The Preparation Of Supported Co₃O₄ Catalysts And Their Utilization In Organic Pollutants Degradation

Sulfate radicals(SO₄^·-)based advanced oxidation processes?AOPs?have attracted intensive attention because of their complete decomposition of organic contaminants.Peroxymonosulfate?PMS?activation using cobalt containing materials as heterogeneous catalysts?Co/PMS?is an efficient way to produce reactive SO₄^·-.Recently,nickel foam?NF?and nitrogen-doped graphene aerogel?NGA?with high porosity,robust ability,thermostability,mass transfer ability and especially 3D interconnected framework are considered as a new prospective catalyst support.In this paper,two new composite catalysts,Co₃O₄/NF and Co₃O₄/NGA,were prepared by using Co₃O₄ load to nickel foam and nitrogen doped graphene aerogel,and their catalytic performance was studied by using acid orange 7?AO7?as a model compound.The main research contents are as follows:?1?Cobalt oxide?Co₃O₄?nanowires and nanoflowers grown on nickel foam?NF?are fabricated by a hydrothermal and calcination method.The prepared 3D Co₃O₄/NF catalyst is characterized and applied as a heterogeneous catalyst for PMS activation to generate sulfate radicals for decomposition of AO7.The results show that the AO7 degradation rate increases with cobalt loading and PMS dosage,but decreases with the increase of solution pH.The Co₃O₄/NF catalyst using 2 mM Co?NO₃?₂·6H₂O as cobalt source exhibits highest activity,and almost complete decolorization could be achieved within 30 min.The diverse effects of coexisting anions(SO₄^2-,HCO₃^-,NO₃^-and Cl^-)on AO7 degradation are observed and explained.After 10 consecutive runs,excellent catalytic reactivity of the catalyst remains while the level of leached cobalt during the catalyst usage is much lower than the maximum allowable concentration in drinking and natural water.Scavenging experiments results suggest that SO₄^·-may play a primary role in AO7 oxidation by Co₃O₄/NF/PMS system although hydroxyl radical?^·OH?was also involved in this process.?2?Co₃O₄/NGA hybrids were prepared by an one-step hydrothermal method followed by freeze drying,characterized by field-emission scanning electron microscope?FESEM?,X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FT-IR?,Raman and energy-dispersive X-ray spectrometer?XPS?techniques and used for the degradation of Acid Orange 7 in aqueous solutions.The results demonstrated the degradation efficiency of Acid Orange 7 was influenced by PMS concentration and reaction temperature.At temperature 298 K,When PMS concentration was 2 mM,the catalyst showed can completely degrade Acid Orange 7 in aqueous solution within 30 min.Meantime,the composites also has an excellent long-term stability and recycling performance.After five runs,the activity of the catalyst dropped slightly compared with the fresh catalyst.Moreover,quenching tests indicated that the generated sulfate radicals in Co₃O₄/NGA/PMS system play dominant role in AO7 degradation although hydroxyl radicals also participate in this process.