Activation Of Peroxymonosulfate By Carbonylation Nanodiamonds For Elimination Of P-chlorophenol

Advanced oxidative process(AOPs)are widely used for decomposition of toxin organic contaminants in the field of industrial wastewater treatment and environmental remediation.Catalysis of persulfate activated by transition metal is a widespread used advanced oxidation process increasingly gaini ng attention as an effective way to oxidize toxic refractory wastewater.However,metal leaching from catalysts during persulfate activation limits the application in the area of environment due to the demands of the sustainable development.Nanocarbon,no metal loaded or added,is an important type of metal-free catalysts and the carbon itself is used as the catalyst,which can catalyze persulfate to generate reactive oxygen species.The active sites are the defective structure or functional groups on the carbon surface.Compared with a metal-based catalyst,nanocarbon has attracted much attention for their advantages of large specific surface,good stability under mild conditions,high efficiency and environmental friendliness.Thus,metal-free carbonaceous materials can be used as a promising alternative due to the prevention of metal leaching and secondary contamination to water environment.Ketonic groups,an important Lewis base sites,have been proposed as catalytic center of the nanocarbon.As a result,it's important to study the role of ketonic groups in activation of persulfate,which can help us to reveal the catalytic mechanism and contribute to syntheses carbonaceous materials with high efficiency.In this experiment,nanocarbons were prepared with different ketonic groups through mild thermal treatment of nanodiamonds in argon atmosphere.It was found that no significant impact occurred at the temperature range except for ketonic groups,because all these temperatures can only induce surface oxygen groups functionalization,but are not higher enough for the structural change in bulk nanodiamonds.First,peroxymonosulfate(PMS)was activated by nanocarbons with different ketonic groups for p-chlorophenols degradation.In order to educate the relationship between ketonic groups and the catalytic performance,we correlate the values of apparent degradation rate constants of p-chlorophenols with the surface concentration of ketonic groups.By correlational analyses,the ketonic groups and catalytic performance have good correlations.Then,in-situ electron paramagnetic resonance(EPR)technology and classical quenching tests were employed to elucidate the reactive oxygen species.Both implies that singlet oxygen could be the reactive oxygen species responsible for p-chlorophenols degradation.Besides,there is a good liner relationship of between the yield of singlet oxygen and the concentration of ketonic groups.This result indicates that ketonic groups on nanocarbons work as active site to catalyze PMS decomposition into singlet oxygen for the degradation of p-chlorophenols.And the singlet oxygen derives from dissociating of O-O bond in PMS instead of dissolved oxygen in the system.To better demonstrate the oxidation ability of singlet oxygen produ ced from PMS activated by carbonylation nanocarbons,the mineralization efficiency and the degradation pathways of p-chlorophenols were discussed.It turns out that singlet oxygen produced in the system show good mineralization performances.The degradation begins at the chlorine oxidized by singlet oxygen to generate hydroquinone and hydroquinone was dehydrogenated to form benzoquinone.After that,the ring of hydroquinone was cleaved by attack of singlet oxygen and p-chlorophenols were finally decomposed into carbon dioxide and water.In addition,the effects of background substances in the natural water body on singlet oxygen were further determined.The experiments show that natural organic matters,p H values,cation and anion which are common ingredients in water exhibit minor effect on the degradation of p-chlorophenols.Even in the practical water body,degradation efficiency of p-chlorophenols in PMS system activated by carbonylation nanocarbons is superior to cobalt and ferrous ions.