Abstract
Water is effective in leaching out Cr
6+
from a mixture of paint powders and abrasive blast media. However, acids such as HNO
3
, HCl, and H
2
SO
4
significantly enhance the leaching procedure. Cr ions in the leaching solutions are successfully removed by electrochemical precipitation. The consumable Fe electrodes generate ferrous ions to cause the reduction of Cr
6
+ to Cr
3
+. Cr
3
+ ions along with Fe
2
+ and Fe
3
+ are then removed mainly by precipitation as Cr(OH)
3
, Fe(OH)
2
, and Fe(OH)
3
near the cathode where OH
-
ions are generated by water electrolysis. The electrochemical process is capable of discharging low levels of Cr
6
+, less than 1 mg/L, without pH adjustment.