Decolorizing of lignin wastewater using the photochemical UV/TiO2 process

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

“…In general, UV alone is not considered as an effective treatment when applied standalone in comparison to other AOPs (e.g. ozone (Amat et al 2005b) or TiO 2 /UV (Chang et al 2004) (Table 3); although it may be more effective when combined with H 2 O 2 (Ahmed et al 2009), salts of particular metals (Fe), or ozone (see tables 2 and 3).…”

“…The efficiency of the TiO 2 -photocatalytic process, and therefore the required reaction time to maximize it, are influenced by the dosage of TiO 2 itself (Chang et al 2004;Tanaka et al 1999); that is, the degradation of organics is improved until an excessive catalyst dosage causes a shadow effect interfering with the transmission of UV light so the generation of electron-hole pairs cannot effectively occur (Catalkaya and Kargi 2008;Chang et al 2004). Particularly, an optimum dosage of 10 g·L -1 of TiO 2 has been reported for the treatment of lignin powder, resulting in the 50% reduction of the color within the first 10 minutes of reaction (Chang et al 2004); whereas the removal efficiencies of both color and DOC reached about a 90% when the process was extended up to 960 minutes.…”

“…Particularly, an optimum dosage of 10 g·L -1 of TiO 2 has been reported for the treatment of lignin powder, resulting in the 50% reduction of the color within the first 10 minutes of reaction (Chang et al 2004); whereas the removal efficiencies of both color and DOC reached about a 90% when the process was extended up to 960 minutes.…”

“…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).…”

“…The ability of hydroxyl radical to break down the molecular structure of complex organic structures into simpler compounds has long been proven (Bigda 1995), and it has been shown successful for the partial oxidation of non-biodegradable organics such as lignin or chlorinated organics; therefore contributing to increase the biodegradability of the effluent as well (Balcioglu et al 2003;Balcioglu et al 2007;Bijan and Mohseni 2004;Bijan and Mohseni 2005;Bijan and Mohseni 2008;Chang et al 2004;Mansilla et al 1997;Marco et al 1997;Mounteer et al 2007;Oeller et al 1997;Salokannel et al 2007;Yeber et al 1999a;Yeber et al 1999b). The full oxidation of organic compounds is however non-economically feasible because the use of large amounts of energy and chemicals would be necessary for achieving a complete mineralization (Bijan and Mohseni 2005).…”