Study On The Role And Mechanism Of Activated Persulfate In Advanced Processing Of Papermaking Wastewater

This thesis is mainly divided into two parts.The first part takes the wastewater from the secondary sedimentation tank of a papermaking enterprise in Jilin as the research object.It uses ferrous salt to activate persulfate to treat it.The removal rate of CODCr and chroma is the research goal.The process conditions are optimized and the design is continuous.The experiment simulates the actual processing of the factory to get a more direct and valuable reference to the actual application of the factory.Through single factor experiments and orthogonal experiments,the four factors of the amount of PS,the amount of ferrous iron,the initial pH and the reaction time have slightly different effects on the color and removal of CODCr in the treatment of papermaking wastewater by ferrous activated sodium persulfate method:The main order affecting the removal rate of chromaticity is Na2S2O8 dosage>FeSO4·7H2O dosage>pH>reaction time,and the main order affecting CODCr removal rate is Na2S2O8 dosage>FeSO4·7H2O dosage>reaction time>pH.The optimized process conditions are as follows:the amount of sodium persulfate is 436 mg/L,the amount of ferrous sulfate heptahydrate is 654 mg/L,the pH is neutral(unadjusted),the reaction is stable after 11 h of continuous reaction,and the supernatant CODCr removal rate can reach More than 86%,the color removal rate can reach 97%,and the salt content after treatment can be reduced by 22%compared with the Fenton method,reaching the national first-class discharge standard of paper industry wastewater.Through the measurement of the total TOC of the mixed water sample after treatment,it is found that in addition to oxidation,this process also has a greater contribution to flocculation and sedimentation.Using the experiment of the amount of flocculant and the change in the charge density of wastewater,it is concluded that persulfate can improve the organic content of water.The pollutant flocculation effect has a certain effect.According to the GC-MS test results,after the activated persulfate treatment,the relative content of alkanes in the wastewater increased significantly,indicating that the pollutants have been effectively oxidized and degraded.Further characterization by infrared spectroscopy proves that the aromatic compounds are destroyed,the organic chain is cut and shortened,the alcohol,phenol,and aldehydes are increased,the quinones are settled in the sediment,and the nitrogen-containing impurities.The ring compounds are slightly degraded.For the treatment indexes and treatment effects of the ferrous-persulfate method and the Fenton method,the ferrous-persulfate method has obvious advantages in treatment effect and economic cost,and has practical application prospects.The second part selects a representative natural colorant that contributes greatly to the chroma in papermaking wastewater:guaiacol as the model,and explores the mechanism of the typical pollutant action of persulfate on papermaking wastewater through thermal activation.The possible degradation route of guaiacol was characterized by guaiacol removal rate,FTIR and GC-MS:after the guaiacol was attacked by strong oxidizing sulfuric acid radicals,the benzene ring of guaiacol's bond is broken and the ring is opened,the phenolic hydroxyl group becomes an alcoholic hydroxyl group,then gradually oxidized to an aldehyde group,and then gradually oxidized to a carboxyl group,which is then completely oxidized.However,it is difficult to achieve complete mineralization in this process,and more is to improve the flocculation performance of wastewater.