Polydopamine Composite Non-woven Fabrics Strengthen The Study Of Iron-activated Persulfate Oxidative Degradation Of Dyes

In this study,polydopamine-functionalized polypropylene nonwoven(PDA@PP)was prepared by forming a composite layer of polydopamine that strongly attaches to polypropylene nonwoven,so as to introducethe groups of catechol and amine.The degradation and mechanism of Azorubin(ARB)by PDA@PP reinforced persulfate system was studied.The groups of catechol and aminewere employedto promote persulfate activation through controlingthe concentration Fe2+to restrainradicals quenching.At the same time,the reduction of Fe3+ to Fe2+ by phenolic hydroxyl group can promote the recycling of FeLlto activate PScontinuously in the activation process.The composition and morphological structure of the PDA@PP were thoroughly characterized by FTIR,SEM and XPS.The free radical characteristics in PDA@PP strengthened persulfate system were analyzed by ESR.Theelements and groups ofPDA@PP were studied by XPS.At the same time,the degradation performance of dyes by PDA@PP strengthened iron activated persulfate systemwas analyzed,and the mechanism of persulfate catalytic oxidation was discussed.The conclusions are as follows:(1)It was found that PDA@PP can promote the degradation of dyes by iron activated persulfate system through analyzingthe degradation of ARB and PS on PDA@PP/Fe2+/PS and PDA@PP/Fe3+/PS systems.After added PDA@PP,the signal intensity of free radical was significantly higher than that of Fe2+/PS system bythe analysis of ESR.The elements of PDA@PP were analyzed by XPS.The Fe characteristic peak appeared in the XPS spectrum of PDA@PP before and after the reaction.The binding energy of N 1 s and O 1 s are shifted,suggesting the complexation betweenFe2+ andthe groups of catechol and amine could control the concentration ofFe2+ and reduce radicals quenching by excessive Fe2+.(2)PDA@PP/Fe3+/PS system also has a certain effect on the degradation of dyes after controlled trials.It is supposed that phenolic hydroxyl groups could reduce Fe31 to Fe2+and promote the degradation of dyes.(3)The mechanism of Fe2+promoting PS activation with PDA@PPwas further explored.It was found that excessive Fe2+could accelerate SO·-4 quenching reactionto reduce the degradation ARB with the increase of Fe2+/PS mole ratio.When the initial pH was neutral,it was beneficial to ARB degradation by complexation of Fe2+and producing two kinds of free radicalsof SO-4 and ·OH.With the increase of PDA@PP dosage,ihe accessibilityof Fe2+ was reduced,so that the degradation rate of ARB and PS was decreased.Furthermore,the higher the PS concentration,the better the dye degradation.And the higher ARB concentration enhanced the competitive action of radicals,which would promote the system to produce more radicals and increase the decomposition of PS.