BOOK OF ABSTRACTS 161 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Friday, 28 August 2026 / Hall C Travel Awardee Presentations TA1 Coal Fines as a Smart Soil Conditioner via Production of Functional Encapsulation for Use in Modern and Sustainable Systems of Agriculture Hermogenes Bezerra Maia1, Felipe Ramon Freitas Cabral2, Taysa Silva Conde1, Ramom Rachide Nunes2, and Luciane Pimenta Cruz Romão1. 1 Laboratory of Natural Organic Matter, Department of Chemistry, Federal University of Sergipe, São Cristóvão, Brazil. Avenue Marechal Rondon, no number, São Cristóvão, Sergipe, 49100-000, Brazil. 2 Laboratory of Environmental Chemistry, Department of Chemistry, Federal Rural University of Pernambuco. Recife, Brazil. Dom Manoel de Medeiros Street, no number, Recife, Pernambuco, 52171-900, Brazil. hermogenes.maia@academico.ufs.br Tropical soils exhibit low Nutrient Use Efficiency (NUE) due to rapid P fixation and K leaching. ControlledRelease Fertilizers (CRF) mitigate this. This study formulated a CRF using charcoal fines (CF). Native CF presents high aromaticity and hydrophobicity [1]. The CF carbonaceous matrix supported the nucleation of K and P crystals. The core was stabilized via ionotropic gelation in an alginate network. The objective was to characterize the composite structure and evaluate its nutrient and dissolved organic carbon (DOC) release kinetics. CF underwent impregnation to induce K2HPO4 and KH2PO4 neoformation [2], followed by calcium alginate encapsulation. Structure was characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Functionality was evaluated through swelling kinetics (pH 4.5, 6.5, and 7.0). Matrix stability was assessed via TOC analysis (DOC quantification) and UV-Vis spectroscopy (E2/E3 indices). As result, morphological analysis via SEM indicated the surface occlusion of the carbonaceous matrix. The CF surface exhibits open hexagonal macropores common in biomasses. In contrast, the Alg-CF-KxHyPO4 surface appears sealed by a dense framework of tabular crystals. This crystallization correlates with the halite and sylvite phases identified by XRD and acts alongside the alginate matrix to occlude the original porosity, establishing a hybrid physical barrier that modulates mass transport. The functional performance of the composite suggests a pH-responsive system. Swelling kinetics revealed that the polymeric network remains collapsed in an acidic medium at pH 4.5 with expansion below 30%, providing protection in tropical soils, while expanding in a neutral medium at pH 7.0 via Super Case II transport. The suppression of maximum swelling from 1859% in the pure alginate polymer to 965% in the final product indicates matrix densification by charge screening, where high internal ionic strength restricts
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