Fly ash-derived zeolites and their sorption abilities in relation to elemental mercury in a simulated gas stream

Abstract

This study applies the use of fly ash-derived zeolites X and A to capture elemental mercury from a gas stream. A novel hybrid synthesis method was developed, which included the crystallization stage of zeolites, together with silver or iron modification. The method applied resulted in obtaining the pure and high-crystalline zeolites of faujasite and Linde Type A groups. The starting materials – fly ashes, untreated zeolites X and A and their silver- and iron-modified analogues – were subjected to mercury adsorption tests using a novel prototype installation. Untreated zeolites and their iron-activated analogues, had negligible mercury uptake. In the case of silver-modified zeolites, the adsorption of mercury was significantly improved. The starting materials – fly ashes – also presented a positive affinity with mercury removal. The highest mercury uptake was observed for zeolites X, derived from the fly ash obtained after hard coal combustion and modified with variable amounts of silver nitrate. The proposed novel hybrid synthesis method has the potential for implementation for both fly ash utilization, as well as the time and energy saving production of aluminosilicate, i.e., porous materials with high elemental mercury removal efficiency. This fits the idea of the circular economy and creates opportunities for the disposal of hazardous elemental mercury – an unwanted by-product of the energy industry based on coal combustion.