Marcelo Fernandes Vieira

Environmentally friendly biosorbents (husks, pods and seeds) from Moringa oleifera for Pb(II) removal from contaminated water

ABSTRACT Lead is a heavy metal considered highly toxic, responsible for causing several health problems as well as being extremely harmful to fauna and flora. Given this fact, several techniques have been studied for the removal of this metal from contaminated water, in which stands out adsorption. In this sense, the objective of this study was to evaluate the potential of lead(II) biosorption from contaminated water by seed husks, seeds and pods of Moringa oleifera Lam (moringa). Biomass was characterized by energy-dispersive X-ray spectroscopy, Scanning Electron Microscopy and Fourier transform infrared spectroscopy analyses. From the studied parameters, the optimal conditions obtained for the three analyzed biosorbents are: 30 min to equilibrium, pH 6 and 25°C temperature. The pseudo-second-order kinetic model was the best fitted to the experimental data for the three evaluated biosorbents. Regarding the adsorption isotherms, the model that best fitted to the experimental data for seed and seed husk was that proposed by Freundlich, and for the pod the Langmuir model. The analysis of the obtained thermodynamic data showed that the adsorption process is favorable and of exothermic nature. Through the results it was concluded that the evaluated biosorbents are efficient in lead(II) biosorption.

Activated carbon of Babassu coconut impregnated with copper nanoparticles by green synthesis for the removal of nitrate in aqueous solution

ABSTRACT The present study was conducted to impregnate the surface of a carbon of vegetable origin with copper nanoparticles by the green synthesis method with the aqueous extract of Hibiscus sabdariffa flowers, rich in phenolic compounds, which are responsible for the reduction and impregnation of metal nanoparticles. Batch adsorption assays were conducted aimed at nitrate removal with pure (GAC) and impregnated (IGAC) carbon, for comparative purposes. It was found that impregnation increases the efficiency of the carbon by four times in terms of the maximum adsorption capacity, which was 10.13 mg g−1 at 45°C for GAC and 45.01 mg g−1 at 15°C for IGAC, indicating that this is a promising material for the removal of nitrate in waters with an excess of this ion.

Effects of Triton X-100 and PEG on the Catalytic Properties and Thermal Stability of Lipase from Free and Immobilized on Glyoxyl-Agarose

Background: Candida rugosa Lipase (CRL) shows a very low alkaline stability that comprises its immobilization on glyoxyl-agarose, which requires pH above 10. In this way, an adaptation from the original method was used; an enzyme solution at pH 7 was slowly added at a suspension of glyoxyl-agarose prepared in bicarbonate buffer, pH 10. This change of protocol was enough for allowing the preparation of derivatives actives of CRL on glyoxyl-agarose and verifying the effect of this modified procedure on the properties of the immobilized enzyme. The effect of the additives Triton-X-100 and polyethylene glycol (PEG) on the enzymatic activity recovery and immobilized enzyme stability was evaluated. Methods: The glyoxyl-agarose support was prepared by etherification of 6% agarose beads with glycidol and further oxidation with sodium periodate. CRL was immobilized covalently on glyoxyl-agarose support in the absence and presence of 1% (w/v) Triton-X-100 or 5 g L-1 polyethylene glycol (PEG). The lipolysis activity of the free and immobilized enzyme was determined at 37ºC and pH 7.0, using p-nitrophenyl palmitate (p-NPP) as substrate. Profiles of temperature-activity (37-65ºC, pH 7.0) and pH-activity (6.0-9.5, 37ºC) were evaluated as well as thermal (45ºC and pH 8.0) and operational (15 min batches of p-NPP hydrolysis at 50ºC and pH 8.0) stabilities of free and immobilized CRL. Results: Using a single modification of the original protocol, the CRL poorly stable under alkaline conditions could be immobilized on glyoxyl-agarose in its active conformation (recovered activity varying from 10.3 to 30.4%). Besides, the presence of a detergent (Triton-X-100) and an enzyme stabilizer (PEG) contributed to the preparation of more active and more stable biocatalysts, respectively. CRL immobilized on glyoxyl-agarose in the presence of PEG was around 5 times more stable than the free CRL and around 3 times more stable than the CRL immobilized on glyoxyl-agarose in absence of PEG. The higher stability of the CRL-glyoxyl derivative prepared in the presence of PEG allowed its reuse in four successive 15 min-batches of p-nitrophenyl palmitate hydrolysis at 50ºC and pH 8.0. Conclusion: The technique of immobilizing enzymes covalently on glyoxyl-agarose showed promising results for Candida rugosa lipase (CRL). The derivatives prepared in the presence of the additives retained two to three times more activity than those prepared in the absence of additives. The enzyme immobilized in presence of PEG was about three times more stable than the enzyme immobilized in absence of this additive. Maximum catalytic activity of the immobilized CRL (in absence of additives) was observed in a temperature 10ºC above that for the free enzyme and the pH of the maximum activity was maintained in the range 6.5-7.5 for free and immobilized CRL.

