Waste-Derived Zeolite-P (GIS): Synthesis, Polymorphism, Characterization, and Adsorption Applications for Water Purification and Selective Gas Separation

Zeolite-P is a synthetic member of the gismondine (GIS) framework family and is intrinsically microporous, with intersecting eight-membered-ring channels. Mesoporosity reported for some Zeolite-P samples is therefore a secondary textural feature arising from interparticle voids, crystal aggregation, defects, or deliberately hierarchical architectures rather than from the GIS framework itself. This critical review focuses specifically on waste-derived GIS/Zeolite-P and integrates polymorph selection (Na-P1 and Na-P2), phase-purity assessment, precursor-to-property relationships, shaping, regeneration, and adsorption under increasingly realistic conditions. Structural and compositional evidence from X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES), solid-state 29Si and 27Al magic-angle-spinning nuclear magnetic resonance (MAS NMR), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) analysis is evaluated in terms of what each technique can establish specifically for GIS materials. Waste-derived synthesis routes—including hydrothermal, alkali-fusion-assisted, microwave-assisted, ultrasound-assisted, sol–gel, and solvent-free methods—are compared without assuming that a waste precursor or a shorter synthesis is intrinsically lower-impact. Particular attention is paid to water purification, ion exchange, dehydration, and selective gas adsorption, while distinguishing single-solute batch tests from multicomponent, real-water, regeneration, and breakthrough evidence. The review also reconciles computational predictions with experiments: idealized pure-silica GIS models can overpredict CO2 uptake relative to realistic aluminosilicate Na-P1/Na-P2, for which extra-framework cations, hydration, and restricted diffusion strongly affect accessibility. The resulting analysis identifies phase purity, matrix effects, regeneration, leaching safety, shaping, and process-level techno-economic/life-cycle metrics as the key barriers to translation of waste-derived Zeolite-P from laboratory studies to deployable adsorbents.