Method for the Electrochemical Decoloration of Indigo-Containing Aqueous Dispersions
The present invention relates to a process for electrochemical decolorization of indigo-containing aqueous dispersions by direct anodic oxidation on diamond-coated silicon anodes.
1 - 6 . (canceled)
7 . A process for electrochemically decolorizing an indigo-containing aqueous dispersion comprising directly anodically oxidizing said indigo-containing aqueous dispersion on diamond-coated silicon anodes.
8 . The process of claim 7 , wherein said indigo-containing aqueous dispersion has an indigo content in the range from 0.05 g/L to 100 g/L.
9 . The process of claim 7 , wherein said indigo-containing aqueous dispersion has a sulfate concentration of between 1 and 20 g/L of sodium sulfate.
10 . The process of claim 9 , said indigo-containing aqueous dispersion has a sulfate concentration of between 4 and 10 g/L of sodium sulfate.
11 . The process of claim 7 , wherein said process is performed in an undivided electrolytic cell.
12 . The process of claim 7 , wherein said process is performed at temperatures between 15° C. and 80° C., at an anodic current density between 0.001 A/cm 2 and 10 A/cm 2 , and at a pH of from 2 to 13.
13 . The process of claim 7 , wherein said indigo-containing aqueous dispersion is indigo-containing wastewater and wherein the electrochemically decolorized indigo-containing wastewater has a low AOX content.