Elucidation of the methylene blue adsorption mechanism at the interface of powder pumice and aqueous solution by electro-kinetic and static contact angle measurements

Techniques for the decolorisation of colored wastewater resulting from the widespread production and use of dyes have increased significantly, and elucidation of removal mechanisms has become increasingly critical to improve their effectiveness. This study focuses on elucidating the methylene blue adsorption mechanism at the interface of powder pumice and aqueous solution with electro-kinetic and static contact angle measurements with a different approach. For this, batch adsorption experiments were carried out using pumice as an adsorbent at constant temperature at various methylene blue concentrations. Fourier-transform infrared spectra, X-ray powder diffraction and high-resolution transmission electron microscopy images of pumice samples before and after adsorption were taken to examine the relationship between the changes in structural and crystallographic characteristics and functional groups with dye adsorption. Kinetic data showed that the adsorption time of 1 h would be sufficient to ensure equilibrium adsorption. It was found that the adsorption of methylene blue on the powder pumice was exothermic in nature and the isosteric adsorption enthalpy and entropy changes were -13.03 kJ/mol and 13.47 J/K center dot mol, respectively.