Enrichment characteristics, thermal stability and volatility of hazardous trace elements in fly ash from a coal-fired power plant

•Release behavior of five HTEs during re-use of CFA involving heat treatment is investigated.•Burnout degree and specific surface area cause HTEs concentration to decrease in larger CFA.•HTEs thermal stability decreases with increasing temperature or decreasing particle size.•Volatility of HTEs in CFA follows the decreasing order of Hg > As, Cr > Mn, Pb.