Abstract
In recent years, a large amount of emulsified oily wastewaters were produced from petroleum and food industries, resulting in severe environmental problems. In this study, a series of polyvinylpyrrolidone (PVP)-coated Fe3O4 magnetic nanoparticles (MNPs) were prepared via one-step solvothermal method by introducing various amounts or types of PVP. The synthesized MNPs were characterized by multiple techniques, and their demulsification performances were evaluated in petrochemical and vegetable oil wastewaters, respectively. Results showed that the introduction of PVP in solvothermal process could significantly enhance the demulsification efficiency of MNPs, although excessive addition of PVP could not further increase its efficiency. Moreover, the effects of pH, surfactant concentration of wastewater, and the recycle number of MNPs on the demulsification performance were investigated in detail. It was found that the demulsification efficiency decreased with the increase of pH and surfactant concentration, and the synthetic MNPs were still effective after being reused for 5 cycles under acidic and neutral conditions. It is expected that the development of the PVP-coated MNPs can provide a simple and powerful route for the oily wastewater treatment.
Highlights
In recent years, a large amount of emulsified oily wastewaters were produced from petroleum and food industries, resulting in severe environmental problems [1]
Without addition of PVP, the synthesized Fe3 O4 magnetic nanoparticles (MNPs) could not be well dispersed in water
The PVP-coated Fe3 O4 MNPs prepared via solvothermal method exhibited good demulsification performance toward treating petrochemical and vegetable oil wastewaters
Summary
A large amount of emulsified oily wastewaters were produced from petroleum and food industries, resulting in severe environmental problems [1]. The emulsified oil droplets are highly stable due to the presence of surface-active substances, which are either naturally existed or intentionally added [2], making it hard to deal with the emulsified oily wastewaters. Conventional techniques, such as flotation [3], chemical flocculation [4,5] and membrane separation [6,7,8], were used to break emulsions. Flotation was ineffective to treat the nanosized oil droplets, chemical flocculation was effective but time-consuming, and membrane separation was limited by the high energy consumption and membrane fouling in actual application [9]. There remains an urgent need to develop easy and powerful techniques or demulsifiers to achieve efficient emulsified oil-water separation
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