Optimized porous alkali-activated material for superior dye removal: synthesis and performance analysis

Abstract

In this study, a porous alkali-activated material was employed as an efficient adsorbent for the removal of methylene blue (MB). The material, referred to as GP-NC, was synthesized through geopolymerization by activating natural clay (NC) with an alkaline activator solution and incorporating H₂O₂ to induce pore formation within the matrix. The structure, microstructure, and morphology of the samples were extensively characterized using a variety of techniques, including XRD, ²⁹Si and ²⁷Al MAS NMR, FTIR, DTA/TGA, BET, SEM, and TEM. The formation of alkali-activated material was confirmed through XRD, ²⁹Si, and ²⁷Al MAS NMR analyses. The GP-NC exhibited a significantly higher surface area (30.23 m² g⁻¹) compared to NC (15.28 m² g⁻¹). Additionally, FTIR and SEM analyses validated the successful adsorption of methylene blue (MB) onto the alkali-activated material. These findings offer valuable insights into the structural properties and adsorption performance of GP-NC, emphasizing its potential as an effective adsorbent for methylene blue removal from aqueous solutions. The sorption process was best described by the pseudo second order kinetic model and the Langmuir isotherm model, with a maximum adsorption capacity of 98.95 mg g⁻¹ at 25 °C. Furthermore, the calculated mean free energy (E) using the Dubinin-Radushkevich model suggests that the adsorption of MB onto GP-NC follows a physisorption mechanism.