| At present,a large number of studies have shown that the presence of fulvic acid can affect the photochemical degradation of polycyclic aromatic hydrocarbons(PAHs).However,due to the complex structure of fulvic acid,there are many mechanisms for the photolysis of phenanthrene.Therefore,it is feasible to study the mechanism of the effect of fulvic acid on the degradation of phenanthrene by the grouping of fulvic acid by XAD-8 resin.The results are as follows:(1)The fulvic acid the divided into six components of pH4.8,pH7,pH11,water,alcohol and liquid using XAD-8 group means,using the method of ultraviolet spectrophotometric analysis of IR spectra and elemental analysis data analysis,to characterize fulvic acid six grouping component structure.The results showed that the distribution of oxygen functional groups in the components was reduced in order of pH4.8,pH7,pH11,solution,water and alcohol.Aliphatic components increased in turn.The oxygen content of pH4.8 and pH7 components were higher than other components.(2)The photodegradation rate of phenanthrene was higher in the fulvic acid fractions with higher content than that of the lower ones.In the concentration range of fulvic acid fractions in each group,each group acid component content increase ·OH and 1O2 solution in the production of free radicals in the rich,and rich in the increase of the concentration of acid can lead to enhanced the photosensitization,so as to promote the photocatalytic degradation of phenanthrene.Comparison of uniform concentration of fulvic acid fractions on the photodegradation of phenanthrene,pH4.8,group pH7 extraction buffer solution of phenanthrene in the photodegradation rate is higher,and the components of water and alcohol extraction of phenanthrene in the photodegradation rate is low,and that the two fractions containing carboxyl oxygen content and composition more,can produce more OH and 1O2 in the photolysis of.When the concentration is low,the increase of the concentration has a greater influence on the photodegradation rate of phenanthrene in each component.(3)Using two dimethyl sulfoxide(DMSO)as capture agent solution ·OH shielding,furfuryl alcohol(FFA)as a packet capture agent shielding solution 102.The results showed that the photolysis rate of phenanthrene in each component of fulvic acid decreased with the addition of the two kinds of trapping agents.After adding FFA,the decrease was more obvious.These results indicate that the OH and 1O2 play an important role in the degradation of phenanthrene,and the effect of 1O2 on the photolysis of phenanthrene is greater than that of.Comparing the effects of each component on the photodegradation of phenanthrene,it can be found that the photodegradation rate of DMSO and pH7 in the components of pH4.8 and FFA decreased significantly compared with other components.To characterize the structure of FA components,the results showed that pH4.8 and pH7 of the buffer solution extraction more carboxyl groups content of fractions,so OH and 1O2 free radical content of these two components in the photolysis process is also relatively high,when the two radicals are blocked,the effects of pH4.8 and pH7 group the branch has the greater.(4)Due to the obvious difference of the functional groups in the different groups of fulvic acid,the adsorption of phenanthrene by different groups is also very different.In this paper,it is found that the adsorption capacity of the components of the oxygen functional group is weaker than that of the phenanthrene,and the adsorption capacity of phenanthrene is higher than that of the aliphatic functional groups.It is also explained from another aspect that the photolysis rate of phenanthrene in water and alcohol is slower than that of other components,and that of pH4.8 and pH7.0 is faster.(5)Fulvic acid solution components in different pH values of phenanthrene degradation also has a great influence,from this experiment can be seen in the high pH solution of PAHs(phenanthrene)photochemical degradation rate was obviously higher than that of low pH solution.In acidic conditions,with the increase of pH value,the photochemical reaction rate of phenanthrene increased slowly,while in alkaline condition,with the increase of pH value,photochemical reaction speed of phenanthrene increased rapidly,indicating that the high pH value of PAHs(phenanthrene)has greater impact,this may be because of the high pH value in the rich acid solution group carboxyl content more hydroxyl groups,can produce more free radicals in the photolysis process,and phenanthrene photodegradation have greater influence. |
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