title: Determination of metals in coal fly ashes using ultrasound-assisted digestion followed by inductively coupled plasma optical emission spectrometry.
abstract: A method for determination of Co, Cr, Cu, Fe, Mn, Ni, Ti, V and Zn in coal fly ash samples using ultrasound-assisted digestion followed by inductively coupled plasma optical emission spectrometry (ICP-OES) is proposed. The digestion procedure consisted in the sonication of the previously dried sample with hydrofluoric acid and aqua regia at 80 degrees C for 30 min, elimination of fluorides by heating until dryness for about 1h and dissolution of the residue with nitric acid solution. A classical digestion method, used as comparative method, consisted in the addition of HCl, HNO(3) and HF to 1 g of sample, and heating on a hot plate until dryness for about 6h. The proposed method presents several advantages: it requires lower amounts of sample and reagents, and it is faster. It is also advantageous when compared to the published methods, which also use ultrasound-assisted digestion procedure: lower detection limits for Co, Cu, Ni, V and Zn, and it does not require shaking during the digestion. The detection limits (microg g(-1)) for Co, Cr, Cu, Fe, Mn, Ni, Ti, V and Zn were 0.06, 0.37, 1.0, 25, 0.93, 0.45, 4.0, 1.7 and 4.3, respectively. The results were in good agreement with those obtained by the classical method and reference values. The exception was Cr, which presented low recoveries in classical and proposed methods (83 and 87%, respectively). Also, the concentration for Cu obtained by the proposed method was significantly different from the reference value, in spite of the good recovery (91+/-1%).
authors.affiliation: Coordenação de Análises Minerais, Centro de Tecnologia Mineral-CETEM, Av. Pedro Calmon 900, Cidade Universitária, CEP 21941-908, Rio de Janeiro, RJ, Brazil.
authors.forename: Fernanda V M
authors.initials: FV
authors.lastname: Pontes
authors.forename: Bruna A de O
authors.initials: BA
authors.lastname: Mendes
authors.forename: Evelyn M F
authors.initials: EM
authors.lastname: de Souza
authors.forename: Fernanda N
authors.initials: FN
authors.lastname: Ferreira
authors.forename: Lílian I D
authors.initials: LI
authors.lastname: da Silva
authors.forename: Manuel C
authors.initials: MC
authors.lastname: Carneiro
authors.forename: Maria I C
authors.initials: MI
authors.lastname: Monteiro
authors.forename: Marcelo D
authors.initials: MD
authors.lastname: de Almeida
authors.forename: Arnaldo A
authors.initials: AA
authors.lastname: Neto
authors.forename: Delmo S
authors.initials: DS
authors.lastname: Vaitsman