Antibiyotiklerin fotokimyasal ileri oksidasyon prosesleri ile giderimi
Removal of antibiotics by photochemical advanced oxidation processes
Yazar: HANDE GÜLCAN
Danışman: PROF. DR. TUĞBA ÖLMEZ HANCI
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Çevre Mühendisliği Ana Bilim Dalı / Çevre Bilimleri, Mühendisliği ve Yönetimi Bilim Dalı
Derece: Yüksek Lisans, 2019
Konu: Çevre Mühendisliği = Environmental Engineering

Özet:
Antibiyotikler uzun bir süredir tıbbi ilaç olarak kullanılmaktadır ve yakın zamanda çevrede yeni kirletici maddeler olarak ortaya çıkmıştır. Ana antibiyotik bileşikleri ve bunların metabolitleri su arıtma işlemlerinde arıtılamamakta ve çevresel ortamlara karışabilmektedir. Yaygın olarak kullanılan antibiyotikler arasında florokinolonlar önemli bir sentetik antibakteriyel madde grubudur. Florokinolon antibiyotik olarak siprofloksasin, insanlarda ve hayvanlarda birçok bakteriyel enfeksiyonun tedavisi için dünyada en sık kullanılan florokinolonlardan biridir. Siprofloksasinin su ortamında varlığı ekosistemi, insan sağlığını ve atıksu arıtımının biyolojik sürecini düşük konsantrasyonlarda bulunsa dahi önemli ölçüde etkileyebilmektedir.
Mevcut çalışmalar antibiyotiklerin metabolitlerinin kalıcı olabileceğini ve birikerek ciddi kirlenmelere yol açabileceğini göstermektedir. Bu kirlenmelerin ana kaynağı atıksulardır ve konvansiyonel arıtma yöntemleri antibiyotik bileşiklerini tamamen ortadan kaldırmamakta, bu da ortamda mevcut düşük fakat sabit bir konsantrasyona neden olmaktadır. Atıksularda antibiyotik varlığı artmakta ve bunların giderilmesinin yakın gelecekte önemli bir sorun olacağı öngörülmektedir. Antibiyotik bileşikleri konvansiyonel atıksu arıtma tesislerinde verimli bir şekilde arıtılamasa da bu bileşiklerin sucul ortamdan uzaklaştırılması farklı işlemlerle mümkündür. Son yıllarda ileri oksidasyon prosesleri ile yapılan çalışmalar, antibiyotik bileşiklerinin sudan uzaklaştırılması için faydalı olabileceğini göstermiştir.
İleri oksidasyon prosesleri (İOP), oksidasyon potansiyeli yüksek olan serbest radikallerin reaksiyon ortamında üretilmelerine dayanan arıtma yöntemleridir. İOP'de güçlü oksitleyiciler olan serbest radikallerin oluşumuyla, toksik ve kalıcı organik maddeleri güçlü bir oksitleyici olan hidroksil (OH·) oluşumuyla zararsız veya daha az toksik maddelere dönüştürülebilmektedir. HO• en reaktif oksitleyici türdür. HO•'ne alternatif olarak, organik ve inorganik bileşiklerle reaksiyon verebilen, sülfat radikali (SO4•−), gibi yüksek oksitleyici özelliği olan başka radikallerin oksidasyon uygulamalarında kullanılabilirliğinin araştırılması son yıllarda giderek artmaktadır. Sülfat radikal bazlı ileri oksidasyon prosesleri etkili bir çözüm olarak dikkat çekmektedir.
Bu deneysel çalışmada siprofloksasin (CIP) model kirleticisinin arıtımını sağlayabilmek için sülfat radikal bazlı fotokimyasal ileri oksidasyon proseslerinin (persülfat/UV-C, persülfat/UV-A) kullabilirliği araştırılmış ve proses performansları farklı koşullar altında karşılaştırılmıştır. Çalışmada aynı zamanda kirleticinin oksidasyon prosesleri ile giderimi sırasında ve deney sonunda oluşan oksidasyon ürünlerinin toksik etkisi olup olmadığını gözlemlemek amacıyla toksisite analizleri gerçekleştirilmiştir. Su matrisinin proses verimi üzerine olan etkisini değerlendirmek
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amacıyla distile su dışında yüzeysel su örneği de kullanılmıştır. Bu amaçlar doğrultusunda yürütülen deneysel çalışmalarda başlangıç oksidan konsantrasyonunun ve başlangıç pH değerinin incelenen fotokimyasal ileri oksidasyon proseslerinin verimi üzerine olan etkisi incelenmiştir.
