Facile extraction and characterization of calcium hydroxide from paper mill waste sludge of Bangladesh

Herein, paper mill waste sludge (PMS) from two different sources has been investigated to extract calcium hydroxide, Ca(OH)₂ by a facile and inexpensive extraction process. PMS samples, collected from local paper mill plants of Bangladesh, were the main precursors wherein HCl and NaOH were used for chemical treatment. The as-synthesized products were analysed by a variety of characterization tools including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) elemental analyses. Our studies confirm that the extracted product contains Ca(OH)₂ as a major content, albeit it also includes CaCO₃ phase owing to the inescapable carbonation process from the surrounding environment. The particle size of the synthesized products is in the range of 450-500 nm estimated from SEM micrographs. The crystallite domain size of the same estimated from XRD analyses and was found to be approximately 47 and 31 nm respectively for product-A and product-B considering major (101) Bragg peak of Ca(OH)₂. The yield percentage of the isolated products is about 65% for samples collected from both sources.

Phyto-complexation of galactomannan-stabilized calcium hydroxide and selenium-calcium hydroxide nanocomposite to enhance the seed-priming effect in Vigna radiata

The evaluation of nano-priming effect with galactomannan stabilized Phyto-complexed calcium hydroxide (Ca(OH)₂), selenium oxyanion‑calcium hydroxide SeO-(Ca(OH)₂), and selenium‑calcium hydroxide Se-(Ca(OH)₂) nanocomposites was carried out in Vigna radiata (Green gram) seeds. The green source Cassia angustifolia seed rich in galactomannan and other phytoconstituents was detected experimentally and characterized with GC-MS, UV, FT-IR, NMR, XRD, and SEM studies. The highly active galactomannan and other biomolecules, enable their terminal oxygen and hydroxide groups to bind with calcium and selenium ions through bidentate and monodentate chelation, followed by bio-reduction. On the mild-thermal agitation, bio-stabilized (Ca(OH)₂), SeO-(Ca(OH)₂), and Se-(Ca(OH)₂) nanocomposite coated with seed-derived biomolecules were precipitated under an alkaline condition. The size and morphological parameters of bio-fabricated nanocomposites were characterized to exhibit the spherical and hexagonal shape in nanoscale images of size 17.9 nm for (Ca(OH)₂), 56.2 nm for SeO-(Ca(OH)₂), and 69.3 nm Se-(Ca(OH)₂). The sub-standard seed lot of Vigna radiata (Green gram) seeds (71%) was examined using synthesized nanocomposites at various concentrations, and the obtained physiological parameters in seedlings were compared with hydro-primed seeds. The nano-priming action of all the Phyto-complexed nanocomposites was predicted with a positive response, where the porous Se-(Ca(OH)₂) possess high efficacy interaction on seed embryos and beneficially results at 90% germination.

Important role of calcium chloride in preventing carbon monoxide generation during desflurane degradation with alkali hydroxide-free carbon dioxide absorbents

We investigated whether calcium chloride (CaCl₂), a supplementary additive in carbon dioxide (CO₂) absorbents, could affect carbon monoxide (CO) production caused by desflurane degradation, using a Japanese alkali-free CO₂ absorbent Yabashi Lime^®-f (YL-f), its CaCl₂-free and 1% CaCl₂-added derivatives, and other commercially available alkali-free absorbents with or without CaCl₂. The reaction between 1 L of desflurane gas (3-10%) and 20 g of desiccated specimen was performed in an artificial closed-circuit anesthesia system for 3 min at 20 or 40 °C. The CO concentration was measured using a gas chromatograph equipped with a semiconductor sensor detector. The systems were validated by detecting dose-dependent CO production with an alkali hydroxide-containing CO₂ absorbent, Sodasorb^®. Compared with YL-f, the CaCl₂-free derivative caused the production of significantly more CO, while the 1% CaCl₂-added derivative caused the production of a comparable amount of CO. These phenomena were confirmed using commercially available absorbents AMSORB^® PLUS, an alkali-free absorbent with CaCl₂, and LoFloSorb™, an alkali-free absorbent without CaCl₂. These results suggest that CaCl₂ plays an important role in preventing CO generation caused by desflurane degradation with alkali hydroxide-free CO₂ absorbents like YL-f.

Characterization of Chlorhexidine-Loaded Calcium-Hydroxide Microparticles as a Potential Dental Pulp-Capping Material

This study explores the delivery of novel calcium hydroxide [Ca(OH)₂] microparticles loaded with chlorhexidine (CHX) for potential dental therapeutic and preventive applications. Herein, we introduce a new approach for drug-delivery to deep dentin-surfaces in the form of drug-loaded microparticles. Unloaded Ca(OH)₂ [Ca(OH)₂/Blank] and CHX-loaded/Ca(OH)₂ microparticles were fabricated by aqueous chemical-precipitation technique. The synthesized-microparticles were characterized in vitro for determination of surface-morphology, crystalline-features and thermal-properties examined by energy-dispersive X-ray scanning and transmission electron-microscopy (EDX-SEM/TEM), Fourier-transform infrared-spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning-calorimetry (DSC). Time-related pH changes, initial antibacterial/biofilm-abilities and cytotoxicity of CHX-loaded/Ca(OH)₂ microparticles were evaluated. Microparticles were delivered to dentin-surfaces with subsequent SEM examination of treated dentin-substrates. The in vitro and ex vivo CHX-release profiles were characterized. Ca(OH)₂/Blank were hexagonal-shaped with highest z-average diameter whereas CHX-inclusion evidenced micro-metric spheres with distinguishable surface “rounded deposits” and a negative-shift in diameter. CHX:Ca(OH)₂/50 mg exhibited maximum encapsulation-efficiency with good antibacterial and cytocompatible properties. SEM examination revealed an intact layer of microparticles on exposed dentin-surfaces with retention of spherical shape and smooth texture. Microparticles loaded on dentin-surfaces showed prolonged release of CHX indicating substantial retention on dentin-substrates. This study validated the inherent-applicability of this novel drug-delivery approach to dentin-surfaces using micro-metric CHX-loaded/Ca(OH)₂ microparticles.