Application of an Electro-oxidation Treatment Method to Industrial Paper Mill Effluents in the Lab
摘要
This study was conducted in 2 stages to examine the effects of effluent variables and reaction mechanisms on the treatment results of a typical industrial paper mill effluent by an electro-oxidation system. The first-stage study aimed mainly to analyze the contributions of raw materials, including old corrugated containerboard (OCC), from both domestic and imported European sources, and chemical additives, to the electric conductivity build-up of the effluents. In the second stage, the post-primary treatment (dissolved air flotation, OAF) effluent from an industrial paper mitt was treated in a lab-scale fixed-bed electro-oxidation reactor. The reactor contained 2 stainless steel electrode rods wrapped in permeable synthetic fiber membranes, and the cell was filled with iron beads to 80~95% of its volume. The effluent was recirculated in a semi-batchwise manner. The effluent pH was adjusted to 3.0, 6.8, and 9.0, respectively; and the reaction time was between 0 and 120 min. The reactor variables of the hydraulic retention time (HRT) (57 and 180s), electrode gap (5 and 15 mm), and electric current density (287 and 3454 Am^(-2)) were studied in a 2^3 factorial design. The effluent parameters investigated were the removal rates of electrical conductivity, chemical oxygen demand (COD), and true color. The results indicated that both domestic and imported OCC contributed little to the electrical conductivity build up of the effluent. Among the chemical additives, alum contributed the most to the conductivity build-up. As for the electro-oxidation treatment results, increasing the HRT caused a decrease in the COD at an effluent pH of 6.8. None of the variables examined showed a significant influence on electrical conductivity removal, however. Increasing the HRT and reducing the electrode gap caused the true color removal to decrease. The post-treatment effluent was analyzed using cyclic voltammetry (CV) for the presence of redox pairs, and the Fe(superscript 2+)/Fe(supers