Micron-sized Calcium Carbonate Research Articles

CaCO3-based carriers with prolonged release properties for antifungal drug delivery to hair follicles.

Superficial fungal infections are of serious concern worldwide due to their morbidity and increasing distribution across the globe in this era of growing antimicrobial resistance. The delivery of antifungals to the target regions of the skin and sustaining the effective drug concentration are essential for successful treatment of such mycoses. Topical formulations get extra benefits here if they penetrate into the hair follicles since fungal hyphae can proliferate and produce spores in such reservoirs. We designed a novel particulate system for the encapsulation and intrafollicular delivery of griseofulvin (Gf) antifungal drug, which is water-insoluble and currently commercially available in oral dosage forms. Micron-sized calcium carbonate (vaterite) carriers containing 25 ± 3% (w/w) of Gf were prepared via the wet chemical method. The successful in vivo transportation of the carriers into the hair follicles of rats was demonstrated using scanning electron and confocal laser scanning microscopy. In addition, we introduced an approach toward Gf release prolongation for the proposed system. The stabilizing coatings were formed on the surface of the obtained particles via the layer-by-layer technique. The formulations displayed sufficient biocompatibility and good cellular uptake in contact with fibroblast cells in vitro. Four different coatings were tested for their preserving ability in the course of continued carrier incubation in the model media. The best release prolonging formulation liberated 38% of the loaded Gf during 5 days, while the uncoated carriers demonstrated more than 50% drug release within the first 24 h in water. To assess the in vivo release properties, free Gf drug and Gf-loaded carriers (uncovered and covered with the stabilizing shell) were administered topically in rats and the drug excretion profiles were further studied. By comparing the daily Gf levels in urine, we verified the sustained effect (longer than a week) of the stabilizing shell formed on the carrier surface. Conversely, the application of the free drug did not provide reliable Gf detection for this period. These findings open new prospects for the efficiency enhancement of topical therapeutics. Importantly, the elaborated system could be adapted for the dermal delivery of various water-insoluble drugs beyond the scope of antifungal therapy.

Real-time monitoring and insights into process control of micron-sized calcium carbonate crystallization by an in-line digital microscope camera

In the present study, a crystallization monitoring unit consisting of an in-situ digital microscope camera and real-time image analysis is utilized for monitoring and control of a micron-sized, liquid-liquid crystallization of calcium carbonate. The crystallization process is integrated with a membrane contactor-based carbon dioxide capture process to demonstrate a sustainable CO2-to-chemical unit operation. The measurement probe transilluminates the crystal suspension and provides a live view from the crystallizer. In a series of open-loop experiments, the effects of several operating conditions such as feed flow rate and volumetric power on crystal size and particle count are investigated. For comparison purposes, solid product crystals are assessed with an offline laser diffraction technique. In the closed-loop experiments, the controlled variable is average particle diameter, and the manipulated variable is mixing intensity. The implemented set-point tracking PI controller generates actuating signals based on real-time image analysis measurement of the crystal size. Experimental results demonstrate a practical approach for measuring micron-sized particle suspensions, which is a challenge for particles with a mean diameter smaller than 15–20 μm, provides insights into the mixing intensity-based particle size controllability in fast-reaction precipitation systems and offers a framework to implement a direct design feedback control policy.

Buffered accelerated weathering of limestone for storing CO2: Chemical background

We present an evolution of the Accelerated Weathering of Limestone (AWL) method to store CO2 in seawater in the form of bicarbonates. Buffered Accelerated Weathering of Limestone (BAWL) is designed to produce a buffered ionic solution, at seawater pH, which derives from the reaction between a CO2 stream and a powder of micron-sized calcium carbonate particles in a long tubular reactor. Addition of calcium hydroxide to buffer the unreacted CO2 before the discharge in seawater is also provided. BAWL aims to overcome the main limitations of AWL, such as the high amount of water needed, the large size of the reactor, the risk of CO2 degassing back into the atmosphere, if the ionic solution is released into shallow waters, as well as the induced seawater acidification. This paper presents the chemical background of the technology and evaluates its feasibility by considering the chemical equilibria in the different phases of the process. The CO2 emitted for limestone calcination leads to a 24% CO2 penalty; a preliminary cost analysis assesses a storage cost of 100 € per tonne of CO2 from an external source. It finally discusses the main features to be considered for the design at the industrial scale.

