Remoção do corante Azul Reativo 19 por adsorção em carvão ativado e em lama vermelha nas formas naturais e tratadas por ozônio
Carregando...
Arquivos
Data
2017-10-11
Autores
Lopes, Mayara Sakamoto [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
As indústrias têxteis caracterizam-se pelos elevados volumes de água consumida e de efluente lançado, o qual, por possuir coloração intensa, reduz a penetração da luz solar nos corpos hídricos receptores e afeta a fotossíntese. Nesse trabalho, avaliou-se a adsorção do corante Azul Reativo 19 (RA19) por carvão ativado comercial (CAP), CAP tratado por ozônio (CAP – O3), lama vermelha (LV) e LV tratada por ozônio (LV – O3). Os adsorventes foram caracterizados quanto ao pH, condutividade elétrica, número de iodo, índice de azul de metileno, granulometria, composição química, mineralogia e micromorfologia. Investigou-se a influência do pH e da temperatura no processo de adsorção. Além disso, analisou-se a cinética da adsorção de RA19 a diferentes concentrações iniciais (300, 500, 1000, 2000 e 3000 mg/L), por meio dos modelos de pseudo primeira ordem, pseudo segunda ordem, difusão intrapartículas e Elovich; e avaliou-se a capacidade de adsorção dos quatro adsorventes, por isotermas de Langmuir e Freundlich. Os resultados indicaram que o tratamento por ozônio não altera significativamente a composição química do CAP e da LV, mas possivelmente reduz o volume de mesoporos do CAP. A eficiência de remoção do RA19 por CAP independe do pH inicial da solução, mas por LV, é favorecida em pH mais baixo (igual a 3). Observou-se que 120 minutos são suficientes para atingir o equilíbrio da reação; e que o aumento da concentração inicial de corante reduz a eficiência de remoção, mas aumenta a capacidade de adsorção. Os dados experimentais ajustaram-se aos modelos de pseudo segunda ordem e de Elovich, indicando que o processo é controlado por quimissorção. Para todos os adsorventes, a adsorção do RA19 é multicamada em superfícies heterogêneas, visto que os dados se ajustaram à isoterma de Freundlich. Os resultados termodinâmicos sugeriram que existe afinidade entre o RA19 e os adsorventes, sendo que a reação ocorre espontaneamente; além disso, a adsorção por CAP e por CAP – O3 é endotérmica, e a adsorção por LV e por LV – O3 é exotérmica. A maior (216,4 mg/g) e a menor (138,7 mg/g) capacidade de adsorção foram obtidas pelo CAP e pelo CAP – O3, respectivamente. Concluiu-se que a ação do ozônio desfavoreceu a adsorção do RA19, em termos de fração residual, quantidade de corante adsorvido, velocidade de reação, e capacidade máxima de adsorção.
Textile industries are characterized by high water consumption and by large effluent release, which is strongly colored and therefore reduces sunlight penetration into water and affects photosynthesis. This study evaluated the adsorption of Reactive Blue 19 (RB19) by commercial activated carbon (PAC), PAC treated by ozone (PAC – O3), red mud (RM) and RM treated by ozone (RM – O3). The adsorbents were characterized by pH, electric conductivity, iodine number, Methylene Blue index, granulometry, chemical and mineralogical composition and micromorphology. Influence of pH and temperature was investigated. Additionally, the RB19 adsorption kinetics was evaluated at different initial concentrations (300, 500, 1000, 2000 and 3000 mg/L) with the pseudo first order, pseudo second order, intraparticle diffusion and Elovich models; and the adsorptive capacity of the adsorbents was investigated by Langmuir and Freundlich isotherms. The results showed that ozone treatment does not significantly change the chemical composition of PAC and RM, but it possibly reduces PAC’s mesopore volume. The initial pH does not influence the efficiency of RB19 removal by PAC, but it influences the removal by RM, being higher at lower pH (equal to 3). The adsorption reached an equilibrium state at about 120 minutes from the beginning of the experiments; and it was observed that increasing initial dye concentration, removal efficiency was reduced, while adsorption capacity was improved. The experimental data fitted well to the pseudo second order and Elovich kinetics models, which indicate that the process is controlled by chemisorption. The RB19 removal obeys the Freundlich isotherm model, showing multilayer adsorption on heterogeneous surface. The thermodynamic studies indicated that RB19 has affinity to the adsorbents, and the reaction occurs spontaneously; furthermore, the adsorption by PAC and PAC – O3 is endothermic, while the adsorption by RM and RM – O3 is exothermic. The highest (216.4 mg/g) and the lowest (138.7 mg/g) adsorption capacity were obtained by PAC and PAC – O3, respectively. It was concluded that ozone negatively affects RB19 adsorption, in terms of residual fraction, amount of dye adsorbed, reaction rate and maximum adsorption capacity.
Textile industries are characterized by high water consumption and by large effluent release, which is strongly colored and therefore reduces sunlight penetration into water and affects photosynthesis. This study evaluated the adsorption of Reactive Blue 19 (RB19) by commercial activated carbon (PAC), PAC treated by ozone (PAC – O3), red mud (RM) and RM treated by ozone (RM – O3). The adsorbents were characterized by pH, electric conductivity, iodine number, Methylene Blue index, granulometry, chemical and mineralogical composition and micromorphology. Influence of pH and temperature was investigated. Additionally, the RB19 adsorption kinetics was evaluated at different initial concentrations (300, 500, 1000, 2000 and 3000 mg/L) with the pseudo first order, pseudo second order, intraparticle diffusion and Elovich models; and the adsorptive capacity of the adsorbents was investigated by Langmuir and Freundlich isotherms. The results showed that ozone treatment does not significantly change the chemical composition of PAC and RM, but it possibly reduces PAC’s mesopore volume. The initial pH does not influence the efficiency of RB19 removal by PAC, but it influences the removal by RM, being higher at lower pH (equal to 3). The adsorption reached an equilibrium state at about 120 minutes from the beginning of the experiments; and it was observed that increasing initial dye concentration, removal efficiency was reduced, while adsorption capacity was improved. The experimental data fitted well to the pseudo second order and Elovich kinetics models, which indicate that the process is controlled by chemisorption. The RB19 removal obeys the Freundlich isotherm model, showing multilayer adsorption on heterogeneous surface. The thermodynamic studies indicated that RB19 has affinity to the adsorbents, and the reaction occurs spontaneously; furthermore, the adsorption by PAC and PAC – O3 is endothermic, while the adsorption by RM and RM – O3 is exothermic. The highest (216.4 mg/g) and the lowest (138.7 mg/g) adsorption capacity were obtained by PAC and PAC – O3, respectively. It was concluded that ozone negatively affects RB19 adsorption, in terms of residual fraction, amount of dye adsorbed, reaction rate and maximum adsorption capacity.
Descrição
Palavras-chave
Corantes, Adsorção, Carvão ativado, Lama vermelha, Ozônio, Dye, Adsorption, Activated carbon, Red mud, Ozone