Mathematical modelling applied to the rate-limiting mass transfer step determination of a herbicide biosorption onto fixed-bed columns

ABSTRACT The herbicide removal of Diuron in a fixed-bed column packed with the Moringa oleifera bark biosorbent was investigated experimentally and through phenomenological mathematical modelling. To understand the physical phenomena involved, the steps of external mass transfer resistance, internal mass transfer resistance and the adsorption phenomenon itself were considered as possible limiting steps in the herbicide mass transfer from the liquid to the solid phase. In the developing process of the internal mass transfer resistance model, two hypotheses were considered: constant mass transfer coefficient and mass transfer coefficient as a function of the herbicide concentration in the biosorbent. The experimental breakthrough curves were obtained for different flow rates and feed concentrations, in order to evaluate the model’s predictive capacity. The mass transfer parameter values of the mathematical models were estimated using the simplex downhill optimization method. The model that considers the resistance a mass transfer internal with parameter Ks variable represented effectively the dynamic behaviour of the herbicide biosorption process in fixed-bed column, in the various evaluated conditions, indicating that this mechanism controls the biosorption process. Thus, the phenomenological mathematical modelling proved to be an analysis important tool, understanding and the herbicide adsorption systems design in a fixed-bed column. GRAPHICAL ABSTRACT

Assessment of the use of Moringa oleifera seed husks for removal of pesticide diuron from contaminated water

ABSTRACT Considering the need for new technologies for the removal of pesticides from the aqueous environment, the Moringa oleifera seed husks (h-MO) were investigated for the diuron adsorption from contaminated water at different temperatures and solute concentrations. The biosorbent used in this study was characterized by chemical, structural and textural analyses. The best experimental condition for the biosorption was determined by evaluating the mass of the biosorbent and the pH solution. We found a good adsorption capacity for the herbicide where the maximum adsorption capacity was 14.74 mg/g at pH 5 and 45°C. In addition, the adsorption process of diuron by the h-MO occurred spontaneously, in which, ΔG° values increased as the temperature increased, meaning that the process tends to a more energetically favourable process at higher temperatures. Both Langmuir and Sips isotherm models presented satisfactory adjustment at all temperatures and the pseudo-second-order model presented the best fit for the experimental results. The application of the intra-particle diffusion model showed that the adsorption process started instantaneously through the boundary layer of the adsorbent and that the pore diffusion step was a limiting step in the process. Finally, the capacity of the h-MO was compared with other adsorbents that had been used for diuron removal from contaminated where it was found that the adsorption capacity of the h-MO is much higher than other natural adsorbents. GRAPHICAL ABSTRACT

SÍNTESE VERDE DE NANOPARTÍCULAS DE COBRE IMPREGNADAS EM CARVÃO ATIVADO PARA REMOÇÃO DE NITRATO DA ÁGUA

RESUMO Nanoparticulas metalicas apresentam funcionalidades adsorventes, assim como o carvao ativado. Combinando as propriedades de ambos, por meio de impregnacao, e possivel produzir um material que atenda a uma lista de aplicacoes para adsorcao de contaminantes em agua. Existem diferentes metodologias de impregnacao, no entanto, estas sao caras e utilizam produtos poluentes. Assim, o presente trabalho objetiva o desenvolvimento de um processo de sintese “verde”, isto e, ambientalmente correto, para impregnacao das nanoparticulas de cobre em carvao ativado utilizando extratos de folhas de Moringa oleifera, a fim de remover nitrato da agua. Para isso, solucoes de cobre com diferentes concentracoes foram adicionadas ao carvao ativado juntamente com o extrato de folhas de moringa. Em seguida, foram separados por filtracao e secos, sendo caracterizados por BET, MEV, MET e EDS. Foram realizados experimentos de adsorcao para avaliar a eficiencia de remocao de nitrato da agua, sendo as concentracoes determinadas por espectrofotometria UV. Os resultados confirmaram a impregnacao das nanoparticulas metalicas de cobre sobre o carvao e que os mesmos possuem elevada area superficial, apresentando remocao significativa de nitrato apos os testes de adsorcao. Assim, pode-se concluir que a sintese “verde” para impregnacao em carvao ativado foi eficiente e que os materiais produzidos sao potenciais adsorventes para remocao de contaminantes da agua, como o nitrato.

TRATAMENTO DE ÁGUA UTILIZANDO COAGULANTE MAGNÉTICO BASEADO EM EXTRATO DE SEMENTES DE MORINGA OLEIFERA LAM E NANOPARTÍCULAS DE ÓXIDO DE FERRO

Nas estacoes de tratamento de agua, os coagulantes mais empregados sao os inorgânicos, que sao sais trivalentes de ferro e aluminio. Entretanto, a utilizacao de substâncias quimicas para tornar a agua potavel pode acarretar outras contaminacoes, como os subprodutos gerados no processo de desinfeccao por cloracao, os trihalometanos, substâncias com potencial carcinogenico. Alem disto, o aluminio nao e biodegradavel, podendo ocasionar problemas de disposicao e tratamento do lodo gerado. Neste contexto, propoe-se avaliar a eficacia da coagulacao/floculacao (C/F) utilizando o coagulante natural Moringa oleifera Lam (Mo), funcionalizada com nanoparticulas magneticas de oxido de ferro, para obtencao de flocos que sejam atraidos por um campo magnetico externo, permitindo assim uma agil decantacao e separacao do liquido clarificado. Os ensaios foram realizados em Jar Test, utilizando agua proveniente da bacia do rio Pirapo, Maringa, PR. Amostras foram coletadas para avaliar a eficiencia de remocao dos parâmetros de cor aparente, turbidez e compostos com absorcao de UV254nm. Foi possivel constatar que o tratamento de C/F utilizando o coagulante Mo funcionalizada foi capaz de reduzir os valores dos parâmetros fisicoquimicos avaliados sob influencia de um campo magnetico, com reduzido tempo de sedimentacao.