Ion Exchange Properties of Günterblassite and Gmelinite, Prototypes of Microporous Materials for Water Purification

Processes and products of ion exchange of günterblassite (K,Ca,Ba,Na) 3– x Fe 1– y [(Si,Al) 13 O 25 (OH,O) 4 ]·7H 2 O (microporous silicate, structurally intermediate between smectites and zeolites) and three samples of zeolite gmelinite (Na,K,Ca,Mg) x [(Si,Al) 12 O 24 )· n H 2 O of different composition with cations of various metals were studied. It was shown that günterblassite exhibits high activity and sorption capacity with respect to Rb + , Cs + , Ag + cations and, to a lesser extent, Pb 2+ and Ba 2+ : even at room temperature for 1 h, the concentration of M 2 O (M = Rb, Cs, Ag) in the sorbent reaches 10–13 wt %. The ion exchange in gmelinite occurs according to the frontal mechanism, propagating from the periphery of the crystal to its center. In reactions with Pb 2+ , the activity of gmelinite increases with a rise in its sodium content and decreases with a rise in potassium content. The crystal structure of Pb-substituted gmelinite was studied and it was shown that Pb 2+ ions populate both zeolite channels. Synthetic gmelinite obtained from cheap natural raw materials and fly ash from thermal power plants can be used to purify water from lead.