Performance evaluation of different solar advanced oxidation processes applied to the treatment of a real textile dyeing wastewater

The performance of different solar-driven advanced oxidation processes (AOPs), such as TiO2/UV, TiO2/H2O2/UV, and Fe2+/H2O2/UV-visible in the treatment of a real textile effluent using a pilot plant with compound parabolic collectors (CPCs), was investigated. The influence of the main photo-Fenton reaction variables such as iron concentration (20-100 mg Fe2+ L-1), pH (2.4-4.5), temperature (10-50 degrees C), and irradiance (22-68 W-UV m(-2)) was evaluated in a lab-scale prototype using artificial solar radiation. The real textile wastewater presented a beige color, with a maximum absorbance peak at 641 nm, alkaline pH (8.1), moderate organic content (dissolved organic carbon (DOC)=129 mg C L-1 and chemical oxygen demand (COD) = 496 mg O-2 L-1), and high conductivity mainly associated to the high concentration of chloride (1.1 g Cl- L-1), sulfate (0.4 g SO42 -L-1), and sodium (1.2 g Na+L-1) ions. Although all the processes tested contributed to complete decolorization and effective mineralization, the most efficient process was the solar photo-Fenton with an optimum catalyst concentration of 60 mg Fe2+ L-1, leading to 70% mineralization (DOCfinal = 41 mg C L-1; CODfinal < 150 mg O-2 L-1) at pH 3.6, requiring a UV energy dose of 3.5 kJ(UV)L(-1) (t(30 W) = 22.4 min; <(T)over bar> = 30 degrees C (U) over bar (G,n) = 44 W m(-2)) consuming 18.5 mM of H2O2.