Reusable MgO/Geopolymer nanocomposites with high Adsorption capacity for methylene blue as effects of mixed phase diffraction and optical response changes

Abstract 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. A comprehensive study on synthesizing MgO nanoparticles from seawater bittern and compositing them with geopolymer matrix for methylene blue (MB) adsorption was chosen to address the challenge. 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 that proved by mixed phase at 2\(\:θ\:\): 21.12°, 29.47°, and 57.48° indicating the successful synthesis of geopolymer/MgO nanocomposites. Quantitative analysis of the I-R spectra shows the change optical response that proofed by higher \(\:k\) value transitions \(\:\:(LO-TO)\) from 165 cm⁻¹ to 204 cm⁻¹ leading to more specific absorption. Optical response changes correlated with BET analysis with modified surface area of 56.60 m² g⁻¹ and BJH pore size of 1.92 nm with good consequently \(\:D(%)\) >75% degradation performance for MB dye based on UV-Vis absorbance analysis. The maximum adsorption capacity achieved 81.97 mg g⁻¹ with optimum conditions at pH 11 and a contact time of 160 minutes, and the recyclability test shows an efficiency of 59.67% after seven cycles. Finally, synergistic effect between mixed phase diffraction and optical response as a result of dispersion of MgO nanoparticles on geopolymer matrix can be promising candidate as MB adsorbent.