Avaliação termodinâmica e cinética de processos adsortivos do azul de metileno.

Abstract

The evaluation of different types of adsorbents allows the reuse of residues in which they can negatively impact the environment for the treatment of textile effluents that have a large amount of contaminants, in which in this study tests were carried out on different adsorbents in the removal of the methylene blue dye . The objective of this work is the kinetic and thermodynamic evaluation of alternative adsorbents used to remove the dye, thus describing the adsorption behavior. The raw materials used as precursor material were rice husk (Oryza sativa L.), wood in the Neem (Azadirachta indica A. Juss) and Algaroba wood (Prosopis juliflora (Sw.) DC). Samples were used that present in the case of unprocessed rice husk and modifications with CH3COONa, H3PO4 and KOH, Chemically and Physically Activated Carbon from Algaroba and Nim, Activated charcoal from pure rice husk and respective modifications CH3COONa, H3PO4 and KOH. In total, 12 samples were analyzed, according to the data obtained, only the pseudo-second order kinetic model referring to the adsorption kinetics adjusted to the data. When analyzing the results obtained from the adsorption isotherms, the only model that adjusted to Langmuir's data was the Chemically Activated Carbon of the Neem, whereas the Freundlcih model was the chemically / physically and chemically activated coal from Algaroba, Activated carbon from the modified rice husk KOH, H3PO4 fit the model. To understand how temperature affects adsorption, thermodynamic parameters were estimated only for isotherms that are adjustable to the Langmuir and / or Freundlich models. The adsorption is modeled by the pseudo-second order kinetic model, in which, the adsorbent molecules take the surface of the adsorbent through two active sites, the Langmuir model presents monolayer formation between solids / solutions, the Freundlich model of multilayer formation in heterogeneous surface. Analyzing thermodynamic it can be concluded that the adsorption to CATQ of Neem is not favorable, the samples that present favorable adsorption are: CATQF AND CATQ from Algaroba and CA from rice husk modified by KOH and H3PO4.