Gün ışığı altında fotokatalitik yöntemle atık  sudan siprofloksasin (CIP) giderilmesi
Removal of ciprofloxacin (CIP) from wastewater by photocatalytic method under daylight
Yazar: ZOZAN GÜL
Danışman: PROF. DR. GÜLHAYAT NASÜN SAYGILI
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Kimya Mühendisliği Ana Bilim Dalı / Kimya Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: Kimya Mühendisliği = Chemical Engineering
Dizin: Fotobozunma = Photodegradation ; Grafen oksit = Graphene oxide ; Hidroksiapatitler = Hydroxyapatites ; Siprofloksasin = Ciprofloxacin

Özet:
Su kirliliği küresel bir sorun olup günümüzde kritik bir noktaya ulaşmıştır. Su kirliliğinin nedenlerinden biri olan farmasötik kirleticilerin sağlık ve çevresel etkileri dikkate alınması gereken su kirleticileridir. Siprofloksasin (CIP), yaygın kullanımı nedeniyle su kaynaklarında en sık tespit edilen antibiyotiklerden biridir. CIP'in çevrede uzun süre kalıcı olması ve ekosistemdeki mikrobiyal topluluklar üzerindeki olumsuz etkileri dikkate alındığında atık sulardan giderilmesi gerekmektedir.
Hidroksiapatit (HAp), (Ca10(PO4)6(OH)2), yüksek adsorpsiyon kapasitesi, asit-baz ayarlanabilirliği, iyon ayarlanabilmesi, iyon değiştirme kapasitesi ve termal kararlılık gibi önemli özellikleri nedeniyle su kirliliği giderimi ile ilgili çalışmalarda sıklıkla kullanılan bir biyomateryaldir. Grafen Oksit (GO), çevresel iyileştirme uygulamaları için tercih edilen bir malzemedir. GO, sudaki kirleticiler için adsorbe edici alanlar sağlayan hidroksil, karboksil ve epoksi grupları gibi çeşitli fonksiyonel gruplardan oluşmaktadır. GO, düşük maliyeti, kolay işlenebilmesi, çevre dostu olması ve biyouyumluluğu açısından karbon bazlı adsorban malzemeler arasında öne çıkmaktadır.
Bu çalışmada, atık sulardan CIP'in giderilmesi için  farklı konsantrasyonlarda GO içeren HAp-GO fotokatalizörleri hazırlanmıştır. Hazırlanılan HAp-GO fotokatalizörleri FTIR kullanılarak  karakterize edilmiştir. En uygun koşulların belirlenmesi için başlangıç ilaç konsantrasyonu, HAp-GO fotokatalizöründeki GO miktarı, ortam pH'ı ve çalkalama hızı parametre olarak belirlenmiştir. Deney tasarımı yöntemlerinden biri olan "Box-Behnken" kullanılarak Minitab programı ile deneyler tasarlanıp gerçekleştirilmiştir. Her bir deneyde, 50 mg HAp-GO kullanılarak 50 mL ilaç çözeltisi ile çalışmalar yürütülmüştür. Elde edilen deneysel sonuçlar Minitab programı kullanılarak değerlendirilmiştir. Numuneler arasında 150 mg GO içeren HAp-GO fotokatalizörü en iyi fotokatalitik performansa sahip çıkmıştır. Ortam pH'ı 7, başlangıç CIP konsantrasyonu 10 ppm, 150 mg GO ile hazırlanan HAp-GO fotokatalizörü ve çalkalayıcı hızı 125 rpm koşullarında siprofloksasin giderim verimliliği %94,7 olarak  hesaplanmıştır. En yüksek verim alınan fotokatalizörün (HAp-150 GO) FTIR, SEM, XRD, Zeta potansiyel analizleri ile karakterizasyonu yapılmıştır.  Çalışma sonucunda GO ilavesinin HAp'ın fotodegradasyon kapasitesini arttırdığı, HAp-GO'nun CIP degradasyonu için fotokatalizör olma potansiyeline sahip olduğu gözlenmiştir. Fotokatalizör miktarının verime etkisi, optimum koşullarda  25, 50, 75 ve 100 mg HAp-GO fotokatalizörü ilave edilerek araştırılmıştır. 75 ve 100 mg HAp-150 GO fotokatalizörü  ilave edilen deneylerde %100 verim elde edilmiştir.

Abstract:
Water pollution is a global problem and has reached a critical point nowadays. Therefore, it is crucial to keep water sources clean and also, develop effective treatment method in addition to be paying attention to water consuption. Pharmaceutical pollutants, which are one of the causes of water pollution, are water pollutants whose health and environmental effects should be taken into account. The presence of antibiotics in water sources causes living things to develop antibiotic resistance. This may cause the ecosystem balance to be disrupted and various infection treatments to be insufficient. In addition, generally used physical and chemical treatment methods are not sufficient for the removal of antibiotics. For this reason, there is a need to develop an environmentally friendly and effective method. The aim of the study was to find an effective situation for the removal of CIP from wastewater. Therefore, a study was conducted on CIP removal by photodegradation method under sunlight. HAp-GO was used as photocatalyst.
