Abstract
BACKGROUND: The effect of four dye‐auxiliary chemicals, typically employed in acid dyeing, on the performance of UV/H~2~O~2~ decolouration of the model non‐biodegradable dye C.I. Acid Orange 7 (AO7) was investigated. The initial concentration of AO7 was 0.150 g L^−1^, while the concentration of the auxiliary compounds (NaCl, Na~2~SO~4~, Na~2~CO~3~ and CH~3~COOH) was varied in the range 1–10 g L^−1^.
RESULTS: The negative influence of the presence of the dye‐auxiliary compounds studied on the decolouration rate of AO7 decreased in the following order: CH~3~COOH > Na~2~SO~4~ > NaCl > Na~2~CO~3~. Results were quantified in terms of the observed kinetic rate constant, k~obs~ (s^−1^), of AO7 decolouration as a function of dye auxiliary chemical concentration. The decolouration rate of AO7 decreased as the concentration of dye‐auxiliary compound increased in the range 1–5 g L^−1^, while higher concentrations had a minor effect. Upon addition of 5 g L^−1^ of CH~3~COOH, NaCl and Na~2~SO~4~, the kinetic rate constant decreased by 39%, 30% and 12%, respectively.
CONCLUSIONS: It was concluded that the presence of NaCl, Na~2~SO~4~ and above all of CH~3~COOH should be considered in the design of the treatment of real dye‐bath effluents by UV/H~2~O~2~. Copyright © 2008 Society of Chemical Industry