Over the past few decades, researchers have focused on developing new compositions and preparation techniques for geopolymers, as multifunctional products, to optimize their characteristics for use in multiple applications. Therefore, this paper investigates metakaolin geopolymer foam and introduces new geopolymer foams based on hybrid metakaolin and wollastonite mineral precursors for water purification. The geopolymer foams were prepared using an alkaline activator, mineral-based powders (wollastonite and metakaolin), a foaming agent (aluminum powder), and a foam stabilizer (olive oil). In addition to mechanical tests and assessments of the adsorption capacity of heavy metal ions, the geopolymer foams were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The geopolymer foams exhibited unique pore structures, containing four classes of pore networks with diameters around 1000 µm, 25 µm, 3 µm, and a well-arranged mesopore network of 50 nm. The utilization of wollastonite (CaSiO₃) alongside metakaolin as a hybrid precursor led to fundamental changes in the composition of the geopolymer binders: a new crystal phase, Ca₅(SiO₄)₂(OH)₂, was formed, and the Si-Al-Na crystal phase disappeared, which led to an increase in the amorphous phase from 87% to 92%. The adsorption rate of heavy metal ions, namely Cr, Co, Cu, Zn, Pd, and As, increased upon introducing wollastonite as a precursor, with absorption rates ranging from 11% to 68%. The findings also revealed that wollastonite significantly increased the geopolymers foams’ compressive strength and elastic modulus from 30 KPa to 67 KPa and from 31 MPa to 126 MPa, respectively.

In recent decades, researchers have developed innovative compositions and methods to fabricate geopolymers and enhance their properties for diverse multifunctional applications. Geopolymer foams are regarded as promising functional materials across numerous disciplines; however, they face challenges such as brittleness and limited mechanical strength. This investigation aims to produce a geopolymer foam composite by incorporating three-dimensional (3D) Luffa Cylindrical Fibers (LCF) into a metakaolin-wollastonite geopolymer matrix. The composites were synthesized using an alkaline activator, mineral powders (wollastonite and metakaolin), a foaming agent (aluminum powder), and a foam stabilizer (olive oil). Their mechanical characteristics and capacity for Cu and As ion adsorption were examined, with structural analyses supplemented by scanning electron microscopy (SEM) and optical microscopy. Reinforcing with LCF markedly improved mechanical performance: flexural strength increased from 0.27 MPa to 0.60 MPa, while compressive strength rose from 0.04 MPa to 0.34 MPa. In addition to the amorphous structure, two new crystalline phases were detected: analcime and anorthite in the GLF matrix. The geopolymer foam composite (GLF) exhibited adsorption capacities of 4.6 mg/g for Cu, 5.18 mg/g for As, and 5.09 mg/g for methylene blue (MB) dye. The equilibrium adsorption capacity (qe) for Cu ions varies with the GLF mass, with smaller GLF masses yielding higher qe. Specifically, qe increases from 2.1 mg/g to 12 mg/g as the GLF mass decreases from 2 g to 0.25 g. Visual assessments reveal enhanced dye adsorption following LCF incorporation. Its high efficacy in removing Cu ions and metal-uptake capacity underscores its potential for practical water-treatment applications, offering sustainable solutions for environmental management.