A kinetic model that describes removal of chromium VI from rinsing waters of the metal finishing industry by electrochemical processes

A study was made to remove Chromium VI (Cr6+), present in large quantities in the rinsing waters from the plating industry, using electrochemical trea tment. Large amount of Cr6+ are found. It was found that the reaction rate followed a variable kinetic order at concentrations up to 1700 mg Cr6+/L. I t was also noticed that Cr6+ reduction depended on the ferrous ions (Fe2+) released at the anode, the cathode reactions and the acidic corrosion on el ectrodes. Iron salts produced electrode passivation and it caused a 50% inc rease in treatment time and power requirements. Eliminating the salt format ion at the anode could reduce this effect. Using electrochemical processes it is possible to reuse treated waters in the rising stages of the rating i ndustry owing to the fact that final Cr6+ concentration is less than 0.5 mg /L. Finally, a sludge characterization study revealed that residue generate d in the process is not considered dangerous according to Mexican environme ntal protection standards.