Redispersible CuO nanoparticles: preparation and photocatalytic capacity for the degradation of methylene blue†

In this study, redispersible copper oxide nanoparticles (CuO NPs) with an average size of 92.18 nm were synthesized using ethylene glycol as a complexing agent and sodium poly(4-styrenesulfonic acid-co-maleic acid) as a stabilizer. The CuO NP dispersion remained stable for 30 days. In the CuO NPs/methylene blue (MB) system, the MB absorption peak at 664 nm weakened or disappeared, while a new peak at 583 nm emerged, indicating the formation of a charge-interaction complex confirmed by zeta potential measurements. Under UV irradiation, CuO NPs showed weak photocatalytic activity, degrading MB by 8.7%, 8.8%, and 9.7% at dosages of 1.3, 1.9, and 2.5 mM, respectively. At 0.6 mM CuO NPs, flocculation occurred, and FT-IR analysis confirmed MB adsorption onto CuO NPs with a capacity of 217.4 mg g⁻¹, indicating that MB was mainly separated from the system through adsorption by CuO NPs rather than being degraded via photocatalysis. With hydrogen peroxide, CuO NPs achieved nearly complete photodegradation (99.6%) of 53.5 μM MB within 75 minutes. This work offers novel insights into the development of redispersible nanomaterials and their applications in water treatment.