A Study On Preparation Of Fe-C/N Composites And Their Catalytic Performance For Degradation Of Organic Compounds By Persulfate

The advanced oxidation techniques based on persulfate?PS?have been received extensive attention in recent years.However,persulfate is relatively stable at room temperature,how to effectively activate persulfate is the focus of current researchers.In this study,a carbon-coated Fe₃C and Fe₃N composite?abbreviated as Fe-C/N-0.5:1?was prepared to investigate the effect of activating persulfate on the degradation of Acid Red 73?AR 73?and bisphenol A?BPA?.Fe-C/N-0.5:1 solid catalyst?where 0.5:1 refers to the mass ratio of Fe to g-C₃N₄?was prepared by immersion calcination method using g-C₃N₄ and FeC₂O₄·2H₂O as raw materials,and the main phases of the Fe-C/N-0.5:1 solid are Fe₃C and Fe₃N through XRD analysis.The removal efficiency of Fe-C/N-0.5:1/PS system on AR 73was studied,and the impact of various factors on the effect of AR 73 removal was investigated.At room temperature?25°C?,when the dosage of Fe-C/N and PS were both 1.0 g/L at the initial pH of 6.8,the removal of AR 73 was 98.11%in 10 min.However,the removal of chemical oxygen demand?COD?was only 34%within 30min,indicating the accumulation of intermediates.The results of UV-visible adsorption spectroscopy and GC,GC-MS,ion chromatography analysis revealed that the intermediates in the process of AR 73 degradation was mainly benzoic acid,and a small amount of phthalic acid,succinic acid,hexanedioic acid,formic acid,acetic acid.By changing the content of iron in the raw materials,the catalysts with different ratios of Fe₃C and Fe₃N were obtained.It was found that the coinstantaneous presence of Fe₃C and Fe₃N could lead to high degradation efficiency.Therefore,the catalytic effect of Fe-C/N-0.5:1 can be attributed to the synergistic effect between Fe₃C and Fe₃N,and Fe₃C plays a leading role.The leaching iron was 1.932 mg/L by the 1,10-phenanthroline spectrophotometry method,and the degradation rate after the four cycles was still 92.99%,indicating that the catalyst has good stability and recyclability.Through free radical quenching experiments,there are three reactive species in the system:singlet oxygen?¹O₂?,sulfate radical(SO₄^·-),and hydroxyl radical?·OH?,in which ¹O₂ plays a major role.Fe-C/N-0.5:1 was used to degrade bisphenol A?BPA?by activating PS.Under the conditions of the PS concentration of 0.2 g/L and the catalyst dosage of 0.2 g/L,the 20 mg/L bisphenol A was removed by 99.69%in 20 min.The effects of common anions(Cl^-,HCO₃^-,SO₄^2-)on the degradation system were investigated.It was found that the common anions had no obvious inhibitory effect on the degradation efficiency.With the increase of pH,the degradation efficiency decreased slightly,but the degradation efficiencies were almost similar in the range of tested pH?3⁹?after 20min,which might result from the fact that the pH values decreased and eventually tended to be a similar value?final pH 3.4-3.6?.On the basis of the above analysis,one can infer that the Fe-C/N-0.5:1 catalyst can significantly improve the oxidizing ability of PS,and has good removal efficiency for AR 73 and BPA simulated wastewater at room temperature.Moreover,the high stability of the catalyst and easy recycling by magnetic make it a promising application.