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Öğe Bitkisel kökenli maddenin toprak temizlenmesinde kullanılabilirliğinin araştırılması(Bursa Teknik Üniversitesi, 2017) Karataş, Okan; İşleyen, MehmetKalıcı organik kirleticiler, toprağın yapısında çok uzun ömürlü ve besin zinciri boyunca biyoakümülasyon potansiyeli olan kirleticiler olarak tanımlanmışlardır. DDT (2,2-bis(klorofenil)-1,1,1-trikloroetan) 1960-1970'li yıllarda küresel çapta en çok kullanılan böcek öldürücülerden biridir ve 1985'te yasaklanıncaya kadar Türkiye'de yaygın bir şekilde uygulanmıştır. p,p'-DDT, toprakta abiyotik ve biyotik olarak 2,2 bis(klorofenil)-1,1- dikloroetane (p,p'-DDD) ve 2,2- bis(klorofenil)-1,1-dikloroetilen (p,p'-DDE)'e parçalanabilmektedir. p,p'-DDT ve dönüşüm ürünleri kalıcı organik kirleticiler olarak sınıflandırılmıştır ve toprak ile sedimente kuvvetle bağlanmaktadırlar. DDT ve chlordane aşırı derecede hidrofobik organoklorlu bileşikler olup (log Kow>5) zaman içerisinde toprağın yapısında hızlıca bağlanmaktadır ve biyolojik olarak kullanımı azalmaktadır. Fitoremediasyon dışında ki yerinde arıtım teknolojileri, zor ve yeterince verimli değildirlerdir. Ancak kirli topraklarda organik değişiklikler yapabilmek için ucuz, tercih edilen ve yüksek derecede etkili yeni bir remediasyon teknolojisine ihtiyaç duyulmaktadır. Bitkisel bazlı maddenin topraktaki p,p'-DDE'nin desorpsiyonunu değerlendirmek için bir dizi batch ve leachate deneyleri gerçekleştirilmiştir. Çözünme deneylerinde 8 gram p,p'-DDE ile kirlenmiş toprağın olduğu tüplere 0,8 gram BKM ve 150 mililitre safsu eklenmiştir. Kapakları kapalı bir şekilde 6 gün boyunca karıştırıcı tabla üzerinde karışan numunelere sıvı sıvı ekstraksiyon yapılmış ve sıvı fazlardaki p,p'-DDE miktarları GC/ECD ile ölçülmüştür. Sıvı fazdaki ortalama p,p'-DDE konsantrasyonu, kontrol deneylerine kıyasla BKM eklentisi ile 38 kat artmıştır. BKM içeren solüsyon ile yıkanan toprak numunelerinde %46'lık bir p,p'-DDE giderimi gözlemlenmiştir. Leachate deneyleri ise 500 ml'lik ayırma hunilerinde yakılmış cam boncuklar, kum ve 8 gram toprak ile yapılmıştır. 150 ml saf suyun bu faz içerisinden geçişi sağlanmıştır. Sonuçlara göre 0,8 gram BKM eklenen numuneler ile %14 p,p'-DDE giderim verimleri gözlemlenmiştir. BKM ile p,p'-DDE giderimine ilişkin daha fazla araştırmanın yapılması gerekmektedir.Öğe High-performance carbon black electrode for oxygen reduction reaction and oxidation of atrazine by electro-Fenton process(Elsevier, 2021) Karataş, Okan; Gengec, Nevin Atalay; Gengec, Erhan; Khataee, Alireza; Kobya, MehmetThe aim of this study is to produce an electrode that can be used in H2O2 production and Electro-Fenton (EF) process by an effective, cheap, and easy method. For this reason, a superhydrophobic electrode with a higher PTFE ratio and high thickness was produced with a simple press. The produced electrode was used in the production of H2O2 and mineralization of Atrazine. First, the effect of pH, cathode voltage, and operation time on H2O2 production was evaluated. The maximum H2O2 concentration (409 mg/L), the highest current efficiency (99.80%), and the lowest electrical energy consumption (3.16 kWh/kg) were obtained at 0.8 V, 7.0 of pH, and 120 min, and the stability of the electrode was evaluated up to 720 min. Then, the effects of the operational conditions (pH, cathode voltage, operating time, and catalyst concentration) in electro-Fenton were evaluated. The fastest degradation of Atrazine (>99%) was obtained at 2.0 V, 3.0 of pH, and 0.3 mM of Fe2+ in 15 min. In the final part of the study, the degradation intermediates were identified, and the characterization of the electrode was evaluated by SEM, XRD, FT-IR, tensiometer, potentiostat, and elemental analyzer.