Avaliação do uso da casca da semente de Moringa oleifera como biossorvente na remoção do corante azul de metileno
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Data
2021-10-06
Autores
Lopes, Carolina Almeida
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Universidade Estadual Paulista (Unesp)
Resumo
Resíduos agrícolas de cascas de sementes de Moringa oleifera foram usados como adsorvente para remoção do corante azul de metileno em solução aquosa. O adsorvente foi caracterizado por MEV, EDX, DRX, FTIR, BET e pHPCZ. Para avaliar a capacidade de adsorção, foi analisada a influência do pH, cinética, isotermas e propriedades termodinâmicas. Técnicas de caracterização indicaram que as cascas das sementes de M. oleifera apresentam características morfológicas heterogêneas com área superficial específica de 3,24 m2 g-1 e um volume total de poros de 0.010 cm3 g-1, compostas principalmente por celulose distribuída em estrutura amorfa. A isoterma de adsorção-desorção de N2 da C-MO também apresenta um comportamento típico de isotermas do tipo II com histerese do tipo H3. De acordo com o espectro FTIR, a superfície do adsorvente possui uma ampla variedade de grupos funcionais que favorecem o processo adsortivo. A adsorção do corante azul de metileno foi mais favorável em valores de pH acima do pHPZC de 6,6 (valor de pH escolhido de 9,0), utilizando uma dosagem adsorvente de 1,0 g L-1. O equilíbrio foi alcançado nos primeiros 240 min, e o modelo de pseudo-segunda ordem foi adequado para descrever os dados cinéticos. Freundlich foi o modelo mais adequado para descrever as curvas isotérmicas, prevendo uma capacidade máxima de adsorção de 122,7 mg g-1 a 297 K, superior a outros adsorventes naturais reportados na literatura. O processo de adsorção foi espontâneo (ΔG° de −3,88 a −1,06 kJ mol-1) e exotérmico (ΔH° de -45,80 KJ mol-1), indicando que temperaturas mais baixas favorecem a adsorção e que é controlada por forças físicas, principalmente eletrostáticas, ligações de hidrogênio, dipolo-dipolo e interações π-π devido à sua composição superficial. Os dados apresentados indicam que o corante azul de metileno tem potencial para ser tratado com sucesso pela casca da semente de M. oleifera, um adsorvente ecologicamente favorável e de baixo custo.
M. oleifera seed husks agricultural waste was used as adsorbent for removing methylene blue dye from an aqueous solution. The adsorbent was characterized by SEM, EDX, XRD, FTIR, BET, and pHPZC. To evaluate adsorption capacity, the influence of pH, kinetics, isotherms, and thermodynamic properties was analyzed. Characterization techniques indicated that M. oleifera seed husks have heterogeneous morphological characteristics with a specific surface area of 3.24 m2 g-1 and a total pore volume of 0.010 cm3 g-1, mainly composed of cellulose distributed in an amorphous structure. The N2 adsorption–desorption isotherm of H-MO adsorbent also shows a typical behavior of a type II isotherm with type H3 hysteresis. According to the FTIR spectra found, the surface of the adsorbent possesses a wide variety of functional groups that favor the adsorptive process. Methylene blue dye adsorption was favorable mainly at pH values higher than pHPZC of 6.6, (pH value choose of 9.0), using an adsorbent dosage of 1.0 g L-1. The equilibrium was achieved in the first 240 min, and the pseudo-second-order model was suitable for describing the kinetic data. Freundlich was the most adequate model for describing the isotherm curves, predicting a maximum adsorption capacity of 122.7 mg g-1 at 297 K, higher than other natural adsorbents. The adsorption process was spontaneous (ΔG° from −3.88 to −1.06 kJ mol-1) and exothermic (ΔH° of -45.80 KJ mol-1), indicating that lower temperatures favor the adsorption and that it is controlled by physical forces, mainly electrostatic attraction, dipole-dipole hydrogen bonds, and π-π interactions due to its surface composition. The data presented indicate the methylene blue dye has the potential to be successfully treated by the eco-friendly and low-cost adsorbent M. oleifera seed husks.
M. oleifera seed husks agricultural waste was used as adsorbent for removing methylene blue dye from an aqueous solution. The adsorbent was characterized by SEM, EDX, XRD, FTIR, BET, and pHPZC. To evaluate adsorption capacity, the influence of pH, kinetics, isotherms, and thermodynamic properties was analyzed. Characterization techniques indicated that M. oleifera seed husks have heterogeneous morphological characteristics with a specific surface area of 3.24 m2 g-1 and a total pore volume of 0.010 cm3 g-1, mainly composed of cellulose distributed in an amorphous structure. The N2 adsorption–desorption isotherm of H-MO adsorbent also shows a typical behavior of a type II isotherm with type H3 hysteresis. According to the FTIR spectra found, the surface of the adsorbent possesses a wide variety of functional groups that favor the adsorptive process. Methylene blue dye adsorption was favorable mainly at pH values higher than pHPZC of 6.6, (pH value choose of 9.0), using an adsorbent dosage of 1.0 g L-1. The equilibrium was achieved in the first 240 min, and the pseudo-second-order model was suitable for describing the kinetic data. Freundlich was the most adequate model for describing the isotherm curves, predicting a maximum adsorption capacity of 122.7 mg g-1 at 297 K, higher than other natural adsorbents. The adsorption process was spontaneous (ΔG° from −3.88 to −1.06 kJ mol-1) and exothermic (ΔH° of -45.80 KJ mol-1), indicating that lower temperatures favor the adsorption and that it is controlled by physical forces, mainly electrostatic attraction, dipole-dipole hydrogen bonds, and π-π interactions due to its surface composition. The data presented indicate the methylene blue dye has the potential to be successfully treated by the eco-friendly and low-cost adsorbent M. oleifera seed husks.
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Palavras-chave
Adsorvente de baixo custo, Resíduos agrícolas, Mecanismo de adsorção, Isoterma, Poluição da água, Fisissorção, Low-cost adsorbent, Agricultural wastes, Adsorption mechanism, Isotherm, Water pollution, Physisorption