Background and purpose: Enzymatic treatment, due to various benefits, has attracted many researchers since long time ago. Anionic detergents are one of the largest families of detergents that entered into the environment in recent decades. This study investigated the effect of horseradish peroxidase enzyme process on the removal of linear alkaline benzyl sulfonate (LAS) from aqueous solutions.
Materials and methods: In an experimental study on a laboratory scale and in a batch reactor, the enzyme extracted from horseradish root was applied for removal of anionic detergent. Variables such as enzyme concentrations (0.5-2 U/mL), H₂O₂ (0.5-4 mg/l), detergent concentration (100-500 mg/L), and 0-60 min contact time were examined. Effluent concentration of detergent was measured according to the methylene blue method and spectrophotometric in 652 nm wavelength. At the end, kinetics of reactions were also studied.
Results: The enzymatic activity of the extract from horseradish root was 3.15 U/mL, and had the highest activity at neutral pH. Removal efficiency was 98% in optimum condition (enzyme concentration 1.5 U/mL, H₂O₂ 2 mg/L, pH 7.5, and 250 mg/l detergent). Gradual addition of reactants (enzyme and H₂O₂) increased the removal efficiency to 99.5%. The order of reaction of the enzymatic reaction followed the first-order reaction. The correlation coefficient (R²) was higher than 0.99 and mean constant reaction speed was 0.721 mol L^-1min^-1 (P≥0.05).
Conclusion: Enzymatic treatment by horseradish peroxidase can be used as an environmental friendly method in removal of pollutants such as surfactants.
 

Keywords: enzyme, horseradish peroxidase, anionic detergent, linear alkyl benzyl sulfate

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