Transformative Degradation Of 1-naphthylamine And Paracetamol Mediated By Black Carbons

Black carbons（BCs）are ubiquitous in natural environment.Due to its large specific surface area and porosity,it can strongly absorb many organic pollutants and are the most important sink.Recent studies have found that many adsorbed pollutants are not chemically inert.BCs had certain catalytic activity and promoted the conversion and degradation of some organic pollutants.The existence of this phenomenon changes the occurrence pattern and environmental behavior of these pollutants,and also brings uncertainties to their environmental risk assessment and restoration.Therefore,to further understand the phenomenon and mechanism of black carbon substances promoting the transformation and degradation of co-existing pollutants is very important for re-understanding the role of black carbon in nature and for correctly evaluating the migration and transformation behavior of pollutants in the environment.In this paper,we choose the common black carbon materials as adsorbents to study the oxidative transformation of 1-naphthylamine and paracetamol.The main conclusions of this dissertation included:1.We chose graphite,soot and bamboo biochar as the common representatives of BCs.Their mediation effect on the oxidative transformation of 1-naphthylamine under ambient aerobic environment was investigated.It was showed that three BCs significantly promoted the oxidation of 1-naphthylamine in water and the oxidation process of 1-naphthylamine mediated by three BCs was more conformed to the pseudo-second-order model.Under the same specific surface area,the catalytic efficiency of the three black carbon substances was graphite（99.3%）>>biochar（24.7%）>soot（22.4%）.Graphite has the strongest catalytic effect,which may be related to its strong electron transport capacity.Liquid chromatography-mass spectrometry and molecular modeling computation results implied the occurrence of oxidation.The oxidation products of 1-naphthylamine were the coupling oligomers（dimers and trimers）and the oxygen-containing oligomers of 1-naphthylamine（di-OH-1-naphthylamine,OH-azo naphthalene,OH-trimers,amino-naphthoquinone derivatives and some other unknown oxygen-containing compounds etc.）.This reaction indicated that three BCs acted as catalysts,and dissolved oxygen was the oxidant.BCs can catalyze dioxygen into superoxide radical.These superoxide radicals had high reactivity,which then reacted with 1-naphthylamine into H₂O₂ and1-naphthylamine radical.The resulting 1-naphthylamine radicals were coupled to each other to form conjugated oligomers.Moreover,under the catalysis of BCs,H₂O₂ continued to be decomposed into O₂·^-,and which continued to react with 1-naphthylamine to form oligomers and oxygen-containing products.2.Three activated carbon materials of sawdust,nut shell and cocoanut shell were selected as black carbon materials.Their mediation effect on the oxidative transformation of paracetamol under ambient aerobic environment was investigated.The results showed that three BCs significantly promoted the oxidation of paracetamol in water and the oxidation of paracetamol mediated by three BCs was more conformed to the pseudo-second-order model.The catalytic efficiency of coconut shell activated carbon（COAC,42.84%）was higher than that of sawdust activated carbon（SaAC,11.56%）and nut shell activated（ShAC,42.11%）carbon.Using liquid chromatography-mass spectrometry,we identified the coupling products were the coupling oligomers（dimers and trimers）and the oxygen-containing oligomers of paracetamol（OH-1-paracetamol,aminophenol,amino-hydroquinone,and pyrogallol etc.）.The result of FTIR spectra of SaAC,ShAC,CoAC before and after reaction indicated that three BCs only acted as adsorbents and catalysts.Under the catalysis of activated carbon,the dissolved oxygen generated hydroxyl radicals on the solid surface,and then reacted with paracetamol to produce the final coupling oligomers and oxygen-containing products.