| Phenol is difficult to be degraded by traditional methods as a representative organic pollutant,which will do harm to the ecological environment and human health.Hydrodynamic cavitation,a new treatment method,is characterized by treatment thoroughly,economic,high efficiency,simple operation,easy to achieve industrial scale and no secondary pollution.For the first time,the combination of hydrodynamic cavitation and Cl O2 was applied to degrade the Phenol.This study provides a theoretical basis for the treatment of organic wastewater,which has great practical significance.On the basis of reading a large number of domestic and foreign literatures,this study designed a set of practical effective hydrodynamic cavitation installation,which takes the cavitation generator by the orifice plate and venturi tube.Three ways were adopted to deal with phenol wastewater and the effect of different operating parameters on removal of phenol were studied as well.These degradation methods include the technology of ClO2 oxidative degradation,the technology of hydrodynamic cavitation and the technology of ClO2 oxidative degradation combined with hydrodynamic cavitation.The optimal operating conditions and the optimal cavitation generator were determined.The intermediates of the technology of ClO2 oxidative degradation combined with hydrodynamic cavitation on phenol were analyzed using HPLC.The degradation pathway of reaction was also confirmed.Meanwhile the dynamical model of the combined method has been stablished.The main experimental results were as follows:(1)The orifice plate as a cavitation generator for the degradation of phenol was better than that of venturi tube.The degradation efficiency achieved the best when using the orificeplate(Orifice opening rate of 0.0610,annular distribution plate)as the cavitation generator.The optimal reaction condition was concluded as below: inlet pressure was 0.4 MPa,reaction time 90 min,27.6% of phenol can be removed.Through the study on intermediate product and the mechanism of reaction for the degradation of phenol by using hydrodynamic cavitation alone,it was obtained that phenol was first oxidized to benzoquinone,followed by degradation of benzoquinone to maleic acid.(2)Through the laboratorial study on the technology of Cl O2 oxidative degradation of phenolic water,it could be obtained that the extent of degradation increased significantly with the increasing of chlorine dioxide concentration and phenol degradation rate tend to be stable when treatment time was more than 45 min.When the ratio of amount-of-substance concentration of phenol to Cl O2 was 1: 2,87.1 % of phenol can be removed when the processing time was 45 min.When the phenol was treated with ClO2 alone,the phenol could only be oxidized to benzoquinone.(3)The orifice plate(Orifice opening rate of 0.0610,annular distribution plate),which had the best cavitation effect,was used as a cavitation generator.Through the laboratorial study on the technology of combining hydrodynamic cavitation with ClO2 for the degradation of phenol,the optimaldegradation rate of phenol could obtained 92.1% under conditon that the ratio of amount-of-substance concentration of ClO2 to phenol was 1: 1,treated for 30 min.The degradation was 1.4 times more than that the sum of the degradation rate of using hydrodynamic cavitation alone(degradation rate of phenol 17.1%)and using chlorine dioxide alone(degradation rate of phenol 47.9%).(4)The combination of hydrodynamic cavitation and ClO2 followed first-order kinetics for the degradation of phenol,the kinetic rate constants was 1.49×10-3s-1and the half-life was8 min.The degradation of phenol generated synergistic effect with combined method and the synergetic coefficient was 3.18.(5)Through the study on intermediate product and the mechanism of reaction for thedegradation of phenol with combined method,it was obtained that benzoquinone was produced in the first step,then maleic acid and acetic acid were produced which was the result of further oxidation. |
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