Effect of current density on enhanced transformation of naphthalene.

The effect of current density on electrochemically enhanced transformation of naphthalene is evaluated. Electrochemical reactors, composed of an anode and a cathode separated by a Nafion membrane, were used to evaluatethe effect of three current densities (1,9, and 18 mA/ L) on the transformation of naphthalene at two concentration levels (13 and 25 mg/L). Transformation rates varied based on the concentration and current density. Almost 88% of the 13 mg/L naphthalene is degraded after 8 h of treatment under 18.2 mA/L. At the same time, more than 90 h was required to degrade the same amount under 9 mA/ L. The results show that most of the naphthalene degradation occurred in the first 4 h under transformation rates of 2.24 and 1.11 mg/L h under applied currents of 18.2 and 9 mA/L, respectively. Increasing the naphthalene concentration to 25 mg/L produced similar results. Under 18.2 mA/L, the redox potential increased significantly at the anolyte in the first 8 h to about 900 mV. After that, the redox potential continued to increase, but at a lower rate, until it reached 1380 mV at the end of processing. Similar behavior is noted for the anolyte pH, which decreased significantly in the first 8 h to less than 2.5 and continued to decrease until it reached a pH value of 1.86 at the end of testing. Naphthalene transformation can be attributed to electrochemically enhanced oxidation at the anolyte by chlorine gas produced by electrolysis.