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    Conversion of bivalve shells to monocalcium and tricalcium phosphates: An approach to recycle seafood wastes
    (2021-08-02) ; ;
    Chaiseeda, Kittichai
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    Laohavisuti, Nongnuch
    The search for sustainable resources remains a subject of global interest and the conversion of the abundantly available bivalve shell wastes to advanced materials is an intriguing method. By grinding, calcium carbonate (CaCO<inf>3</inf>) powder was obtained from each shell of bivalves (cockle, mussel, and oyster) as revealed by FTIR and XRD results. Each individual shell powder was reacted with H<inf>3</inf>PO<inf>4</inf> and H<inf>2</inf>O to prepare Ca(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·H<inf>2</inf>O giving an anorthic crystal structure. The calcination of the mixture of each shell powder and its produced Ca(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·H<inf>2</inf>O, at 900 °C for 3 h, resulted in rhombohedral crystal β-Ca<inf>3</inf>(PO<inf>4</inf>)<inf>2</inf> powder. The FTIR and XRD data of the CaCO<inf>3</inf>, Ca(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·H<inf>2</inf>O, and Ca<inf>3</inf>(PO<inf>4</inf>)<inf>2</inf> prepared from each shell powder are quite similar, showing no impurities. The thermal behaviors of CaCO<inf>3</inf> and Ca(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·H<inf>2</inf>O produced from each shell were slightly different. However, particle sizes and morphologies of the same products obtained from different shells were slightly different—but those are significantly different for the kind of the obtained products. Overall, the products (CaCO<inf>3</inf>, Ca(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·H<inf>2</inf>O, and Ca<inf>3</inf>(PO<inf>4</inf>)<inf>2</inf>) were obtained from the bivalve shell wastes by a rapidly simple, environmentally benign, and low-cost approach, which shows huge potential in many industries providing both economic and ecological benefits.
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    Influence of Organic Solvent on the Physicochemical Characteristics of Calcium Citrate Prepared from Mussel Shell Waste
    (2025-06-01)
    Punthipayanon, Sirichet
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    Chanwetprasat, Pantita
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    ; ;
    A green and mild chemical reaction of calcium citrate (CC) was successfully prepared from reactions between mussel shell waste and citric acid in the presence of acetone (AC), ethanol (Et), and isopropyl alcohol (IPA). All the synthesized CCs contained the same functional groups such as citrate (C<inf>6</inf>H<inf>5</inf>O<inf>7</inf><sup>3−</sup>), water (H<inf>2</inf>O), and calcium–oxygen (Ca–O). However, the differences in the spectra pointed out the differences in the crystal environment and structure of CCs. CC-AC and CC-IPA mainly crystallized in the monoclinic [Ca<inf>3</inf>(C<inf>6</inf>H<inf>5</inf>O<inf>7</inf>)<inf>2</inf>(H<inf>2</inf>O)<inf>2</inf>]·2H<inf>2</inf>O crystal system, whereas CC-Et mainly crystallized in the triclinic Ca<inf>3</inf>(C<inf>6</inf>H<inf>5</inf>O<inf>7</inf>)<inf>2</inf>∙(H<inf>2</inf>O)<inf>4</inf> structure. The molecular alignments of triclinic CC-Et were different from monoclinic CC-AC and CC-IPA, resulting in differences in thermal behaviors. Two dehydration steps were observed for the monoclinic CC-AC and CC-IPA, whereas the triclinic CC-Et showed a single dehydration process. The TG mass losses further demonstrated that anhydrous Ca<inf>3</inf>(C<inf>6</inf>H<inf>5</inf>O<inf>7</inf>)<inf>2</inf> phase, in addition to the Ca<inf>3</inf>(C<inf>6</inf>H<inf>5</inf>O<inf>7</inf>)<inf>2</inf>∙4H<inf>2</inf>O, was also observed for CC-AC and CC-IPA, whereas CC-Et contained a single Ca<inf>3</inf>(C<inf>6</inf>H<inf>5</inf>O<inf>7</inf>)<inf>2</inf>∙(H<inf>2</inf>O)<inf>4</inf> phase. The morphologies of CC-AC and CC-IPA also differed from that of CC-Et. The differences in some properties of the synthesized CCs could be attributed to the change in the supersaturation state of the reaction solution. Due to the superior polarity, ethanol is more compatible with citric acid. The presence of ethanol could suppress the supersaturation rate of the reaction solution, causing the modulation of the precipitation mechanisms and reducing the particle growth rate of CC-Et, thereby explaining the difference in vibrational, structural, thermal, and morphological characteristics of CC-Et, compared to CC-AC and CC-IPA.
