AN Bacteria-Electric Catalytic Degradation Of Acrylonitrile Wastewater

The amount of acrylonitrile wastewater increases because of the mass production and use of acrylonitrile.Due to the characteristics of complex composition,high toxicity,refractory,the effective treatment of the acrylonitrile continues to be one of the research difficulties in the environmental field.In this paper,we study the removal of acrylonitrile by the nitroguajacolicus ZJUTB 06-99 bacteria(referred to as AN bacteria),activated carbon fiber(referred to as ACF),electric field,AN bacteria-ACF coupling system,electric field-AN bacteria,electric field-ACF,electric field-AN bacteria-ACF coupling system and find the factors that influence the removal rate of acrylonitrile in wastewater.The Electrochemical workstation was used to provide the microelectric field.The working electrode is the composite electrode consisting of ACF and titanium plate,counter electrode is titanium plate,and the saturated calomel electrode is the reference electrode.The effects of electric potential,initial acrylonitrile concentration,pH and other factors on the removal of acrylonitrile were investigated in coupling system.The results showed that the degradation rate of acrylonitrile was increased with the rise of the concentration of acrylonitrile in the AN bacteria system.The degradation mechanism of acrylonitrile is the nitrilase produced by ZJUTB06-99 directly degrade acrylonitrile to acrylic acid.The adsorption equilibrium of Activated carbon fiber(ACF)on the adsorption of acrylonitrile can be achieved in 120 min.The removal rate of acrylonitrile increased with the rise of electric potential in the electric field.The removal rate of acrylonitrile 55.7% in the AN bacteria-ACF coupling system is higher than that in AN bacteria degradation system(40.7%)and in ACF adsorption system(28.9%).When the electric potential is in the range of 0~400mV,the positive electric field can accelerate the AN bacteria to degrade acrylonitrile.The removal of acrylonitrile decreased above 400 mV,but concentration of acrylic acid was still high.The results show the AN bacteria has a certain tolerance for electric field.When the electric potential is in the range of 0~600 mV,the removal rate of acrylonitrile increased with the rise of electric potential in the electric field-ACF coupling system.The results show the positive electric field can increase the removal rate of acrylonitrile in the electric field ACF coupling system.When the electric potential is in the range of 0~-600 mV,the adsorption quantity of acrylonitrile reduced with the decrease of electric potential.The results show the negative electric potential is not conducive to the adsorption of acrylonitrile.The best reaction pH value and temperature is 5 and 25 ℃,respectively.The better electric potential is 400 mV in electric field-AN bacteria-ACF coupling system and the removal rate of acrylonitrile is 62.9%.When the cell concentration is 100 g/L,the removal rate of the acrylonitrile reached 100%.When the electric potential is in the range of 0~400 mV,the removal rate of acrylonitrile increased with the rise of electric potential.The removal of acrylonitrile decreased above 400 mV.The neutral and alkaline environment is better for the degradation of acrylonitrile by AN bacteria.The appropriate reaction temperature is 30 ℃.The pH value,the concentration of total nitrogen and concentration of ammonia nitrogen decreased in the reaction solution after reaction of 8 h.When the composite electrode is the working electrode,the concentration of the total nitrogen and the concentration of ammonia nitrogen in the solution is lower than that of the titanium sheet.Product analysis by GC-MS showed that the product contained acrylic acid and formic acid.The degradation mechanism of acrylonitrile maybe that acrylonitrile is first degraded by AN bacteria to acrylic acid,and then the acrylic acid is degraded to formic acid under the action of electricchemcial catalysis.