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Author: search.filters.author.Chaiseeda, KittichaiSubject: search.filters.subject.Ca(H2PO4)2·H2O

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    Item type:Publication,
    Recrystallization of Triple Superphosphate Produced from Oyster Shell Waste for Agronomic Performance and Environmental Issues
    (2022-02-01)
    Seesanong, Somkiat
    ;
    Seangarun, Chaowared
    ;
    Boonchom, Banjong
    ;
    Sronsri, Chuchai
    ;
    Laohavisuti, Nongnuch
    Calcium dihydrogen phosphate monohydrate (Ca(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·H<inf>2</inf>O) (a fertilizer) was successfully synthesized through a recrystallization process using prepared triple superphosphate (TSP) derived from oyster shell waste as the starting material. This bio-green, eco-friendly process to produce an important fertilizer can promote a sustainable society. The shell-waste-derived TSP was dissolved in distilled water and kept at 30, 50, and 80<sup>◦</sup>C. Non-soluble powder and TSP solution were obtained. The TSP solution fractions were then dried, and the recrystallized products (RCP30, RCP50, and RCP80) were obtained and confirmed as Ca(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·H<inf>2</inf>O. Conversely, the non-soluble products (NSP30, NSP50, and NSP80) were observed as calcium hydrogen phosphate dihydrate (CaHPO<inf>4</inf>·2H<inf>2</inf>O). The recrystallized yields of RCP30, RCP50, and RCP80 were found to be 51.0%, 49.6%, and 46.3%, whereas the soluble percentages were 98.72%, 99.16%, and 96.63%, respectively. RCP30 shows different morphological plate sizes, while RCP50 and RCP80 present the coagulate crystal plates. X-ray diffractograms confirmed the formation of both the NSP and RCP. The infrared adsorption spectra confirmed the vibrational characteristics of HPO<inf>4</inf><sup>2−</sup>, H<inf>2</inf>PO<inf>4</inf><sup>−</sup>, and H<inf>2</inf>O existed in CaHPO<inf>4</inf>·2H<inf>2</inf>O and Ca(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·H<inf>2</inf>O. Three thermal dehydration steps of Ca(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·H<inf>2</inf>O (physisorbed water, polycondensation, and re-polycondensation) were observed. Ca(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf> and CaH<inf>2</inf>P<inf>2</inf>O<inf>7</inf> are the thermodecomposed products from the first and second steps, whereas the final product is CaP<inf>2</inf>O<inf>6</inf>.