[Study on the occurrence of ferrum in coal by ultrasound-assisted sequential chemical extraction].

To reveal the occurrence of Ferrum in coal, seven coal samples were selected according to the different contents of ferric oxide in the coal ash, and the content of Ferric element was determined by atomic absorption spectrophotometer (AAS) using nitric acid-perchloric acid-hydrofluoric acid wet digestion. Modes of occurrence of ferrium in the seven coal samples were studied by AAS using ultrasound-assisted sequential chemical extraction experiment (SCEE). Ultrasound promoted the contact of the extraction reagent with the coal particles and enhanced the dissolution process by producing characteristic acoustic cavitations, which greatly shortened the experimental time.