A self-powered photoelectrochemical biosensor for H2O2, and xanthine oxidase activity based on enhanced chemiluminescence resonance energy transfer through slow light effect in inverse opal TiO2

TiO2 inverse opal photonic crystals (IOPCs) were fabricated by using polystyrene template. TiO2 IOPCs based photoelectrochemical (PEC) biosensor was fabricated for the precise and stable detection of Heme without external irradiation. Then, the sensitization of TiO2 IOPCs was fulfilled with CdS quantum dots (QDs) by SILAR method to form ITO-TiO2 IOPCs-CdS:Mn electrode, which in turn was used to construct a PEC biosensor. The uniform porous structure of IOPCs with a large surface area is conducive to the excellent electronic transmission and QDs deposition. Also, the energy level matching between the conduction bands of CdS QDs and TiO2 IOPCs widened the range of light absorption, allowing for electron injection from excited CdS QDs to TiO2 upon luminol chemiluminescence, which enhanced the photocurrent. Furthermore, when the red edge of the photonic stop band of TiO2 IOPCs overlapped with the band gap of TiO2, and chemiluminescence emission of luminol, a substantial photocurrent increment was observed due in part to the slow light effect. The biosensor possesses a large linear detection range of 0.063-4 mM with a LOD of 19 mu M for H2O2. Also, xanthine oxidase activity was determined with a linear measurement range of 0.01-15 mU/mL. Our strategy opens a new horizon to IOPCs based and QDs sensitized PEC sensing, which could be more sensitive, convenient and inexpensive for clinical and biological analysis. As far as we know, the largest photocurrent generation by luminol chemiluminescence was observed thanks to the use of semiconducting hybrid IOPCs material even at 0 V

Contact time optimization of two-stage batch adsorber design using second-order kinetic model for the adsorption of phosphate onto alunite

The adsorption of phosphate onto alunite in a batch adsorber has been studied. Four kinetic models including pseudo first- and second-order equation, intraparticle diffusion equation and the Elovich equation were selected to follow the adsorption process. Kinetic parameters, rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the adsorption of phosphate onto alunite could be described by the pseudo second-order equation. Adsorption of phosphate onto alunite followed the Langmuir isotherm, A model has been used for the design of a two-stage batch adsorber based on pseudo second-order adsorption kinetics. The model has been optimized with respect to operating time in order to minimize total operating time to achieve a specified amount of phosphate removal using a fixed mass of adsorbent. The results of two-stage batch adsorber design studies showed that the required times for specified amounts of phosphate removal significantly decreased. It is particularly suitable for low-cost adsorbents/adsorption systems when minimising operating time is a major operational and design criterion, such as, for highly congested industrial sites in which significant volume of effluent need to be treated in the minimum amount of time. (c) 2006 Elsevier B.V. All rights reserved

Alunit cevherinin kalsinasyon ve alkali ortamda liç kinetiği

Bu tezin, veri tabanı üzerinden yayınlanma izni bulunmamaktadır.ÖZET Anahtar kelimeler: Alunit, alumina, kalsinasyon kinetiği, Uç, liç kinetiği. Bu çalışmada Şaphane alunit cevherinin kalsinasyon ve sodyum hidroksit çözeltisindeki liç kinetiği incelenmiştir. Çalışmalarda, kalsinasyon sıcaklığı, kalsinasyon süresi, alkali derişimi, reaksiyon sıcaklığı, reaksiyon süresi, tane boyutu, kati/sıvı oranı gibi paramatreler değiştirilmiş ve çözeltiye geçen alüminyum miktarı izlenerek, kinetik modeller ortaya konulmuştur. Çalışma sonunda, alunit cevherinin 973 K de 120 dakika süre ile kalsine edilmesi, çözelti olarak 9 M NaOH kullanılması, tane boyutunun -90/mı olması, kati/sıvı oranının 3 g/ 100 mi olması, reaksiyon sıcaklığının 383+5 K ve reaksiyon süresinin 60 dakika olması durumunda cevherdeki alüminyumun %99.66 oranında çözelti fazına alındığı bulunmuştur. Alunitin kalsinasyon reaksiyonunun, yüzey reaksiyonu ile kontrol edilen, heterojen bir reaksiyon olduğu ve heterojen reaksiyonun aktivasyon enerjisinin 95.52 kJ/mol olduğu bulunmuştur. Alunitteki alüminyumun liç işlemi reaksiyonunun, ürün katmanında difüzyon kontrollü heterojen bir reaksiyon olduğu ve heterojen reaksiyonun aktivasyon enerjisinin 21.31 kJ/mol olduğu bulunmuştur. Liç işleminde reaksiyonların 60 dakikadan daha fazla sürdürülmesi durumunda cevherden Si02 in de çözünmeye başladığı ve çözeltiye geçen aluminanm sodyum alüminyum silikat şeklinde çöktüğü bulunmuştur. Reaksiyonlara 60 dakikadan fazla devam edilmemesi gerektiği tesbit edildiğinden kinetik değerlendirmeler 60 dakikaya kadar yürütülen reaksiyonlar için yapılmıştır. xııCALCINATION AND LEACHING KINETICS OF ALÜNTTE ORE IN ALKALINE MEDIA Key words: Alunite, alumina, calcination kinetics, leaching, leaching kinetics. In this study, the calcination and leaching kinetics, in NaOH solution, of Şaphane alunite ore has been investigated. In experiments the parameters such as calcination temperature, calcination time, alkaline concentration, reaction temperature and period, particle size, solid/liquid phase ratio have been varied and some kinetic models have been tested in tracing the aluminium quantity which passes on to the solution. In the end of study, 99.66% aluminium in the ore has been taken to the solution in the following conditions. These are: the calcination of alunite ore at 973 K for 2 hours, 9 M NaOH solution, particle size of -90 /jm, solid/liquid ratio of 3 g/100 ml, reaction temperature of 373+5 K and reaction duration of 60 minutes. Alunite calcination reaction is the one that is controlled by surface reaction and also heterogeneous one, and its activation energy is found to be of 95.52 kJ/mol. It is also found that the leaching process that is the diffusion-controlled reaction in the product layer and its activation energy being 21.3 1 kJ/mol. In case of maintaining the reaction in the leaching process over 60 minutes, it is found that silica (SiO^ in the ore starts to dissolve, and alumina, that passes on to the solution, precipitates as sodium aluminium silicate. Since it has been verified that reactions would not be continued over 60 minutes kinetic evaluations have been made for the reactions that are conducted up to 60 minutes. x

