A FAST METHOD FOR RECYCLING FLY-ASH - MICROWAVE-ASSISTED ZEOLITE SYNTHESIS

Zeolitic material was synthesized from fly ash by conventional and mic rowave-assisted hydrothermal alkaline activation experiments. The zeol ite synthesis was studied as a function of temperature, time, and acti vation solution concentration. K+-Na+/NH4+ exchange properties of the zeolitic material synthesized were studied as a function of time and z eolite type. The zeolitic material synthesized from the same fly ash b y changing the synthesis parameters contained: NaP1, hydroxysodalite, hydroxycancrinite, analcime, tobermorite, and nepheline hydrate using NaOH as an activation agent and F linde zeolite, kalsilite, and philli psite-KM zeolite from KOH activation. Synthesis yields and zeolite typ es obtained from the microwave and conventional experiments were very similar, but the activation time needed was drastically reduced by usi ng microwaves (from 24-48 h to 30 min). Consequently, the industrial a pplication of the synthesis process is enhanced by the microwave-assis ted method. From this point of view, the most interesting zeolites syn thesized are NaP1, KM-phillipsite, and F linde zeolites since the NH4 retention capacities obtained far the activation products were close to 20 and 30 mg of NH4+ g(-1). The experiments performed also showed t hat high NH4+ retention capacities are attained after a few minutes of equilibrium with NH4+-rich solutions.