Degradation Of P-chloronitrobenzene By Reduction-oxidation Method Coupling Zero-valent Iron With Hydrogen Peroxide

The random discharge of industrial wastewater has made water pollution problems increasingly serious.Chloronitrobenzene is a typical organic pollutant that cannot be ignored in our country’s water body.Generally,a single reduction technology can only reduce chloronitrobenzene to chloroaniline and other intermediate products.It is difficult to completely degrade chloronitrobenzene due to it contains strong electron-withdrawing-NO2 and-Cl.So a single oxidation technology is difficult to mineralize chloronitrobenzene.If the chloronitrobenzene is reduced to the reduction intermediate product,and then the reduction intermediate product is further mineralized by the oxidation reaction,it is expected to realize the complete removal of the chloronitrobenzene.Based on the above ideas,this study used p-chloronitrobenzene(p-CNB)as a model pollutant,selected zero-valent iron and hydrogen peroxide to construct a reduction-oxidation coupling system to efficiently remove p-CNB.The reduction-oxidation coupling degradation mechanism of p-CNB in this system was also discussed.The specific research contents are as follows:1.A reduction-oxidation coupling system(ZVI/H2O2)was constructed using ZVI and H2O2 to degrade p-CNB.The performance of degrading p-CNB by ZVI/H2O2 and traditional Fenton technology(Fe(Ⅱ)/H2O2)was compared and studied.The results showed that under pH value of 3.0,the degradation efficiencies of p-CNB in ZVI/H2O2 and Fe(Ⅱ)/H2O2 systems in 4 hours were 99.7%and 90.7%,respectively.But the mineralization efficiencies of p-CNB in 4 hours were 50.0%and 0%,respectively.The effect of mineralization of p-CNB in the ZVI/H2O2 system was significantly better than that of Fe(Ⅱ)/H2O2.The quantitative analysis of ·OH showed that ZVI/H2O2 system produced more ·OH than the Fe(Ⅱ)/H2O2 system.GC-MS results showed that the ZVI/H2O2 system could simultaneously generate reduction products such as p-chloroaniline(p-CAN)and oxidation products such as p-chlorophenol,while the Fe(Ⅱ)/H2O2 system only generated oxidation products.It proved that there was a reduction-oxidation coupling effect in the ZVI/H2O2 system.Specifically,ZVI could reduce p-CNB to p-CAN and other reduction products that were easier to be oxidized and degraded.At the same time,ZVI could reduce Fe(Ⅲ)to Fe(Ⅱ).Fe(Ⅱ)could activate H2O2 to produce ·OH,which promoted the continuous progress of Fenton oxidation reaction.2.B2O3 and ZVI mechanical ball milling were used to prepare boride zero-valent iron(B-ZVIbm),and the performance of B-ZVIbm and ball-milling zero-valent iron(ZVIbm)to remove p-CNB was compared.Then,a reduction-oxidation coupling system(B-ZVIbm/H2O2)was constructed to efficiently degrade p-CNB.The results showed that when pH=6.8,the efficiency of B-ZVIbm and ZVIbm to remove p-CNB in 4 hours was 95.6%and 36.7%,respectively.The products were p-chloronitrosobenzene and p-chloroaniline.The removal rates of p-CNB and TOC in the B-ZVIbm/H2O2 system were 90.1%and 35.0%,respectively,while those in the ZVIbbm/H2O2 system were only 39.4%and 17.2%.This showed that the B-ZVIbm/H2O2 system could more efficiently mineralize p-CNB.The results of Tafel curve and hydrogen radical detection showed that B-ZVIbm had better electron transport performance and hydrogen radical generation ability,and therefore had stronger p-CNB reduction ability.XPS results showed the proportion of Fe(Ⅱ)on the surface of B-ZVIbm increased.Fe(Ⅱ)could effectively activate H2O2 to produce more·OH,and then efficiently degraded p-CNB.