Analysis of commonly used batch adsorption kinetic models derived from mass transfer-based modelling.

Modelling of liquid-solid batch adsorption based on mass transfer and conservation equations results in differential equations that may have or not an analytical solution. Even when analytical solutions are available, several simplified models can be considered for evaluating kinetic data of batch adsorption experiments. However, these simplified models are commonly used regardless of the premises considered in its development, and the analysis of the kinetic experiments based on these simplified models may be severely compromised. For this reason, this work presents a detailed development of the phenomenological models, and the hypotheses considered in its development are clearly stated. Typical simplified models derived from the phenomenological ones are obtained, and the conditions considered in the simplification are critically assessed. It was observed that the simplified models fail mainly for considering the concentration of the bulk phase constant over time or considering a linear adsorption isotherm. It must be emphasised that even when phenomenological models must be solved through numerical procedures, its use must be preferred, since the agreement with model premises and experimental conditions are closer, ensuring the quality of the kinetic data analysis.

Evaluation of biobutanol production by Clostridium beijerinckii NRRL B-592 using sweet sorghum as carbon source / Avaliação da produção de biobutanol por Clostridium beijerinckii NRRL B-592 usando sorgo sacarino como fonte de carbono

In this research it was evaluated the production of biobutanol by Clostridium beijerinckiiNRRL B-592 using sweet sorghum juice as carbon source. Operational variables, like pH and initial inoculum size, as well as supplementation of industrial media with yeast extract and tryptone, were evaluated. The maximum butanol obtained was 2.12g kg^-1 using 12.5% of inoculum size, 0.05g 100mL^-1 of tryptone and 0.1g 100mL^-1 of yeast extract and initial pH of 5.5. The main contribution of this research was to show a systematic procedure for development of a low cost industrial media for biobutanol production from sweet sorghum.

Neste trabalho, foi avaliada a produção de biobutanol por Clostridium beijerinckiiNRRL B-592 usando o caldo de sorgo sacarino como fonte de carbono. Foram avaliadas as variáveis operacionais como pH e densidade de inóculo, bem como a suplementação de meios industriais com extrato de levedura e triptona. A máxima concentração de butanol obtida foi de 2,12g kg^-1, utilizando 12,5% de inóculo, 0,05g 100mL^-1 de triptona e 0,1g 100ml^-1 de extrato de levedura e pH inicial de 5,5. A principal contribuição deste trabalho foi o de mostrar um procedimento sistemático para o desenvolvimento de um meio industrial de baixo custo para a produção de biobutanol a partir de sorgo sacarino.

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.