Adsorption of anionic (Borutosol KRN, Siarczanol N-2) and nonionic (Rokafenol N-8) surfactants onto chitin and dye-modified chitin (Brillantorange 3R, Scarlet R and Black DN) was investigated. Experiments were carried out at pH 3.0 and pH 6.2. The Langmuir-Freundlich model was used to describe adsorption isotherms. It was proved that adsorption isotherms of SAAs* onto chitin were S-type. The adsorption was the most effective for anionic SAAs. It was stated that adsorption of SAAs onto dye-modified chitin depended on dye type, bound previously onto chitin and on pH adjustment. At pH 3.0, for vinyl dye-modified chitin (Brillantorange 3R, Scarlet R) the highest adsorption capacities at plateau region were stated for Borutosol KRN (320 and 330 mg/g d.w., respectively) and Siarczanol N-2 (290 and 310 mg/g d.w.). However, for Black DN-modified chitin, the mass of adsorbed anionic surfactants was distinctly lower – 120 mg/g d.w. for Borutosol KRN and 13 mg/g d.w. for Siarczanol N-2. The pH increase from 3.0 to 6.2 caused a drop in amount of SAAs adsorbed at plateau region. Dye solubilization was demonstrated for dye-modified chitin. The amount of dissolved dyes in solution depended on pH adjustment as well as SAA type. At pH 3.0, for anionic SAAs dye solubilization increased clearly with the increase of SAA concentrations. Nonionic Rokafenol N-8 almost did not cause dye solubilization. At pH 6.2 dye solubilization was nearly independent of SAA concentration.
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