Laboratory Scale Unit for Photocatalytic Removal of Organic Micropollutants from Water and Wastewater. Methyl Orange Degradation

An innovative laboratory scale unit was used to carry out UV photoinduced catalytic degradation of methyl 9 orange. For this purpose, the experimental system was made of a bottom and an upper reservoir (∼120 L each) which were connected by an inclined channel through which water was recirculated. TiO2 (Anatase) was deposited (∼10−2 mg/cm2) at the bottom of the connecting channel while the Methyl Orange solution was exposed to the UVB radiation (λ ≈ 300 nm) during its recirculation through the connecting channel. The unit was first characterized from both the hydrodynamic and the hydraulic points of view. Photodegradation kinetics were followed by UV−vis absorption measurements of the residual methyl orange solution concentration along time, and the synergic effect of the catalyst and the intensity of the UV radiation in promoting degradation of the substrate was demonstrated. The abatement efficiency of the UV/TiO2 system toward methyl orange was evaluated in the concentration range 0.3−8.5 mg/L. Kinetic patterns were described by first (or pseudofirst) order theoretical models up to the concentration of 0.7 mg/L, whereas at higher concentrations kinetic trends were better described by zero-order models independently from the substrate concentration in the liquid-phase. The proposed solution, after an upscale field investigation, may represent a valuable alternative to the methods conventionally used for the abatement of textile dyes from wastewater, that is, water clarification, reverse osmosis, activated carbon sorption, and biosorption.