2. Experimental
2.1. Instrumentation
An analytical balance Kern 410 model was used to measure the mass of the samples. An ultrasonic cleaning bath GA1000/TA1800 (Thornton; São Paulo, Brazil) with a frequency of 25 Hz was used for the extraction of arsenic from mining tailings samples.
A closed vessel microwave oven (Ethos 1, Milestone; Sorisole, Italy) was used to decompose the sample in order to compare the efficiency between the open ultrasonic bath using optimized conditions and the experiment performed under microwave conditions. The extracts were analyzed in an inductively coupled plasma optical emission spectrometer (ICP OES) model: DV 7200 (Perkin Elmer instruments, Shelton, USA) with hydride generation. The operational conditions are presented in