Framework-preserving structuring of zeolites for continuous-flow water treatment: From powders to additively manufactured and cold-consolidated monoliths

Zeolites are effective and economical ion exchangers for water treatment, but their physical form limits continuous-flow application. Fine powders provide rapid exchange yet require downstream solid–liquid separation. In contrast, granules and pellets are easier to operate in fixed beds but may suffer from mass-transfer limitations, attrition, flow maldistribution, and incomplete utilization of internal exchange sites. This critical review frames zeolite shaping as a framework-preservation problem: retention of crystallinity, accessible micropore volume, exchange-site accessibility, connected transport porosity, and hydraulic function during fabrication. Conventional pelletization, extrusion, binder addition, and thermal sintering are assessed alongside additive manufacturing and low-temperature pressure-assisted routes. Additive manufacturing provides geometric control but commonly requires binders and post-treatment. Cold consolidation instead seeks the minimum interparticle bonding required for mechanical and hydraulic stability while preserving transport pathways and is distinguished from densification-oriented cold sintering. The analysis covers LTA, FAU, CHA, MOR, and HEU frameworks and relates topology, Si/Al ratio, cation form, and chemical stability to shaping tolerance and ion-exchange performance. Ammonium and metal-ion removal are used as representative applications and benchmarked against granular natural clinoptilolite. Binder-free clinoptilolite monoliths formed at room temperature near 200 MPa with 3 wt% water have achieved flexural strengths approaching 10 MPa while retaining substantial ammonium uptake under long-residence-time conditions. However, the present evidence remains at the laboratory scale and is concentrated within one research group. Independent replication, standardized breakthrough testing, repeated regeneration, long-term hydraulic evaluation, and scale-up remain necessary.