Optimizing Microwave Digestion for Trace Element Determination in Fly Ash
Introduction
Fly ash, a silicate-rich by-product of combustion processes, contains trace metals of environmental significance. Applications involving fly ash range from resource recovery to potential health hazards. Accurate determination of its trace element composition is essential for environmental monitoring, regulatory compliance, and resource recovery assessments. However, achieving complete dissolution of fly ash remains challenging due to its chemically resilient mineral composition. Microwave-assisted acid digestion is widely used to prepare fly ash samples for elemental analysis by ICP-OES or ICP-MS. Hydrofluoric acid (HF) is traditionally incorporated to break down refractory silicates; however, its extreme hazard profile motivates evaluation of safer alternatives. As a result, interest has grown in evaluating alternative acid matrices that balance digestion efficiency, analytical accuracy, and operational safety. This study compares three acid matrices—conventional HF digestion, tetrafluoroboric acid (HBF4) as a potential HF substitute, and a simplified acid leach—to assess differences in digestion completeness, as well as elemental recovery and analytical reliability via inductively coupled plasma mass spectrometry (ICP-MS). The goal is to identify optimized, safer digestion strategies that maintain robust trace-element determination in fly ash.
