Synthesis, Characterization And Properties Of A/X Composite Zeolites

Under hydrothermal treatment without template, the composite NaA/X zeolites were successfully synthesized. On the basis of many experiments, the preparation conditions were optimized. The results were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Infrared spectroscopy (FTIR). The calcium ion exchange capacity、magnesium ion exchange capacity and the change of ion exchange rate in different conditions of A/X composite zeolite were measured by ion exchange and ion exchange rate of experiments.The preparation process conditions of A/X composite zeolite were optimized by single-factor tests. The results showed that A/X composite zeolite synthesized when using the molar ratios of silica alumina ratio n (SiO2)/n (Al2O3) between2.6-2.8, basicity range in n(H2O)/n(Na2O)=25-30and n(Na20)/n(Si02)=1.6-3.0. A gelification stage for30min-110min at20±3℃-60℃and an ageing stage for0.5h-4h at60℃～80℃were done. The resulting mixture was crystallized for1h-5h at70℃～95℃. At the end of the process the solid was separated by filtration, washing several times with distilled water (until the solution reached pH=10) and then dried8h at100℃. Scanning electron microscope analysis shows that the particle size of as synthesized composite zeolite was uniform of about150nm.The calcium ion exchange capacity and magnesium ion exchange capacity of the optimized composite zeolites A/X were measured through national standard test methods. The results showed that the ion exchange capacity of A/X composite zeolites was quite high than the pure zeolites which used as detergent builders. The ion exchange capacity for magnesium was increase with increasing content of zeolite X while the calcium ion exchange capacity stay the same.The exchange of calcium and magnesium ions by synthesized products was studied. It was found that under the neutral or weak alkaline solution, when the dosage of zeolite was about1.5g solution, and the temperature was between25℃～50℃, the exchange equilibrium can been quickly reached. The time has little effect on the ion exchange performance though the exchange time curve, the exchange rate of composite zeolite for Ca2+and Mg2+can reach90%and70%, indenpently, which showed that the exchange rate of A/X composite zeolite was fast and the ion exchange amount of A/X composite zeolite was much.