Influence of silver on the catalytic properties of the cryptomelane and Ag-hollandite types manganese oxides OMS-2 in the low-temperature CO oxidation

Manganese oxide octahedral molecular sieves (OMS) are important materials in environmental chemistry, electrochemistry, and heterogeneous catalysis. Cryptomelane and Ag-hollandite type manganese oxides (OMS-2) were synthesized by microwave-reflux and hydrothermal methods, respectively. In this current study, silver doping of cryptomelane and Ag-hollandite was performed using both UV irradiation and KBH4 reduction methods. The formation process, particle size, crystallite size, crystal structure, and properties of these nanomaterials were characterized by powder X-ray diffraction, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and nitrogen sorption. Studies by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) showed that the produced OMS-2 have a nanofiber structure. The produced catalysts showed high activity, as high as 100% in the low-temperature CO oxidation at 140 degrees C. The catalysts doped with silver by KBH4 reduction method showed higher activities than other doping methods and template catalysts. In longtime stability tests, 80% CO conversion can be maintained for 26 h at 120 degrees C. The high activities, and stabilities of the Ag/K-OMS-2-KBH and Ag/Ag-OMS-2-KBH were attributed to the stable presence of Ag-0 and Ag+ species and the unique morphologies of the cryptomelane and Ag-hollandite nanofibers. CO oxidation is believed to follow the Mars-van Krevelen mechanism via the Ag+ - O2- - Mn4+ Ag-0 - Mn3+ + O-2 redox reaction. (C) 2013 Elsevier B.V. All rights reserved

Adsorption of phosphate from aqueous solution onto alunite

The phosphate removal potential of alunite, a low cost and abundantly available material, has been investigated. The effects of calcination temperature and time of alunite, adsorbent particle size, pH and initial phosphate, concentration on the phosphate adsorption by the calcined alunite have been studied. Phosphate removal was seen to increase with increasing calcination temperature, decreasing adsorbent particle size and pH. Adsorption of phosphate followed first-order rate kinetics. Langmuir and Freundlich adsorption isotherm constants and correlation coefficients were calculated and compared. It was concluded that the adsorption data of phosphate onto calcined alunite fitted to the Langmuir model more than Freundlich model. Specific surface areas of the calcined alunite were calculated at different calcination temperatures and particle sizes. (C) 2003 Elsevier Science Ltd. All rights reserved

Phosphate adsorption characteristics of alunite to be used as a cement additive

The adsorption of phosphate from aqueous solution by alunite has been investigated as a function of calcination temperature, particle size, pH, agitation time and initial phosphate concentration. Phosphate adsorption was seen to increase with increasing calcination temperature, decreasing adsorbent particle size and pH. The adsorption isotherm data were fitted to the Langmuir isotherm. The alunite exhibited the highest phosphate uptake capacity at 1073 K calcination temperature, at a particle size of 90-150 mum, at the initial pH of 5.0, at an equilibrium time of 60 min and at the initial phosphate concentration of 20 x 10(-4) mol/l. The adsorption capacity, Q, was 4.697 x 10(-3) mol/g at initial pH 5.0. (C) 2003 Elsevier Ltd. All rights reserved

Meşe palamutundan (Valonia) elde edilen Tanin’in su arıtımında doğal polieloktrolit olarak kullanılması üzerine bir araştırma

