Theoretical Studies On Oxidation Of Anthracene In Water And Isoprene In Atmosphere By Sulfate Radical

Sulfate radical(SO4·-)plays an important role in environmental chemistry,it has a high REDOX potential and reactivity.Thus,it can act as a strong.oxidant in the wastewater treatment to degrade the contaminants.In addition,it can not only degrade the organic pollutants in the atmosphere,but also can react with some volatile organic compounds(VOCs)to form organosulfates,which can accelerate the formation of secondary organic aerosols(SOA).Nowadays,there are many experimental and theoretical studies on SO4·-.Anthracene,a linear polycyclic aromatic hydrocarbon(PAHs)containing three benzene rings,is widely existed in environment,and it has bioaccumulation that can cause adverse effects on human health.ANT was listed as one of the 16 priority pollutants by the US Environmental Protection Agency.Thus,investigating the degradation mechanism of ANT is crucial to research the PAHs degradation in the future.Isoprene is one of the most abundant VOCs,it can react with the oxidants in the atmosphere easily.Although isoprene is insoluble in water,a small amount can dissolve in the atmospheric aqueous system,becoming an important source of aqueous-SOA.Isoprene can react with SO4·-to form C5 organosulfate.Based on quantum chemistry theory,the reaction of ANT with SO4·-and isoprene with S04-are studied at M06-2X/6-311++G(d,p)//M06-2X/6-311++G(3df,3pd)level using density functional theory.The kinetic calculations of initiation reactions are studied based on transition states theory(TST).The conclusions of this article are as follow:1.Theoretical studies on reactions of ANT with sulfate radical and hydroxyl radicalSulfate radical(SO4·-)and hydroxyl radical(·OH)generated from persulfate or peroxymonosulfate in AOPs have been widely used in contaminant degradation.Anthracene(ANT)can be decomposed by SO4·-and-OH.The processes of ANT decomposition were investigated using theoretical calculations in this paper.The initiation reactions of ANT,anthrone(AO),anthraquinone(ATQ)and 1-hydroxylanthraquinone(1-hATQ)by two radicals are studied.The highest free energy barriers of initiation reactions are 22.30 kcal mol-1 in ATQ+SO4·-reaction and 6.84 kcal mol-1 in ATQ+·OH reaction.Comparing the rate constants of initiation reaction through the two radicals at 273-373 K,it can be concluded that SO4·-and·OH both play important roles on the initiation of ANT and AO at lower pH.For ATQ and 1-hATQ,·OH is more important than SO4·-in the initiation process,which indicates that the indirect influence of SO4·-are more significant in the degradation processes of ATQ and 1-hATQ.This study provides theoretical confirmations for the mechanisms of reactions of ANT with SO4·-and ·OH,and evaluates the importance of SO4·-and ·OH according to the reaction rates.The work can give more insight into the degradation of PAHs by radicals2.Theoretical study on the reactions of isoprene with sulfoxy radicals to form organosulfur compoundsIsoprene can react with sulfoxy radicals(SO4·-and SO3·-)to form organosulfur compounds in aqueous phase,and the organosulfur compounds are important tracers of secondary organic aerosols(SOA).To make sure the specific configurations of the products and the role of SO4·-and SO3·-in the formation of organosulfur compounds,the reaction mechanisms are studied by theoretical calculations.The lowest Gibbs free energy barrier of addition of SO3·-onto isoprene is 24.06 kcal mol-1 at C4 site.And the Gibbs free energy barriers of addition of SO4·-onto isoprene at C1 and C4 sites are barrierless and 0.92 kcal mol-1.It elucidates that organosulfates are easier to be formed As for the products P1(with alcohol group)and P2(with aldehyde group),the lowest Gibbs free energy barrier of PI is 3.17 kcal mol-1,and that of P2 is 15.84 kcal mol-1,which means that the product with alcohol group are easier to be formed than that with aldehyde group.