A comprehensive review of phosphate-based acid geopolymers: production, properties, and applications

Phosphate-based geopolymers have emerged as versatile and sustainable materials with distinct advantages over traditional binders. Formed through acid-based activation, typically using phosphoric acid, these geopolymers exhibit unique features such as enhanced chemical resistance, tunable porosity, and compatibility with a wide range of raw materials, including industrial residues. This review provides a comprehensive overview of the synthesis mechanisms, structural evolution, and functional properties of phosphate-based geopolymers. Particular emphasis is placed on their applications in waste stabilization, soil remediation, and adsorption and catalytic processes for environmental management. Additionally, this study discusses current challenges and future research directions, including the optimization of synthesis parameters, the incorporation of additives such as laponite, bentonite, and silica to improve rheology and mechanical strength, and the development of hybrid systems that combine inorganic and organic components to tailor performance. By integrating recent findings, this review underscores the potential of phosphate-based geopolymers as next-generation materials for sustainable engineering and environmental remediation. This review adopts a process-structure-property-application framework to explain how precursor selection, mix design, and curing conditions govern the viability of phosphate geopolymers across targeted environmental and high-temperature applications, including emerging extrusion-based additive manufacturing.