Investigation of dimethenamid-P degradation in an aqueous environment using various physico-chemical methods

Predmet ove doktorske disertacije je proučavanje degradacije herbicida dimetenamida-P u vodenoj sredini. Dimetenamid-P spada u grupu hlorcetamida. Zahvaljujući svojoj velikoj selektivnosti, kao aktivna materija sredstava za zaštitu bilja, primenjuje se u suzbijanju jednogodišnjih travnih i širokolisnih korova u usevima velikog broja poljoprivrednih kultura. To su šećerna repa, kukuruz, soja, suncokret, krompir, pasulj, krastavac i dr. U uslovima savremene poljoprivredne proizvodnje i sve veće primene pesticida, ispitivanja u cilju zaštite životne sredine su pokazala prisustvo tragova ovog herbicida u površinskim i podzemnim vodama. S obzirom na relativno veliku rastvorljivost u vodi, postoji opravdana opasnost od migracije dimetenamida-P u ekosistem. Degradacija dimetenamida-P je ispitivana sprovođenjem procesa fotokatalitičke degradacije u prisustvu TiO2 kao katalizatora. Proučavana je i elektrohemijska aktivnost dimetenamida-P. Direktna elektrohemijska degradacija ispitivana je primenom ciklične voltametrije na elektrodi od zlata, a indirektna metodom elektrolize. Naučni cilj ovog rada je da se primenom viših oksidacionih procesa izvrši potpuna oksidacija dimetenamida-P u kratkom vremenskom periodu, bez nastajanja policikličnih produkata. Fokus istraživanja bio je usmeren na praćenje efekata eksperimentalnih parametara koji utiču na brzinu degradacije ciljanog hloracetamida. Na prvom mestu su to, koncentracija fotokatalizatora početna koncentracija dimetenamida-P, početna vrednost pH rastvora, efekat neorganskih soli, uticaj vodonikperoksida, odnosno uticaj organskog rastvarača. Pored toga identifikovani su nastali joni u procesu degradacije, čime se došlo do važnih informacija o mineralizaciji dimetenamida-P i koncentraciji osnovnog jedinjenja u vodi. Za proučavanje kinetike, mehanizma degradacije, odnosno za kvalitativno i kvantitativno određivanje dimetenamida-P u rastvorima pre i nakon određenih reakcija degradacije korišćene suμ tečna hromatografija visoke efikasnosti sa detektorom na bazi niza dioda (HPLC-DAD)...The subject of this doctoral thesis is the investigation of degradation of dimethenamid-P herbicide in aquatic environment. Dimethenamid-P is classified into chloroacetamides. Due to its high selectivity, this active ingredient of pesticides is applied in controlling of annual grass weeds, as well as annual broadleaved weeds in crops of great number of agricultural cultures. Among them, there are sugar beet, corn, soya, sunflower, potato, beans, cucumber and others. In terms of modern agricultural production and constantly increasing pesticide application, the investigations aiming at environmental protection showed the presence of this herbicide in traces in surface and underground waters. Considering relatively high solubility in water, there is reasonable danger of migration of dimethenamid-P into ecosystem. The degradation of dimethenamid-P was investigated by conducting the process of photocatalytic degradation in the presence of TiO2 as catalyst. Electrochemical activity of dimethenamid-P was also investigated. Direct chemical degradation was investigated by the application of cyclic voltammetry at gold electrode, and the indirect degradation by electrolysis. Scientific objective of this paper is to perform total oxidation of chloroacetamide in a short period of time by the application of advanced oxidation processes, without the occurrence of polycyclic products. The investigative focus was directed to monitoring the effects of experimental parameters which influence the degradation speed of the aimed chloroacetamide. Primarily, those are: photocatalyst concentration, initial concentration of dimethenamid-P, initial pH value of the solution, the effect of inorganic salts, the influence of hydrogen peroxide presence, i.e. the influence of organic solvent presence. Beside that, ions generated in the degradation process were identified, which provided important information about mineralization of dimethenamid-P and the content of this compound in water. For the investigation of kinetics and mechanism of degradation reaction, i.e. for qualitative and quantitative establishing of dimethenamid-P..