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    Simple Rapid Production of Calcium Acetate Lactate from Scallop Shell Waste for Agricultural Application
    (2025-05-01)
    Mongkol, Sorakit
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    ; ;
    Laohavisuti, Nongnuch
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    Calcium acetate lactate (CAL) was rapidly synthesized for the first time using the reaction between the scallop shell-derived calcium carbonate (CaCO<inf>3</inf>) and the binary phase of acetic and lactic acids. Calcium acetate (CA) and calcium lactate (CL) synthesized from the reaction of scallop shell-derived CaCO<inf>3</inf> with each acid by similarity routes are compared with the obtained CAL product. The production yields are 88.24, 79.17, and 96.44%, whereas the solubilities are 93.77, 90.18, and 95.08% for CA, CL, and CAL, respectively. All the synthesized CA, CL, and CAL samples were characterized and confirmed by X-ray fluorescence (XRF) to examine the calcium main element and other impurities of minor elements, X-ray diffraction (XRD) to investigate the crystallography, Fourier transform infrared (FTIR) to characterize the vibrational characteristics of the functional groups, scanning electron microscope (SEM) to observe the sample morphologies, and the thermogravimetric analysis (TGA) to investigate the thermal decomposition processes of samples. The experimental results pointed out that the synthesized CA, CL, and CAL were the monohydrate, pentahydrate, and dihydrate forms with chemical formulae of Ca(CH<inf>3</inf>COO)<inf>2</inf>·H<inf>2</inf>O, Ca(CH<inf>3</inf>CHOHCOO)<inf>2</inf>·5H<inf>2</inf>O, and Ca(CH<inf>3</inf>COO)(CH<inf>3</inf>CHOHCOO)·2H<inf>2</inf>O, respectively. The final thermal decomposition product of all calcium compounds was calcium oxide (CaO). The CAL sample’s vibrational characteristics, crystal phases, and morphologies show the binary acetate and lactate anion phases, confirming the new binary anionic calcium acetate lactate obtained. In conclusion, this research proposes an easy and low-cost technique to prepare a new valuable CAL compound using scallop shell waste as a cheap and renewable calcium source.
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    Valorization of Mussel Shell Waste to Chitin, Chitosan, and Calcium Lactate for Bio-Green-Circular Management
    (2026-04-01)
    Seangarun, Chaowared
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    ; ; ;
    Punthipayanon, Sirichet
    This study presents a green bio-upcycling strategy for converting mussel shell biowaste into three value-added products: chitin, chitosan, and calcium lactate. Mussel shells were treated chemically with lactic acid during demineralization, yielding a solid fraction rich in chitin and a liquid fraction containing calcium and lactate ions. The solid fraction was sequentially purified by deproteinization and decolorization, then deacetylated to obtain chitosan, while the liquid fraction was evaporated to obtain calcium lactate. Notably, 2.37 g of raw chitin, 2.15 g of purified chitin, and 275.87 g of calcium lactate were obtained from 100 g of mussel shells, demonstrating the efficiency of the process. FTIR spectra revealed characteristic absorption bands corresponding to α-chitin and chitosan functional groups, while XRD patterns indicated the crystalline α-chitin structure and the formation of calcium lactate pentahydrate. TGA demonstrated the high thermal stability of chitin and chitosan and confirmed the presence of crystallization water in calcium lactate. In conclusion, these results confirmed the successful preparation of α-chitin, chitosan, and calcium lactate pentahydrate, with improved purity compared to previous studies. This approach highlights the potential of the green bio-upcycling process of mussel shell waste as a renewable source for the eco-friendly production of biopolymers and calcium salts, supporting sustainable waste management and the development of the Bio-Circular-Green (BCG) economy.
