Hydrogen Production by Solar Photoreforming of Urban Wastewaters in Thin-Layer Flat Catalytic Panels

Abstract

The effective simultaneous production of hydrogen and removal of organic pollutants by solar photoreforming of various real urban wastewater effluents using a Pt/TiO2 photocatalyst is proven. Initial testing in laboratory-scale batch photocatalyst suspensions experiments, under both UV and simulated sunlight, result in photocatalytic H2 production (along with variable CO2 amounts) from urban wastewaters; photoreforming efficiency decreases in the following order: influent stream > primary sludge > final sludge. Hydrogen evolution exceeds 1500 µmol gcat−1 after 3 h under UV. Further development is undertaken in an outdoors pre-pilot-plant scale flat solar panel reactor having a thin layer of photocatalyst (7 g m−2, thickness: 4–30 µm) exposed to natural sunlight. The proof-of-concept solar photoreforming of an influent urban sewage stream in the flat solar panel proceeds with remarkable activity and stability for almost one month (27 d, irradiation time ≈160 h). Despite operated in late autumn at 41.1 ° North latitude, gas production is sustained and consistently correlated with solar irradiances (600–900 W m−2). Furthermore, wastewater decontamination is proven by sustained decrease in chemical oxygen demand and pH, whereas conductivity tended to increase slightly, most likely owing to the breakdown of complex organic matter.