Application of the reactor based on dielectric barrier discharge for the decolorization of reactive textile dyes

[B. Dojčinović]

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Hemija životne sredine / Environmental Chemistry

Dekolorizacija reaktivnih boja za tekstil Reactive Black 5, Reactive Blue 52, Reactive Yellow 125 i Reactive Green 15 je ispitana pomoću unapređenog oksidacionog procesa u netermalnom plazma reaktoru, koji je baziran na koaksijalnom dielektričnom barijernom pražnjenju (DBD) sa tankim vodenim filmom rastvora koji se tretira i konstantno obnavlja. Početne koncentracije boja u rastvoru su bile 40,00 i 80,00 mg/L. U prvom delu rada ispitan je uticaj različitih polaznih pH vrednosti (9,00; 7,00; 5,00) rastvora boje i dodatak homogenih katalizatora (H2O2, Fe2+, Fe3+ Mn2+ i Cu2+) na efikasnost dekolorizacije tokom uzastopnih recirkulacija rastvora boje kroz DBD reaktor, tj. primenjene gustine energije (45–315 kJ/L).Uticaj vremena stajanja rastvora nakon tretmana plazmom je ispitivan tokom perioda od 24 h. Promena pH vrednosti i uticaj pH podešavanja rastvora boje posle svake recirkulacije na efikasnost dekolorizacije je testirana. Potvrđeno je da početna pH vrednost i pH korekcija rastvora boje posle svake recirkulacije nemaju uticaja na dekolorizaciju. Efikasnost tretmana plazmom se značajno intenzivira sa dodatkom vodonik-peroksida. Najefikasnija dekolorizacija od 97 % je dobijena u prisustvu 10 mM H2O2 u sistemu od 80,00 mg/L boje Reactive Black 5 i pri primenjenoj gustini energije od 45 kJ/L, posle vremena stajanja od 24 h od tretmana plazmom. Takođe, efekat tretmana plazmom može se poboljšati sa dodatkom soli gvožđa(II) ako su uslovi za Fentonovu reakciju ispunjeni. Tokom tretmana, u pražnjenju se generišu azotasta i azotna kiselina koje smanjuju pH vrednost rastvora. Ispitan je uticaj dodatka različitih visokih koncentracija neorganskih soli (NaCl, Na2SO4 i Na2CO3) na stepen dekolorizacije boje Reactive Black 5 (40,0 mg/L). Takođe, ispitana je promena pH vrednosti i provodljivosti rastvora boje posle svake recirkulacije. Rezultati pokazuju da je dekolorizacija značajno ograničena u prisustvu soli. Sa povećanjem koncentracije neorganskih soli, smanjuje se efikasnost dekolorizacije boje, a stepen inhibicije zavisi od soli koja se koristi. Najefikasnija dekolorizacija od 90 % je dobijena u prisustvu 50 g/L NaCl pri primenjenoj gustini energije od 135 kJ/L posle vremena stajanja od 24 h nakon tretmana plazmom. Povećanje dekolorizacije u prisustvu 50 g/L NaCl je objašnjeno formiranjem hipohlorita iz hlorida tokom tretmana plazmom. Dekolorizacija rastvora koji sadrže neorganske soli Na2SO4 i Na2CO3 je bila manja nego kod rastvora bez dodatka soli. U drugom delu rada ispitana je efikasnosti dekolorizacije i degradacije pri visokim koncentracijama boje Reactive Black 5 (40, 80, 200, 500 i 1000 mg/L). Efikasnost degradacije i mogući putevi degradacije praćeni su merenjem HPK vrednosti, jonskom hromatografijom (IC) i HPLC tehnikom. Pored toga, u okviru ovog rada, značajno je unapređena i optimizovana metoda za merenje HPK vrednosti pomoću kontrolisanog mikrotalasnog tretmana. Toksičnost je ispitana pomoću Artemia salina test organizama. Toksikološki testovi, izvedeni pomoću A. salina, pokazuju da je toksičnost rastvora boje smanjena ili je ostala nepromenjena nakon tretmana, sa izuzetkom za boju Reactive Green 15, gde je detektovan blagi porast toksičnosti samo za jednu vrednost koncentracije.

