Comparação da biossorção de Ce3+ e La3+ pelos fungos pigmentados Aspergillus nidulans (mutante MEL1) e Cladosporium sp.: Efeito do pré-tratamento da biomassa
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Data
2018-11-13
Autores
Andrade, Jazmina Carolina Reyes
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Universidade Estadual Paulista (Unesp)
Resumo
A biossorção é considerada uma tecnologia eficiente, economicamente viável e ecologicamente sustentável comparada aos métodos convencionais para a remoção e recuperação de metais de alto valor agregado, como as terras-raras (TRs), presentes em efluentes industriais. No entanto, o grande desafio para o sucesso deste processo é selecionar um biossorvente com alto desempenho, seletividade, disponibilidade em grande quantidade e baixo custo. Neste contexto, o presente estudo avaliou a capacidade de biossorção dos elementos cério e lantânio pela biomassa pigmentada produzida pelos fungos Aspergillus nidulans (mutante MEL1) e Cladosporium sp. como também o efeito dos pré-tratamentos físicos e químicos. Dentre os biossorventes estudados, a biomassa de A. nidulans (mutante MEL1) foi selecionada por apresentar uma maior taxa de crescimento (37,5 mg L-1 h-1) como também uma capacidade de remoção para íons Ce3+ (27%) e La3+ (21%) superior ao Cladosporium sp. Os resultados referentes ao efeito dos pré-tratamentos mostraram que a biomassa pré-tratada com CaCl2 (0,5 mol L-1 à temperatura ambiente) exibiu uma maior capacidade biossortiva para Ce3+ (qmax = 76,92 mg g-1), enquanto que a biomassa pré-tratada com NaOH (0,2 mol L-1 à temperatura ambiente) apresentou maior biossorção para La3+ (qmax = 96,15 mg g-1). Em relação a manutenção do pH em 5,1 durante o processo de biossorção foi observado um aumento de 33% e 20% na capacidade biossortiva de Ce3+ e La3+ respectivamente, em comparação ao processo sem ajuste de pH. Com a caracterização da biomassa por MEV foi possível observar a natureza irregular e porosa do material, o que proporciona uma maior área de superfície e favorece a adsorção dos metais na superfície. Os espectros EDS confirmaram a presença de Ce3+ e La3+ na superfície da biomassa. As análises de FTIR indicaram a presença de grupos carboxílicos, amínicos e hidroxílicos na parede celular do fungo, os quais podem interagir com metais. A modificação química da superfície do biossorvente por metilação e esterificação confirmou que os grupos amina e carboxílicos participam como sítios ligantes para Ce3+ e La3+. Com o objetivo de utilizar as biomassas pré-tratadas em processo de larga escala, foi realizado a imobilização em alginato de cálcio e o encapsulamento em membrana de celulose. Os estudos cinéticos mostraram que o tempo de equilíbrio para as biomassas encapsuladas ou imobilizadas (180 minutos) foi maior comparado com a biomassa livre (90 min), provavelmente devido ao aumento da resistência de transferência de massa nas formas imobilizadas e encapsuladas. Os dados experimentais foram mais bem ajustados (r2 > 0,99) ao modelo de Langmuir, o qual descreve que a adsorção em monocamada sobre uma superfície homogênea. Também foi observado que a capacidade máxima de biossorção de Ce3+ e La3+ para as biomassas encapsuladas em membrana e imobilizadas em alginato foi maior comparada com a biomassa livre, sendo que o aumento variou de 32 a 72%. Comparando as biomassas encapsuladas em membrana e imobilizadas em alginato, verifica-se que as capacidades máxima de biossorção são muito semelhantes para ambos os metais, porém, a biomassa encapsulada apresentou uma maior porcentagem de remoção de Ce3+ e La3+. Assim, pode-se concluir que as biomassas pré-tratadas com CaCl2 (0,5 mol L-1 à temperatura ambiente) e NaOH (0,2 mol L-1 à temperatura ambiente) encapsuladas em membrana de celulose podem ser consideradas um biossorvente promissor e de baixo custo com potencial de aplicação no tratamento de efluentes de indústrias de mineração, visando a remoção e posterior recuperação desses metais para aplicações futuras.
