Abstract
The aim of this study was to evaluate the textural changes produced by metal-chloride-assisted carbonization of wood sawdust in a bentonite matrix and to compare FeCl3-, NiCl2-, and CoCl2-containing formulations under the same thermal regime. Composites were prepared from 2 g of bentonite and 1 g of sawdust with the corresponding metal chloride, dried at 80 °C for 24 h, and carbonized at 550 °C for 1 h under argon. Nitrogen physisorption at 77.35 K was used to determine BET specific surface area and BJH pore parameters for raw bentonite and three carbonized composites: B-Co (0.75 g CoCl2), B-Fe (0.50 g FeCl3), and B-Ni (0.50 g NiCl2). The BET surface area increased from 45.836 m² g⁻¹ for raw bentonite to 223.915, 248.350, and 233.406 m² g⁻¹ for B-Co, B-Fe, and B-Ni, respectively, corresponding to 4.89-, 5.42-, and 5.09-fold increases. At the same time, BJH adsorption pore volume decreased from 0.012 cm³ g⁻¹ to 0.007–0.008 cm³ g⁻¹, and the characteristic BJH pore radius decreased from 2.152 nm to 1.626–1.955 nm. These results indicate that the additional nitrogen-accessible surface is not explained by an increase in BJH mesopore volume and is consistent with the development of finer porosity and carbon–clay interfacial surface. Among the tested formulations, B-Fe exhibited the highest BET area. Thus, FeCl3-assisted carbonization provides the strongest basis for subsequent structural characterization and adsorption testing, although graphitic ordering and sorption capacity require independent verification.