Characterization of Zeolite Types Contained in Sangaredi Bauxite in the Republic of Guinea

Abstract

Since their discovery, zeolites have generated significant interest in various technological fields, such as molecular sieves, ion exchangers, catalysts, and especially as adsorbents. This article focuses on characterizing the types of zeolites present in Sangarédi bauxite. To achieve this objective, we conducted a physico-chemical characterization (moisture, particle size, volumetric density, porosity) and determined the optimal conditions for activating the zeolite samples (15% H 2 SO 4 concentration, L/S ratio of 2, temperature of 70˚C, duration of 3 hours). Techniques used to characterize the samples included desiccation gravimetry, mechanical sieving, X-ray fluorescence (atomic percentage), X-ray diffraction, BET method, and water pycnometry. Additionally, we assessed the adsorption capacity of zeolites activated by the elimination of methylene blue in an aqueous solution, which was selected as a model water pollutant. According to X-ray fluorescence and diffraction data, there are nine types of zeolite in Sangarédi bauxite, divided into five families. Regarding physical activation, a good porous structure was observed at a temperature of 300˚C to 340˚C for 4 hours. Above this range, material condensation occurs, leading to a sudden increase in mass loss, which can be explained by a change in their crystalline structure. After treatment with sulfuric acid, the activated samples showed an increase in specific surface area (from 72 to 130.25 m 2 ∙g − 1 on average) and porosity (from 0.07% to 0.3%), as well as an increased susceptibility to methylene blue discoloration (from 13.58% to 30.35%). These results confirm the improvement in the microporous structure and the formation of a more developed molecular sieve network. Thanks to the identified structural and textural characteristics, it can be concluded that the activated zeolites obtained are extremely reactive materials and can be used effectively in water treatment.