Electrochemically assisted production of biogenic palladium nanoparticles for the catalytic removal of micropollutants in wastewater treatment plants effluent

Biogenic palladium nanoparticles (bio-Pd NPs) are used for the reductive transformation and/or dehalogenation of persistent micropollutants. In this work, H₂ (electron donor) was produced in situ by an electrochemical cell, permitting steered production of differently sized bio-Pd NPs. The catalytic activity was first assessed by the degradation of methyl orange. The NPs showing the highest catalytic activity were selected for the removal of micropollutants from secondary treated municipal wastewater. The synthesis at different H₂ flow rates (0.310 L/hr or 0.646 L/hr) influenced the bio-Pd NPs size. The NPs produced over 6 hr at a low H₂ flow rate had a larger size (D50 = 39.0 nm) than those produced in 3 hr at a high H₂ flow rate (D50 = 23.2 nm). Removal of 92.1% and 44.3% of methyl orange was obtained after 30 min for the NPs with sizes of 39.0 nm and 23.2 nm, respectively. Bio-Pd NPs of 39.0 nm were used to treat micropollutants present in secondary treated municipal wastewater at concentrations ranging from µg/L to ng/L. Effective removal of 8 compounds was observed: ibuprofen (69.5%) < sulfamethoxazole (80.6%) < naproxen (81.4%) < furosemide (89.7%) < citalopram (91.7%) < diclofenac (91.9%) < atorvastatin (> 94.3%) < lorazepam (97.2%). Removal of fluorinated antibiotics occurred at > 90% efficiency. Overall, these data indicate that the size, and thus the catalytic activity of the NPs can be steered and that the removal of challenging micropollutants at environmentally relevant concentrations can be achieved through the use of bio-Pd NPs.