Gerçekleştirilen deneysel çalışmalarda CIP kirleticisinin sülfat radikali bazlı fotokimyasal ileri oksidasyon prosesleri ile yüksek oranlarda giderimi sağlanmıştır. Başlangıç persülfat dozajının incelendiği çalışmalarda PS dozajının artırılması ile CIP giderim veriminde de artışlar kaydedilmiştir. PS/UV-C prosesinde 120 dakikalık reaksiyon süresi içerisinde en düşük dozajda (0,05 mM) tam giderim sağlanamazken, diğer dozajlarda (0,1 Mm ve 0,25 mM) 60 dakikalık süre içerisinde %100 giderim sağlanmıştır. PS/UV-A prosesinde ise tüm dozajlarda yüksek giderim oranları sağlansa da %100 giderim elde edilememiştir. Başlangıç pH değerinin incelendiği çalışmalarda önemli bir değişiklik gözlenmemiştir. Su matrisinin proses verimi üzerine olan etkisi değerlendirmek amacıyla distile su dışında yüzeysel su örneği de kullanılmıştır.
Çalışmanın diğer aşamasında CIP'in PS/UV-C ve PS/UV-A ile arıtıldığı deneylerde V. fischeri toksisite analizleri yapılmış ve inhibasyon etkisi görülmemiştir.

Abstract:
Antibiotics have long been used as medical drugs and have recently emerged as new pollutants in the environment. The presence, fate and risks of antibiotics in the natural environment have emerged as a growing concern. Recently, it has become the focus of environmental research.
Antibiotics are antimicrobial agents that inhibit or kill the growth of microorganisms. Antibiotics are nonbiodegradable, can survive at aquatic environments for long periods and they have a great potential bio-accumulation potential in the environment. They are extensively metabolized by humans, animals and plants. After metabolization, antibiotics or their metabolites are discharged into the aquatic environment. Antibiotics are known as potential pollutants due to their adverse effects on the aquatic ecosystem, humans and animals, even at very low concentrations. The removal of these compounds from the aquatic environment is feasible by different processes. However, conventional treatment systems are insufficient for the removal of antibiotics. Antibiotics are partially degraded or result in poor mineralization in these processes.
At this point, there is a need for alternative treatment technologies. In recent years, studies with advanced oxidation processes (AOPs) for the removal of these compounds from water have shown that they can be beneficial for removing them exactly. Advanced oxidation processes (AOPs) are promising alternatives to remove these contaminants from wastewater treatment plants and natural waters. Advanced oxidation processes (AOP) based on the production of free radicals with high oxidation potential in the reaction. AOP applies radicals as oxidants that can directly destroy the molecular structure of antibiotics. With the free radicals (HO• and SO4•-) used in the advanced oxidation processes, it is possible for the contaminant to decompose completely and turn into harmless decomposition products. HO• is the most reactive oxidizing species. The generation of hydroxyl radicals might be by the use of UV/H2O2, UV/O3, O3/H2O2/UV, Fe2+/ H2O2, TiO2/H2O2 and other processes.
As an alternative to HO, the use of other radicals with high oxidizing properties such as sulfate radical (SO4•-) which can react with organic and inorganic compounds has been increasing in recent years. Sulfate radical-based advanced oxidation processes stand out as an effective solution. Sulfate radicals are generally produced from peroxymonosulfate (PMS) and persulfate (PS). Activation of PMS and PS can be accomplished by a variety of methods such as heat, UV, ultrasound or heterogeneous and homogeneous catalysis. UV plays an effective role in the activation of PM and PMS.
Fluoroquinolone antibiotics are important synthetic bacterial agents among commonly used antibiotics. The use of fluoroquinolones (FQ) antibiotics as therapeutic agents and growth promoters is increasing worldwide. FQs have also become one of the main pollutants in the wastewater bodies that are not completely removed during the treatment processes.
Ciprofloxacin, as a fluoroquinolone antibiotic, is one of the most commonly used fluoroquinolones in the world in the treatment of many bacterial infections in humans and animals. The presence of ciprofloxacin in the aquatic environment can significantly threaten the ecosystem, human health and the biological process of wastewater treatment even at low concentrations. Commonly used FQs have low removal efficiency in conventional wastewater treatment plants, therefore they occur regularly in surface waters. Numerous studies have suggested some methods for removing ciprofloxacin. However, very few studies have been done using the UV / S2O82- process. This study consists of seven chapters.
