Electrochemical pretreatment of wastewater containing methylene blue was studied on an Pb/PbO2 electrode and showed enhancement of the color removal efficiency for increasing current density and decreasing dye concentration. The effect of the temperature was more pronounced at a high initial dye concentration (134 mg L–1) compared to a low initial concentration (12 mg L–1), whereas it was the opposite for the agitation speed. The model obtained by central composite design led to the following optimal conditions for MB degradation: 41 ≤ T ≤ 60 °C, 10.66 ≤ i ≤ 25 mA cm–2, [MB]0 = 134 mg L–1, and ω = 720 rpm, which gave 95.61% degradation efficiency. Electrolysis improved biodegradability from 0.034 to 0.54 for the BOD5/COD ratio, indicating the feasibility of a biological treatment combined to an electrochemical pretreatment process. The degradation of the generated intermediate compounds was performed using activated sludge and led to 92.03% mineralization (overall DOC removal).

International audienceThe UV/TiO2/H2O2 degradation of Basic Yellow 28 dye (BY28) in aqueous solutions was investigated with immobilized P-25 TiO2 powder on a glass plate by a heat attachment method. A central composite design (CCD) was employed for the screening of the significant parameters (flow rate, initial dye concentration, solution pH, and initial H2O2 concentration) and to identify the most relevant interactions between the operating parameters. Results showed that solvent type and thickness of the coating are very effective on the photoactivity of immobilized TiO2. The model equation obtained led to a classification of the parameters based on their level of significance. In addition, a relevant interaction between the initial dye concentration and the initial H2O2 concentration was highlighted. After performing a screening of the various operating parameters, response surface analysis led to the optimal conditions for the yield of BY28 degradation, resulting in 96% decolorization yield

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