Experimental Study On Treatment Of Two Kinds Of Organic Wastewater By Zero-Valent Iron Fenton-Like Technology

To explore the treatment effect and mechanism of zero-valent-iron-based Fenton-like technique on wastewater containing complex heavy metal ions and N,N-dimethylfor-mamide（DMF）.A coupling process of zero-valent-iron-based Fenton-like technique and A/O process was constructed,and the treatment effect of this process on wastewater containing complex heavy metal ions was studied.Zero-valent-iron-based Fenton-like technique was used to treat organic wastewater containing complex heavy metal ions.Under the optimum conditions of initial p H value of 3,dosage of H₂O₂of 1.5 m L/L,dosage of zero-valent iron（Fe⁰）of 30 g/L,and reaction time of60 min,the COD removal rate was 71%,The Cu²⁺,Pb²⁺and Ni²⁺removal rates were 98%,98%and 97%,respectively.After repeated experiments for five times,the removal rates of target pollutants COD,Cu²⁺and Ni²⁺remained at 61%,89%and 90%respectively,indicating that this technology has good repeatability.Under the same dosage of H₂O₂,compared with the Fenton oxidation method,the removal rates of COD,Cu²⁺,Ni²⁺and Pb²⁺by zero-valent-iron-based Fenton-like technique are 15%,10%,12%and 12%higher,respectively.At the same time,the zero-valent-iron-based Fenton-like technique uses cheaper chemicals and produces less iron mud.Therefore,it shows that zero-valent-iron-based Fenton-like technique has good economic benefits in the treatment of this kind of wastewater.The DMF wastewater was treated by zero-valent-iron-based Fenton-like technique.When the initial p H was 2,the dosage of H₂O₂was 20 m L/L,the reaction time was 120 min,and the dosage of Fe⁰was 100 g/L,the removal rates of COD and DMF reached 48%and61%,respectively.DMF wastewater was treated by Fenton oxidation method.Through orthogonal test,the relationship between the four conditions and the reaction was as follows:H₂O₂dosage>n（H₂O₂）:n(Fe²⁺)>p H>reaction time.Under the conditions of H₂O₂dosage of 30m L/L,molar ratio of n（H₂O₂）:n(Fe²⁺)of 3:1,initial p H of 2 and reaction time of 120 min,the removal rates of COD and DMF reached 63%and 88%respectively.Under the same dosage of H₂O₂,compared with the Fenton oxidation method,the removal rates of COD and DMF by zero-valent-iron-based Fenton-like technique are 9%and 10%lower respectively.It shows that the Fenton oxidation method is more efficient in treating organic pollutants with high COD value.The coupling process of zero-valent-iron-based Fenton-like technique and A/O process was used to treat the organic wastewater containing complex heavy metal ions.Firstly,the wastewater is treated by zero-valent-iron-based Fenton-like technique,and then enters the A/O process reactor for biochemical treatment.In the biological treatment part,macroporous polyurethane foam was used as the carrier,and the microorganisms were immobilized,cultured and domesticated.After the coupled process treatment,the target pollutants in the wastewater include COD,Cu²⁺,Pb²⁺and Ni²⁺,all of which have good removal effects,with removal rates of 90%,86%,87%and 80%respectively.In the final effluent index,the COD value is lower than 100 mg/L,and the concentrations of heavy metal ions such as Cu²⁺,Pb²⁺,Ni²⁺are all lower than 1 mg/L.