Remoção do corante verde malaquita por adsorção em biocarvão do endocarpo de coco (Cocos nucifera L.)
Nenhuma Miniatura disponível
Data
2023-02-22
Autores
Alves, Ruan de Oliveira
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Federal do Espírito Santo
Resumo
The textile industry is among the largest sectors that require high amounts of water for their operation, and in general, their effluents have high concentrations of synthetic dyes, including malachite green. Various methods are used for treating this type of effluent, but adsorption stands out for its high capacity to remove specific compounds present in aqueous media. Thus, in this study, biocarbon from coconut endocarp (Cocos nucifera L.) was produced and characterized, and the adsorption kinetics of malachite green dye in aqueous solution was evaluated. The biocarbon synthesized at 600°C in N₂ atmosphere had an amorphous structure with a porous surface area of 34,978 m2 g -1 and a pHpzc of 7.82. The influence of pH on adsorption, performed in the pH range of 2 to 7, showed an increase in the removal capacity from 5.63 to 84.46% with increasing pH. The adsorption kinetics were evaluated by the models of PseudoFirst Order, Pseudo-Second Order, Elovich, Avrami, and intraparticle diffusion, where data fitting showed that the Avrami model describes the adsorption mechanism, while the diffusion model elucidated that the transport process is not governed by intraparticle diffusion with an apparent activation energy of 84.95 kJ mol-1 , characterizing adsorption as a chemisorption process. In the equilibrium study, the experimental data were best described by the Sips model. The adsorption isotherm at 25 °C showed a qmax of 37.42 mg g-1 with a removal of 75.36%, while at 55 °C, a qmax of 44.87 mg g-1 with a removal of 92.57% of malachite green was obtained. Furthermore, the variation in Gibbs free energy (ΔG) from -20.652 to -25.857 kJ mol−1 showed that the adsorption process was spontaneous, while the positive value of (ΔH) of 30.956 kJ mol−1 indicated an endothermic process. Similarly, an increase in the degree of disorder at the liquid-solid interfaces was observed from the variation in entropy (ΔS) of 172.512 J mol K-1 . Thus, according to the observations, the study revealed that the adsorption process was feasible, spontaneous, and endothermic, and the application of biocarbon is a promising option for removing malachite green.
Descrição
Palavras-chave
Biocarvão , Verde malaquita , Corantes têxteis , Coco-da-baía