Decolorization of reactive textile dyes Reactive Black 5, Reactive Blue 52, Reactive Yellow 125 and Reactive Green 15 was studied using advanced oxidation processes (AOPs) in a non-thermal plasma reactor, based on coaxial water falling film dielectric barrier discharge (DBD). Used initial dye concentrations in the solution were 40.0 and 80.0 mg/L. The effects of different initial pH (9.00; 7.00; 5.00) of dye solutions, and addition of homogeneous catalysts (H2O2, Fe2+, Fe3+ Mn2+ and Cu2+) on the decolorization during subsequent recirculation of dye solution through the DBD reactor, i.e. applied energy density (45–315 kJ/L) were studied. Influence of residence time was investigated over a period of 24 h. Change of pH values and effect of pH adjustments of dye solution after each recirculation on the decolorization was also tested. It was found that the initial pH of dye solutions and pH adjustments of dye solution after each recirculation did not influence the decolorization. The effect of plasma treatment can be significantly intensified with addition of hydrogen peroxide. The most effective decolorization of 97% was obtained with addition of 10 mM H2O2 in a system of 80.0 mg/L Reactive Black 5 with applied energy density of 45 kJ/L, after residence time of 24 h from plasma treatment. Also, the effect of plasma treatment can be enhanced with addition of iron(II) salts if the conditions for Fenton reactions are fulfilled. During the treatment, the discharge generates other species like nitrous and nitric acids which decrease the pH values of solutions. The effects of addition of inorganic salt different high concentrations (NaCl, Na2SO4 and Na2CO3) on the degree of decolorization of dye Reactive Black 5 (40.0 mg/L) were studied. Changes of pH values and the conductivity of dye solution after each recirculation were tested. The results indicated that decolorization of the dyes was significantly limited in the presence of salts. The increase of concentrations of inorganic salts in water reduced the efficiency of decolorization of dyes, in a varying degree depending of the salt used. The most effective decolorization of over 90 % was obtained with the addition of NaCl (50 g/L), applied energy density of 135 kJ/L and after residence time of 24 hours of plasma treatment. The increased decolorizatin with addition 50 g/L NaCl was explained by forming of hypochlorite from chloride during the plasma treatment. Decolorization of solutions containing inorganic salts Na2SO4 and Na2CO3 were lower than for the solution without salt. In the second part the effectivenes of decolorization and degradation of high concentrations dye Reactive Black 5 (40, 80, 200, 500 and 1000 mg/L) was examined. Efficiency degradation and possible degradation pathways were monitored by measuring the COD value, ion chromatography (IC) and HPLC technique. In addition, as part of this work, has significantly improved and optimized method for measuring the COD value by controlled microwave treatment. Toxicity was evaluated using the brine shrimp Artemia salina as a test organism. Toxicity tests, performed using A. salina, have shown that toxicity of dye solutions was reduced or maintained at the same level after the treatment, except for Reactive Green 15 where slight increase of toxicity was detected for only one concentration value.

dekolorizacija, reaktivne tekstilne boje, unapređeni oksidacioni postupci (AOP), plazma tretman, dielektrično barijerno pražnjenje (DBD), homogeni katalizatori, neorganske soli, DBD reaktor, UV-VIS, ICP-OES, HPLC, IC, Artemia salina- toksikološki test

decolorization, reactive textile dyes, advanced oxidation processes (AOPs), plasma treatment, dielectric barrier discharge (DBD), homogeneous catalysts, Inorganic salts, DBD reactor, UV-VIS, ICP-OES, HPLC, IC, Artemia salina- toxicity test

677.255(043.3) ; 66.05(043.3)

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