Growth behavior of spinel in stainless steel slag during cooling process

Spinel is an appropriate phase for sequestrating chromium in stainless steel slag to prevent chromium from polluting, and the crystal size of spinel has a significant effect on the stability of chromium and the extraction efficiency of spinel. The enrichment behavior of chromium in spinel during cooling process was investigated, and the growth process of spinel was studied based on the crystal size distribution theory. The results showed that the enrichment degree of chromium in spinel increased from 88.5% to nearly 100% during the cooling process from 1773 to 1573K at a rate of 5K/min. The mean diameter of spinel in stainless steel slag had an obvious growth in the cooling process, and a rapid growth of spinel occurred during the cooling process from 1623 to 1523K. Leaching results indicated that the leaching amount of chromium could reduce to less than 0.01mg/L by controlling the cooling condition. The growth mechanism of spinel was investigated and proposed to consist of two stages: in the first stage, the spinel was in the surface-controlled growth with a decaying nucleation rate from 1773 to 1573K, and in the second stage, the growth mechanism was transformed to supply-controlled Ostwald ripening below 1573K.