Degradation Of Phenol By CoFe₂O₄/AA Activated Persulfate Oxidation

With the rapid development of industrialization in China,phenol?Ph?has become an important and urgent toxic organic pollutant in industrial wastewater.Therefore,it is imperative to study an effective and low-cost method for the removal of phenolic wastewater.Among the new advanced oxidation technologies,the sulfate radical SO₄^-?has gradually become an important research object in the field of water treatment due to its strong oxidizability.Persulfate(PDS,S₂O₈^2-)are activated in the presence of specific conditions such as transition metal ions,ultraviolet irradiation,etc.,to produce strong oxidizing sulfate radical?SO₄^-??,can degrade most organic pollutants.Among them,Fe²⁺/S₂O₈^2-system is the most widely used.However,there are still some problems to be solved:?1?The activity is higher in acidic solutions and the pH is restricted;?2?The catalyst in the homogeneous system is difficult to separate and recover;?3?Fe²⁺is easily oxidized to form a precipitate,resulting in low catalyst utilization.In response to the above problems,magnetic nano-cobalt ferrite?CoFe₂O₄?was prepared as a solid activator of PDS,and ascorbic acid?AA?was introduced into the system to propose a new system of CoFe₂O₄/AA/PDS.Through a series of characterization methods and phenol degradation experiments,the reaction mechanism of CoFe₂O₄ and AA synergistic activation of PDS was analyzed.The phenol degradation behavior was investigated by kinetics,the changing law of the reaction rate constant k was discussed,and the kinetic empirical equation was derived.Finally,the optimal conditions for the degradation of phenol were predicted by the design of response surface methodology.The experimental conclusions obtained were as follows,provide theoretical basis for phenol wastewater treatment project.1.Research and application of CoFe₂O₄/AA activated PDS oxidative degradation of phenol system:The structure and composition of the catalyst were analyzed by X-ray diffraction?XRD?,scanning electron microscope?SEM?,and specific surface area analyzer?BET?.By optimizing the experimental parameters,it was determined that the optimal degradation experiment conditions when the initial concentration of phenol was 50.00 mg/L were:PDS dosage was 4.20 mmol/L,AA dosage was 0.10 mmol/L,and CoFe₂O₄ dosage was 1.00 g/L,phenol removal rate could reach 90.11%after 2h.The metal ion dissolution experiment proves that phenol degradation was a heterogeneous reaction on the catalyst surface.The cycle experiment showed that CoFe₂O₄ had good stability and reusability.The free radical trapping experiment verified that the dominant active free radical was SO4^-?.2.Study on phenol degradation kinetics.Under different pH,initial concentration of phenol,CoFe₂O₄ dosage,PDS dosage and AA dosage,the phenol degradation behavior conforms to the quasi-first order reaction kinetic equation.Using MATLAB software to fit the experimental data to get the kinetic equation of phenol degradation fitting:lnC_t=A^0.2036B^0.7597C^-0.0248D^0.0630E^0.5352+0.1256 A^-0.3016B^-0.1756C^0.1520D^0.2985E^-0.3993 lnt3.Optimization of experimental conditions of response surface method.Using the Central-Composite model in Design Expert software to design a 5-factor 3-level optimization experiment,the influence between p H,initial concentration of phenol,CoFe₂O₄ dosage,PDS dosage and AA dosage on the removal rate of phenol was studied.From the model variance analysis results and response surface plots,the model was significant and there was a certain interaction between variables,which could be used to optimize the removal of phenol by CoFe₂O₄/AA/PDS.