Experimental Study On Oxidative Degradation Of Carbamazepine By Potassium Ferrate

Pharmaceutical and Personal Care Products（PPCPs）are used in many areas of people’s production and life.As PPCPs cannot be effectively removed in the conventional wastewater treatment process,they are widespread in surface water,groundwater,and soil with potential ecological risks.Since carbamazepine（CBZ）is difficult to degrade after entering the environment,it was detected at a high level in water bodies,and is often used as an indicator compound for PPCPs pollution.Potassium ferrate has been a new green water treatment agent with strong oxidizing ability and without secondary pollution in recent years.Some studies have shown that potassium ferrate has potential in the treatment of refractory organic pollutants.In this study,carbamazepine,a typical PPCPs substance,was selected as the target pollutant,and potassium ferrate was used as the oxidant to investigate the effects of different p H,potassium ferrate dosage,initial CBZ concentration,temperature,and coexisting substances on the degradation efficiency of potassium ferrate for CBZ.The reaction kinetic equation between CBZ and potassium ferrate was established,and the reaction rate constants under different reaction conditions were calculated.The response surface analysis method was used to establish a fitting model between the degradation rate of CBZ and the main influencing factors;the reaction pathway of potassium ferrate to degrade CBZ was discussed,the research results obtained are as follows:（1）p H had a great influence on the removal effect of CBZ,the initial reaction rate was higher under acidic conditions but the final degradation rate was lower than that under alkaline conditions,the degradation rate was highest at p H=8.0,which could reach 80.9%by using 20μM potassium ferrate to degrade 4μM CBZ within 120 min.The CBZ degradation ratio increased at a higher potassium ferrate concentration,under the condition of p H=8.0,potassium ferrate above 30μM could completely remove 4μM of CBZ.The CBZ degradation ratio decreased at a higher initial CBZ concentration,while the total amount of the degraded CBZ increased apparently.The effect of temperature increased on the degradation rate of CBZ was not obvious.Na⁺,K⁺,Cl^-and SO₄^2-had almost no effect on the degradation effect,and Ca²⁺,Mg²⁺,HCO₃^-had a slight inhibitory effect on the degradation effect,while NOM had a significant inhibitory effect on the degradation effect of CBZ.（2）The degradation of CBZ by potassium ferrate was suitable for the second-order reaction kinetics:the reaction rate constant was negatively correlated with p H and the initial concentration of CBZ,and positively correlated with potassium ferrate dosage and temperature.The activation energy of the oxidation reaction of CBZ with potassium ferrate calculated by Arrhenius equation was 27.7 k J/mol.（3）On the basis of single factor experiments,the Box-Behnken Design（BBD）method was used to fit the regression equations between CBZ degradation rate and p H,potassium ferrate dosage,and initial CBZ concentration,the model had good fitting accuracy and predictability.The best conditions for potassium ferrate to degrade CBZ predicted by this model were:p H=7.7,2μM initial CBZ,40μM potassium ferrate,and the theoretical CBZ degradation rate could reach 99.54%under these conditions.The experimental verification of the predicted value proved that the prediction was basically accurate and credible.（4）A total of 8 different degradation products have been detected by LC/MSMS,it was speculated that the CBZ degradation by potassium ferrate proceeded mainly through the attack of potassium ferrate on olefin double bonds on the CBZ aza ring to form an epoxy structure and further oxidation of the structure to complete the removal of CBZ.