Study On Waste Catalyst Recycling Of Dye Wastewater Treated By Fenton Process

Fenton's reagent is chemically reacted by the formed Fenton system,and the·OH producted is highly oxidizing and can degrade organic compounds to remove contaminants.The Fenton oxidation method based on this has the advantages of being friendly to the environment,small space occupation,large operational flexibility,low initial cost,and strong oxidizing ability.However,there are also disadvantages such as yellowing of the effluent color,reaction under acidic conditions,and low utilization of H₂O₂.The catalyst added in the Fenton process is finally discharged as precipitated sludge and cannot be recycled to become a spent catalyst.This kind of sludge is generally stored,transferred and disposed according to the environmental management requirements of hazardous wastes,which not only has a great impact on the environment,but also requires high environmental management costs and disposal costs.In this paper,three kinds of dyes simulated wastewater?Reactive Red 2,Alkaline red,Methylene blue?took as object.Based on the experimental screening of Fenton treatment catalyst and obtaining the best conditions,the research focuses on the catalyst failure mechanism and the ways and methods of waste catalyst regeneration,which has practical and theoretical significance for reducing wastewater treatment costs.This paper has carried out research work on the following aspects:?1?Six ions of Mn²⁺,Al³⁺,Zn²⁺,Cu²⁺,Fe³⁺and Fe²⁺were used as catalysts to conduct a Fenton oxidation experiment with H₂O₂ to treat activated red 2 simulated wastewater.Experimental results show that the effect of Fe³⁺and Fe²⁺constituted?like?Fenton system is better with H₂O₂,while Cu²⁺have some effect,Mn²⁺,Al³⁺,Zn²⁺may be considered substantially no effect.Under the same ion concentration,the catalytic effect of Fe³⁺is similar to that of Fe²⁺.It is indicated that Fe³⁺can also be used as a catalyst for Fenton reaction with H₂O₂ to form like Fenton system to produce·OH.?2?Fenton oxidation treatment of alkaline red simulated wastewater,the removal of color and COD reagent ratio and dosage have a big difference.For chromaticity,the optimum treatment conditions are:initial p H is 3,C(Fe³⁺):C?H₂O₂?=1:5,C(Fe²⁺):C?H₂O₂?=1:5,reaction 30min.Fe³⁺,Fe²⁺are added under the optimal conditions to make C(Fe³⁺)=1mmol/L,C(Fe²⁺)=1mmol/L,C?H₂O₂?=5mmol/L,and the color removal efficiency of the Fenton system was 95.68%and 92.30%,respectively.For COD,the optimum treatment conditions are:initial p H is 3,C(Fe³⁺):C?H₂O₂?=1:20,C(Fe²⁺):C?H₂O₂?=1:30,reaction 40min.The Fenton system consists of Fe³⁺and H₂O₂,under the optimal conditions,when C(Fe³⁺)=6mmol/L and C?H₂O₂?=120mmol/L,the COD removal rate was 93.37%.The Fenton system composed of Fe²⁺and H₂O₂ had the COD removal rate of 96.68%when C(Fe²⁺)=4mmol/L and C?H₂O₂?=120mmol/L were added under the optimal conditions.?3?The iron sludge after the Fenton reaction cannot be directly used as a catalyst.The reason for the inactivation of iron sludge is not the loss of iron in the precipitation filtration process or the residual organic matter in the precipitate.But the Fe OOH with high degree of hydroxylation generated by Fe³⁺in the sedimentation process of iron sludge cannot interact with H₂O₂.?4?Activation treatment of iron mud can destroy the iron ion hydroxylation structure.The effects of activator dosage,activation time,activation temperature,iron precipitation separation p H and Fenton reaction time on the Fenton effect were investigated.It indicates that the more the activator dosage and the longer the activation time,the better the Fenton effect.The longer the Fenton reaction time,the better the Fenton effect.The activation temperature has little effect on the Fenton effect.The optimal p H of iron precipitation separation is about 10,the iron precipitation is incomplete at too low p H,and the high p H makes the hydroxylation of iron stronger,which reduces the catalytic effect of iron.?5?The ferric sulfate was used as the catalyst Fenton to treat the alkaline red simulated wastewater.The initial Fenton conditions were:C(Fe³⁺)=4mmol/L,C?H₂O₂?=80mmol/L,reaction p H=3,reaction 40min,precipitation p H=10.The activation time and the Fenton reaction time were changed after activation treatment,and the iron sludge was repeatedly used as a catalyst.Under the condition of activation time 2h and reaction time2h,the first COD removal rate of iron mud recycling was 90.29%,and the sixth time could still reach 81.22%.Under the condition of activation time of 4h and reaction for40min,the first COD removal rate was 83.58%,and the 5 removal rate could still reach76.78%.?6?The effect of treating methylene blue simulated wastewater with ferric sulfate as catalyst Fenton verified the feasibility of Fenton method catalyst recycling.Treatment of200m L Alkaline Red Simulated Wastewater by Fenton Oxidation with Ferric Sulfate as Catalyst,based on the 6 times of COD removal effect,the benefit analysis is performed.The wastewater treatment cost can be reduced,and the catalyst recycling is economical.