Lucas Meili

Adsorption of leather dye onto activated carbon prepared from bottle gourd: equilibrium, kinetic and mechanism studies

Activated carbon prepared from bottle gourd has been used as adsorbent for removal of leather dye (Direct Black 38) from aqueous solution. The activated carbon obtained showed a mesoporous texture, with surface area of 556.16 m(2) g(-1), and a surface free of organic functional groups. The initial dye concentration, contact time and pH significantly influenced the adsorption capacity. In the acid region (pH 2.5) the adsorption of dye was more favorable. The adsorption equilibrium was attained after 60 min. Equilibrium data were analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The equilibrium data were best described by the Langmuir isotherm, with maximum adsorption capacity of 94.9 mg g(-1). Adsorption kinetic data were fitted using the pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. The adsorption kinetic was best described by the second-order kinetic equation. The adsorption process was controlled by both external mass transfer and intraparticle diffusion. Activated carbon prepared from bottle gourd was shown to be a promising material for adsorption of Direct Black 38 from aqueous solution.

Use of papaya seeds as a biosorbent of methylene blue from aqueous solution

In this study papaya seeds were used to remove methylene blue dye from aqueous solution. Papaya seeds were characterized as possessing a macro/mesoporous texture and large pore size. Studies were carried out in batches to evaluate the effect of contact time and pH (2-12) on the removal of dye. It was observed that the adsorption of dye was better in the basic region (pH 12). The equilibrium data were analyzed using Langmuir, Freundlich, Dubinin-Raduschkevich, Tempkin, Jovanovich, Redlich-Peterson, Sips, Toth and Radke-Prausnitz isotherms. The equilibrium data were best described by the Langmuir isotherm with a maximum adsorption capacity of 637.29 mg g(-1). Adsorption kinetic data were fitted using the pseudo-first-order and pseudo-second-order model. The adsorption kinetic is very fast and was best described by the pseudo-second-order model.

Ouricuri (Syagrus coronata) fiber: a novel biosorbent to remove methylene blue from aqueous solutions

In this work, the potential of ouricuri (Syagrus coronata) fiber as a novel biosorbent to remove methylene blue (MB) from aqueous solutions was investigated. The fiber was prepared and characterized according to the fundamental features for adsorption. A 23 experimental design was used to evaluate the effects of adsorbent dosage (M), fiber diameter (D) and agitation (A) on the adsorption capacity. In the more adequate conditions, kinetic and equilibrium studies were performed. The experimental design results showed that M = 10 g L-1), D = 0.595 mm and A = 200 rpm were the more adequate conditions for MB adsorption. Based on the kinetic study, it was found that the adsorption process was fast, being the equilibrium was attained at about 5 min, with 90% of color removal. The isotherm was properly represented by the Sips model, and the maximum adsorption capacity was 31.7 mg g-1. In brief, it was demonstrated that ouricuri fiber is an alternative biosorbent to remove MB from aqueous media, taking into account the process efficiency and economic viewpoint.

Comparison between Brazilian agro-wastes and activated carbon as adsorbents to remove Ni(II) from aqueous solutions

This research was performed to find an alternative, low-cost, competitive, locally available and efficient adsorbent to treat nickel (Ni) containing effluents. For this purpose, several Brazilian agro-wastes like sugarcane bagasse (SCB), passion fruit wastes (PFW), orange peel (OP) and pineapple peel (PP) were compared with an activated carbon (AC). The adsorbents were characterized. Effects of fundamental factors affecting the adsorption were investigated using batch tests. Kinetic and equilibrium studies were performed using conventional models. It was verified that the adsorption was favored at pH of 6.0 for all agro-wastes, being dependent of the Ni speciation, point of zero charge and surface area of the adsorbents. The Ni removal percentage was in the following order: SCB > OP > AC > PFW > PP. From the kinetic viewpoint, the Elovich model was appropriate to fit the Ni adsorption onto SCB, while for the other adsorbents, the pseudo-first-order model was the most suitable. For all adsorbents, the Langmuir model was the more adequate to represent the equilibrium data, being the maximum adsorption capacities of 64.1 mg g(-1), 60.7 mg g(-1), 63.1 mg g(-1), 48.1 mg g(-1) and 64.3 mg g(-1) for SCB, PFW, OP, PP and AC, respectively. These results indicated that mainly SCB and OP can be used as alternative adsorbents to treat Ni containing effluents.

ESTUDO DA SECAGEM E EXTRAÇÃO DE SEMENTES DE MAMÃO (CARICA PAPAYA L.)

Em virtude de características como o alto teor em óleo, quantidade expressivas de glucosinolatos, fonte de pectina, entre outros, buscou-se através desse trabalho avaliar as melhores condições de secagem e extração do óleo das sementes de mamão do tipo Caricapapaya L. Para o desenvolvimento deste, as sementes foram secas em estufa de esterilização nas temperaturas de 60 e 70°C e, em seguida, foram realizadas extrações via sonicação de amostras com diâmetros médio de 1,200 mm, 0,780mm e inferior a 0,655mm. Com os dados obtidos, curvas de secagem foram construídas e ajustadas segundo modelos matemáticos. Espectros de absorbância em função do comprimento de onda também foram construídos e analisados.

