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Effective recovery of phosphate from wastewater using biodegradable calcium-rich shell wastes composite macroporous cryogel
Author(s)
Kaewnoo, Satabodee
Wongniramaikul, Worawit
Boonkanon, Chanita
Taweekarn, Tarawee
Kleangklao, Bussakorn
Limwongsakorn, Somsak
Aga, Diana S.
Choodum, Aree
Date Issued
June 20, 2024
Type
Article
Abstract
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.
Citation
Colloids and Surfaces A Physicochemical and Engineering Aspects, 691, 2024