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    Microparticles of calcium carbonate CaCO3, calcium hydrogen phosphate hydrate CaHPO41.9H2O and tricalcium phosphate Ca3(PO4)2 prepared from golden apple snail shells (Pomacea canaliculata)
    The golden apple snail shell was mechanically milled to transform to 400 mesh sizes of calcium carbonate CaCO3. The obtained CaCO3 was reacted with phosphoric acid by a simple rapid reaction to prepare dicalcium phosphate hydrate CaHPO4<sup>.</sup>1.9H2O. Thermal transformation products of the as-synthesized CaCO3 and CaHPO4<sup>.</sup>1.9H2O samples occurred at above 750 <sup>o</sup>C indicating the temperature condition to synthesize tricalcium phosphate Ca3(PO4)2 by solid state route. The as-synthesized CaCO3 and CaHPO4 powders were well mixed in the mole ratio of 1:2, then calcined at 800 <sup>o</sup>C for 2 hrs. and the obtained product was Ca3(PO4)2. The XRD and FTIR results indicate that the as-prepared CaCO3, CaHPO4 and Ca3(PO4)2 samples without the presence of any phase impurities crystalize in orthorhombic of aragonite, anorthic, rhombohedral phases respectively, The SEM micrographs show nonuniform, wooden fiber-like, grainy rice-like and irregular and non-uniform shapes for the as-prepared CaCO3, CaHPO4 and Ca3(PO4)2 samples respectively.
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    Low-Cost and Eco-Friendly Calcium Oxide Prepared via Thermal Decompositions of Calcium Carbonate and Calcium Acetate Precursors Derived from Waste Oyster Shells
    (2024-08-01) ;
    Seangarun, Chaowared
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    Laohavisuti, Nongnuch
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    Waste oyster shells were utilized to produce calcium carbonate (CaCO<inf>3</inf>) by grinding. This CaCO<inf>3</inf> was then reacted with acetic acid to yield calcium acetate monohydrate (Ca(CH<inf>3</inf>COO)<inf>2</inf>·H<inf>2</inf>O). Both CaCO<inf>3</inf> and Ca(CH<inf>3</inf>COO)<inf>2</inf>·H<inf>2</inf>O were used as precursors for synthesizing calcium oxide (CaO) through thermal decomposition at 900 °C and 750 °C, respectively. The yields of CaO from both precursors, determined through calcination experiments and thermogravimetric analysis (TGA), exceeded 100% due to the high purity of the raw agents and the formation of calcium hydroxide (Ca(OH)<inf>2</inf>). X-ray fluorescence (XRF) analysis revealed a CaO content of 87.8% for CaO-CC and 91.5% for CaO-CA, indicating the purity and contamination levels. X-ray diffraction (XRD) patterns confirmed the presence of CaO and minor peaks of Ca(OH)<inf>2</inf>, attributed to moisture adsorption. Fourier-transform infrared (FTIR) spectroscopy identified the vibrational characteristics of the Ca-O bond. Scanning electron microscopy (SEM) showed similar morphologies for both CaO-CC and CaO-CA, with CaO-CA displaying a significant amount of rod-like crystals. Based on these results, calcium acetate monohydrate (CA) is recommended as the superior precursor for synthesizing high-purity CaO, offering advantages for various applications.
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    Influence of ethephon spraying on the growth and yield of Stevia (Stevia rebaudiana Bertoni.)
    (2023-05-01)
    Chumthong, B.
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    Detpiratmongkol, S.
    The effects of ethephon spraying on the growth and yield of stevia (Stevia rebaudiana Bertoni) was investigated. The results indicated that spraying ethephon for three times leaded to the highest growth parameters in term of stem, leaf, root and total dried weight and yield, followed by spraying two and one times. The ethephon spraying to stevia at concentration of 200 ppm gave the highest total dried weight and yield. It is concluded that application of ethephon at concentration of 200 ppm to stevia for three times at 30, 60 and 90 DAT gave the highest vegetative growth and yield.
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    Bio-green synthesis of calcium acetate from oyster shell waste at low cost and reducing the emission of greenhouse gases
    (2023-12-01) ;
    Seangarun, Chaowared
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    Laohavisuti, Nongnuch
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    Thompho, Somphob
    Biological wastes obtained from food, oyster shells, were recycled to calcium carbonate and then used as bio-green raw material to replace limestone/carbonate stone for calcium acetate (Ca(CH<inf>3</inf>COO)<inf>2</inf>·H<inf>2</inf>O) production. The conditions (ambient temperature occurred in an exothermic reaction, drying time, yield, and solubility) of the reaction between the bio-green CaCO<inf>3</inf> and three different acetic (CH<inf>3</inf>COOH) concentrations (8, 10, and 12 M) were investigated. The product's maximum yield (93%) with a shorter drying time (18 h) was obtained from the reaction between the bio-green CaCO<inf>3</inf> with 12 M acetic acid revealing a lower cost. The chemical compositions without any toxic metal impurity revealed by the X-ray fluorescence technique would be useful to suggest use in the specific application. The X-ray diffraction, Fourier Transform Infrared, and Thermogravimetric analysis data of Ca(CH<inf>3</inf>COO)<inf>2</inf>·H<inf>2</inf>O prepared by the bio-green CaCO<inf>3</inf> obtained from oyster shell wastes in this work and those in previous works used other calcium sources were consistent. The morphologies with different sizes of the obtained Ca(CH<inf>3</inf>COO)<inf>2</inf>·H<inf>2</inf>O depend on the CH<inf>3</inf>COOH concentrations reported in this work and were different from those reported in previous works because of different calcium sources. According to the observation, it can be concluded that the low-cost and bio-green technique without the environmental effects was successfully applied to produce cheap Ca(CH<inf>3</inf>COO)<inf>2</inf>·H<inf>2</inf>O and reduce greenhouse gas emissions, which can be used in the specific industry.
