-tumor effects, which can significantly inhibit the proliferation of tumor cells and play a direct killing effect. These findings indicated that therapeutic strategies based on ionic interference and PTT had great therapeutic potential, providing new insights into antitumor therapy.Graphical

Density functional theory assessed molecular insights into asphaltene interactions within silica and calcium carbonate surface with deep eutectic solvents

Deep Eutectic Solvents (DES) have gained recent attention as asphaltene solvents due to their low cost and eco-friendliness. However, identifying the intermolecular behavior of asphaltene with different DESs using experimental methods is costly and time-consuming. Therefore, this study investigates the intermolecular interactions and electronic properties of DESs with model asphaltene in the presence of sandstone (SiO2) and carbonate (CaCO3) surfaces using Density Functional Theory (DFT) calculations. The study focuses on understanding the binding energies, interaction energies, band gap, and intermolecular mechanism between SiO2 surface, asphaltene, and DESs (SiO2-Asp-DESs systems) and CaCO3 surface, asphaltene, and DESs (CaCO3-Asp-DESs systems). The investigation yields valuable insights into the interactions, stability, and affinity of the asphaltene and DES in the overall system, enhancing understanding of asphaltene behavior in solvent environments. The study shows that DES containing choline chloride as a hydrogen bond acceptor (HBA) outperforms in the presence of both surfaces (SiO2 and CaCO3) with asphaltene. For the SiO2-Asp-DES system, which contains DES as choline chloride and ethylene glycol, a higher intermolecular interaction energy of − 747.174 kJ/mol is observed. In contrast, for the CaCO3-Asp-DES system, DES as choline chloride and glycerol show higher intermolecular interaction energy of − 259.154 kJ/mol. Variations in interaction and binding energies for the systems further show that the effectiveness of DES with asphaltene varies depending on the type of surface (SiO2/CaCO3). As for the overall reactivity, CaCO3-Asp-DESs systems show comparatively less reactivity than SiO2-Asp-DESs systems that show smaller band gaps.

Superhydrophobic fluorescent micro-/nano-composites from carbon dots encapsulated in CaCO3-SiO2

ABSTRACT In this paper, polyamine-functionalized carbon dots (CDs) were synthesized by means of low temperature (<100°C) carbonization of citric acid at the presence of polyethylenimine (PEI), resulting spherical calcium carbonate micro-particles from inverse micro-emulsion system. Nanoscaled spherical silicas were prepared by Stöber method via deposition on the surface of micron calcium carbonate. Scanning- and transmission-electron microscopic analysis confirmed a micro-/nano-complex structure, enabling the composite material coating possessed coarser surface similar to those of ‘lotus leaf’. After modification with 1 H, 1 H, 2 H, 2 H-perfluorodecanethiol, both good super hydrophobicity and good fluorescent performance were confirmed by the water contact angle of 154.1°±1.5°, their surface-free energy, and fluorescence quantum yield of 14.1%, which provides an inexpensive and easy way to fabricate superhydrophobic material with fluorescence characteristics and promotes high value application of inorganic materials.

Enhanced Water Absorbency and Water Retention Rate for Superabsorbent Polymer via Porous Calcium Carbonate Crosslinking.

To improve the water absorbency and water-retention rate of superabsorbent materials, a porous calcium carbonate composite superabsorbent polymer (PCC/PAA) was prepared by copolymerization of acrylic acid and porous calcium carbonate prepared from ground calcium carbonate. The results showed that the binding energies of C-O and C=O in the O 1s profile of PCC/PAA had 0.2 eV and 0.1-0.7 eV redshifts, respectively, and the bonding of -COO- groups on the surface of the porous calcium carbonate led to an increase in the binding energy of O 1s. Furthermore, the porous calcium carbonate chelates with the -COO- group in acrylic acid through the surface Ca2+ site to form multidirectional crosslinking points, which would increase the flexibility of the crosslinking network and promote the formation of pores inside the PCC/PAA to improve the water storage space. The water absorbency of PCC/PAA with 2 wt% porous calcium carbonate in deionized water and 0.9 wt% NaCl water solution increased from 540 g/g and 60 g/g to 935 g/g and 80 g/g, respectively. In addition, since the chemical crosslinker N,N'-methylene bisacrylamide is used in the polymerization process of PCC/PAA, N,N'-methylene bisacrylamide and porous calcium carbonate enhance the stability of the PCC/PAA crosslinking network by double-crosslinking with a polyacrylic acid chain, resulting in the crosslinking network of PCC/PAA not being destroyed after water absorption saturation. Therefore, PCC/PAA with 2 wt% porous calcium carbonate improved the water-retention rate by 244% after 5 h at 60 °C, and the compressive strength was approximately five-times that of the superabsorbent without porous calcium carbonate.