Integration of a calcium carbonate crystallization process and membrane contactor–based CO2 capture

This research work presents the integration of polypropylene hollow fiber membrane contactor–based CO2 absorption unit using aqueous sodium hydroxide (NaOH) as the absorbent solution, and precipitation of high-quality calcium carbonate by addition of calcium chloride. The integrated crystallization process bypasses the need for cost-intensive energy regeneration of the absorbent solution. Given the lifetime of high added value precipitated calcium carbonate, the proposed approach for integrating solid particle formation and a carbon dioxide mitigation technique can be considered as a potential post-combustion technology for carbon capture, utilization and sequestration (CCUS). The overall CO2 mass transfer coefficient in the membrane contactor and subsequent crystallization process was investigated by conducting the experiments at different operating conditions. For a maximum hydroxide concentration of 5.01molL-1, an overall mass transfer coefficient of 2.25·10-4ms-1 and CO2 flux of 2.45·10-4molm-2s-1 were obtained for a 0.5Lmin-1 of gas flow rate. The proposed liquid–liquid crystallization process produces a narrow size distribution of micron-sized calcium carbonate with a mean diameter of 3–8 µm that can be used in the paper, coatings, food and biomedical industries.

Dynamic modeling and semibatch reactive crystallization of calcium carbonate through CO2 capture in highly alkaline water

A laboratory scale integration of carbon capture and utilization (CCU) technique operating based on highly alkaline aqueous hydroxide sorbents with a semibatch reactive crystallization process of calcium carbonate is presented. The study was conducted with a focus on investigating the kinetics of the crystallization process for CCU applications, where the production of micron-sized calcium carbonate particles occurs by direct addition of CO2-loaded solution to a crystallizer containing calcium chloride.Within this system, the need for high temperature heat consumption above 800 °C (109.4 kJ/mol CO2) for CO2 decomposition from Na2CO3 is avoided by production of value-added chemical from carbonate reach solution. The current set-up enables potential pre-treatment of carbon emission sources due to separate absorption and liquid-liquid crystallization processes. This leads to production of high-purity solid particles in comparison to conventional industrial practices.Experiments were carried out at several operating conditions at ambient temperature and pressure and effect of the absorbent solution concentration on CO2 capture efficiency and subsequently the precipitation yield was analyzed. Based on coupling the standard method of moments approach of the population balance formulation with power-law kinetic expressions, a correlation was extracted between the growth rate constant and feed flow rate for the adopted process. Moreover, characterization of the precipitated sample indicates the vaterite polymorphs of calcium carbonate as the dominant crystals in the pH range of 7.9–10.4. These types of demonstrations could contribute to circular economy processes using waste materials and can be considered as a potential approach toward an efficient carbon capture and valorization technique.

Improve Plant Photosynthesis by a New Slow-Release Carbon Dioxide Gas Fertilizer.

In the natural state, the concentration of carbon dioxide in the atmosphere is about 300 μmol mol–1. Plants need a suitable balance of CO2 to achieve optimal growth. The optimum CO2 content corresponding to a high photosynthesis rate is between 0.1 and 1.0% by volume. However, air has only a CO2 content of 0.03% by volume, so plants cannot use all of their growth potential. The use of fertilizer to assist in the supply of CO2 increases the rate of photosynthesis. In this work, a slow-release CO2 gas fertilizer inspired by polyphenol chemistry was prepared to provide sustainable CO2 that could improve plant photosynthetic capacity and get a higher crop yield. The core–shell structure was designed to confer gas fertilizers slow-release property. Micron-sized calcium carbonate particles with uniform particle size and regularity morphology, as carbon sources for plant photosynthesis, was a core, and tannic acid was coated on it as a shell via oxidative oligomerization and cross-linked by polyetherimide. The structure and morphology of fertilizers were characterized by scanning electron microscopy, X-ray energy dispersive spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. In vitro experiments, the prepared fertilizers were proved to have slow-release properties. And then through net photosynthesis rate, chlorophyll fluorescence parameters, chlorophyll content, leaf area, leaf mass per area, and dry matter to study the effects of slow-release CO2 gas fertilizers on plant physiology of Brassica chinensis. The results revealed that the slow-release CO2 gas fertilizers not only had good slow-release properties but also can well improve plant photosynthesis.

