Nanofluid-peroxydisulfate integrated volumetric solar interfacial evaporation system for water evaporation and organic pollutant removal

Solar evaporation exhibits significant potential for the treatment of high-salt organic wastewater. However, it's also confronted with challenges due to the accumulation of organic pollutants and salts in the concentrated wastewater following evaporation, which compromises the long-term stability of evaporation unit and complicates subsequent treatment processes. To address these challenges, a volumetric solar interfacial evaporation (VSIE) system by integrating Fe3O4-H2O nanofluids and peroxydisulfate (PDS) were proposed in this study. In VSIE system, Fe3O4 magnetic nanoparticles (NPs) were prepared as solar receivers to form a volume-absorbing solar energy interface and enhance evaporation efficiency. The results show that the evaporation rate was 1.412 kg/(m2 center dot h) and the solar efficiency reached 93.75 % as the temperature rose to 57.2 degrees C. Additionally, the high thermal conductivity of Fe3O4 facilitated the effective heat transfer to the fluid and provided sufficient thermal energy to activate PDS, thereby removing 99.3 % of Rhodamine B (RhB). Fe3O4 NPs effectively promoted the generation of reactive species including SO4 center dot- , center dot OH, O2 center dot- and 1O2 from PDS and the four main stages including N-de-ethylation, chromophore cleavage, ring-opening, and mineralization were proposed as the possible degradation pathway of RhB. This study provides a reference for developing V-SIE system and highlights the positive effect of nanofluids in advanced oxidation processes.