Research About The Cod Removal Rate Of Orange G Via Fenton Reagent Process

The Fenton reagent is very effective to remove variety of hazardous substances in wastewater. The main benefit of Fenton reagent is that it can decompose the hazardous substancescompletely to the harmless matirals, such as CO₂、H₂O and tnorganic salt. Fenton reagentcause oxidant and formation of·OH. The·OH attack and destroy organic molecule. The Fe²⁺in Fenton reagent cause decomposition of H₂O₂. Fenton reagent was used to treat wastewaterof reactive orange G. The effect of reaction time, concentration of H₂O₂, FeSO4amount andpH on removal efficiency were investigated. The reaction mechanism was discussed too. Thestudies get the following major findings:（1） the effect of pH on COD removal efficiencyThe results showed that COD removal efficiency was highest when pH range from2to3.It is disbennifit to Fenton reagent when pH was less than2or more than3. But in the actualproduction, pH value is not able to achieve2to3. The reason is that strong acidic conditionsis corrosive to reaction vessels and pipelines, and it is not allowed that pH is too low. Toreduce pH will increase waste water treatment costs or introduce new pollutants. So in theactual production, Fenton reagent will be used in the condition of pH less than5.（2） the effect of reaction time on COD removal efficiencyIn the condition of the certain initial concentration of the raw water、pH、Fe²⁺/H₂O₂ratio, COD removal efficiency is raised in advance, and then tends to smooth. At the time of15min～20min, COD removal efficiency changes small.（3） the effect of reaction temperature on COD removal efficiencyAppropriately increase reaction temperature can increase the average kinetic energy ofreactant, activate·OH free radical, and accelerate the reaction rate, improve the oxidationefficiency. But too high temperature will induce vice-reaction, decompose H₂O₂to O₂, andhinder the process of Fenton reaction. When the temperature reach to40⁵0℃, COD removalefficiency is highest. But the increasement is very limited. This shows that the effect of CODremoval efficiency depend on increase temperature is unconspicuous.（4） the effect of the concentration of Fe²⁺and H₂O₂on COD removal efficiencyWith the increasement of H₂O₂, degradability of organic matter is improved, but at thesame time the existence of H₂O₂is harmful for activity organic substances. In addition,because it is free radical quenching agent, the existence of H₂O₂inhibit·OH free radical, consequently it decreases the rate of Fenton oxygenation. Though the higher concentration ofFe²⁺accelerates the rate of Fenton oxygenation, it need a fat lot Fe²⁺to catalyse on the H₂O₂decomposition process. Fenton reagent have different process on the different ratio of[Fe²⁺]/[H₂O₂]. When Fe²⁺is more than H₂O₂in liquor, the process tends to the occurrence ofchemical flocculation. When H₂O₂is more than Fe²⁺in liquor, the process tends to theoccurrence of chemical oxidation. So the ratio of them is lower than1in Fenton oxidation.In the experiment, for the orange G dye wastewater is200mg/L, the optimum concentrationof Fe²⁺is200mg/L（1.32×10-3mol/L）, the optimum concentration of H₂O₂is0.75ml/L（6.6×10-3mol/L）,[Fe²⁺]/[H₂O₂]=0.22＜1, belong to the low ratio of [Fe²⁺]/[H₂O₂].