Environmental syntheses of nanosized zeolites with high yield and monomodal particle size distribution

Colloidal LTA and FAU type zeolites have been prepared by a multi-step synthesis approach based on re-using of non-reacted aluminosilicate mother liquors after separating crystalline zeolite particles following each individual synthesis step. The colloidal zeolites extracted from successive synthesis batches have the same crystalline structure and particle size, but differ slightly in their chemical composition. The change in the chemical composition of the crystals has been attributed to the gradual depletion of the sodium content in the reacting system during the multi-step syntheses. This suggests that the non-reacted compounds in the solutions can be recovered after each synthesis step, leading to successful nucleation and crystallization of the same zeolite phase. The current approach enables a substantial rise in the crystalline yield of colloidal zeolites and keeping the particle size constant. From an environmental perspective, this process is extremely beneficial since the re-use of the starting compounds minimizes the amount of waste produced during the synthesis of colloidal zeolites. (c) 2006 Elsevier Inc. All rights reserved.