Environmental Valorization of Industrial Waste: Alkali-Activated Geopolymers for Potential Bone Tissue Engineering | ||||
| Egyptian Journal of Chemistry | ||||
| Articles in Press, Accepted Manuscript, Available Online from 27 August 2025 | ||||
| Document Type: Review Articles | ||||
| DOI: 10.21608/ejchem.2025.400740.11997 | ||||
 View on SCiNiTO | ||||
| Authors | ||||
Kesmat yosri Morgan  1; Hisham Khater2; Tarek Osman3; Ayman A. Abdel Aziz4
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| 1Raw duilding material, Housing and building national research center | ||||
| 2Housing and Building National Research Center (HBNRC) | ||||
| 3Professor at Housing and Building National Research center HBRC, Cairo, Egypt. | ||||
| 4Chemistry Department, Faculty of Science, Ain Shams University | ||||
| Abstract | ||||
| This study presents a sustainable approach to industrial waste valorization by investigating the effect of sodium hydroxide (NaOH) molarity on the bioactive characteristics of dual-source geopolymers synthesized from coal fly ash and metakaolin waste streams. As a circular economy solution, geopolymer samples were synthesized using NaOH solutions at three concentrations (1 M, 3 M, and 5 M) to determine sustainable processing conditions that maximize waste utilization efficiency and material bioactivity. The waste-derived materials underwent comprehensive characterization using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), real-time pH monitoring, and compressive strength testing. The findings demonstrated that NaOH concentration significantly influences both environmental sustainability and the material's ability to form hydroxyapatite (HA). Geopolymers activated with 1 M NaOH exhibited optimal bioactive performance while requiring lower chemical consumption, representing the most environmentally favorable processing condition. This low-molarity activation resulted in uniform hydroxyapatite layer formation through moderate pH conditions and controlled crystallinity. Conversely, 5 M NaOH activation increased environmental burden through higher chemical consumption while producing unfavorable surface conditions for HA nucleation due to excessive alkalinity and crystallinity. This research establishes that environmentally-conscious geopolymer processing using lower NaOH concentrations reduces chemical consumption and environmental impact while enhancing bioactive performance, demonstrating synergy between sustainable processing and functional properties. These findings contribute to eco-efficient waste valorization strategies and provide a framework for converting industrial by-products into high-value sustainable materials for biomedical and environmental applications. | ||||
| Keywords | ||||
| Waste valorization; Fly ash geopolymers; Alkali activation; Environmental sustainability; Hydroxyapatite formation | ||||
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