Degradacija amoksicilina i azitromicina u vodenoj sredini primenom različitih fizičko-hemijskih metoda

Abstract

Predmet ove doktorske disertacije je proučavanje degradacije amoksicilina i azitromicina u vodenoj sredini, primenom određenih elektrohemijskih i unapređenih oksidacionih procesa, ispitivanjem degradacionih proizvoda nakon različitih tipova forsiranih degradacija. Naučni cilj doktorske disertacije je da se primenom viših oksidacionih procesa izvrši potpuna oksidacija amoksicilina u kratkom vremenskom periodu, bez nastajanja policikličnih produkata, i da se ispita mogućnost uklanjanja azitromicina iz ekosistema postupkom forsirane razgradnje. U tom smislu vodeni rastvor amoksicilina je bio podvrgnut odabranim fotokatalitičkim degradacionim procesima. Radi sticanja potpunijeg uvida u stepen mineralizacije odabrane su jonska hromatografija (IC) i metoda određivanja ukupnog organskog ugljenika (TOC). Ispitivana je indirektna oksidacija azitromicina na Ti/RuO₂ anodi, galvanostatskom tehnikom u vodenom elektrolitu koji sadrži NaCl. Na elektrodi od staklastog ugljenika je elektroanalitički praćeno smanjenje koncentracije azitromicina kao posledica njegove degradacije u gore pomenutom elektrolitu. Za proučavanje stepena degradacije azitromicina korišćena je diferencijalna pulsna voltametrija (DPV) i tečna hromatografija visokih performansi sa detektorom u ultraljubičastoj oblasti (HPLC-UV), a za detekciju proizvoda degradacije tečna hromatografija-masena spektrometrija (LC-MS). Za definisanje stepena mineralizacije odabrana je metoda određivanja ukupnog organskog ugljenika (TOC).

Nanocrystalline TiO2, synthesized by sol-gel route and characterized by XRPD,BET and SEM measurements, was applied in the photocatalytic degradation ofamoxicillin, using an Osram Ultra-Vitalux® lamp as the light source. Amoxicillin is a semi-synthetic penicillin type antibiotic active against a widerange of gram-positive and a limited range of gram-negative organisms. The continuous release of antibiotics and their persistence in the environment mayresult in serious irreversible effects on aquatic and terrestrial organisms. Heterogeneous catalysis, which uses catalysts like TiO2, is a promising route for the degradation of organic pollutants including antibiotics. The effects of initial concentration of catalyst, initial salt concentration (NaCl and Na2SO4), ethanol and pH on the photocatalytic degradation of amoxicillin were studied. The mineralization of amoxicillin was analyzed by ion chromatography as well as by total organic analysis. The catalytic properties of nanocrystalline TiO2 were compared to Evonik P25 catalyst.The electrodegradation of azithromycin was studied by its indirect oxidation using dimensionally stable Ti/RuO2 anode as catalyst in the electrolyte containing methanol, 0.05 M NaHCO3, sodium chloride and deionized water. The optimal conditions for galvanostatic electrodegradation for the azithromycin concentration of 0.472 mg cm–3 were found to be NaCl concentration 7 mg cm–3 and the applied current 300 mA. The differential pulse voltammetry using glassy carbon electrode was performed for the first time in the above mentioned content of electrolyte for the nine concentration of azithromycin (0.075 mg cm−3 - 0.675 mg cm−3) giving the limits of azithromycin detection and of quantification The calibration curve was constructed enabling the electrolyte analysis during its electrodegradation process. The electrolyte was analyzed and by high performance liquid chromatography and electro spray ionization time-of-flight mass spectrometry. The electrooxidation products were identified and after 180 min there was no azithromycin in the electrolyte while TOC analysis showed that 79% of azithromycin was mineralized. The proposed degradation scheme is presented.