Phd Degree / Doktora

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Browsing Phd Degree / Doktora by Author "03.07. Department of Environmental Engineering"

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    Doctoral Thesis
    A Comparative Study of Thin-Film Coated Silicon Wafer Surfaces for Laser-Induced Breakdown Spectroscopic Analysis of Liquids
    (01. Izmir Institute of Technology, 2021-07) Aras, Nadir; Yalçın, Şerife Hanım; 03.07. Department of Environmental Engineering; 04.01. Department of Chemistry; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    Laser-Induced Breakdown Spectroscopy, LIBS, is a relatively new atomic emission spectroscopic technique that shows rapid growth due to its many special peculiarities, like its ability to provide spectral signatures of all chemical species at the same time, in all environments of solid, liquid, or gas. Liquid sample analysis by LIBS is more troublesome compared to analysis of solids. Therefore, liquid analysis by LIBS requires some pretreatment steps to be applied before direct analysis of the samples. In the literature, a variety of approaches has been successfully applied and there is still plenty of room to improve methodologies used in the liquid-LIBS analysis. The main purpose of this thesis study was to perform studies for the development of a LIBS-TARGET for sampling liquids on it, after drying, by repetitive laser pulses. With this purpose, silicon wafer-based substrates with differing surface compositions; uncoated (crystalline silicon, c-Si), oxide-coated silicon, SiO2, and nitride coated silicon, Si3N4, were tested for several experimental parameters. Within the content of this study, a fast and accurate methodology for direct analysis of aqueous samples by LIBS is proposed. This methodology has two important attributes: one is the use of the non-metal substrate, silicon wafer, for the first time for direct analysis of aqueous samples dried on, and two is the use of high energy laser pulses focused outside the minimum focal point of a plano-convex lens at which relatively large laser beam spot covers the entire droplet area for plasma formation. Si-wafer-based substrates were used for both qualitative and quantitative analysis of Cd, Cr, Cu, Mn, and Pb elements, and analytical figures of merit were determined. The analytical performance of each substrate was evaluated from the experiments performed with aqueous standards and real water samples. Silicon nitride-coated substrate has shown superior properties in terms of enhancing the LIBS signal and as low as 11 pg detection limits for Pb were obtained.
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    Doctoral Thesis
    Enzymatic Degradation of Phthalic Acid Esters
    (Izmir Institute of Technology, 2013) Baytak, Derya; Sofuoğlu, Sait Cemil; 03.07. Department of Environmental Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Endocrine disrupting compounds (EDCs) are environmental pollutants which interfere with the hormone system even at low concentrations resulting in adverse health effects on both human and wildlife. In this study, we aimed to investigate enzymatic degradation of diethylhexyl phthalate (DEHP) and diethyl phthalate (DEP) using both commercial porcine pancreas lipase and lipase from recombinant E.Coli strains that contain lipase genes from thermophilic Bacillus sp. isolated from Balçova Geotermal region in İzmir. Incubation of 20 mg/L DEHP with 20,000 U/L PPL enzyme for 7 days resulted in formation of monoethyl phthalate (MEHP), phthalic acid (PA), and dimethyl phthalate (DMP) which are the possible metabolites of DEHP. The percent decrease in DEHP (20 mg/L) was found to be 92% compared to positive control samples. In the case of DEP, about 53% decrease was obtained after incubation with 20.000 U/L for 7 days. Hydrolysis constants for DEHP ranged between 0.13 and 0.22 d-1, whereas those for DEP ranged 0.43 and 0.54 d-1. As a result of enzymatic hydrolysis of DEHP (1-20 mg/L) with 4000 U PPL enzyme, DEP was produced as hydrolysis product of DEHP after 44 h. In the case of DEP (1-20 mg/L) incubated with 4000 U crude lipase solution for 140 h, DMP was obtained as a possible product of transesterification reaction. The maximum rate (Vmax) of enzymatic hydrolysis reaction for DEHP and DEP was calculated as 0.79 mg/L.h and 1.83 mg/L.h, respectively. The Michealis-Menten constants (Km) for enzymatic hydrolysis of DEHP and DEP were calculated as 2.45 and 2.12 mg/L, respectively.
