Cationic dye molecule with a quaternary ammonium cation, cation in the section has a basic group because of its molecular structure, also known as alkaline base dye or pigment. Cationic dyes are usually bright color, good water solubility, are special dyes for acrylic fibers. Water-soluble cationic dyes are strong, low molecular weight, water molecules and combines ability strong, its wastewater is not only complex, high COD concentration, salinity, pH and color up to tens of thousands of times to hundreds of thousands of times, poor biodegradability, BOD/COD is about 0.2, and some are even lower. According to the statistics, each producing 1 ton of dyes, to waste water loss 2% products. Total COD in waste water itself mainly comes from the variety of hardly degradable additives and dyes, color is caused by residual dyes.
Due to the cationic dyes containing a complex of biodegradability of aromatic groups and discolored. Chemical reduction or anaerobic biological treatment of dye decolorization of azo bond reduction for amino, but amine intermediate product toxicity, and partial reduction product color reversion in aerobic conditions. Therefore, the effective removal of color is more important.