Investigation of degradation kinetics and color removal of 2-(4-hydroxyphenylazo)benzoic acid dye

Textile wastewater generally contains a significant amount of dissolved dyes, the majority of which are composed of azo dyes. Advanced oxidation methods offer a promising technology in the removal of dyestuff impurities in wastewater due to their high color removal efficiency. In this study, color removal and degradation kinetics of 2-(4-hydroxyphenylazo)benzoic acid (HABA) azo dye has been investigated by using H2O2, H2O2/UV, NaOCl and NaOCl/UV methods. Degradation studies with UV light were carried out in Spectroline Model CM-10A photoreactor which has UV lamps irradiating at 254 and 365 nm wavelengths. All experimental studies were performed at room temperature in 0.04 M Britton Robinson buffer (pH:2.0-12.0). For this purpose, the degradation kinetics of HABA was investigated depending on pH, initial concentration of dye and H2O2 concentration. Optimum conditions were determined as 3.5x10-5 M for HABA and 3.57x10-2 M for H2O2. When UV-Vis spectrum belongs tothe degradation of 3.5x10-5 M HABA in H2O2 medium was examined, π → π * electronic transition of –N = N– azo group was observed at 399 nm, whereas at 262 nm, π → π * transition was observed due to aromatic structure. When UV-Vis spectrum belongs tothe degradation of 3.5x10-5 M HABA in NaOCl medium was examined, it was observed that absorbance peaks of azo group and aromatic structure decreased and disappeared with time. When UV-Vis spectrum belongs tothe degradation of 3.5x10-5 M HABA in NaOCl/UV medium was examined, the absorbance peaks of azo group and aromatic structure decreased with time and disappeared after a certain time. When the results obtained are taken into consideration, it has been concluded that NaOCl and NaOCl/UV methods are more effective methods for color removal compared to H2O2 and H2O2/UV methods for HABA dye. Keywords: Azo dye, 2-(4-hydroxyphenylazo)benzoic acid, Advanced Oxidation Techniques, Photocatalytic Degradation, Sodium Hypochlorite.