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    Simple recycling of biowaste eggshells to various calcium phosphates for specific industries
    (2021-12-01)
    Laohavisuti, Nongnuch
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    ; ;
    Chaiseeda, Kittichai
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    Egg consumption is very high throughout the world and with it comes enormous amount of waste eggshells. To reduce and utilize these wastes, eggshell wastes were simply transformed to low- or high-purity calcium carbonate grades by washing, crushing, and drying to use as raw materials for producing highly valuable calcium phosphate products. Low-purity calcium carbonate grade was used to prepare triple superphosphate for using in fertilizer industry, whereas high-purity calcium carbonate grade was used to produce dicalcium phosphate dihydrate, monocalcium phosphate monohydrate, and tricalcium phosphate for using in mineral feed and food additive industries. All calcium phosphate samples obtained by simple, rapid, cheap, and environmentally safe method using eggshells and phosphoric acid were identified and their structural phases and impurities were determined by XRF, XRD and FTIR techniques. Thermal behaviors of raw materials and the prepared calcium phosphates excepted tricalcium phosphate were investigated by TG/DTG techniques. The methodologies described here will be useful to manage eggshells by converting them to highly valuable products, which can solve eggshell wastes problem from industries and communities. This finding supports the viewpoint of zero waste operation to produce value-added products for obtaining sustainable development, which may be selected as an alternative way for material recycling and waste management in the future.
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    A Simple and Rapid Synthesis of Spherical Silver Phosphate (Ag3PO4) and Its Antimicrobial Activity in Plant Tissue Culture
    (2025-08-01)
    Laohavisuti, Nongnuch
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    ; ; ;
    A simple and rapid precipitation process was successfully employed to prepare silver phosphate (SP, Ag<inf>3</inf>PO<inf>4</inf>). Two different phosphate sources: diammonium hydrogen phosphate ((NH<inf>4</inf>)<inf>2</inf>HPO<inf>4</inf>) and dipotassium hydrogen phosphate (K<inf>2</inf>HPO<inf>4</inf>) were applied separately as the precursor, obtaining ((NH<inf>4</inf>)<inf>2</inf>HPO<inf>4</inf>)<sup>−</sup> and K<inf>2</inf>HPO<inf>4</inf><sup>−</sup> derived SP powders, named SP-A or SP-P, respectively. Fourier transform infrared (FTIR) spectra pointed out the vibrational characteristics of P–O and O–P–O interactions, confirming the presence of the PO43– functional group for SP. X-ray diffraction (XRD) patterns revealed that the SP crystallized in a cubic crystal structure. Whereas the field emission scanning electron microscope (FESEM) exposed spherical SP particles. The potentially antibacterial activity of SP-A and SP-P against bacterial Bacillus stratosphericus, yeast Meyerozyma guilliermondii, and fungal Phanerodontia chrysosporium was subsequently investigated. All studied microorganisms were recovered and isolated from the aquatic plant during the tissue culture process. The preliminary result of the antimicrobial test revealed that SP-A has higher antimicrobial activity than SP-P. The superior antimicrobial efficiency of SP-A compared to SP-P may be attributed to its purity and crystallite size, which provide a higher surface area and more active sites. In addition, the presence of potassium-related impurities in SP-P could have negatively affected its antimicrobial performance. These findings suggest that SP holds potential as an antimicrobial agent for maintaining sterility in tissue cultures, particularly in aquatic plant systems. The growth of both B. stratosphericus and M. guilliermondii was suppressed effectively at 30 ppm SP-A, whereas 10 ppm of SP-A can suppress P. chrysosporium development. This present work also highlights the potential of SP at very low concentrations (10–30 ppm) for utilization as an effective antimicrobial agent in tissue culture, compared to a commercial antimicrobial agent, viz., acetic acid, at the same concentration.