PURIFICAÇÃO ÁCIDO-BASE EXPERIMENTAL DE CASCAS DE ARROZ CARBONIZADAS: EXPLORANDO SUA EFICÁCIA NA ADSORÇÃO DE RESÍDUOS NÃO VALORIZADOS DA INDÚSTRIA DE ARROZ

The burning of rice husks produces natural silica and generates charcoal with excellent properties for the adsorption of different pollutants. The objective of this study was to enhance the adsorption properties of this industrial residue from burning rice husk through acid and base purifications. The raw coal (RC) was initially modified with HCl(aq.) and then with NaOH(aq.), and subsequently renamed MC. Efficiency was verified by the adsorption of methylene blue (MB) dye, considering a concentration of 10 mg L-1, dosage of 0.05 g L-1, pH 6.7, and 120 min. MB removal was 78% for RC and 97% for MC, with experimental capacities of 144.78 mg g-1 and 180.78 mg g-1, respectively. The kinetics were better adjusted by Avrami (R2 0.99, error <2.8%). The properties of charcoal improved with the modification, presenting a more porous structure, greater surface area and functional groups that contributed to adsorption, proving that simple purification methods, such as acid-base purification, can be crucial for waste reuse.