Sequential bleaching

Meyer, T. E., Bartsch, R. G., and Cusanovich, M. A., 1991b, Adduct formation between sulfite and the flavin of phototrophic bacterial flavocytochromes c. Kinetics of sequential bleach, recolor, and rebleach of flavin as a function of pH. Biochemistry 30 8840118845. 

MG Paice, R Bourbonnais, ID Reid. Sequential bleaching of kraft pulp with oxidative enzymes and alkaline hydrogen peroxide. Tappi J 78(9) 161-170, 1995. 

Azelaic acid is a non-phenolic derivative (1,7-hep tanedicarboxylic acid) used at concentration of 10-20% twice a day to treat melasma with minimal side effects (allergic reactions). It acts to disturb the tyrosinase synthesis and can be used as a bleaching agent in patients sensitive to hydroquinone. Better results are obtained if a glycolic acid cream is applied sequentially to azelaic acid treatment. 

Higher levels of whiteness and more attractive tones (i.e. neutral or bluish rather than yellowish or reddish whites) are attainable with hypochlorite, although whites of the highest quality are produced using the two bleaching agents sequentially. 

Prasad, D.Y. Joyce, T.W. Sequential treatment of Ej stage Kraft bleach plant effluent. Biores. 

Figure 9. Beads (similar to FISH spots) were excited every minute sequentially with a 488 nm and a 568 nm laser. The mean intensity of the bead was measured every minute for 3.3 hours (200 sample times). The pattern shows periodic fluctuations in intensity over time indicating an unstable system (6-11). The mean intensity also drops overtime, which implies that the sample is either going out of focus, is emitting less light or is bleaching and emitting less light. Newer microscopes have controls that can correct such a stage drift.

Figure 25. The sequential photocatalytic treatment of the effluent previously treated with Trametes Versicolor. The irradiation time used was 60 min. Reprinted from, Aura M. Pedroza, Rodolfo Mosqueda, Nicolas Alonso-Vante and Refugio Rodriguez-Vazquez, Sequential treatment via Trametes versicolor and UV/Ti02/RuxSey to reduce contaminants in waste water resulting from the bleaching process during paper production, Chemosphere 67 (2007) 793, Copyright (2007), with permission from Elsevier.

FIGURE 2.26 Cohesive force measured in the contact between two bleached cellulose fibers in a solution of papermaking cationic polyacrylamide. The effect of sequential rupturing and reformation of contacts between the same fibers is shown. (Zelenev, A.S. and Shchukin, E.D., unpublished results.)... 

After a prehydrolysis step (0.05 M HCl, pH 1.4, 2h at 70°C), the solution was cooled to room temperature and adjusted to pH 10.2 with ammonium hydroxide. After a sequential extraction with ammonium hydroxide, alkaline ethanol and alkaline water (both at room temperature and elevated temperature (70 C), the filtrates were bleached (50% H2O2, 2 days, 40 C). After ultrafiltration and spray... 

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