Preparation of Zeolites from Coal Fly Ash and Their Application in Remediation Heavy Metals Contaminated Soils

Document Type : Original Article

Author

Department of Soil Chemistry and Physics, Desert Research Center, Cairo - Egypt.

Abstract

This study presents experimental results transacting with the potential of transforming coal fly ash to zeolitic materials to be applied as a cheap immobilizer for heavy metals in contaminated soils. Coal fly ash (CFA) was used to prepare synthetic zeolites by alkaline fusion prior the hydrothermal treatment as a function of the ratio of CFA to NaOH (1:1.4, 1:1.8) and (activation and crystallization) temperature 60 °C and 95°C, four samples of synthesized zeolites were formed and characterized using various techniques such as X-ray diffraction XRD, scanning electron microscopy-energy dispersive X-ray SEM-EDX and BET method. The results showed increase the crystallinity of the obtained zeolites with increasing mass ratio of CFA/NaOH and increasing the crystallization temperature from 60 °C to 95 °C. The formed zeolites contained different crystalline phases of sodalite (SOD). Zeolite-A (LTA), cancrinite (CAN), and analcime (ANA), sodalite was the predominant crystalline phase in all samples where its highest content was in sample IV (84%) which synthesize with a CFA/NaOH mass ratio of 1:1.8 and a crystallization temperature of 95°C. The results showed that the sample I was synthesized at 1:1.4 ratio of CFA/NaOH and a temperature of crystallization 60 °C has the highest value of specific surface area (SBET). The surface areas of the mesopores form the major part of the total specific surface area in samples III and IV. The synthesized zeolite samples were used to study their immobilization efficiency for Cu and Pb in the soil. It was noticed that increase the application rate of the synthesized zeolite in soil, improved their effectiveness to immobilize Cu and Pb. Applying 1% synthetic sample IV treatment was significantly the most effective in lowering the DTPA extracted Cu and Pb with maximal immobilization efficiencies (E %) 39.55% and 78.37 % respectively.

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