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Author: search.filters.author.Taweekarn, TaraweeSubject: search.filters.subject.Phosphate removal

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    Calcium silicate hydrate–embedded porous concrete for efficient phosphate removal and recovery in concentrated eluates
    (2026-01-01)
    Wongniramaikul, Worawit
    ;
    Choodum, Aree
    ;
    Pasitsuparoad, Pakorn
    ;
    Cotchim, Suparat
    ;
    Phawachalotorn, Chanadda
    Phosphate remediation and recovery from wastewater remain challenging due to limitations in adsorbent stability and real–world applicability. This study presents a sustainable porous concrete–calcium silicate hydrate (PC–CSH) column engineered for continuous–flow phosphate removal and resource recovery. Synthesized CSH nanoparticles were incorporated into a porous cement matrix, and comprehensive characterization confirmed the formation of calcium phosphate phases, including hydroxyapatite (HAP), CaHPO₄, and Ca(H₂PO₄)₂. The results indicate that surface-induced microprecipitation, driven by Ca²⁺ and OH⁻ released from both added and in situ–formed CSH, is the dominant removal mechanism. Externally added nanoparticles contributed 40.05% of total uptake, while the remainder originated from CSH generated during cement hydration. Breakthrough analysis showed that increasing column height enhanced longevity, whereas higher influent phosphate concentration and flow rate accelerated saturation. Under optimal conditions (7.5 cm column, 50 mg L⁻¹ phosphate, 10 mL min⁻¹ flow), the system achieved >99% removal with a total adsorption capacity of 3599.7 mg. The nonlinear Yoon–Nelson model best described the breakthrough behavior. Application to real municipal wastewater (initial phosphate 4.57 mg L⁻¹) achieved 99.3% removal with minimal influence from coexisting anions (SO₄²⁻, NO₃⁻, CO₃²⁻). Phosphate was efficiently recovered using 0.5 M HCl (100.4% desorption), and performance was restored by reloading fresh PC–CSH slurry. The column retained 73.9% phosphate removal efficiency after four adsorption–desorption cycles with real wastewater, demonstrating excellent reusability and practical potential. Overall, the PC–CSH column offers a robust, semi–regenerable platform for sustainable phosphate mitigation and recovery in wastewater treatment.
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    Effective recovery of phosphate from wastewater using biodegradable calcium-rich shell wastes composite macroporous cryogel
    (2024-06-20)
    Kaewnoo, Satabodee
    ;
    Wongniramaikul, Worawit
    ;
    Boonkanon, Chanita
    ;
    Taweekarn, Tarawee
    ;
    Kleangklao, Bussakorn
    The recovery of phosphorus from wastewater holds promise as a sustainable source of organic phosphorus for agricultural use while aiding in meeting legislative discharge limits for phosphorus to control and mitigate eutrophication. This study introduces a novel approach in which calcium-rich calcined oyster shell (Ca–COS) is immobilized on a starch-based monolithic cryogel, resulting in a green tablet (Cry–Ca–COS) capable of efficiently recovering phosphate from water through chemisorption on the material surface and precipitation in the liquid phase. The formed tablet prevents sorbent loss post-adsorption, facilitating reusability. Under optimal conditions (i.e., three 0.83 cm thick Cry–Ca–COS tablets, an initial phosphate concentration of 12 mg L<sup>−1</sup> in 1 L without pH adjustment (pH 6.3), and a contact time of 60 minutes), a phosphate removal efficiency of 83.11% ± 0.68% and a maximum removal capacity of 9.97 mg g<sup>−1</sup> were achieved. Both the Langmuir isotherm model and pseudo-second-order kinetic model exhibited good fits to the experimental data, with an estimated activation energy of 81.9 kJ mol<sup>−1</sup> and a positive enthalpy of 9.3 kJ mol<sup>−1</sup>, indicating an endothermic chemisorption process with a monolayer surface coverage of phosphate on Cry–Ca–COS. In real samples, Cry–Ca–COS demonstrated a high removal efficiency ranging from 98.48% ± 1.87%–99.16% ± 0.72%, with the adsorbed material biodegrading within 24 days under soil burial conditions. A preliminary study was conducted to explore the feasibility of utilizing phosphate-adsorbed Cry–Ca–COS as a fertilizer for cultivating water spinach (Ipomoea aquatica Forsk.), and further in-depth investigation is required for a comprehensive report in the future. Thus, Cry–Ca–COS emerges as an environmentally friendly and effective tool for phosphate removal and recovery.