Ozonation Of Atrazine Wastewater

Ozonation is a promising alternative in water treatment for the removal of water pollutants,but ozone is also well-known as a highly selective oxidant without the potential to further oxidize intermediates with refractory property.Atrazine (6-chloro-N-ethyl-N'-isopropyl-1,3,5-triazinedyl-2,4-diamine)as a refractory herbicide have been the increasing concern for environmental issues.Two parts of experimentswith atrazine as target contaminant:single ozonation and catalytic ozonation carried out in laboratory bubble columns in this study,contaminantIn the 4th chapter,It was found that chemical oxidation of atrazine by ozone is a very slow process,whose absolute reaction rate is about 7.9M^-1s^-1.So the rate of the whole process was contrlled by the reaction rate of ozone in aqueous.Atrazine is oxidized through hydroxyl radical mechanism which was proved by that the one-relationship of atrazine degraded amount and the reaction time.Among of the parameters,some ones which accelerate the ozonation rate will be more effective,.the ifferent value corresponds the relevant solution pH.The degradation of atrazine has been carried out by ozonation in the absence and presence of 0.5 -5.0 mg L^-1of metal ions,which are catalytic amounts typically found in wastwater purification processes.The influence of pH has also been assessed in the range of 3 -11.Different to ozonation of phenol,the chemical reaction was the bottle-neck step of the whole process.Three familiar transition metal ions(Mn²⁺,Fe³⁺,Cu²⁺)were introduced as catalyst into the degradation of atrazine by ozone,manganese ion behaved the best catalysis,Fe³⁺took the second place,however Cu²⁺did not enhance the oxidation of atrazine.Some experimental parameters,especially such as pH value and concentration of metal ions,effect strongly the reaction,pH is the key factor which whether determined the oxidation reaction take place,and the best efficiency of catalysis is gained at moderate concentration of catalyst.In the 5th chapter it was found that the GAC-loaded MnO_x-catalyzed degradation of atrazine solutions have the similar characteristic.The degradation mechanism of catalytic ozonation(either homogeneous or heterogeneous catalysis)of atrazine in aqueous solution was investigated by concerning relevant issues.The enhanced degradation of atrazine by Mn(â…¡)and GAC-loaded MnO_x was devoted to by two reaction:(1)Mn(â…¡)and MnO_x/GAC accelerated the directed reaction of ozone and atrazine solutes,(2)Mn(â…¡)and MnO_x /GAC enhance the generation of hydroxyl radical to indirectly improve degradation of herbicide atrazine.The experimental result indicated the Mn(â…¡)and MnO_x/GAC have the catalysis potential to oxidize simulated atrazine wastewater with single component,but helpless to the industrial wastewater containing complicated components.In order to generalize the treatment technology,the further study was required.