The Removal Efficiency And Degradation Mechanism Of Two Typical PPCPs By Commonly Used Preoxidant

Because of the considerable production and use of pharmaceuticals and personalcare products (PPCPs), as well as the improvements of related instrumentation analysistechnology, such kind of trace contaminants were detected frequently in the waterenvironment and they had caused acute or chronic damage to environment, ecosystem,biological and human health with their features of cumulative effect, biological activityand refractory.Non-steroidal anti-inflammatory drug like ibuprofen and sulfa antibiotics likesulfamethoxazole were chosen as the target samples. In this paper the removalefficiency and degradation mechanism of two typical PPCPs ibuprofen andsulfamethoxazole by the commonly used pre-oxidants were investigated. Furthermore,this paper also studied the effect of contact time, initial concentration of the targetobject, pH, organic matter in natural water on removal efficiency in order to providethe basis foundation for theoretical analysis and practical engineering applications.The removal efficiency of ibuprofen oxidized by potassium permanganate,sodium hypochlorite, ozone tended to be stable on the whole after contact30min andreached59.07%,11.72%,88.42%respectively. Although the removal efficiencyreduced when the initial concentration of ibuprofen increased, the removal amount ofunit dosage of pre-oxidant increased. The form of ibuprofen molecule and performanceof oxidant were different under different pH conditions. The removal efficiency ofibuprofen oxidized by potassium permanganate and sodium hypochlorite was higher atpH5.14than at pH8.30. On the contrary, the ozone reached a higher removalefficiency at pH8.30. The humic acid existed in the solution would inhibit the removalefficiency of three pre-oxidants substantially and the inhibition would be more obviousif the concentration of humic acid was higher, but it would slightly promote theremoval efficiency with a lower concentrations. By measuring the mineralization ofibuprofen oxidized by pre-oxidant and infrared spectra of degradation products, itshowed that the removal efficiency of ibuprofen by pre-oxidant was apparentlyefficient and generated a large number of intermediate products in the oxidationprocess. Furthermore, the TOC removal efficiency was lower as5.58%-18.11%.The removal efficiency of sulfamethoxazole oxidized by the three pre-oxidant tended to be stable on the whole after contact30min and the removal efficiency byozone and sodium hypochlorite reached98.49%and96.93%respectively which wasmuch higher than potassium permanganate. The removal amount of unit dosage ofpre-oxidant increased when the initial concentration of ibuprofen increased, and theremoval amount of ozone and sodium hypochlorite was far higher than that ofpotassium permanganate. Besides, the ozone was slightly higher than that of sodiumhypochlorite. The form of SMX molecule and performance of oxidant was differentunder different pH conditions. The removal efficiency of SMX oxidized by potassiumpermanganate and ozone was higher at pH8.22than at pH4.60, but the sodiumhypochlorite reached a higher removal at pH4.60.The effects of humic acid on theSMX oxidized by three pre-oxidants were different. For pre-oxidation system,although the pre-oxidant for SMX removal efficiency was very high, the removal ofTOC was only5.12%,4.77%and16.71%respectively and generated a large number ofintermediate products in the oxidation process.Based on the LC-MS/MS analysis, the degradation products and pathways werestudied. The reactivity parts of the SMX were mainly the S-N bond of benzene ringamide, aromatic amino, carbon-carbon double bond at the isoxazole ring and theconnected methyl groups. The three pre-oxidant reacted according to the oxidationcharacteristics of itself. Proposed degradation pathways of potassium permanganateand ozone included S-N bond cleavage, oxidation of the amine group at the benzenering, hydroxylation of the benzene ring, oxidation of the double bond C=C at theisoxazole ring and oxidation of the methyl group at the isoxazole ring. Exceptoxidizing the SMX, sodium hypochlorite could easily react with aromatic amineaniline loci for chlorine substitution reaction and generate p-Quinone-4-chloroimidewhich is a toxic substances. Comprasion in the safety and efficiency, it showed that theozone was optimum pre-oxidant for the removal of SMX.