Significantly enhanced alkaline stability and cyanide suppression of Prussian blue analogues using montmorillonite for high-performance cesium removal

•A safety, non-toxic and high effective material for Cs+ remediation is developed.•KCuFC/M−MT has low cyanide release, high stability in pH 2–12 and non-toxic to HepG2 cells.•High effective and high selectivity of Cs+ adsorption is demonstrated.•The adsorption mechanism and stabilization mechanism were systematically studied.•It gives the future directions of new and selective Cs+ decorporation agent.