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Doğal polielektrolit, sentetik polielektrolit, tanin, AN913, alüminyum sülfat, koagülasyon, flokülasyon, bulanıklık giderilmesi, fosfat giderilmesi. Bu çalışmada, doğal polielektrolit olan taninin su arıtımında koagülant ve flokülant yardımcısı olarak kullanılıp kullanılamayacağı araştırılmıştır. Bu maksatla, tanin koagülasyon ve flokülasyon prosesine tatbik edilmiş ve elde edilen sonuçlar alüminyum sülfat ve sentetik polielektrolit AN913 ile mukayese edilmiştir. Farklı bulanıklık ve pH değerlerindeki su numuneleri üzerinde tanin, AN913 ve alüminyum sülfat ile yapılan deneylerde elde edilen supernatant bulanıklığı ve koagülant dozları arasındaki ilişkiler pH ya göre incelenmiştir. Optimum dozlarda karıştırma hızının ve süresinin etkisi incelenmiştir. Optimum deney şartlarında bulanıklık gidermeye çeşitli iyonların etkileri incelenmiş ve tanin ile bulanıklık gidermeye bilhassa Mg2+ ve Fe iyonlarının etkili olduğu bulunmuştur. Farklı bulanıklıktaki sentetik su numuneleri üzerinde A12(S04)3 - tanin ve Aİ2(S04)3 - AN913 ile yapılan deneylerde bulunan supernatant bulanıklığı ve flokülant yardımcısı dozları arasındaki ilişkiler incelenmiştir. Ekonomik açıdan da mukayese yapılarak; Aİ2(S04)3 - tanin karışımının, alüminyum sülfattan ~ %50 ve Aİ2(S04)3 - AN913 ten ~ %25 daha ucuz olduğu gösterilmiştir. Sağlık açısından da A12(S04)3 - taninin kullanılmasının, A12(S04)3 ve AN913 karışımından daha yararlı olduğu belirlenmiştir. Ayrıca, üç koagülantın ve flokülant yardımcılarının optimum dozlarda meydana getirdikleri çamurların özgül dirençleri, flok ilk oluşum zamanlan ve çökme hızlan da incelenmiştir. Gerek bulanık sudan süspansiyonla birlikte ve gerekse bulanık olmayan sudan tek başına fosfatın giderilmesi incelenmiştir. Farklı miktarlarda fosfat ihtiva eden süspansiyonlardan bulanıklığın giderilmesinde; düşük bulanıklıklarda Aİ2(S04)3 in etkili, yüksek bulanıklıklarda A12(S04)3, A12(S04)3 - tanin ve A12(S04)3 - AN913 ün benzer sonuçlar verdiği bulunmuştur. Bulanık sulardan fosfat gidermede ise A12(S04)3 m etkili olduğu bulunmuştur. Ancak ikili kullanımlarda, tanin ve AN913 ün, benzer davranış göstererek A12(S04)3 tan daha iyi sonuçlar verdikleri belirlenmiştir. Bulanıklık içermeyen sulardan fosfat gidermenin Al2(S04)3 miktarı ile ilişkili ve A12(S04)3 m polielektrolitlerden daha etkili olduğu tesbit edilmiştir. Yine ikili kullanımlarda, polielektrolitlerin, A12(S04)3 tan daha iyi neticeler verdiği bulunmuştur.A STUDY ON THE USE OF TANNINS, OBTAINED FROM OAK ACORNS (VALONIA), AS NATURAL POLYELECTROLYTE IN WATER TREATMENT SUMMARY Keywords: Natural polyelectrolytes, synthetic polyelectrolytes, tannin, AN913, aluminium sulphate, coagulation, flocculation, turbidity removal, phosphate removal. In this study, it was investigated whether or not a tannin, a natural polyelectrolyte, can be used as a coagulant and flocculant aid in the water treatment process. For this purpose, tannin was coagulated and flocculated and thus the results obtained were compared with aluminium sulphate and synthetic polyelectrolyte AN913. The relation between supernatant turbidity and coagulant dosage obtained from the experiments done on the water samples which have different turbidity and pH with tannin, AN913 and aluminium sulphate was investigated according to pH level. The effect of stirring velocity and time were investigated for the optimum dosage. At the optimum experimental conditions the effects of various ions on turbidity was investigated and it was shown that Mg2+ and Fe3+ions were effective in the removal of turbidity by tannin. The relation between supernatant turbidity and flocculant aid dosage found from the experiments carried out with Aİ2(S04)3 - tannin and Aİ2(SC>4)3 - AN913 on synthetic water samples which have different turbidity was investigated. Economically, it was shown that Aİ2(S04)3 - tannin was 50% cheaper than Aİ2(SC>4)3 and was 25% cheaper than A12(S04)3 - AN913. For human health purposes A12(S04)3 - tannin usage was recommended when compared with Aİ2(S04)3 and AN913. And also the sludge specific resistance,time first floe and settling rate were investigated for three coagulant and for flocculant aid dosage at optimum dosage. The removal of phosphate from turbidity water with suspension and that from non- turbidity water was investigated. For low turbidity water, to remove turbidity from suspansions including phosphate, A12(S04)3 was shown to be effective. For high turbidity water the effects of A12(S04)3, A12(S04)3 - tannin and A12(S04)3 - AN913 were the same. To remove phosphate from turbidity water, it was seen that Aİ2(SC>4)3 was effective. However, when tannin and AN913 were used with A12(S04)3 respectively shown that those were better than the results obtained from single usage ofA]2(S04)3. xlv