Degradation Of Typical PPCPs In Water By UVC/persulfate And UVC/chlorine Processes

Pharmaceutical and Personal Care Products?PPCPs?,as an emerging pollutant,are frequently detected in water sources,posing a threat to ecosystems and human health.This paper utilized UVC-based advanced oxidation processes to degrade typical PPCPs,including tetracycline?TC?and carbamazepine?CBZ?,and its degradation performance,influencing factors,degradation mechanism,product toxicity and economy were illuminated.The comparative study on the elimination of TC utilizing UVC and UVC/PS processes was systematically conducted.The TC degradation via UVC irradiation and UVC/Persulfate?PS?treatment well fitted pseudo-first-order kinetics.The combination of UVC and oxidant was beneficial to the decomposition of TC,and the degradation effect followed UVC/PS>UVC/Peroxymonosulfate>UVC.Hydroxyl radicals?·OH?and sulfate radicals?SO₄^-·?were identified as the primary reactive species in UVC/PS process.Based on competition kinetic method,the second-order rate constants of TC reacting with·OH and SO₄^-·were calculated and the contributions of UVC photolysis,·OH and SO₄^-·to TC degradation were determined.The TC degradation in UVC and UVC/PS process was highly p H-dependent and enhanced with the increase of solution p H.Water matrix constituents played the multiple roles in TC degradation,acting as radical sensitizer,radical quencher and light absorber.Natural organic matters,CO₃^2-and HCO₃^-enhanced the degradation during UVC photolysis,whereas the opposite phenomenon occurred in UVC/PS process.Cl^-presented the inhibitory effect,while TC degradation can be accelerated by NO₃^-both in UVC and UVC/PS processes.The TC degradation in UVC/PS process can be classified into the hydroxylation,demethylation,decarbonylation,photocyclinzation,dehydration and cleavage of C-N bond.After UVC and UVC/PS pretreatment,the decreased formation of dichloroacetic acid and trichloroacetic acid and the increased production of trichloromethane have been found.The TC removal was evaluated in terms of electrical energy per order,and its value can be considerably reduced via the combination of UVC and PS.Except for ultrapure water,the removal of TC from real waters by UVC/PS treatment could also be desirable.The elimination of CBZ via UVC irradiation was insignificant.After adding oxidants,the effect was significantly increased,following UVC/chlorine>UVC/PS.SO₄^-·and·OH were the main free radicals that degraded CBZ in UVC/PS system.RCS and·OH were the main active substances for CBZ removal in UVC/chlorine process.According to the probe method,the second-order rate constants of CBZ reacted with·OH,SO₄^-·and Cl·were calculated and the contributions of different radicals to CBZ degradation were determined.In both processes,CBZ decomposition conformed to pseudo-first-order kinetics.Increasing oxidants dosage and rising temperature was favorable for elimination,while increasing CBZ concentration retarded its degradation rate.The coexisting of NOM,SO₄^2-and CO₃^2-/HCO₃^-presented the inhibitory effect,while NO₃^-promoted the removal.NH₄⁺exerted an inhibitory effect in UVC/chlorine process,while exerted no obvious influence in UVC/PS system.Cl^-posed a promoting role in UVC/PS system and a dual effect in UVC/chlorine process.p H affected the quantum yield of chlorine photolysis and the formation of·OH and RCS.The degradation of CBZ via UVC/chlorine process was more p H-dependent.12 and 14 CBZ oxidation intermediates were identified in UVC/PS and UVC/chlorine systems,respectively.SO₄^-·,RCS and·OH were readily to attack C=C in CBZ molecule,mainly generating hydroxylated CBZ,epoxy CBZ,pyridine aldehydes and ketones.Considering the power efficiency,oxidant cost and influencing factors,UVC/chlorine process was more economical and effective,but UVC/PS process was safer in terms of Disinfection by-products?DBPs?control and the toxicity of intermediates.Both UVC/PS and UVC/chlorine processes are promising water treatment technologies,but further research is needed on the control of DBPs during application.