Synergistic Degradation Of Dyes In Water Coupling Persulfate With H₂O₂ Catalyzed By Nano Zero Valent Iron

The single oxidant system of peroxynitrite（PDS）or hydrogen peroxide（H₂O₂）could remove the pollutants well,but it was found that the single system only decomposed the pollutants into small molecular intermediates,and its mineralization ability was limited.Therefore,a dual oxidant system based on peroxynitrite and hydrogen peroxide was developed.The dual oxidant system was able to overcome the problem of too fast decomposition of H₂O₂in the traditional Fenton system and solve the problem of insufficient mineralization of pollutants in the peroxynitrite system.There were few studies on the removal of pollutants by double oxidants,therefore,this paper took the azo dye reactive brilliant red X-3B as the test object and investigates in depth the mechanism of pollutant degradation by the nZVI/PDS/H₂O₂system in comparison with the nZVI/PDS system.The degradation of reactive brilliant red X-3B by the nZVI/PDS system was investigated using the prepared nano-zero-valent iron.The effects of PDS concentration,nZVI dosage and initial p H on the degradation of reactive brilliant red X-3B were investigated,and it was found that the removal rate of reactive brilliant red X-3B gradually increased with the increase of PDS concentration and nZVI dosage,and the optimal ratio of nZVI to PDS was 1:2.The optimal initial p H was determined to be 7 under the optimal ratio,and the removal rate of reactive brilliant red X-3B was increased under the optimal reaction conditions.The removal rate of brilliant red X-3B could reach 96.2%under the optimal reaction conditions.The radical quenching and EPR experiments confirmed that SO₄^?-and?OH were the major radicals in the system,with SO₄^?-contributing 49.0%and?OH 30.4%of the removal rate.nZVI/H₂O₂system had an optimum reaction p H of 3,which had no effect on the removal of pollutants under neutral and alkaline conditions,and the removal rate of reactive brilliant red X-3B at an initial p H of 3 was 95.0%.The degradation of reactive brilliant red X-3B by the nZVI/PDS/H₂O₂system was investigated on the basis of the nZVI/PDS system.The effects of the molar ratio of PDS to H₂O₂,nZVI dosage,H₂O₂dosage time and initial p H on the degradation of reactive brilliant red X-3B were investigated.Under the optimum experimental conditions,the nZVI/PDS/H₂O₂system was able to remove 60.27%of TOC for 120 min,while the nZVI/PDS system only achieved 29.37%.It was determined that the main radicals in the system were?OH,which contributed 67.8%of the removal rate,and SO₄^·-which contributed 19.5%.The nZVI/PDS/H₂O₂system was found to have a higher radical strength than the nZVI/PDS system.nZVI/PDS/H₂O₂created a system in which?OH was the dominant radical and SO₄^?-was the secondary radical.nZVI/PDS/H₂O₂promoted the cycling of Fe²⁺and Fe³⁺by the addition of H₂O₂and also promoted the production of more SO₄^·-,which enhanced the bond-breaking effect and strengthens the mineralisation of the contaminants.