One-pot synthesis of bio-inspired layered materials of 3D graphene network/calcium carbonate

A bio-inspired layered material of reduced graphene oxide (RGOs) and calcium carbonate was synthesized via a one-pot strategy in DMF/H2O mixed solvent. The experimental results show that the product is a layered material of wrinkled RGOs networks and micron-sized calcium carbonate particles with uniform granular diameter and homogeneous morphology, which are distributed between the layered gallery of the graphene scaffold. The polymorph and the morphology of the in-situ produced calcium carbonate particles can be manipulated by simply changing the temperature scheme. Besides, the graphene oxide was reduced to a certain extent, and the hierarchical wrinkles were generated in the RGOs layer by the in-situ formation of the calcium carbonate particles. This work provides a facile and controllable strategy for synthesizing layered material of RGOs and carbonates, and also presents a platform for making three-dimensional porous wrinkled RGOs networks.

Study of mechanical and physical properties of LLDPE-G-MA injection grade reinforced with coffee husk post-industrial waste

In this work, the evaluation of a post-industrial residue of coffee industry (coffee husk) as organic filler in functionalised linear low-density polyethylene matrix was investigated. The properties of these composites were compared with more widely used inorganic fillers, such as calcium carbonate and SiO2. All the composites were prepared by grafting of linear low-density polyethylene maleic anhydride and then by melt mixing of fillers. The rheological behaviour of the compounds during processing was established to evaluate the effects of a nanosized (SiO2), micron sized calcium carbonate and coffee husk fillers. Additionally, thermal, morphological and mechanical properties of the polymer composites were evaluated. The results indicated an increase in tensile modulus and tensile strength resulting from incorporation of fillers in the polymer matrix. Some relevant modifications of melting temperature and crystallinity degree for coffee husk composites were observed, but not observed for inorganic fillers composites. The properties of the composites prepared with coffee husk were comparable to those obtained with inorganic fillers, demonstrating that this coffee residue can be used as filler for obtaining composites for many possible applications.

Study of Tribological Behavior of ABS/ CaCO3 Composite Using Grey Relational Analysis

The tribological properties of acrylonitrile-butadiene-styrene (ABS) polymer filled with micron-sized calcium carbonate (CaCO3) are studied in this paper. Filler content, normal load and sliding speed are considered as design parameters and coefficient of friction (COF) and specific wear rate are considered as the responses. The experiments are conducted on multi-tribotester (block-on-roller configuration) based on L27 orthogonal array (OA). The optimum design parameter combination for minimum coefficient of friction and specific wear rate are found using grey relational analysis. The optimum parameter combination is found to be 5% of filler content, 35N of load and 120rpm of speed. Analysis of variance (ANOVA) is also used to find out the most influential factor which affects the tribological properties. The most influential factor is normal load followed by sliding speed and filler content. Further, a confirmation test is carried out to validate the result and it is seen that the grey relational grade is increased about 72.56% from the initial to the optimum condition. Finally, surface morphology is studied using scanning electron microscopy (SEM).