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    Doctoral Thesis
    Estimation of Exposure To Persistent Organic Pollutants and Associated Health Risks
    (01. Izmir Institute of Technology, 2024) Genişoğlu, Mesut; Genişoğlu, Mesut; Sofuoğlu, Aysun; Sofuoğlu, Sait Cemil; Sofuoğlu, Sait Cemil; Sofuoğlu, Aysun; 03.02. Department of Chemical Engineering; 03.07. Department of Environmental Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Kalıcı Organik Kirleticiler (POPs), çevresel bozunmaya karşı dirençli, uzun mesafeler boyunca taşınabilen ve organik maddelere olan yüksek afiniteleri nedeniyle çevresel ortamlarda ve gıda zincirinde biriken, küresel olarak yaygın maddeler oldukları için insan sağlığı açısından önemli riskler oluşturur. Pertikül ve hava, toprak ve hava, sedimen ve su arasında dağıldıkları için tarım ürünlerinde, etlerde ve deniz ve tatlı su ürünlerinde bulunurlar. Bu da yutma, soluma ve deri teması yoluyla maruziyete ve sağlık risklerine yol açar. Sonuç olarak, mümkün olduğunca çok sayıda POP grubunu araştırmak için kapsamlı bir tarama çalışması tasarlanmıştır. İzmir'de rastgele seçilen ev ve okullardan, iç ve dış mekan havasıyla beraber çökelmiş toz ve yemek örnekleri toplanmıştır. Ayrıca, kafe/bar/restoranlardan iç mekan çökelmiş toz örnekleri toplanmıştır. Örnekler hazırlık, ekstraksiyon ve temizleme işleminden geçirildikten sonra, PAH'lar, PCB'ler, PBDE'ler, NBFR'ler ve OPFR'lerin hedef bileşikleri GC/MS cihazıyla analiz edilmiştir. Ölçülen konsantrasyonlar ve toplanan maruziyetle ilgili anket bilgileri, USEPA maruziyet-risk modellerine girdi değişkenleri olarak kullanılarak yutma ve soluma maruziyetlerini (kronik günlük alım) Monte Carlo yöntemi kullanılarak ilgili sağlık riskleri simüle edilmiştir. Örnekleme yerleri, kentleşmenin etkisini araştırmak için kırsal, banliyö, kentsel alanlar ve bir sanayi bölgesinin rüzgaraltı yerleri arasında mekansal olarak dağıtılmıştır. Bu tez çalışması kapsamında, küresel literatüre girmiş çalışmalar arasında çevresel ve gıda örneklerinde analiz edilen bu kadar yüksek sayıda hedef POP bileşiği düzeyleri konusunda bilgi veren en kapsamlı veriseti oluşturulmuştur.
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    Doctoral Thesis
    Investigation of Bioelectrochemical Treatment Efficiency for Removal of Boron From Geothermal Waters
    (Izmir Institute of Technology, 2022-07) Gören, Ayşegül Yağmur; Ökten, Hatice Eser; Baba, Alper; 03.07. Department of Environmental Engineering; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Microbial desalination cell (MDC) is a promising technology due to its simultaneous features of electricity production, wastewater treatment, and desalination. In this thesis, boron (B) removal from geothermal water and organic matter removal from yeast wastewater with energy production was studied using a three chamber (anode/desalination/cathode) lab-scale MDC system. Among operational conditions, electrode surface area was proven to be significant on B removal efficiency. Then, anode chamber of the conventional MDC was modified to include three-dimensional (3D) cubic electrodes as a novel design. B and organic matter removal efficiencies and the produced power density results were promising for 3D-electrodes. Further studies in order to increase the efficiency of MDC system was conducted by synthesizing 3D hybrid sponge electrodes with activated carbon-chitosan (AC-CS). MDC with 3D AC-CS anode provided a higher power density of 970 mW/m2 , B removal efficiency of 75.9%, and COD removal efficiency of >90% under optimized conditions. Furthermore, phytoremediation performance of Lemna minor L. on B removal was found to be 96.7 %. Also, removal of B and heavy metals from reverse osmosis (RO) permeate and concentrate streams using RO-MDC hybrid process was studied. The performance of ROMDC system was proven to be significant on B and heavy metals removal efficiency. Lastly, feasibility of B removal from geothermal water using MDC-Donnan dialysis hybrid process was evaluated. The most important output of this study was decreased frequency for pH adjustment. Overall, MDC, being in its early levels of technology readiness, produced promising desalination and energy production results in removal of boron from geothermal brine.