Activation of persulfate using copper oxide nanoparticles for the degradation of Rhodamine B containing effluents: Degradation efficiency and ecotoxicological studies

• PS activation using Cu-NPs was used to treat effluents contaminated with organics. • Taguchi experimental design allowed identifing the optimmum conditions for dye removal. • [PS] 0 =1 mM, CuO=0.5 g/L at pH=7.5 and 45 °C led to complete removal of RhB(50 mg/L). • Untreated and treated effluents were still both very toxic to B. calyciflorus . • PS/CuO reaction products were proposed as responsible for the observed toxicity. The development and implementation of advanced oxidation processes (AOP) are intended to assist in the treatment of effluents produced during anthropogenic activities, reducing their potential toxicity to the environment. The present work is intended to assess the chemical and ecotoxicological efficiency of AOP using copper oxide nanoparticles (CuO-NP) and persulfate (PS-as an oxidation agent) for the removal of Rhodamine B (RhB) from an aqueous solution. For this, CuO-NPs were prepared and used as a sole catalyst or combined with thermal treatmentto activatePS for the degradation of RhB (in distilled water-DI and ASTM medium). Kinetic and mechanistic studieswere employed to understand the performance of the system. The lethalecotoxicity of the untreated and treated RhBwas characterized using rotifer Brachionus calyciflorus .Complete removal of RhB was achieved at [RhB] 0 =50 mg/L, [PS] 0 =1 mM, CuO=0.5 g/L under pH=7.5 at 45°Cfor DI and ASTM. Brachionus calyciflorus mortality pointed to a very high ecotoxicity of the effluent before and after the AOP treatment; the former was less toxic than the latter: LC 50,24h = 44.3% and 8.24%, respectively.Mortalityobserved in the treated effluent was most probably due to the presence of reaction products (e.g., activated PS) rather than RhB,since CuO/PS system was able to remove > 90% of RhB. The obtained results demonstrated that although the proposed method is applicable to deal with high concentrations of recalcitrant organic compounds, the treated effluents can cause high ecotoxicity when released into the environment.