Inserção da temperatura no modelo de Langmuir aplicado na adsorção de íons cobre por zeólita 5A : experimental e estatística Bayesiana

Abstract

The treatment of wastewater contaminated by heavy metals represents a significant environmental challenge, with adsorption being one of the main approaches for removing these contaminants, as it exhibits high efficiency in molecular separation. Understanding the interaction between adsorbent and adsorbate is essential for predicting dynamics under different operational conditions. Thus, the use of modeling techniques in isotherm prediction allows for estimating adsorption performance, reducing the need for intensive experimentation, while promoting process optimization. Considering these factors, this work aimed to develop a predictive model capable of estimating adsorption isotherms of copper ions by zeolite 5A at different temperatures. The methodology involved the production and characterization of kaolin waste, metakaolin, and the zeolitic product, utilizing characterization techniques such as X-ray Fluorescence Spectrometry (XRF), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and thermal analyses, including Thermogravimetry (TG), Differential Thermogravimetry (DTG), and Differential Scanning Calorimetry (DSC), to determine the chemical and mineralogical composition, morphology, and thermal stability of the material. Adsorption isotherms of copper ions were performed at temperatures of 25 ºC, 35 ºC, 45 ºC, 55 ºC, 65 ºC, 75 ºC, 85 ºC, and 95 ºC. To study the adsorption mechanisms and the adsorbent/adsorbate interaction, the Markov Chain Monte Carlo (MCMC) method with the Metropolis-Hastings algorithm was used to estimate model parameters and subsequently fit them to the experimental data. Based on these data, the Langmuir model was adapted to incorporate temperature, in the range of 25 ºC to 150 ºC, followed by the calibration, validation, and prediction of adsorption dynamics. The characterization results confirmed the potential use of kaolinitic waste for zeolite synthesis, as well as the successful formation of zeolite 5A through its chemical composition, mineralogy, and morphology. The isotherms revealed that copper removal capacity increased proportionally with temperature, obtaining a maximum adsorption capacity of 754.85 mg/g at 95 ºC. The parameter estimation validated the adaptation of the Langmuir model for different thermal conditions, which proved effective in predicting the isotherms, optimizing the adsorption process at different temperatures, and providing a good model estimate, thus enabling the reduction of extensive experimental activities.