Properties of the printing wastewater
Real printing wastewater, collected from a printing factory lo- cated in Taichung City of Taiwan, was used for the electrocatalytic oxidation experiments. The wastewater was discharged during the cleaning procedure (to remove ink and surfactants) after the com- pletion of the printing process, which contained a high concentra- tion of organics and chroma. This wastewater was characterized with a high pH (around 13), a high conductivity (60–700 mS cm1) and a high TOC concentration (28,000–30,000 mg L1). A TOC ana- lyzer (O.L. Analytical, Auroramodel 1030W) and a spectrophotom- eter (Yi-Hung Inc., U-2001) were used for TOC and chroma measurements, respectively. In terms of chroma analysis, the wastewater sample was first subjected to full wavelength scanning to obtain the maximum absorption wavelength (i.e., 360 nm), and then the chroma variation was monitored at this wavelength.
2.3. Experimental system for electrocatalytic treatment of wastewater
The experimental system for the electrocatalytic treatment of real printing wastewater is illustrated in Fig. 2, where a cylindrical tank was used as the reactor (17 cm diameter 16 cm height). An electromagnetic stirrer was placed beneath the tank to completely mix the reaction solution during operation. Three electrocatalytic