Zeolite P was synthesized for the first time via a novel water-bathing route at 90 C using scrubbed diatomite,sodium hydroxide,and aluminum hydroxide as precursor,with SiO 2/Al 2 O 3,SiO 2/Na 2 O,and H 2 O/Na 2 O molar ratios of 7.43,3.81,and 80.00,respectively.The as-fabricated samples were characterized by means of scanning electron microscopy,X-ray diffraction,and nitrogen adsorption measurements.This study showed that (i) treating the diatomite raw material with sodium hexametaphosphate could open the pores in the diatomite via removal of the clay clogged in its pores;(ii) tetragonal mesoporous zeolite P samples with a surface area of 56-60 m 2/g could be generated after 6-24 h of water-bathing reaction at 90 C;(iii) extension of water-bathing reaction time could improve the mesoporous structure of zeolite P;and (iv) Ca 2+ adsorption capacity of the zeolite P sample was about 300 cmol/kg.Such high-surface-area porous zeolite P could be used as an effective adsorbent for the treatment of water containing calcium and magnesium ions. Zeolite P was synthesized for the first time via a novel water-bathing route at 90 C using scrubbed diatomite, sodium hydroxide, and aluminum hydroxide as precursor, with SiO 2 / Al 2 O 3, SiO 2 / Na 2 O, and H 2 O / Na2O molar ratios of 7.43, 3.81, and 80.00, respectively. As-fabricated samples were characterized by means of scanning electron microscopy, X-ray diffraction, and nitrogen adsorption measurements. This study showed that (i) treating the diatomite raw material with sodium hexametaphosphate could open the pores in the diatomite via removal of the clay clogged in its pores; (ii) tetragonal mesoporous zeolite P samples with a surface area of ​​56-60 m 2 / g could be generated after 6-24 h of water-bathing reaction at 90 C; (iii) extension of water-bathing reaction could could improve the mesoporous structure of zeolite P; and (iv) Ca 2+ adsorption capacity of the zeolite P sample was about 300 cmol / kg. Such high-surface-area porous zeolite P could be used as an effective adsorbent for the treatme nt of water containing calcium and magnesium ions.