PH-controlled drug loading and release from biodegradable microcapsules

Microcapsules made of biopolymers are of both scientific and technological interest and have many potential applications in medicine, including their use as controlled drug delivery devices. The present study makes use of the electrostatic interaction between polycations and polyanions to form a multilayered microcapsule shell and also to control the loading and release of charged drug molecules inside the microcapsule. Micron-sized calcium carbonate (CaCO 3) particles were synthesized and integrated with chondroitin sulfate (CS) through a reaction between sodium carbonate and calcium nitrate tetrahydrate solutions suspended with CS macromolecules. Oppositely charged biopolymers were alternately deposited onto the synthesized particles using electrostatic layer-by-layer self-assembly, and glutaraldehyde was introduced to cross-link the multilayered shell structure. Microcapsules integrated with CS inside the multilayered shells were obtained after decomposition of the CaCO 3 templates. The integration of a matrix (i.e., CS) permitted the subsequent selective control of drug loading and release. The CS-integrated microcapsules were loaded with a model drug, bovine serum albumin labeled with fluorescein isothiocyanate (FITC-BSA), and it was shown that pH was an effective means of controlling the loading and release of FITC-BSA. Such CS-integrated microcapsules may be used for controlled localized drug delivery as biodegradable devices, which have advantages in reducing systemic side effects and increasing drug efficacy.

Study on mechanical property of epoxy composite filled with nano-sized calcium carbonate particles

Epoxy resin (EP) is used widely nowadays as a structural, adhesive and electronic material due to exhibiting high strength, high elastic modulus, high insulation etc. [1]. However, EP may show limitations, especially over-fragility in application, so other constituents have to be added to improve its performance. Methods of toughening EP has long been sought, and one of the most common methods is the incorporation into EP of a dispersed rubbery elastomer, which can enhance impact strenght of EP at the expense of weakening rigidity and heat-resistance of the matrix as well as raising cost [2]. Calcium carbonate is considered as a suitable substitute for rubbery elastomer in EP matrix because it demonstrates high rigidity and may overcome the shortcomings of rubbery elastomer if incorporated well into the EP matrix. Traditionally, micron-sized calcium carbonate is added into polymers for the purpose of reducing formulation cost of the polymer-based composites. Nevertheless, micron-sized calcium carbonate may have negative impact on the mechnical performance of polymers. It was reported that mechanical properties of polymers could be otherwise improved by adding nano-sized fillers. Generally, mechanical behaviors of particulate-filled polymers, which have a very complex dependence on the interfacial bonding between the filler and the matrix, are influenced strongly by factors such as size, content and shape of the filler. Of these fillers, nano-sized calcium carbonate (nano-CaCO3) particles have attracted considerable attention and play effective role in many composite systems [3]. This work reports an investigation of the influence of nano-CaCO3 on the mechanical properties fo EP composite. Nano-CaCO3 employed in this experiment, with a cubic shape and an average diameter of 40 nm (Fig. 1), was synthesized by the reactive precipitation reaction method under high gravity environment. Detailed methodology and basic theory about the preparation of nano-CaCO3 by this method can be found in the reference [4]. The dispersion degree of the filler in the matrix will significantly influence the properties of composite. However, it is very difficult to disperse nano-sized particles in a high viscous polymer matrix. Generl method is to introduce a high shearing force to the mixture in order to intermix the fillers with the matrix [5].

Strengthening acrylonitrile-butadiene-styrene (ABS) with nano-sized and micron-sized calcium carbonate

ABS was reinforced by both micron-sized (MCC) and nano-sized precipitated calcium carbonate (NPCC) particles through melt compounding. The MCC/ABS composites were found to have higher modulus but lower tensile and impact strength than neat ABS. In contrast, NPCC increased modulus of ABS whilst maintained or even increased its impact strength for a certain NPCC loading range. SEM examinations revealed that NPCC particles/agglomerates were distributed in much smaller sizes in the composites than its MCC counterparts. The larger interfacial area between NPCC and ABS and cavitation-induced shear yielding in the ligament are believed to be the main reasons of the mechanical property improvement of the NPCC/ABS composites. NPCC/ABS also shows completely different rheological behavior from MCC/ABS, such as the loss of Newtonian region, high G′ at low frequencies and the appearance of yield phenomenon. A NPCC network structure was believed to be formed in the composites and induced these pseudo-solid-like rheological behaviors.