Immobilization of inulinase obtained by solid-state fermentation using spray-drying technology

Abstract This work focuses on the immobilization of a crude inulinase extract obtained by solid-state fermentation using spray-drying technology. Maltodextrin and arabic gum were used as immobilizing agents. The effects of inlet air temperature, maltodextrin/arabic gum ratio and mass fraction of crude enzyme extract on the activity of immobilized inulinase were assessed using a central composite rotatable design (CCRD) (23). The optimum operational conditions for the immobilization of inulinase by spray-drying was obtained at an inlet air temperature of 200°C, mass fraction of crude enzyme extract of 0.5 wt% and using only arabic gum as immobilizing agent. The immobilized enzyme had good thermostability, comparable with other inulinases obtained from different microorganisms. The method used gave good enzyme activity after immobilization and could be applied to other enzymes which have good thermal stability.

Mathematical Modeling of Thin Layer Drying of Papaya Seeds in a Tunnel Dryer Using Particle Swarm Optimization Method

The processing of papaya generates a significant amount of solid wastes. The seeds represent a significant amount and a source of untapped products. Papaya seeds have useful compounds, which can be obtained from its extracts or oils and can be a very effective biosorbent. For good results in the compounds achievement and the pretreatment, it is essential the appropriated choice of the drying conditions. This article proposes the study of the drying of papaya seeds in a tunnel dryer at three drying temperatures (40, 70, and 100°C) and three air drying velocities (1.0, 1.5, and 2.0 m · s−1). Empirical and semi-empirical models were proposed to adjust the kinetic parameter as a function of the drying conditions. The particle swarm optimization method was used, obtaining, as a result, an exponential model with good prediction quality and with few parameters to be adjusted.

CARACTERIZAÇÃO E PROCESSAMENTO DE TELAS DE LCD DE CELULARES VISANDO A RECICLAGEM

The great technological development leads to a large consumption of electronic products. The electronics are increasingly becoming obsolete and faster discarded, often without adequate treatment, contaminating water, soil and air by being exposed to the environment. Among these products are the mobile phones which have as a major component the LCD panel (Liquid Crystal Display). The LCD panel consists of multilayers of different materials, some with high added value, such as indium tin oxide (ITO). The presence of noble materials in the composition of this type of residue makes its recovery profitable. The objective of this study is to characterize and separate the different materials that constitute the LCD panels of cell phones into disuse. Initially, the different materials that form the panels are manually separated such as adhesives, diffusive sheets , reflective sheets, connectors, polarizing film, plastic frame and the glass panel with ITO. The polarizing film that adheres to glass was removed through a bath of solvent. Then, we performed a milling of the screen in a knives mill. In this milling process were used screens containing polarizing film and screens without the film, in order to obtain a uniform particle size aiming the recovery of the elements present. With these procedures the mass ratio of each material present in the cellular LCD panels was obtained, as well as a material with low particle size, suitable to undergo to a hydrometallurgical processes.

Adsorption of methylene blue on agroindustrial wastes: Experimental investigation and phenomenological modelling

In this work, agro-wastes coming from soursop (peel, seeds and pulp fiber) and sugarcane (bagasse) are used as low-cost biosorbents to remove methylene blue (MB) from aqueous media. Batch experiments are performed under different experimental conditions investigating the effects of biosorbent amount, dye concentration and stirring rate. The best results were found using soursop wastes for a MB concentration of 100 mg L-1, using 0.75 g of residue and a stirring rate of 110 rpm, removing a percentage above 90%. Theoretically, adsorption kinetic can be successfully described by the pseudo-second order model. Redlich-Peterson and Sips models are adopted to interpret the equilibrium adsorption of MB on sugarcane bagasse and soursop residue, respectively. Interestingly, the monolayer model with single energy derived by statistical physics theory is also applied for a deeper explanation of the adsorption mechanism of MB on both the adsorbents. The application of this model allows defining the adsorption geometry of the investigated adsorbate and provides important information about the interactions between the adsorbate and sorbents. In particular, the modelling analysis by statistical physics allows defining that the dye molecules are adsorbed in vertical position and the adsorption process is multi-molecular (i.e. n > 1). Finally, the estimation of adsorption energy suggested that MB adsorption on biosorbent is a physisorption process.

INFLUÊNCIA DA TEMPERATURA NOS RENDIMENTOS DOS PRODUTOS DA PIRÓLISE DO ENDOCARPO DO OURICURI (SYAGRUS CORONATA (MART) BECC.)

O licuri ou ouricuri, Syagrus coronata (Mart) Becc., e uma palmeira cuja distribuicao se estende ate o litoral brasileiro, cresce bem nas restingas baianas, mas tem preferencia pelas regioes de caatinga, crescendo em areas altamente pedregosas e castigadas pelo sol, ate outras com melhores condicoes de solo, tornando-se parte da vegetacao predominante de algumas regioes. Um estudo realizado em Buique (PE), mostrou que a importância do ouricuri esta relacionada predominantemente ao uso da amendoa. Como forma de aproveitar o endocarpo (material lignificado que envolve a amendoa), este trabalho objetiva o estudo da pirolise do endocarpo do ouricuri, agregando valor, por meio da geracao de produtos com potencial comercial. Avaliou-se o rendimento dos produtos obtidos para diferentes temperaturas finais (400, 500, 600 e 700oC), com taxa de aquecimento de 10oC/min e o tempo de residencia de 2h (duas horas), alem de vacuo constante de 50mmHg, para controlar a atmosfera do reator, evitando queima. Com o aumento de temperatura, o rendimento em carvao diminuiu devido a decomposicao dos constituintes do endocarpo. Por sua vez o rendimento em gases foi crescente com o aumento da temperatura e o rendimento da mistura liquida aumentou na faixa de 400oC a 600oC, mas decresceu a temperatura de 700oC, devido ao craqueamento dos vapores condensaveis.