Study On Degradation Of Organic Pollutant Phenol In FeMoO₄/Persulfate Heterogeneous System

Phenol is a highly toxic and difficult-to-degrade protoplasmic poison,which is extremely harmful to human health,animal and plant growth,and the ecological environment.It has been included in the list of priority control pollutants by the US Environmental Protection Agency（US EPA）.With the rapid development of urban and industrial industries,the discharge of phenolic wastewater is increasing rapidly,and there is an urgent need for efficient treatment methods.Advanced oxidation processes based on sulfate radical is a popular method to treat phenolic wastewater in recent years,in particular,the heterogeneous system oxidation method has attracted a great deal of attention because of its low energy consumption,efficient and clean.The focus of the oxidation method is to develop high-efficiency catalysts.In this paper,FeMoO₄and FeMoO₄@C were synthesized to study the performance of activating persulfate on the removal of phenol in heterogeneous systems.And their structure and morphology were characterized by X-ray diffraction（XRD）,Scanning electron microscope（SEM）,Raman spectroscopy（Raman）and Fourier infrared spectroscopy（FTIR）.The following are the research content and results:（1）Rod-shaped FeMoO₄ was synthesized by hydrothermal method at 180℃.The main objectives of this work investigated the effects of reaction factors and coexisting ions on the removal of phenol,the genres of active free radicals that played a leading role in heterogeneous FeMoO₄/persulfate system were preliminarily analyzed.At the same time,the reusability of FeMoO₄was also studied.The result showed that FeMoO₄had superior catalytic activity in a relatively wide p H range.Properly increasing the mass concentration of FeMoO₄or persulfate could promote the degradation of phenol.The dosage of the FeMoO₄was 0.4 g/L,the concentration of phenol was 25 mg/L,n（persulfate）∶n（phenol）=25∶1,the phenol degradation rate was 98.55%in 6 h when the temperature was 30℃and the initial p H was 3.00.The degradation of phenol followed reaction kinetic model of first order in the system.The activation energy was 53.49 k J/mol.The coexisting ions such as Cl^-,NO₃^-,HPO₄^2-and CO₃^2-had different effects on the reaction.Cl^-and NO₃^-had a little interference effect while HPO₄^2-and CO₃^2-had a significant inhibitory effect on the degradation of phenol.The free radical quenching experiment showed that SO₄^-·which played a critical role and·OH participated in the degradation of phenol at the same time.The degradation of phenol was only 27.12%in 6 h after 3 cycles of reaction,indicating that the reusability of FeMoO₄was a bit poor and needed to be improved in the future.（2）In order to reduce the agglomeration of FeMoO₄and improve the catalytic activity of it,FeMoO₄was loaded on the surface of biochar to prepare supported catalyst FeMoO₄@C.The effects of catalyst loading and reaction factors on the degradation of phenol were studied in heterogeneous FeMoO₄@C/persulfate system,and the catalyst’s reusability was evaluated.The experimental result displayed that 3-FeMoO₄@C₈₀₀had the most optimal catalytic performance in a comparatively broad p H range.The degradation rate of phenol improved with the appropriate increase of the dosage of catalyst 3-FeMoO₄@C₈₀₀and persulfate.The dosage of the 3-FeMoO₄@C₈₀₀was 0.3 g/L,n（persulfate）∶n（phenol）=25∶1,the concentration of phenol was 25 mg/L,the phenol degradation rate was 97.60%in 3 h when the temperature was 30℃and the initial p H was 3.00.The activation energy was 41.80k J/mol.Although the degradation rate of 3-FeMoO₄@C₈₀₀was only 43.75%within 3 h after being reused for three times,reaction cycle was shortened by half compared with pure FeMoO₄,and the catalytic activity was significantly improved.