Effective degradation of phenacetin in wastewater by (photo)electro-Fenton processes: Investigation of variables, acute toxicity, and intermediates

Electro-Fenton (EF) and solar photoelectro-Fenton (SPEF) processes were employed at different scales to degrade phenacetin (PNT), the first synthetic analgesic. EF experiments were conducted at lab scale, whereas SPEF experiments were performed in an 8 L pre-pilot plant using an electrochemical filter-press cell. Under optimal conditions (25 mg L−1 PNT, 25.3 mg L−1 Fe2+, and current density of 59.5 mA cm−2), EF resulted in degradation and mineralization degrees of 83.9% and 45.2% at 14 and 230 min, respectively. Similarly, PNT was spiked into real wastewater from a municipal secondary treatment plant, resulting in degradation of 68.0% and mineralization of 39.4%, with an energy consumption of 7.0 kWh g−1. The optimal conditions of SPEF (16.8 mg L−1 Fe2+ and current density of 45.9 mA cm−2) led to degradation and mineralization degrees of 55.9% and 37.1% at 36 and 181 min, respectively, with a low energy consumption of 0.142 kWh g−1. Both processes effectively detoxified the solutions, as demonstrated by tests with Artemia salina and Lactuca sativa. Three distinct degradation pathways were proposed based on the identification of eleven reaction intermediates formed upon •OH attack. In conclusion, the low energy cost of the SPEF process underscores its potential for pharmaceutical degradation in wastewater

Development of TiO2-based photocatalysts with high photocatalytic activity under simulated solar light: Metoprolol degradation and optimization via Box-Behnken

The photocatalytic activity of N-doped TiO2 nanoparticles to degrade metoprolol (MET) has been investigated. The materials were synthesized via sol-gel method and characterized using different techniques. All materials revealed the formation of anatase phase, with a band gap energy close to 3.12 eV, which suggests that the N doping did not cause substantial variations as compared to pure TiO2. However, the TiO2-5%N photocatalyst exhibited a reduction in nanoparticle size and a surface area 0.4-fold larger than undoped TiO2. The influence of pH, catalyst concentration, and doping percentage was investigated through a Box-Behnken experimental design. Under the best conditions (0.5 g L−1 of TiO2-5%N, solution pH 6.0), 98% MET degradation and 42% mineralization could be achieved, and the process by-products were non-toxic to Artemia salina