Reusable MgO/Geopolymer Nanocomposites with High Adsorption Capacity for Methylene Blue as Effects of Mixed-Phase Diffraction and Optical Response Changes

Water contamination due to synthetic dyes has continued to increase in recent years and has become a significant environmental problem. The development of effective and sustainable materials to address these problems is essential. To address the challenge, a comprehensive study on synthesizing MgO nanoparticles from seawater bittern and compositing them with a geopolymer matrix for methylene blue (MB) adsorption was chosen. The SEM results show the presence of MgO, which acts like particles attached to the geopolymer grains and gives a more compact boundary effect. X-ray diffractograms showed structural changes, proved by mixed-phase, indicating the successful synthesis of geopolymer/MgO nanocomposites. Quantitative analysis of the I-R spectra shows the change in optical response that is demonstrated by higher \({\varvec{k}}\) value transitions \(\Delta \left({\varvec{L}}{\varvec{O}}-{\varvec{T}}{\varvec{O}}\right)\) leading to more specific absorption. Optical response changes correlated with BET analysis with modified surface and BJH pore with good consequently \({\varvec{D}}(\boldsymbol{\%})\) >75% degradation performance for MB dye based on UV–Vis absorbance analysis. The maximum adsorption capacity achieved was 81.97 mg g⁻¹ with optimum conditions at pH 11 and a contact time of 160 min, and the recyclability test showed an efficiency of 59.67% after seven cycles. Finally, the synergistic effect between mixed phase diffraction and optical response due to the dispersion of MgO nanoparticles on the geopolymer matrix can be a promising candidate for MB adsorbent.