Biosorption is considered to be an efficient, economically viable and ecologically sustainable technology compared to conventional methods for the removal and recovery of high value - added metals, such as rare earths (TRs), present in industrial effluents. However, the major challenge for the success of this process is to select a biosorbent with high performance, selectivity, availability in large quantity and low cost. In this context, the present study evaluated the biosorption capacity of the cerium and lanthanum elements by the pigmented biomass produced by the fungi Aspergillus nidulans (MEL1 mutant) and Cladosporium sp . as well as the effect of physical and chemical pre - treatments. Among the biosorbents studied, A. nidulans biomass (MEL1 mutant) was select ed because it presented a high growth rate (37.5 mg L - 1 h - 1 ) as well as a higher removal capacity for Ce 3+ (27%) and La 3+ (21%) than Cladosporium sp . The results sh owed that the free biomass pretreated with CaCl 2 (0.5 mol L - 1 at environment temperature) showed higher biosortive capacity for Ce 3+ (q max = 76.92 mg g - 1 ), while the biomass pretreated with NaOH (0.2 mol L - 1 at environment temperature) presented higher biosorption for La 3+ (qmax = 96.15 mg g - 1 ). In relation to the maintenance of pH in 5.1 during the biosorption process, a 33% and 20% increase in the bioso rtive capacity of Ce 3+ and La 3+ , respectively, was obse rved, compared to the process without pH adjustment. With the characterization of the biomass by SEM it was possible to observe the irregular and porous nature of the material, which provides a larger surface area and favors the adsorption of the metals on the surface. EDS spectr a confirmed the presence of Ce 3+ and La 3+ on the biomass surface. FTIR analysis indicated the presence of carboxylic, amine and hydroxyl groups on the cell wall of the fungus, which can interact with metals. The chemical modificatio n of the surface of the biosorbent by methylation and esterification confirmed that the amine and carboxyl groups participate as binding sites for Ce 3+ and La 3+ . In order to use pretreated biomasses in a large - scale process, immobilization was carried out in calcium alginate and encapsulation in cellulose membrane. Kinetic studies showed that the equilibrium time for encapsulated or immobilized biomasses (180 minutes) was higher compared to free biomass (90 min), probably due to increased mass transfer resistance in immobilized and encapsulated forms. The experimental data were better adjusted (r 2 > 0.99) to the Langmuir model, which describes the monolayer adsorption on a homogeneous surface. It was also observed that the maximum biosor ption capacity of Ce 3+ and La 3+ for membrane encapsulated and alginate immobilized biomasses was higher compared to free biomass, and the increase varied from 32 to 72%. Comparing the membrane - encapsulated and alginate - immobilized biomasses, it was found that the maximum bi osorption capacities were very similar for both metals, however, the encapsulated biomass presented a higher percentage of removal of Ce 3+ and La 3+ . Thus, it can be concluded that biomasses pretreated with CaCl2 (0.5 mol L - 1 at environment temperature) and NaOH (0.2 mol L - 1 at environment temperature) encapsulated in cellulose membrane can be considered a biosorbent promising and low cost with potential of application in the treatment of effluents of mining industries, aiming the removal and subsequent reco very of these metals for future applications.
Biosorption is considered to be an efficient, economically viable and ecologically sustainable technology compared to conventional methods for the removal and recovery of high value - added metals, such as rare earths (TRs), present in industrial effluents. However, the major challenge for the success of this process is to select a biosorbent with high performance, selectivity, availability in large quantity and low cost. In this context, the present study evaluated the biosorption capacity of the cerium and lanthanum elements by the pigmented biomass produced by the fungi Aspergillus nidulans (MEL1 mutant) and Cladosporium sp . as well as the effect of physical and chemical pre - treatments. Among the biosorbents studied, A. nidulans biomass (MEL1 mutant) was select ed because it presented a high growth rate (37.5 mg L - 1 h - 1 ) as well as a higher removal capacity for Ce 3+ (27%) and La 3+ (21%) than Cladosporium sp . The results sh owed that the free biomass pretreated with CaCl 2 (0.5 mol L - 1 at environment temperature) showed higher biosortive capacity for Ce 3+ (q max = 76.92 mg g - 1 ), while the biomass pretreated with NaOH (0.2 mol L - 1 at environment temperature) presented higher biosorption for La 3+ (qmax = 96.15 mg g - 1 ). In relation to the maintenance of pH in 5.1 during the biosorption process, a 33% and 20% increase in the bioso rtive capacity of Ce 3+ and La 3+ , respectively, was obse rved, compared to the process without pH adjustment. With the characterization of the biomass by SEM it was possible to observe the irregular and porous nature of the material, which provides a larger surface area and favors the adsorption of the metals on the surface. EDS spectr a confirmed the presence of Ce 3+ and La 3+ on the biomass surface. FTIR analysis indicated the presence of carboxylic, amine and hydroxyl groups on the cell wall of the fungus, which can interact with metals. The chemical modificatio n of the surface of the biosorbent by methylation and esterification confirmed that the amine and carboxyl groups participate as binding sites for Ce 3+ and La 3+ . In order to use pretreated biomasses in a large - scale process, immobilization was carried out in calcium alginate and encapsulation in cellulose membrane. Kinetic studies showed that the equilibrium time for encapsulated or immobilized biomasses (180 minutes) was higher compared to free biomass (90 min), probably due to increased mass transfer resistance in immobilized and encapsulated forms. The experimental data were better adjusted (r 2 > 0.99) to the Langmuir model, which describes the monolayer adsorption on a homogeneous surface. It was also observed that the maximum biosor ption capacity of Ce 3+ and La 3+ for membrane encapsulated and alginate immobilized biomasses was higher compared to free biomass, and the increase varied from 32 to 72%. Comparing the membrane - encapsulated and alginate - immobilized biomasses, it was found that the maximum bi osorption capacities were very similar for both metals, however, the encapsulated biomass presented a higher percentage of removal of Ce 3+ and La 3+ . Thus, it can be concluded that biomasses pretreated with CaCl2 (0.5 mol L - 1 at environment temperature) and NaOH (0.2 mol L - 1 at environment temperature) encapsulated in cellulose membrane can be considered a biosorbent promising and low cost with potential of application in the treatment of effluents of mining industries, aiming the removal and subsequent reco very of these metals for future applications.
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Palavras-chave
Biossorção, Terras-raras, Fungo pigmentado, Pré-tratamento, Biomassa encapsulada, Biomassa imobilizada, Remoção de metais, Biosorption, Pigmented fungus, Pretreatment, Encapsulated biomass, Biomass immobilized, Metal removal