Enhanced phosphate adsorption using chemically modified walnut shell biochar: A comparative study of activation methods, isotherm uncertainty analysis and modelling
[EN] Phosphorus contamination in aquatic environments promotes eutrophication, even at trace levels. This study evaluates the phosphate adsorption capacity of walnut shell-derived biochar modified via hydrochloric acid, sodium hydroxide, and magnesium chloride, including a novel dual-step acid/base...
| Autores: | , |
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| Formato: | artículo |
| Fecha de publicación: | 2025 |
| País: | España |
| Recursos: | Universitat Politècnica de València (UPV) |
| Repositorio: | RiuNet. Repositorio Institucional de la Universitat Politécnica de Valéncia |
| Idioma: | inglés |
| OAI Identifier: | oai:riunet.upv.es:10251/229583 |
| Acesso em linha: | https://riunet.upv.es/handle/10251/229583 |
| Access Level: | acceso abierto |
| Palavra-chave: | Walnut-shell biochar Phosphate Adsorption Uncertainty analysis Model |
| Resumo: | [EN] Phosphorus contamination in aquatic environments promotes eutrophication, even at trace levels. This study evaluates the phosphate adsorption capacity of walnut shell-derived biochar modified via hydrochloric acid, sodium hydroxide, and magnesium chloride, including a novel dual-step acid/base activation followed by magnesium impregnation. The base-activated and magnesium-modified biochar (MBWBC) achieved the highest phosphate removal reported for walnut shell biochars, improving performance by a factor of 2.9. Under varying environmental conditions, biochars removed 74-89 % of phosphate within 24 h, with efficiency increasing up to fourfold at higher initial concentrations. Desorption tests confirmed stable performance over five cycles, retaining 80-88 % of initial adsorption capacity and showing minimal magnesium loss (2.5-4 %). Adsorption behaviour aligned with Langmuir and Complete Temkin isotherms (R2: 0.86-0.95), indicating monolayer adsorption on heterogeneous surfaces. Mechanistic analysis revealed that phosphate removal was driven by electrostatic attraction, surface complexation, limited ion exchange, and stable phosphate-magnesium complex formation. Monte Carlo simulations assessed model reliability, showing adsorption capacity parameters were more sensitive to experimental variability (8.2-9.2 %) than interaction strength parameters (1.2-5.1 %). A predictive model based on point of zero charge and magnesium content accurately estimated phosphate adsorption capacity. These findings demonstrate the effectiveness of tailored chemical modifications in enhancing biochar performance for sustainable water treatment applications. |
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