Advanced Analysis of the Adsorption Mechanism of Textile Pollutant on Britholites: Modelling via Statistical Physics

Two britholites silicate Ca₄Nd₆(SiO₄)₆O were prepared by different synthesis methods and assessed to remove methylene blue (MB), as a relevant pollutant, from water. Milled and calcined samples of britholites were characterized by different technical. XRD analysis revealed the presence of only phase, whereas the morphologic study pointed out an improvement of the crystallinity degree and a decrease in the crystal size of these samples. ²⁹Si MAS NMR analysis indicated the presence of only one resonance peak attributed to Q⁰silicon species. The analysis of the preferential occupancy of the rare earth (Nd) of both crystallographic sites revealed that the neodymium preferred the Me (2) sites of the samples obtained from both preparation methods. Comparatively, the adsorbents displayed high adsorption capacities for the depollution of MB from aqueous solutions. The milled sample showed a maximum experimental adsorption capacity of 475 mg g^–1 at 333 °C, which outperformed the values showed for other materials. An advanced modelling based on the statistical physics theory was used to understand and explain the dye adsorption mechanism. The results showed that a monomolecular adsorption process occurred during the removal of this pollutant where electrostatic interactions and hydrogen bonding were involved. Regeneration studies indicated that both adsorbents showed a dye removal higher than 80% after five adsorption/desorption cycles. Overall, this study introduces an alternative adsorbent to handle dye-based water pollution and the corresponding analysis of its adsorption properties.