Study On Sulfate Radical Activation By Microwave And Its Application

The sulfate radical?SO₄^-·?based advanced oxidation processes one of the most promising technology applied for wastewater disposal in recent years.The sulfate radical which is made by activating persulfate can degrade recalcitrant organic compounds pollutant in wastewater efficiently.The conventional ways to activate persulfate are transition metal activating,heat activating and ultraviolet activating.However there are many shortages in these ways,such as larger persulfate dosage,lower sulfate radical formation rate and lower reaction rate.Nowadays,microwave is applied in many field more and more,it has the characteristics of high efficiency and easy to control.Activating sulfate radical by microwave is a new research hotspot.Therefore,in this work landfill leachate was chosen as the target contaminant to investigate the effectiveness of persulfate activation by water-bath heat,microwave,combined microwave/Fe₃O₄ and combined microwave/NiZn ferrite respectively.Study on the water-bath heating activation included the influence of persulfate dosage and temperature on landfill leachate degradation.Research on the microwave activation involved the influence of persulfate dosage and microwave power on landfill leachate degradation.And comparison on the water-bath heating activation and the microwave activation was studied to learn the mechanism of the microwave activation.The correlativity between resistance of solution and COD removal rate was also discussed.The results revealed that a higher persulfate dosage and temperature would significantly increase the landfill leachate degradation by water-bath heating activation.When the persulfate dosage reached 0.1mol/L,COD removal rate decreased faintly.And a higher persulfate dosage and microwave power would increase the landfill leachate degradation by microwave activation.The results of comparison experiments showed that COD removal rate reached 68.28%?sodium persulfate?and 61.61%?potassium peroxymonosulfate?after 20 min by microwave activation,while the COD removal rate reached 64.48%?sodium persulfate?and 58.85%?potassium peroxymonosulfate?after20 min by water-bath heating activation.The effects of microwave activation could be divided primarily into thermal and non-thermal effects.The result showed a significant inverse correlation between resistance of solution and COD removal rate.Investigation on the combined microwave/Fe₃O₄ activation involved the influence of Fe₃O₄ dosage,persulfate dosage,microwave power,and initial pH on landfill leachate degradation.The correlativity between resistance of solution and COD removal rate was also discussed.The results indicated that the COD removal rate increased with increasing Fe₃O₄ dosage,persulfate dosage and microwave power,while a slight decrease in COD removal was observed when the Fe₃O₄ dosage exceeded 0.05mol/L.COD removal rate showed less dependence on initial pH.The optimum conditions were that Fe₃O₄ dosage was 0.05mol/L,persulfate dosage was0.1mol/L,microwave power was 700W and initial pH was 5,the COD removal rate reached 92.87%?sodium persulfate?and 83.91%?potassium peroxymonosulfate?after20 min at the optimum conditions.The result showed an inverse correlation between resistance of solution and COD removal rate by combined microwave/Fe₃O₄activation.Research on the combined microwave/NiZn ferrite activation included the influence of NiZn ferrite dosage,persulfate dosage,microwave power,and initial p H on landfill leachate degradation.And comparison on disposal of different processes was studied.The correlativity between resistance of solution and COD removal rate was also discussed.The result showed that the COD removal rate increased with increasing NiZn ferrite dosage,sodium persulfate dosage and microwave power,while a slight decrease in COD removal was observed when the NiZn ferrite dosage exceeded0.005mol/L?sodiumpersulfate?and0.01mol/L?potassium peroxymonosulfate?.The optimum conditions were that NiZn ferrite dosage was0.005mol/L?sodium persulfate?and 0.01mol/L?potassium peroxymonosulfate?,persulfate dosage was 0.1mol/L,microwave power was 700W and initial pH was 5,the COD removal rate reached 97.13%?sodium persulfate?and 89.43%?potassium peroxymonosulfate?after 20 min at the optimum conditions.The results of comparison experiments showed that the rates of COD removal in the process of MW-NiZn-Persulfate were significantly higher than those other treatments.There might be certain cooperation actions in MW-NiZn-Persulfate system during the degradation of COD.The result showed an inverse correlation between resistance of solution and COD removal rate by combined microwave/NiZn ferrite activation.