Research On The Degradation Of Difenoconazole By Activated Persulfate

Difenoconazole is a representative species of triazole fungicides.It is widely used in rice fungal diseases in our country.Its chemical properties are stable,and it is difficult to spontaneously degrade under natural conditions.It is easy to stay in the water environment for a long time and has potential risks.In this paper,aiming at the potential hazards of difenoconazole in water bodies and the limitations of related removal research,this article explored the degradation effects of difenoconazole by UV/PS and Fe²⁺/PS oxidation systems,and investigated the conventional influencing factors?Oxidant dosage,p H,etc.?and environmental factors?bicarbonate ion,humic acid?on the oxidation efficiency of difenoconazole,and analyzed the intermediate products and degradation paths of the oxidation process of UV/PS system,Used ECOSAR software to predict biological toxicity.The research results show that UV/PS is mainly based on SO₄^-·oxidation difenoconazole.The increase of PS dosage and the decrease of the initial concentration of difenoconazole will promote the reaction;changing the initial p H value will degrade the phenyl ether The effect of meticonazole is not significant;the best reaction conditions:the concentration of difenoconazole is 1mg/L,the dosage of PS is 0.8mmol/L,the p H is 5,the temperature is?25±2??,and the reaction is 20min Then,the removal rate can reach 96.37%.The concentration of bicarbonate and humic acid can inhibit degradation,and the inhibitory effect of humic acid is more obvious.In the feasibility analysis of the UV/PS system,it was found that PS alone does not have the ability to oxidatively degrade difenoconazole.Although UV alone can cause direct photolysis of difenoconazole,its reaction rate is far lower the oxidation rate of SO₄^-·difenoconazole produced by UV/PS system.The results of free radical capture experiments in the UV/PS system show that the types of free radicals produced under different p H conditions are different.Under acidic conditions,since there are no conditions for producing OH·,the effective free radical species is SO₄^-·;under neutral conditions,it is mainly SO₄^-·coexists with a small amount of OH·,and both dominate the degradation of difenoconazole;while OH·is the main effective free radical in the degradation process under alkaline conditions.In Fe²⁺/PS system,changing the initial concentration of difenoconazole,the initial p H value of the solution,the dosage of Fe²⁺,the concentration of bicarbonate and the dosage of humic acid and other reaction conditions affect the apparent rate of degradation of difenoconazole The effect shows a good linear relationship?R²?90%?,which is in line with the quasi-first-order kinetic process;the reaction is highly dependent on p H,and it is more conducive to the removal of difenoconazole under acidic conditions;bicarbonate and humus Acids will affect the degradation efficiency of difenoconazole to varying degrees,and the inhibitory effect of bicarbonate is stronger.UV/Fe²⁺/PS system can improve the effect of different initial p H and bicarbonate concentration on Fe²⁺/PS system and UV/PS system.When p H=3,UV/Fe²⁺/PS system reacts to difenoconazole The rate can reach 0.2208 min^-1,which is higher than the0.1561 min^-1of the UV/PS system and the 0.1999 min^-1of the Fe²⁺/PS system;compare the UV/PS system and Fe²⁺/PS with the same concentration of bicarbonate In the system,the reaction rate of degrading difenoconazole was increased by 4%and 22%respectively.The UV/PS system degradation intermediate products were analyzed by GC/MS,and 13 products were detected,mainly phenolic organics,ketones,etc.The degradation pathways mainly involve ether bond cleavage,dechlorination and hydrogenation,and dechlorination and hydroxylation.,Chlorination and dehydrogenation reactions.The ECOSAR software was used to predict the biological toxicity of the intermediate products in the degradation of difenoconazole in the UV/PS system.The results showed that almost all the intermediate products had lower toxicity than the parent difenoconazole,which reduced the environmental threat.