Treatment of textile wastewaters by solar-driven advanced oxidation processes

• Published in: Solar energy 2011-09, Vol.85 (9), p.1927-1934
• Main Authors: Vilar, Vítor J.P., Pinho, Lívia X., Pintor, Ariana M.A., Boaventura, Rui A.R.
• Format: Article
• Language: English
• Subjects: AOPs; Applied sciences; Biodegradability; Catalysts; Chemistry; Chlorides; Compound parabolic collectors; Crack opening displacement; Energy; Exact sciences and technology; General and physical chemistry; Mineralization; Natural energy; Organic chemicals; Oxidation; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Pilot plant; Solar energy; Solar radiation; Textile wastewater; Textiles; Titanium dioxide; Waste water; Water treatment
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2011.04.033

► Solar photo-Fenton reaction enhances the biodegradability of textile wastewaters. ► Solar AOPs are robust methods of purifying textile wastewaters at lower cost and with less energy. ► AOPs become even more attractive if they can use solar energy, which is a relevant resource in most countries with high textile industry. Heterogeneous (TiO 2/UV, TiO 2/H 2O 2/UV) and homogenous (H 2O 2/UV, Fe 2+/H 2O 2/UV) solar advanced oxidation processes (AOPs) are proposed for the treatment of recalcitrant textile wastewater at pilot-plant scale with compound parabolic collectors (CPCs). The textile wastewater presents a lilac colour, with a maximum absorbance peak at 516 nm, high pH (pH = 11), moderate organic content (DOC = 382 mg C L −1, COD = 1020 mg O 2 L −1) and high conductivity (13.6 mS cm −1), associated with a high concentration of chloride (4.7 g Cl − L −1). The DOC abatement is similar for the H 2O 2/UV and TiO 2/UV processes, corresponding only to 30% and 36% mineralization after 190 kJ UV L −1. The addition of H 2O 2 to TiO 2/UV system increased the initial degradation rate more than seven times, leading to 90% mineralization after exposure to 100 kJ UV L −1. All the processes using H 2O 2 contributed to an effective decolourisation, but the most efficient process for decolourisation and mineralization was the solar-photo-Fenton with an optimum catalyst concentration of 100 mg Fe 2+ L −1, leading to 98% decolourisation and 89% mineralization after 7.2 and 49.1 kJ UV L −1, respectively. According to the Zahn–Wellens test, the energy dose necessary to achieve a biodegradable effluent after the solar-photo-Fenton process with 100 mg Fe 2+ L −1 is 12 kJ UV L −1.