Ultrasound-facilitated electro-oxidation for treating cyan ink effluent

Abstract

The feasibility of using ultrasonication in combination with the Fenton's reaction was investigated for treating cyan ink effluent. A two-step treatment process was developed-the first step was an ultrasound-assisted electro-oxidation, while the second was chemical oxidation through the addition of hydrogen peroxide. The use of electro-oxidation in the first step significantly reduced the amount of iron needed compared with the conventional Fenton's reaction, resulting in a 98% reduction in the amount of sludge produced. A simple technique based on refractive index measurements was introduced as a rapid way to quantify the amount of sludge produced. It was postulated that ultrasonication in the presence of iron (from electrolysis) in the first step converted the ink components into reaction intermediates which were more amenable to peroxide oxidation in the second step. These intermediates were quantified by ultra-violet absorption at wavelengths of 275-400 nm. The two-step treatment process was able to reduce the COD and copper contents in the ink waste water to within the discharge limit, which conventional Fenton's reaction was unable to meet for copper discharge. The same COD removal was also achieved in about half the time. Kinetics study performed to further understand the reaction mechanisms show second-order kinetics for both steps with activation energies of 18.2 and 20.4 kj/mol for steps 1 and 2, respectively. © 2008 Canadian Society for Chemical Engineering.