Study On Performance And Mechanism Of Atrazine Degradation By Penicillium Sp./nano Fe₃O₄ Composites

Over the years,it was found that the atrazine concentrations in water and soil often exceeded the maximum permissible levels of EU?0.1 ug/L?in many countries.Atrazine is teratogenic and carcinogenic,which is harmful to human beings and animals.Therefore,there was an urgent need to find more effective ways to solve the problem of Atrazine pollution.Microbial remediation was widely used in water treatment projects because of its green economy,environmental friendliness and no secondary pollution.With the development of technology,researchers had also found that Penicillium sp.has great potential in microbial remediation.In addition,nano Fe₃O₄ could degrade atrazine and provide magnetism for subsequent separation.Therefore,nano Fe₃O₄ was prepared by coprecipitation method at first.A new material,Penicillium sp.yz11-22N2 doped with nano Fe₃O₄ entrapped in polyvinyl alcohol-sodium alginate gel beads?PFEPS?,was successfully prepared.And the degradation performance and mechanism of atrazine in water were investigated.In this paper,the properties of nano Fe₃O₄ and PFEPS were characterized by the SEM,TEM,FTIR and hysteresis loop.Among them,TEM,FTIR and hysteresis loop were used to characterize nano Fe₃O₄.The results showed that the diameter of nano Fe₃O₄ was about 40 nm,and polyethylene glycol was well coated on the surface of nano Fe₃O₄.The saturation magnetization of nano Fe₃O₄ was 37.0 emu/g,and it had superparamagnetism.The results of SEM showed that Penicillium sp.was well embedded in the encapsulated pellets and grew well.In addition,PFEPS had large void fraction and specific surface area,which could increase the contact opportunities between PFEPS and atrazine.In this paper,the effects of some factors on atrazine degradation by PFEPS were studied,including the influence of pH value,temperature,rotational speed,initial concentration of atrazine,concentration of exogenous nitrogen source,exogenous carbon source and nitrogen source.When the pH value was 7.00,the rotational speed was 150 rpm,the temperature was 280C and the initial concentration of atrazine was 8 mg/L,the degradation rate of atrazine was the highest,the maximum value was 91.2%.When the pH value was 7.00,the rotating speed was 150 rpm,the temperature was 28? and the initial concentration of atrazine was 15 mg/L,the maximum degradation capacity of atrazine was 7.94 mg/g.Penicillium sp.could use atrazine as the sole carbon or nitrogen source.And when Penicillium sp.used atrazine as the sole carbon source,the degradation rate of atrazine was the highest.In addition,the concentration of nitrate nitrogen will affect the degradation rate of atrazine.The higher the concentration of nitrate nitrogen,the higher the degradation rate of atrazine.The degradation mechanism of atrazine was also studied by studying the degradation performance of three kinds of embedding materials and free Penicillium sp.,carbon transformation,nitrogen transformation and intermediate products in the process of atrazine degradation.The results indicated that the Penicillium sp.played a dominant role in the degradation of atrazine.There was a synergistic effect between Nano Fe₃O₄ and Penicillium sp.,which could improve the degradation rate of atrazine.In addition,according to the results of the intermediates,a possible pathway of atrazine degradation was speculated,including dealkylation,hydrolytic dechlorination,side chain oxidation and ring opening.