Decolorization of Kraft Bleaching Effluent by Advanced Oxidation Processes Using Copper (II) as Electron Acceptor

Abstract

Two advanced oxidation processes (AOPs), TiO2/UV/O2 and TiO2/UV/Cu (II), were used to remove color from a Kraft bleaching effluent. The optimal decoloration rate was determined by multivariate analysis, obtaining a mathematical model to evaluate the effect among variables. TiO2 and Cu (II) concentrations and the reaction times were optimized. The experimental design resulted in a quadratic matrix of 30 experiments. Additionally, the pH influence on the color removal was determined by multivariate analysis. Results indicate that color removal was 94% at acidic pH (3.0) in the presence of Cu (11) as an electron acceptor. Under this condition, the biodegradation of the effluent increased from 0.3 to 0.6. Moreover, 70% of COD (chemical oxygen demand) was removed, and the ecotoxicity, measured by Daphnia magna, was reduced. Photocatalytic oxidation to remove the color contained in the Kraft mill bleaching effluent was effective under the following conditions: short reaction time, acidic pH values, and without the addition of oxygen due to the presence of Cu (II) in the effluent. Moreover, residual Cu (II) was a minimum (0.05.mg L(-1)) and was not toxic to the next biological stage. The experimental design methodology indicated that a quadratic polynomial model may be used to representthe efficiencyfor degradation of the Kraft bleach pulp effluent by a photocatalytic process.

The application of advanced oxidation technologies to the treatment of effluents from the pulp and paper industry: a review

“…On the other hand, a 64% color removal was reported at pH = 7 for lignin decomposition, whereas a 99% was achieved at pH = 3 (Chang et al 2004). Correspondingly, Boroski et al (2008) and Rodrigues et al (2008) also reported the highest efficiency of this process at pH = 3 (Table 4), which was attributed to the positive charge that TiO 2 surface acquire in acid solutions, which favors the adsorption of anionic compounds to be prioritized resulting in a great decolorization of the effluent (Yeber et al 2007).…”

“…Biodegradation efficiency might also be improved using metallic ions as electron acceptors, as proposed by Yeber et al (2007) in the same essay the aeroxide treatment just described was also assessed. In short, it was confirmed that copper (II) efficiently acted as an electron acceptor when photocatalytic treatment was applied to an ECF bleaching pulp effluent to which this metallic ion was added.…”

“…Furthermore, Yeber et al (2007) reported the removal of 70% of the COD, 50% TOC, 94% color, and 50% toxicity, when applying this treatment to effluents from the first extraction step of ECF bleaching pulp (Table 4). Finally, applying either UV/TiO 2 /O 2 or UV/ZnO/O 2 processes to an effluent from a bleaching sequence, Yeber et al (1999b) also reported the release of chloride ions to the solution, which maximum content was detected after five minutes of treatment.…”

“…During pulping, most of the contaminants are released. During bleaching, residual lignin is removed to enhance brightness (Wang et al 2004), and different chlorinated organic compounds can be generated in low proportions in Elemental Chlorine Free processes (Balcioglu et al 2003;Yeber et al 2007); whereas bleaching with alkaline hydrogen peroxide causes an additional load of 5-15 Kg·T -1 BOD 7 and 15-40 kg·T -1 COD, decreases hemicelluloses content, and increases the presence of pectin, lignin and aliphatic carboxylic acids. Alkalinity strongly influences the dissolution of hemicelluloses and pectin, and the release of dissolved and colloidal material (Sundholm 1999;Miranda and Blanco 2010).…”

“…Soluble biodegradable organic compounds may efficiently be removed by combinations of anaerobic and aerobic processes (Ordóñez et al 2010), but these treatments do not prevent the accumulation of the non-biodegradable organic chemical fraction (Ahmad et al 2007;Habets and Knelissen 1997), such as high molecular weight organics (>1000 Da) (Yeber et al 2007), lignin and lignin-derived compounds (Chang et al 2004;Dahlman et al 1995;Eriksson and Kolar 1985;Thompson et al 2001), toxic chlorinated organics (Balcioglu et al 2007), and pollutants with sulfonic groups (Beltrán et al 2000;Masuyama et al 2000), among others. These chemicals usually produce alterations in the activity of biological reactors (Habets and Knelissen 1997).…”