Influence of magnetic field on the physicochemical properties of water molecule under growing of cucumber plant in an arid region

This study highlights the potential impact of magnetic fields on water quality, which could have implications for plant growth and development. Theoretical estimates of changes in surface tension, pH, and some other properties due to passing water through a magnetic field for a certain period were experimentally validated in this study. Overall, the results revealed changes in the physicochemical properties of water after magnetic field application. In accordance, pH significantly (p < 0.05) increased from 2 to 2.25, from 4 to 4.5, from 6 to 6.45, from 7.3 to 7.8, and from 8 to 8.7 and except at pH10, which decreased from 10 to 9.7. In addition, the model developed in this study indicated that the change of electrical conductivity (EC) decreased from 9 to 6.11 dS m−1 with an increasing number of run flow through the magnetic field. The decline in EC can be described as follows: magnetically treated water contains fine colloidal molecules and electrolytic chemicals that respond to a magnetic field by enhancing their ability for precipitation, resulting in a fall in EC. Moreover, the Hardness values of recirculated water were decreased after magnetic field application. This corroborates the decline of calcium carbonate adhesion and surface tension values as increases in hydrogen bonding between protons and water molecules and changes in the distribution of molecules in magnetized water. As the internal electrical field grew and the hydration shells surrounding the constituent ions weakened, EC decreased. Lastly, by using an electronic microscope, observing the water in regular, such as regular hexagonal tree shape instead of random irregular shapes after magnetic field application, confirming that the magnetic field had a significant effect on the physical properties of water molecules. In conclusion, magnetic behavior may improve water quality, resulting in increased development and plant growth.

MICROBIAL-INDUCED CALCITE PRECIPITATION" AS A POTENTIAL SUSTAINABLE TECHNIQUE FOR POLLUTED SOIL BIOREMEDIATION: A REVIEW

Industrialization and population growth have increased the emission and buildup environmental heavy metals. These components' bioaccumulations as exposure have been related to a range of illnesses and cancer, and the mechanical and physical properties of soil are altered. The "Microbial Induced Calcite Precipitation" is environmentally green, friend and sustainable method. This review focused on the metal remediation technology's effects and how to make them sustainable and more environmentally friendly. Many bacteria that produces urease, bacillus is a more common type. Bacteria, with sizes ranging from 0.5 to 3.0µm, are the most common microbes found in soils. It is critical to examine the type of soil, Bacterial size, and size of pore throat. The calcium carbonate majority tend to coat the surface of soils with coasrse particles in state of the contact points in soils with particles smaller than bacterial size (heterogeneous and limited precipitation). The bacterial concentration appears to affect crystal shape, calcium carbonate formation, and the cementation effect of geomaterials. Calcite precipitation takes place most when the pH is between 7.5 and 9.5. Calcite is formed three times at 50°C, while the unconfined compressive strength is only 60% of that at 25°C.Calcium carbonate can be immobilized or formed into undissolved compounds by binding free ions to the calcium carbonate's surfaces, resulting in a form of non-toxic and chemically stable.

Fabrication of Porous Phosphate/Carbonate Composites: Smart Fertilizer with Bimodal Controlled-Release Kinetics and Glyphosate Adsorption Ability.

A simple method to prepare phosphate/carbonate composites for use as porous sponge-like phosphate fertilizers (ps-PO4Fs) is presented. The composites ps-PO4Fs were prepared by ion-exchange implantation of phosphate onto the surface of vaterite-phase calcium carbonate (CaCO3) microparticles. The ps-PO4Fs obtained under the optimized conditions were found to contain a nanoscale porous network of calcium phosphate covering the CaCO3 support. In addition, ps-PO4Fs exhibited two distinct phosphate release modes having different kinetics: a fast-release step over the initial 24 h period following a parabolic diffusion model, indicating controlled diffusion from external surfaces/edges, and a second slow-release step over the course of a month following the Ritger–Peppas model, indicating the release and diffusion of phosphate adsorbed at specific sites. The ps-PO4Fs also adsorbed glyphosate well because of their porous structure and large surface area. However, glyphosate adsorption prevented phosphate release at concentrations greater than 10 mg L–1. The ps-PO4Fs were tested for their effects on plant growth and showed effects similar to commercial fertilizers. In summary, these smart, eco-friendly, and multifunctional fertilizers having two-stage phosphate release could enable the application of lower amounts of fertilizer and remove excess glyphosate from the environment.

