Study On Degradation Of Propranolol In Aqueous Solution By Persulfate Activated By Different Methods

Propranolol(PRO)is a widely used β-blockers and is usually employed for the treatment of hypertensio,angina,and arrhythmia.Because of the incomplete removal in conventional wastewater treatment process,PRO was frequently detected in the aquatic environment,and the concentrations reached ng·L-1-μg·L-1 level.Several studies have also found that low concentration PRO in the aquatic environment have significant effect on reproductive system of aquatic animals and photosynthesis of plants.Therefore,developing an economic,high efficient,and environmentally friendly treatment technology to control and eliminate the contamination of PRO in water environment has important practical significance.As an effective treatment method for organic pollutants,advanced oxidation processes(AOPs)no matter in treatment efficiency or on the cost has obvious advantages,and is more suitable for wide application in engineering.Compared with hydroxyl radicals(HO·),sulfate radicals(SO4·-)activated by persulfate(PS)have stronger oxidant capacity,longer half-life,better selectivity,wider pH range,and show a great application prospect in the treatment of organic pollutants.Among various activation methods,heat-activated PS and UV-activated PS oxidation processes are less affected by pH,and have strong oxidizing and mild reaction conditions,which have been widely used in the treatment of organic pollutants of soil and groundwater.In this study,we chose PRO as a target pollutant,and studied the kinetics and mechanisms of PRO degradation in heat-activated PS system and UV-activated PS(UV/PS)system,respectively.Meanwhile,the transformation products and pathways,and the effects of water coexisting substances also were investigated.Firstly,this paper investigated the degradation kinetics and mechanisms of PRO in heat-activated PS system.The transformation products and pathways,as well as the effects of bicarbonate and humic acid(HA)also were investigated.The experimental results showed that the degradation of PRO in heat-activated PS system followed pseudo-first-order reaction kinetics.The degradation rate constant(kobs)was increased markedly with increasing initial concentration of PS and reaction temperature.Basic condition was more beneficial for PROdegradation than acidic and neutral conditions.Radical scavenging tests revealed that SO4·-was predominant oxidizing species at acidic and neutral conditions,while HO· played a critical role at basic condition.The presence of bicarbonate manifested promoting effect on PRO degradation,while HA reduced it.Increasing initial PS concentration and prolonging reaction time could improve the mineralization rate of PRO.Four transformation products were identified via UPLC/Q-TOF-MS technology in heat-activated PS oxidation system,and thus speculated that the transformation pathways of PRO included the hydroxylation of naphthalene ring and the cleavage of C-N bond of the secondary amine group.This paper also investigated the kinetics and mechanisms of PRO degradation in UV/PS system.The transformation products and pathways,as well as the effects of inorganic anions and HA also were investigated.Meanwhile,the second-order rate constants of PRO reacting with SO4·-and HO· were determined through competition kinetic methods.The experimental results demonstrated that the degradation of PRO in UV/PS system followed pseudo-first-order reaction kinetics.The rate constant was increased markedly with the increasing initial PS concentration or the decreasing initial PRO concentration.Compared with acidic and neutral conditions,basic condition was more beneficial for PRO degradation.Radical scavenging tests showed that SO4·-played a critical role on PRO degradation in UV/PS system at neutral condition.The mineralization rate of PRO and PS consumption were improved with prolonging the reaction time.The inorganic anions in natural water bodies(Cl-,NO3-,and HCO3-)and HA have different effects on PRO degradation.Chloride ion and bicarbonate manifested promoting effect on PRO degradation,while nitrate ion and HA reduced it.The second-order rate constants of PRO reacting with SO4·-and HO· were determined to be 1.94×1010 and 6.77×109 L·mol-1·s-1,respectively.Fifteen transformation products were identified via UPLC/Q-TOF-MS technology in UV/PS oxidation system,and thus speculated that the transformation pathways of PRO included the hydroxylation of naphthalene ring and the secondary amine group,dehydration,naphthalene ring opening,and the cleavage of aldehyde group.