Degradation Of Polychlorinated Biphenyls In Soil By Metal Oxide

Thermal degradation dechlorination technology for the treatment of polluting organic matter is cheap,efficient,by means of the degradation of chlorinated aromatic compounds have been widespread concern of many scholars.In this paper,Fe2O3,Fe-Al composite oxide and red mud three kinds of metal oxides were selected as the catalyst,and the degradation effect of the above three kinds of metal oxides on PCBs was studied.The factors influencing the catalytic effect of Fe2O3 were discussed,and the effect of Fe2O3 degradation on PCB30 was optimized by center response surface analysis.The catalytic efficiency of Fe-Al composite oxide under different conditions and dosage was investigated.The modified red mud particles were prepared and their catalytic degradation effect on PCB30 was studied.The treatment conditions were optimized,and the red mud particles were subjected to repeated reuse test.The effect of red mud particles as catalyst on soil was studied.(1)The optimum catalytic conditions were as follows:the dosage of catalyst was 0.23 g,the reaction temperature was 333.33 ?,the reaction time was 38 min,and the degradation rate of PCB 30 under the catalysis of Fe2O3 was studied by CCD center response surface analysis method.The average degradation rate was 99.7%,and the predicted model was accurate and reliable for the prediction of catalytic degradation efficiency.(2)The Fe-Al composite oxide prepared by coprecipitation method has good catalytic performance to PCB30,and is superior to single metal oxide catalysis under certain preparation conditions.The molar ratio of Fe and Al has a great effect on the catalytic effect of the composite oxide.When the molar ratio is 1:1,the degradation rate can reach 76.73%.The Fe element is Fe2O3,Fe2O3·H2O and Fe1.833(OH)0.5O0.25,and Fe2O3 is the main form.The Al element exists only in the Al2O3 form.(3)The Fe element in the red mud is mainly in the form of hematite,and a small amount is in the form of goethite,and there is also a small amount of composite oxide such as aluminousite,alumite,twelve calcium aluminate and calcium orthosilicate in red mud The After the Bi modification,the red mud particles have better catalytic degradation of the PCB30 effect than the unmodified red mud particles.When the calcination temperature is 500 ? and the Bi doping content is 8 g,the catalyst performance is the best.The degradation rate of PCB30 was 92.48%at 300 ? for 30 min.Red mud particles as a catalyst in the heating conditions on the soil only caused by Fe,Ca concentration increased slightly,with good stability,will not cause secondary pollution of heavy metals in the soil.After calcination,the red mud has certain anti-friction,impact and other stress ability,recyclable and reusable,and has certain application prospect in dealing with PCBs soil.