APPLICATION OF COAL FLY ASH-BASED SORPTION MATERIALS IN HIGHLY MINERALIZED WASTEWATER TREATMENT

Abstract

The results of the study showed that Ukrainian coal fly ash (CFA) and acid mine drainage (AMD) can be successfully processed into zeolite-like sorptive material (ZSM) to extract pollutants from AMD. This approach provides a twofold benefit: firstly, the interaction between CFA with AMD provides an alternative method of conditioning AMD. Secondly, the solid residues contain a lot of Al and Si so they can be used for the synthesis of ZSM. The synthesis was done via alkaline conversion followed by hydrothermal crystallization. ZSM can be effectively used as an ion exchanger and sorbent for the conditioning of highly saline wastewater. Mercury, which is considered a priority pollutant, can be removed to levels below the permission level. Anion species were also removed from the solution by mechanisms other than ion exchange, e. g. arsenic.
 Studies discovered the following results:
 - pH plays a key role in the formation of metal ions as well as the charge of the surface functional groups of the ZSM, thus changing the physicochemical interactions between the ZSM and pollutant ions.
 - in addition to ion exchange, other mechanisms are also suggested, including adsorption, and the formation of complex compounds that significantly contribute to the purification process.
 Given its simplicity, this technology can be implemented as the first stage in the treatment of metal-containing wastewater at an operating or decommissioned coal mining enterprise. This technology can also be implemented as part of the desalination stages at TPP treatment plants. The proposed method is based on waste utilization, so it can be considered an eco-friendly low-cost method of wastewater treatment. However, on an industrial scale, hydrothermal activation will lead to increased operating costs due to increased energy consumption. Therefore, future research should be conducted on the application of ZSM in a pilot plant.
 Since this technology can be applied to the removal of both cations and anions, it will undoubtedly attract interest, provided the synthesis technology is optimized. First of all, it is necessary to optimize the synthesis method in order to use low-temperature activation methods to lessen operating costs.