Degradation of surfactants using dielectric barier discharge reactor

Abstract

Surfactants are a group of compounds, which are widely used in industrial, agricultural, and pharmaceutical markets in various products, including detergents, pesticides, petroleum products, cosmetics and pharmaceuticals. Surfactants and their degradation products are widely detected in domestic and industrial wastewater. Due to their significant effects on the aquatic environment, degradation of surfactants is subject of many research papers. In addition to the classical wastewater treatment a lot of research is addressed to the usage of advanced oxidation process for removal of various surfactants. The aim of this study was to investigate using of non-thermal plasma (water falling film dielectric barrier discharge plasma reactor) for degradation of two anionic surfactants (sodium dodecyl sulfate - SDS and sodium dodecylbenezene sulfonate - DBS) and two nonionic surfactant (Triton X-100 and nonylphenol ethoxylate - NPE ). Surfactants examined in this research are predominantly used in formulations of laundry detergents and for industrial cleaning application. The effects of two catalytic plasma systems,( iron (II) salt and hydrogen peroxide), were tested to improve the degradation of surfactants. Efficiency of degradation was determined by spectrophotometric determination of decrease of surfactants concentration. Decrease of chemical oxygen demand and total organic carbon were measured to determine degree of mineralization. In cases of two nonionic surfactants and sodium dodecylbenzene sulpfonate catalytic systems exhibited significant improvements in degradation efficiency especially in beginning of treatment. In the case of sodium dodecyl sulphate catalysts have no effect on surfactant degradation. Mineralization of surfactants in all cases was significantly improved in presence of catalyst. Toxicity test with Artemia salina (A. salina) test organisms showed that toxicity in all case were decreased after treatment of solutions in water falling film dielectric barrier discharge plasma reactor.

Surfaktanti predstavljaju grupu jedinjenja koja se šitoko koristi u industriji, poljoprivredi i farmaceutskoj industriji u različitim proizvodima uključujući detergente, pesticide, proizvode petrohemijske industrije, kozmetičke proizvode i lekove. Surfaktanti i prozvodi njihove degradacije su vrlo često prisutni u kanalizacionim i industrijskim otpadnim vodama. Usled njihovog efekta na vodene organizme degradacija surfaktanata predstavlja značajnu oblast istraživanja. Pored klasičnih tretmana otpadnih voda istraživanja su usmerena i ka primeni unapređenih oksidacionih procesa za uklanjanje različitih surfaktanata iz otpadnih voda. Predmet ovoga rada je ispitivanje mogućnosti primene netermalne plazme (korišćenjem reaktora sa dielektričnim barijernim pražnjenjem kroz tanak film vode) za degradaciju dva anjonska surfaktanta (natrijum-dodecil-sulfata i natrijum-dodecilbenzensulfonata) i dva nejonska surfaktanta (Triton X-100 i nonilfenol etoksilata). Ovi surfaktanti se koriste u formulacijama detergenata za pranje veša i u procesima industrijskog pranja. Pored toga ispitani su i efekti homogenih katalizatora (soli gvožđa (II) i vodonik-peroksida na poboljšanje efikasnosti degradacije. Efikasnost degradacije je praćena spektrofotometrijskim određivanjem smanjenja koncentracije surfaktanata. U cilju određivanja stepena mineralizacije odnosno potpune razgradnje organske supstance određeni su hemijska potrošnja kiseonika i ukupan organski ugljenik nakon tretmana. U eksperimentima sa dva nejonska surfaktanta i natrijum-dodecilbenzen-sulfonata katalitički sistemi su pokazali značajan efekat u povećanju efikasnosti degradacije posebno pri nižim vrednsotima primenjene energije. U eksperimentu sa natrijum-dodecil-sulfatom katalizatori nisu pokazali uticaj na efikasnost degradacije. U svim eksperimentima katalizatori su pokazali značajan uticaj na mineralizaciju rastvora odnosno na razgradnju organske supstance. Testovi ispitivanja toksičnosti sa Artemia salina organizmima su pokazali da je u svim eksperimentima toksičnost rastvora smanjena nakon tretmana u reaktoru sa dielektričnim barijernim pražnjenjem.