Alkaline Hydrothermal Conversion of Fly Ash Filtrates Into Zeolites 2: Utilization in Wastewater Treatment

Filtrates were collected using a codisposal reaction wherein fly ash was reacted with acid mine drainage. These codisposal filtrates were then analyzed by X-ray Fluorescence spectrometry for quantitative determination of the SiO₂ and Al₂O₃ content. Alkaline hydrothermal zeolite synthesis was then applied to the filtrates to convert the fly ash material into zeolites. The zeolites formed under the experimental conditions were faujasite, sodalite, and zeolite A. The use of the fly ash–derived zeolites and a commercial zeolite was explored in wastewater decontamination experiments as it was applied to acid mine drainage in different dosages. The concentrations of Ni, Zn, Cd, As, and Pb metal ions in the treated wastewater were investigated. The results of the treatment of the acid mine drainage with the prepared fly ash zeolites showed that the concentrations of Ni, Zn, Cd, and Hg were decreased as the zeolite dosages of the fly ash zeolite (FAZ1) increased.

Keywords:

• Acid mine drainage
• Cation exchange capacity
• Fly ash
• Hydrothermal synthesis
• Metal ions
• Wastewater
• XRD
• Zeolites.

ACKNOWLEDGMENTS

We are grateful to the Water Research Commission (WRC), Coaltech 2020, and the National Research Foundation (NRF) for funding and financial support to perform this study. The assistance provided by the CSIR and Eskom in the collection of fly ash samples, iThemba labs for XRD analysis, and the Chemistry Department of the University of the Western Cape are also appreciated.