Physicochemical Characterization of a Clay from Sergipe State and its Potential as an Adsorbent

Abstract

Water treatment is fundamental to removing industrial dyes, such as methylene blue, and to mitigate their severe environmental impacts. In this context, adsorption stands out as a promising solution due to its efficiency and low cost. The use of clays, especially regional ones, is particularly strategic as it utilizes a local and abundant resource to develop a sustainable, accessible treatment technology that adds value to the region’s economy. Thus, this work aims to characterize a regional clay with possible application in the adsorption process. Through the analysis performed, the presence of quartz, calcite, hematite, and feldspar was verified via XRD, in addition to clay minerals such as kaolinite and montmorillonite, which are also part of its composition. The clay minerals are the main components in the adsorption process. From FTIR, it was possible to observe the presence of the 3695 cm⁻¹ band, characteristic of kaolinite clays, in addition to confirming the presence of characteristic bands related to the lamellar structure of clays containing tetrahedral and octahedral layers, such as the bands at 984, 914, 796, and 691 cm⁻¹. Through TGA and DTG, the decomposition of kaolinite was noted at temperatures of 480 °C and 680 °C, along with a total mass loss of 1%. With SEM, a low agglomeration of particles was observed due to the low concentration of montmorillonite in its composition; thus, less agglomerated structures tend to have a larger surface area and more free active sites for the adsorption process. And, through BET, it was found that this clay is microporous (Dp = 1.56 nm and Vp= 0.047 cm³/g) and has a high surface area (S_BET = 36.75 m²/g), and high inter-pore area, in addition to exhibiting a type IV isotherm with H3 hysteresis, typical of materials with a lamellar structure. Furthermore, preliminary adsorption tests validated this potential, achieving a maximum removal of 89.39% of the dye using a 0.3 g mass.