Synthesis of Zeolites Materials Using Fly Ash and Oil Shale Ash and Their Applications in Removing Heavy Metals from Aqueous Solutions

Fly ash and oil shale ash generated from power plants can be transformed to suitable materials usable for removal of heavy metals. Due to their high silica content, fly ash and oil shale ash have been considered as the main stone of zeolite synthesis. In this work, we synthesized zeolites from class F fly ash (FA) and modified oil shale ash (MOSA) by alkaline fusion followed by refluxing. Our synthesis process focused on the effect of quantity of NaOH on the crystallinity of the reaction products: Na-P1 and Na-P2 type zeolites synthesized, respectively, from FA and MOSA. The effect of NaOH mass (1, 2, 4, and 8 g) was investigated with the following synthesis conditions: 2 h fusion at 650 degrees C, 2 h agitation, and refluxing for 12 hours. The experimental results demonstrated that the crystallinity of Na-p1 and Na-P2 zeolites increased with increasing the mass of NaOH. The resulting products were characterized with X-ray diffraction, FTIR, and scanning electron microscopy. The reaction products ZV4 and ZM4 synthesized, respectively, from FA and MOSA and containing main zeolite phases with a crystallinity of 92.7% of Na-P1 and 83.6% of Na-P2, respectively, were chosen as adsorbents for the adsorption experiments. Series of experiments were carried out to study the removal of lead, zinc, and chromium by ZV4 and ZM4. The results allowed us to know the optimal conditions of adsorption for the three heavy metals. Adsorption data have been interpreted in terms of Langmuir and Freundlich isotherms. The results showed that lead has a higher affinity for ZM4 than ZV4 and zinc has similar adsorption efficiency for both sorbents that was remarkably reduced for chromium. The results of the present work suggest that zeolites synthesized from MOSA may be considered as effective as those synthesized from FA for heavy metals adsorption.