Degradation Of Bisphenol A In Aqueous Solution By Persulfate Activated With Transition Metals

In recent years,more and more endocrine disruptors have been detected in water.As a toxic and refractory endocrine disruptor,bisphenol A produces great harm to the human health and the environment.Thanks to the generation of hydroxyl radical,bisphenol A can be removed from water through advanced oxidation technology.The essence of classic Fenton technology is that hydrogen peroxide can be activated by ferrous ions and generate hydroxyl radical.Persulfate,a solid-type oxidant,can also be activated by transition metal ions to generat sulfate radical to degrade the pollutants.Sulfate radical based advanced oxidation processes have attracted extensive interests in water and wastewater treatment in recent years.The homogeneous activation of persulfate system has the advantages of easy to operate and low energy consumption,but high stoichiometric amounts of metal ions are needed and these ions may precipitate in neutral or alkaline condition and operability only within a narrow p H range.Therefore,there is a need to prepare the solid catalyst which is inexpensive and readily available without secondary pollution to activate persulfate.Accordingly,in this study,two different transition metal solid catalysts were prepared from different raw material with different preparation methods,and were used to activate persulfate and remove bisphenol A（BPA）,an endocrine disruptor in water.The removal efficiency and degradation mechanism in different systems were explored,the reusability and stability of solid catalysts were investigated.The main contents are as follows:CuMnO₂ catalyst were prepared by low temperature hydrothermal method using pure chemical reagents.The synthesized CuMnO₂ was characterized by X-ray diffraction spectroscopy,field emission scanning electron microscopy and energy dispersive X-ray spectroscopy.The results showed that the purity CuMnO₂ was successfully prepared and the nanoscale CuMnO₂displayed a prismatic shape.CuMnO₂was employed as catalyst to degrade bisphenol A in CuMnO₂/peroxomonosulfate system.A 95.5%BPA（0.1 m M）removal was achieved at peroxomonosulfate concentration of 0.4 m M,CuMnO₂ dosage of 0.2 g L^-1,with p H 8 buffered with 20 m M borate in 60 min,and 74.0%of total organic carbon was removed from BPA solution.The results that phosphate exerts a masking effect in CuMnO₂/peroxomonosulfate system indicates that surface hydroxyl groups play a significant role in peroxomonosulfate activation.The surface properties of CuMnO₂ nanoparticles before and after reaction were investigated by X-ray photoelectron spectroscopy,based on the results,peroxomonosulfate can be activated by≡Cu（I）and≡Mn（III）and generate reactive radicals.The formation of reactive radicals was verified by electron paramagnetic resonance spectroscopy and radical quenching experiments,the surface-bound hydroxyl radicals and sulfate radicals play a major role in the degradation of bisphenol A.In response to the current state of the waste alkaline zinc-manganese batteries,waste batteries were recovered and heavy metal ions were extracted therein.manganese-zinc ferrite(Mn_0.6Zn_0.4Fe₂O₄)catalyst was prepared by a gel method using spent alkaline Zn-Mn batteries as raw materials.The morphology and the microporous structure of the prepared catalyst were characterized by X-ray diffraction spectroscopy,field emission scanning electron microscopy,transmission electron microscopy and N₂-physical adsorption analysis.The prepared manganese zinc ferrite displayed a quasi-spherical shape.Mn_0.6Zn_0.4Fe₂O₄ was employed as catalyst to degrade bisphenol A by electro-enhanced heterogeneous activation of peroxydisulfate.Preliminary experiments were carried out to investigate BPA removal in different systems,the results show that the electric field enhanced manganese-zinc ferrite activated persulfate system has a good synergistic effect.The surface properties of Mn_0.6Zn_0.4Fe₂O₄ catalyst before and after reaction were investigated by X-ray photoelectron spectroscopy,the results indicate that Zn（II）was not involved in the peroxydisulfate activation.The results of radical quenching experiments and electron paramagnetic resonance spectroscopy analysis indicate that surface-bound sulfate and hydroxyl radicals played an important role in BPA removal,hydroxyl radical was mainly generated from the reaction of sulfate radical with water or hydroxide ion.The stability of Mn_0.6Zn_0.4Fe₂O₄ catalyst was investigated by cycling experiments,which indicates Mn_0.6Zn_0.4Fe₂O₄ is stable and can be reused.This work also provides an alternative way for the reutilization of spent alkaline Zn-Mn batteries.