Study of parameter affecting morphology of electrospun poly (lactic acid) (PLA) fibers loaded with Ag/CaCO3 filler

Silver nanoparticles (AgNPs) are widely used as antimicrobial agent in commercial products like textiles, cosmetics and drugs. AgNPs deposited on the surface of calcium carbonate (CaCO3) particles, serve as sustained release of antimicrobial activity. The silver nanoparticles embedded calcium carbonate particles (Ag/CaCO3) are prepared by a precipitation method. In this study, precipitated (Ag/CaCO3) filler will be used for preparation of Ag/CaCO3-poly(L-lactic acid) (Ag/CaCO3-PLA) nanofibers by electrospinning. Polymer concentration and functional filler amount in binary solvent system will be studied. The condition for fabricating electrospun PLA and Ag/CaCO3-PLA was a 15 cm of collection distance and 15 kV of working voltage. Morphology of Ag/CaCO3 loaded PLA electrospun fibers will be investigated by the field emission scanning electron microscope (FE-SEM). The electrospun fibers will be further applied as the antimicrobial material.

Silver@Hydroxyapatite functionalized calcium carbonate composites: characterization, antibacterial and antibiofilm activities and cytotoxicity

Silver@Hydroxyapatite functionalized calcium carbonate composites have been prepared through different sustainable methods, without involving the use of organic solvents and additional reagents. The composites were characterized by X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, spectrophotometric measurements and X-ray photoemission spectroscopy. From the characterization techniques, the obtained nanoparticles resulted constituted essentially by Ag3PO4 nanostructures, whose size varied from 70 to 100 nm and were uniformly distributed on the calcium carbonate surface. Upon VIS irradiation, the formation of plasmonic nanostructures with a more defined dimensional distribution and reduced size could be obtained, as a prove of a partial silver reduction. All composites exhibited good antimicrobial and antibiofilm activities against Staphylococcus aureus and Pseudomonas aeruginosa whereas they showed low cytotoxicity effects towards human skin keratinocytes and human fibroblasts. These results enable these composites to be promising candidates for biomedical and pharmaceutical applications.

Regenerable solvents mediate accelerated low temperature CO2 capture and carbon mineralization of ash and nano-scale calcium carbonate formation

The dual need to remove CO2 from our emissions and treat alkaline industrial residues such as ash materials motivate the design of innovative pathways to simultaneously capture and convert CO2 into mineralized carbonates. Direct carbon mineralization is one approach that addresses the need to simultaneously treat alkaline industrial residues and mineralize CO2 emissions. Low CO2 solubility in water and slow kinetics at ambient temperature have challenged the direct carbon mineralization of alkaline industrial residues. To address these challenges, the use of CO2 capture solvents that enhance CO2 solubility and facilitate accelerated carbon mineralization of fly ash at temperatures below 90 °C is investigated. Calcium carbonate formation results in the inherent regeneration of the solvent. The carbon mineralization extents of non-calcium carbonate content in fly ash were 50% and 51% and in waste ash were 58% and 62% in 2.5 M sodium glycinate and 30 wt% MEA solutions, respectively. The experiments were performed at 50 °C for 3 h with CO2 partial pressure of 1 atm in a continuously stirred slurry environment with 15 wt.% solid. Furthermore, nanoscale CaCO3 is successfully synthesized from dissolved calcium using CO2-loaded sodium glycinate and surfactants such as CTAB (Cetyl Trimethyl Ammonium Bromide). Surfactants such as CTAB bind to the calcium carbonate surface and regulate the growth of calcium carbonate particles. These innovative approaches demonstrate the feasibility of directly storing CO2 in fly ash and waste ash as calcium carbonate and producing nanoscale calcium carbonate using regenerable CO2 capture solvents.

Properties and Degradability of Poly(Butylene Adipate-Co-Terephthalate)/Calcium Carbonate Films Modified by Polyethylene Glycol.

Poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable polymer synthesized from petrochemical resources. PBAT has an exceptionally high elongation at break values which makes it one of the most promising substitutes for LDPE packaging films. However, the applicability of PBAT films is still limited by low strength and high production costs. In this work, we used polyethylene glycol 600 (PEG-600) as a coating agent to modify the surface of calcium carbonate and improve compatibility with the polymer matrix. A series of PBAT/CaCO3 composite films having different CaCO3 particle size and content of coating agent was prepared using extrusion blow molding. The effect of particle size of CaCO3 filler and the content of a coating agent on the mechanical and rheological properties of composite films have been studied. The biodegradation properties have been tested by burying the samples in soil or keeping them in artificial seawater for 90 days. It was shown that the addition of PEG-600 improves compatibility between the matrix and CaCO3 filler as polar –OH groups of PEG have a high affinity toward the polar surface of CaCO3. Moreover, the hydrophilicity of PEG-600 increased the diffusivity of water molecules and facilitated PBAT degradation. This work provides experimental data and theoretical guidance that support the development of high-performance PBAT/calcium carbonate films for the single use packaging industry.

Characteristics of sandy soil treated using EICP-based urease enzymatic acceleration method and natural hemp fibers

This study presents the use of biocementation process with EICP-based urease enzymatic acceleration method and natural hemp fibers to improve the strength of sandy soil. The amount of hemp fibers mixed in the sandy soil is varied up to 20% by volume. Different tests are used, and results are observed. From real-time bender element tests, the optimum amount of natural hemp fibers for mixing in biocemented sand is found to be 2.5% by volume, based on shear wave velocity and initial shear modulus. Moreover, the process of biocementation requires a few days before the start of reaction, and the reaction fully occurs at 4-day while finishes at 6-day. Using pH meter, it is found that the process of biocementation reaches its maximum value at 3-day, because the solution pH in sand becomes higher than 7. After that, the biocementation reaction rate decreases due to the reduction of the solution pH. From spectophotometer, the ammonification occurs from 0-day to 4-day, and reaches its maximum at 4-day. After that, it gradually decreases showing the gradual end of biocementation reaction. The SEM results show that the surface of natural hemp fibers and precipitated calcium carbonate (CaCO3) crystals are rough indicating the potential for bonding between them. The SEM results also show that the precipitated CaCO3 fills within the voids between sand particles and natural hemp fibers, resulting in the enhancement of sandy soil strength. The XRD results show the relationship between the occurrence of CaCO3 and the process of biocemented in sand. Finally, the direct shear tests confirm the improvement of sandy soil properties via increasing cohesion and internal friction angle due to biocementation and hemp fibers.

Preparation and Characterization of Starch Active Interface Calcium Carbonate for Biodegration

Calcium carbonate is so hard to be further developed in polymer applications because it is difficult to combine with other materials. Starch-coated calcium carbonate was prepared by using starch as the main modifier and sodium stearate and sodium hexametaphosphate as the auxiliary modifiers. Optimal modification conditions were tested by single factor experiment and orthogonal experiment optimization. Manifestation was evaluated with the help of Fourier infrared spectrometer (FT-IR) and laser particle size analyzer and other test instruments. Results showed that a starch film was successfully coated on the surface of calcium carbonate, and the edges and corners of the modified coated calcium carbonate were passivated, and the particles were rounded. The active interface calcium carbonate has a broad application prospect in the field of degradable biomaterials.

Calcium Carbonate@silica Composite with Superhydrophobic Properties.

In this paper, spherical calcium carbonate particles were prepared by using CaCl2 aqueous solution + NH3·H2O + polyoxyethylene octyl phenol ether-10 (OP-10) + n-butyl alcohol + cyclohexane inverse micro emulsion system. Then, nanoscale spherical silica was deposited on the surface of micron calcium carbonate by Stöber method to form the composite material. Scanning electron microscope (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and structure of the composite material. It is found that the surface of the composite material has a micro-nano complex structure similar to the surface of a “lotus leaf”, making the composite material show hydrophobicity. The contact angle of the cubic calcium carbonate, spherical calcium carbonate and CaCO3@SiO2 composite material were measured. They were 51.6°, 73.5°, and 76.8°, respectively. After modification with stearic acid, the contact angle of cubic and spherical CaCO3 were 127.1° and 136.1°, respectively, while the contact angle of CaCO3@SiO2 composite was 151.3°. These results showed that CaCO3@SiO2 composite had good superhydrophobicity, and the influence of material roughness on its hydrophobicity was investigated using the Cassie model theory.