PHOTOCATALYSIS BY IRON-RICH MONTMORILLONITE FOR THE TREATMENT OF DYEING WASTEWATER

Abstract

This study investigates the photocatalytic degradation of dyeing wastewater by iron-rich montmorillonite (MMt) under a 25 W low-pressure mercury lamp (λ = 254 nm, I = 48.4 μW/cm²). Exposing MMt to UV irradiation worked to catalyze the photobleaching of wastewater used in the dyeing process. COD removal efficiencies of 65.0% and 74.0% were achieved in 1 g/L MMt suspensions at a pH of 3 in the absence and presence of 30 min of UV irradiation, respectively. A decolorization efficiency of 71.4% was reached with 1 g/L MMt suspensions at a pH of 3 after 30 min of UV irradiation, while only 4.9% decolorization was attained in darkness. These results indicate that iron-rich MMt is a good photocatalyst for decolorization and COD removal in wastewater from dyeing processes. A low pH value is beneficial to the decolorization of dyeing wastewater. A preliminary photocatalytic mechanism is proposed: the iron in the MMt is responsible for the decolorization of the wastewater because it produces a highly oxidative species of hydroxyl radicals (^•OH).

Keywords:

• Decolorization
• Dyeing wastewater
• Hydroxyl radical
• MMt
• UV irradiation

Notes

Conditions: initial montmorillonite concentration of 1 g/L, pH 3, initial color 350 times, initial COD of 351.2 mg/L, room temperature, λ = 254 nm, irradiation/adsorption time of 30 min.