Recycling and Environmental problem. Plasma treatment of aluminum dross.

In the recycling process of aluminum , a waste called aluminum dross is produced. It contains many kinds of refractory compounds like aluminum oxide and nitride, chlorides, and also heavy metals. Because arc plasma can generate high temperature, 5000~10000 K, it can be used to dissolve aluminum dross which has high melting point. Aluminum dross sample, 160 g in weight, was pressed into pellets (10×50×20 (mm)) to be dropped into the plasma chamber easily. In the chamber the sample pellets were dissolved by plasma arc, and analyzed with X-ray diffraction (XRD), electron probe microanalysis (EPMA), inductively coupled plasma atomic emission spectrometry (ICP-AES), and atomic absorption spectrometry (AAS). The volume of the sample after the plasma treatment is reduced to about 40 % of that before treatment. During the plasma treatment the constituents of the sample were changed, aluminum oxide increases from 33.1 mass% to 77.1 mass%, aluminum decreases from 23.0 mass% to 1.5 mass%, nitrogen from 3.0 mass% to 0.9 mass%, chlorine from 7.32 mass% to 0.0080 mass% (=80 ppm). Arc plasma can be applied to dissolve the dross and the experimental results of plasma arc harmless treatment are described.