Öğe Peroxydisulfate activation by in-situ synthesized Fe3O4 nanoparticles for degradation of atrazine: Performance and mechanism(Elsevier, 2020) Keyikoğlu, Ramazan; Karataş, Okan; Khataee, Alireza; Kobya, Mehmet; Can, Orhan Taner; Soltani, Reza Darvishi CheshmehHerein activation of persoxydisulfate (PDS) was achieved by in-situ synthesized Fe3O4 nanoparticles (NPs) from a sacrificial iron anode in an electrochemical (EC) cell. The as-synthesized Fe3O4 NPs were characterized to be in spherical and in the nano size. The performance of the process, EC-Fe3O4/PDS, was investigated in terms of atrazine (ATZ) degradation. Optimum process conditions were determined as initial pH of 5, electrolyte (Na2SO4) concentration of 1 mM, a current density of 1.67 A m(-2), PDS concentration of 0.5 mM and initial ATZ concentration of 10 mg L-1. At optimum conditions, the EC-Fe3O4/PDS process could effectively degrade 80% of ATZ in an aqueous solution within a short reaction time of 20 min. The electrical energy consumption of the process was found to be quite low with 0.0307 kWh/m(3). Based on the LC/MS analysis, the degradation pathway of ATZ with seven transformation products was proposed. Finally, a possible mechanism of the EC-Fe3O4/PDS process was put forward, which includes the activation of PDS and the role of radicals in the degradation of ATZ. In conclusion, the combination of Fe3O4 NPs catalyzed PDS oxidation with the EC process was very effective in the degradation of ATZ to dechlorinated final products. The strong synergistic effect makes this process superior to conventional methods due to the high degradation efficiency with low electrical energy and chemical consumption. Application of this method, with very low current density, may not only minimize the electrical energy consumption but also help reduce the sludge production due to the lower iron dissolution.Öğe Removal of ammonium ions by capacitive deionization and membrane capacitive deionization units(Desalination Publ, 2017) Sakar, Hacer; Karataş, Okan; Canbolat, Cigdem Balcik; Keskinler, Bulent; Karagunduz, AhmetIn this study, capacitive deionization (CDI) and membrane capacitive deionization (MCDI) unit cells were used to remove NH4+ ions. The influences of operating parameters such as the applied voltage, the initial ammonium concentration and the flow rate on the effectiveness of ammonium removals were investigated. In addition, the effects of different membrane types on MCDI performances were also studied. The results showed that, the electrosorption performances of CDI and MCDI increased by increasing the initial concentration, flow rate and the applied potential. It was observed that the adsorption capacity of MCDI unit was much higher than that of CDI due to the presence of ion-exchange membranes. MCDI technology may provide better advantages on ammonium removal.Öğe A review on dendrimers in preparation and modification of membranes: progress, applications, and challenges(Elsevier, 2021) Karataş, Okan; Keyikoğlu, Ramazan; Gengec, N. Atalay; Vatanpour, V.; Khataee, A.Although membrane technologies have been used for different purposes because of their selective permeability and suitability for modifications, fouling is the most important limiting parameter. Intensive research is being conducted to solve the membrane fouling problem, and in this context, dendrimers, as a macromolecule, have attracted wide interest with their unique chemical and structural properties. This review provides a comprehensive overview of the production methods, challenges, and applications of dendrimer-modified membranes. Modification methods include grafting, coating, and addition of dendrimers as a hydrophilic additive. These modifications, especially using polyamidoamine dendrimers, have improved separation performance, selectivity, and antifouling properties in microfiltration, ultrafiltration, reverse osmosis, forward osmosis, nanofiltration, and gas separation membranes. We also highlight the use of various nanomaterials in membrane modifications along with dendrimers because of the different structures and properties they can offer. Finally, the development prospects and key challenges of the dendrimer-modified membranes are briefly discussed.
