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Continuous-flow phosphate removal using Cry-Ca-COS Monolith: Insights from dynamic adsorption modeling
(2025-05-01)
Phawachalotorn, Chanadda
;
Wongniramaikul, Worawit
;
Kaewnoo, Satabodee
;
Choodum, Aree
This study rigorously evaluates the adsorption performance of the Cry-Ca-COS monolith for phosphate removal in a column operation mode. Characterization of the material both before and after exhaustion in a continuous flow system (column form) showed no difference compared to results from a batch system (tablet form). The XPS results indicated that the adsorption mechanism of phosphate on the Cry-Ca-COS column involved surface microprecipitation and ligand exchange (inner-sphere complexation). A systematic examination of key parameters revealed that higher column height, lower flow rate, and higher initial phosphate concentration favor increased phosphate adsorption in continuous mode. The application of the developed system to a real wastewater sample resulted in a satisfactory removal efficiency of 99.16 %, along with a concurrent reduction in total suspended solids (TSS) by 63.07 %. The adsorption data were analyzed using five dynamic adsorption models—Adam-Bohart, Wolborska, Thomas, Yoon-Nelson, and Yan—employing both linear and non-linear approaches. The non-linear models demonstrated a better fit with the experimental data, as indicated by higher correlation coefficients (R² = 0.9994 in the Yoon-Nelson model). An analysis of comprehensive errors was also conducted to assess the adequacy and precision of the model equations.
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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−1 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−1 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−1 and a positive enthalpy of 9.3 kJ mol−1, 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.

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