Energy recovery during advanced wastewater treatment: Simultaneous estrogenic activity removal and hydrogen production through solar photocatalysis

Abstract

Simultaneous estrogenic activity removal and hydrogen production from secondary effluent were successfully achieved using TiO2 microspheres modified with both platinum nanoparticles and phosphates (P–TiO2/Pt) for the first time. The coexistence of platinum and phosphate on the surface of TiO2 microspheres was confirmed by transmission electron microscope, energy-dispersive X-ray and X-ray photoelectron spectroscopy analyses. P–TiO2/Pt microspheres showed a significantly higher photocatalytic activity than TiO2 microspheres and TiO2 powders (P25) for the removal of estrogenic activity from secondary effluent with the removal ratio of 100%, 58.2% and 48.5% in 200 min, respectively. Moreover, the marked production of hydrogen (photonic efficiency: 3.23 × 10−3) was accompanied by the removal of estrogenic activity only with P–TiO2/Pt as photocatalysts. The hydrogen production rate was increasing with decreased DO concentration in secondary effluent. Results of reactive oxygen species (ROS) evaluation during P–TiO2/Pt photocatalytic process showed that O2−and OH were dominant ROS in aerobic phase, while OH was the most abundant ROS in anoxic phase. Changes of effluent organic matter (EfOM) during photocatalysis revealed that aromatic, hydrophobic, and high molecular weight fractions of EfOM were preferentially transformed into non-humic, hydrophilic, and low MW fractions (e.g. aldehydes and carboxylic acids), which were continuously utilized as electron donors in hydrogen production process.