ABSTRACT
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.
Subject(s)
Adsorption , KineticsABSTRACT
O objetivo deste trabalho foi relatar e discutir por meio da apresentação de casos clínicos a utilização de duas diferentes técnicas de microabrasão do esmalte na remoção de manchas. No primeiro caso clínico, utilizou-se uma mistura de pedra-pomes e ácido fosfórico 37%. No segundo caso clínico, foi utilizado ácido clorídrico 6% e carbeto de silício. Independentemente da técnica selecionada, o sucesso na remoção das manchas está relacionado a corretos diagnósticos. Pode-se concluir que as duas técnicas de microabrasão do esmalte foram capazes de remover as manchas intrínsecas do esmalte, mostrando sua eficácia e, assim, restabelecendo a estética dos elementos dentários envolvidos.
The aim of this study was to report and discuss, through the presentation of clinical cases, the use of two different enamel microabrasion techniques to remove stains. Two techniques were compared between themselves. In the first clinical case used a mixture of pumice and 37% phosphoric acid. In the second case was used 6% cloridric acid and siliceous carbide. Regardless of the technique selected the successful of spots removal is related to a correct diagnosis. It can be concluded that two enamel microabrasion techniques were able to remove intrinsic stains from enamel, demonstrating its effectiveness and thus restoring the esthetics of the teeth involved.