CIP is one of the most commonly detected antibiotics in water resources due to its widespread use. Another reason why it is one of the most frequently detected drugs in wastewater is that it has a poor metabolism and dissolves slowly.It is generally used in the treatment of skin infections, typhoid and lower respiratory tract infections. Considering the long-term persistence of CIP in the environment and its negative effects on microbial communities in the ecosystem, it is necessary to remove it from wastewater. CIP is zwitterionic and has two pKa values, 6.2 and 8.8. CIP is cationic below 6.2, anionic above 8.8. Also, it is zwitterionic between 6.2 and 8.8.
Hydroxyapatite (HAp), (Ca10(PO4)6(OH)2), is a biomaterial that a frequently preferred material in biomedical applications from past to present due to its chemical similarity to human bone and tooth structures and its bioactive and osteoconductive properties.In addition to biomedical applications, HAp is frequently used in studies in the field of water pollution removal due to its important properties such as high adsorption capacity, acid-base adjustability, ion exchange capacity, and thermal stability, environmentally friendly. HAp(Ca10(PO4)6(OH)2) is a calcium phosphate compound with a hydroxyl group. HAp has a hexagonal and crystal structure. In addition, it has low water solubility and high stability under oxidizing and reducing conditions.
There are differences in various properties of calcium phosphate compounds, such as solubility and crystal structure, depending on the Ca/P ratio. HAp, with its Ca/P ratio of 1.67, stands out from other calcium phosphate compounds because it is a stable material.
Graphene oxide, obtained as a result of the oxidation of graphene. is used in various fields such as electronic applications, energy storage, sensors, composite material studies and biomedical applications due to its properties. GO stands out among carbon-based adsorbent materials in terms of low cost, easy processing, environmental friendliness, and biocompatibility.  Graphene Oxide (GO) is also a preferred material for applications in environmental remediation. GO consists of several functional groups such as hydroxyl, carboxyl, and epoxy groups, which provide adsorbing sites for pollutants in water. Negatively charged GO has a hydrophilic structure. It disperses easily in water GO contains both aromatic (sp2) and aliphatic domains (sp3) in its structure, allowing an increase in the types of interactions that can occur on its surface.
The basic principle of the photodegradation method is the degradation of the material molecule by the absorption of photons. In this way, photons can break molecules into smaller pieces and change the shape of the molecule, changing it irreversibly. The photocatalytic method is a type of photodegradation. The photodegradation process is stabilized by using a suitable photocatalyst. Photocatalysis, which works with sunlight, stands out because it does not contain pollutants, is abundant in nature and is renewable. In general, antibiotics have a hydrophobic structure. Therefore, it makes removal by sorption method difficult. For this reason, the photocatalytic method has begun to take place in wastewater treatment applications.
In this study, photocatalyst were synthesized by using HAp and GO materials for the removal of CIP from wastewater. The synthesized HAp-GO photocatalyst was successfully characterized using FTIR. In order to determine the most suitable removal conditions, the initial drug concentration, weight of GO in the composite structure, ambient pH, and agitation speed were determined as parameters. The determined parameters are as follows, 3, 7, and 11 for pH; 50,100 and 150 mg for the amount of GO in the HAp-GO photocatalyst; 50,125 and 200 rpm for agitation speed; for the initial drug concentration, it is 10, 25 and 40 rpm. Samples were prepared as 50 mg composite and 50 mL drug solution. Experiments were designed and carried out with Minitab program using "Box-Behnken", one of the experimental design methods. 27 experimental plans were created with four parameters and three levels via Minitab. Thanks to the Box-Behnken design used, fewer experiments were performed and less resources were consumed. As a result of the studies, a suitable conditions for removal was searched. The experimental results obtained were evaluated using the Minitab program. 
Efficiency was calculated with data of the initial drug concentration and the drug concentration amounts at the 300th minute. The highest efficiency, with 94.73%, is the condition in which the HAp-150 GO photocatalyst is used, the pH value is 7, the initial drug concentration is 10 ppm, and the agitation speed is 125 ppm. Also, contour graphs show that the parameters pH, initial drug concentration and amount of GO in the HAp-GO photocatalyst are effective for this study, while the agitation speed is not effective. As drug concentration increases, efficiency decreases. This may be due to the decrease in the amount of interacting photons with increasing drug concentration. The surface area of the HAp-GO photocatalyst was increased with the change in the amount of GO, thereby increasing the exposure and allowing light absorption to increase. The catalytic activity of the photocatalyst increased.
Among the samples, the HAp-GO composite consisting of 150 mg GO has the best photocatalytic performance. As a result of the study, it was observed that GO addition increased the photodegradation capacity of HAp, and HAp-GO has a potential as a photocatalyst for CIP degradation. The effect of the amount of composite on the efficiency was investigated by adding 25, 50, 75, and 100 mg of the HAp-GO composite under the experimental conditions with the highest efficiency. In experiments with 75, and 100 mg HAp/150GO composite added, 100% yield was obtained. As the amount of photocatalyst increased, the removal efficiency increased.HAp-50 GO, HAp-100 GO, HAp-150 GO, GO and HAp were characterized by using FTIR. In addition, HAp-150 GO was characterized by using XRD, SEM, Zeta potential.