Indium components have been successfully recovered from indiumcontaining scrap powders collected by the sand-blasting of sputtering chamber walls. A two-step air-classifier was used for the classification of the scrap powder. The raw scrap powders containing 10 wt% indium were classified into 12 lots according to the revolutions per minute of a classifying wheel: 6,000, 8,000, 10,000, and 12,000 rpm. The enrichment of indium component was possible in fine overflow fraction, that is, the third classified fractions at all wheel speeds, while the indium components were not concentrated in the first classified fraction. The grade of the indium components became higher with decreasing particle size and the highest grade was obtained in the third classified fraction. The purity of the indium component improved to 17.4 wt% and the recovery of the indium component was in the range 94.2-96.2% for the second and third classified fractions. The recovery and enrichment of indium should be optimized for the maximum recycling of the indium components, which can be used as raw materials in the subsequent electro-refining processes.

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································································································································································································································Abstract Fundamental experiences have been studied for development of pre-treatment process of Sn by-products such as solders. Dry and wet separation/recovery processes were considered by the differences of physical properties. The by-products, which are analyzed by solder metal and oxides. The metal and oxide were simply separated by dry ball-milling process for 12 hours, after that recovery metal powder might be reusable as lead or lead-free solders. In terms of wet separation process, samples were dissolved in HNO 3 + H 2 O 2 and the precipitation were analyzed by SnO 2 . Overall efficiency of recovery might be increasing via developing simple pre-treatment process.

Raw scrap powders containing 10 wt.% In were recovered by sand-blasting chamber shields of sputter coaters and used as a sole source of indium components for both sieving and air-classification. Sieving was performed first as a feasibility test, and enrichment of indium component was possible up to 19 wt.% with a mesh size of 635. With this experimental basis, the raw scrap powders were air-classified into 12 lots according to the revolution per minute (r/min) of a single horizontally arranged classifying wheel: 4000, 6000, 8000, 10000, 12000, and 14000 r/min. The particle cut size varied from 56 to 5 μm with turbo wheel speeds corresponding to 4000 to 14000 r/min, respectively, and enrichment of indium component was possible in fine overflow fractions at all turbo wheel speeds while the indium components were not concentrated in all of the coarse underflow fractions. The grade of the indium components became higher with decreasing particle size of the air-classified scrap powders, with the highest grade obtained in the fine overflow fraction with a turbo wheel speed of 14000 r/min. The amount of indium in the fine overflow fractions varied between 15.9 wt.% and 31.5 wt.%. All in all, the grade or purity of the indium component improved rather significantly from 15.9 wt.% to 31.5 wt.% by air-classification, but this also resulted in overall decrease in recovery rate from 99.33% to 49.64%. Therefore, enrichment and separation of indium should be optimized for maximum recovery and grade of the indium components, which can be used as raw materials in the subsequent electro-refining processes.