In the first part, the purpose and scope of the study are explained briefly.
In the second part, detailed information about the definition, classification and properties of antibiotics is given. Basic information about AOP, various AOP applications and basic reactions in these processes are explained in this section. Studies on the treatability of antibiotics have been mentioned. The basic information about toxicity analyzes and toxic effect tests conducted with Vibrio fischeri are summarized briefly.
In the third section, materials and methods are explained. In this context, the chemicals used in the experimental study, the experimental planning, the conduction of oxidation experiments and toxicity experiments are explained. Analytical measurements and instruments which were also used at the experimental part of the thesis were explained at this part.
In the fourth chapter, the treatability of CIP was investigated. Firstly, the determination of the appropriate concentration of PS oxidant used in the treatment of CIP material with PS/UV-C processes and the effective initial pH values were investigated. After, the same processes were tested in the UV-A and PS / UV-A processes. The results obtained from the experimental studies are given and discussed.
In the fifth and final section, theoretical information and experimental study results are evaluated together and recommendations are presented.
In this experimental study, the availability of sulfate radical based photochemical advanced oxidation processes (persulfate/UV-C, persulfate/UV-A) was investigated in order to provide treatment of ciprofloxacin (CIP) model pollutant and process performances were compared under different conditions.
Within the scope of this study, the selected photochemical oxidation processes that comparatively evaluated in terms of initial oxidant concentration and initial pH values.
The optimum conditions for the study were determined as 2 mg/L CIP model pollutant.
Sulfate radical based photochemical advanced oxidation treatment studies of CIP pollutant were carried out for initial PS concentrations (0,05 mM, 0,1 mM, 0,25 mM) and initial pH values (4, 5,5, 7, 8,5, 10) for UV-A and UV-C separately. The reactions were carried out for 120 minutes experiment period. CIP measurements were made with an HPLC device.
In another phase of the study, toxicity analyses were performed on the samples taken at a specific time during the reaction. Inhibition measurements were conducted with V. fischeri test organism, a marine photobacterium commonly used in routine bioassays. The acute toxicity experiments were conducted with PS/UV-C and PS/UV-A treated CIP in distilled water. In order to eliminate their effect on acute toxicity measurements, residual PS was removed with sodium thiosulfate, which was found to be the most suitable quenching agent to eliminate bioassay interference. V. fischeri toxicity assays were measured using a commercial bioassay kit (BioToxTM, Aboatox Oy, Finland) according to the ISO 11348-3 test protocol.
In CIP treatment studies conducted with the PS/UV-C process at pH 8,5, 0.1 mM and 0,25 mM PS beginning concentrations with 60 minutes treatment were reached the 100% removal efficiency. For the initial PS concentration of 0.05 mM, complete removal was not achieved within the reaction time of 120 minutes, while 98% removal efficiency was obtained. Although increasing the PS concentration shows significant removal changes during the first 15 minutes, the removal rates become approximately equal as time progresses. The effectiveness of PS oxidant with UV-C increases with time. In PS/UV-C experiments investigating the effect of initial pH at PS 0,1 mM, no significant effect of initial pH values (4, 5,5, 7, 8,5, 10) were observed. The effect of water matrix on PS / UV-C and CIP removal was also investigated. The initial concentration of PS oxidant used for these experiments was selected to be 0.25 mM and the experiments were carried out at pH = 8.5. The fastest CIP removal was achieved in the distilled water matrix at 100% after 15 minutes. CIP was completely removed under the same reaction conditions studied in the surface water sample, but the treatment time increased to 30 minutes.
In CIP treatment studies conducted with the PS/UV-A process at pH 8,5, there was a significant difference in removal efficiency between the absence and presence of PS oxidant in the reaction medium in the first 15 minutes. CIP removal was greatly improved by PS addition (0,05 mM, 0,1 mM, 0,25 mM), %85-90 yield was obtained. In the experiments with PS/UV-A for different pH initial values at PS 0,1 mM, 10 minutes was sufficient to provide about 80% yield for all studied initial pH values. In the following minutes, no significant increase in removal was observed. It was observed that pH = 7 has a lower yield than other pHs. The highest removal was recorded at pH = 4 with 95% removal efficiency.
Toxicity test results for CIP indicated that 2 mg/L CIP pollutant during PS / UV-C and PS / UV-A processes and after processes had no inhibitory effect on Vibrio fischeri.