Ozgul Dere Ozdemir

Synthesis and characterization of MCM-41 with different methods and adsorption of Sr2+ on MCM-41

Mesoporous silica MCM-41 was prepared by classical and ultrasound methods as an adsorbent for the removal of Sr2+ from aqueous solution. The physical properties of the synthesized materials were investigated by X-ray diffraction and Brunauer-Emmett-Teller analysis. The results showed that MCM-41 prepared by the classical method had higher specific surface area and pore volume than those prepared by the ultrasound method. Therefore, it was selected as an adsorbent for the investigation of adsorption isotherms and kinetics. Adsorption of Sr2+ to MCM-41 was strongly dependent on pH values. Three two-parameter (Langmuir, Freundlich, and Temkin) and two three-parameter (Redlich–Peterson and Koble–Corrigan) adsorption isotherms were employed to model the equilibrium data of Sr2+ on the mesoporous adsorbent. The results indicated that the adsorption isotherm data fitted better to the Freundlich isotherm than to the Langmuir, Temkin, Redlich–Peterson, and Koble–Corrigan isotherms. The experimental data was described very well by the pseudo-second-order kinetic model.

DETERMINATION OF THE EFFECT OF LEMON ADDITION UPON ELEMENT CONCENTRATIONS IN TEA

Consumption of tea is a popular tradition in Turkey. In this article, non essential and toxic element concentrations were determined in infusions and lemon added infusions in widely consumed Turkish teas (black, earl grey, and green tea). Element concentrations were found to be in the order of aluminum > nickel > barium in black and earl grey teas. In green tea, the order was changed to aluminum > nickel > lead > barium. The concentrations of arsenic and antimony were below the detection limit of the inductively coupled plasma optical emission spectrometry method employed. The addition of lemon increased aluminum, cadmium, and lead concentrations in all teas whereas nickel concentration increased in black and green tea but decreased in earl grey. The barium concentration was same at all tea samples. In comparison with the recommended daily allowance ratios, the amount of aluminum consumed is between 13.167–24.396% in males and 17.556–32.528% in females for people who consume 200 mL of teas daily. Other elements (cadmium, lead, nickel, barium) which are a concern for tea consumption were determined and the hazard index of daily tea drinking was found to be in the safe range except for green tea with lemon addition.

The synthesis of silica-based aerogel from gold mine waste for thermal insulation

Energy consumption and increase in the greenhouse gases are very critical problem for all countries. In order to solve this problem, researches are focused on new thermal insulation materials that are the essential part of the energy-efficient buildings. Aerogels are called ‘the best thermal insulating materials’ due to their extremely low thermal conductivity. In this study, silica-based hydrophobic aerogel was synthesized by sol–gel method via ambient pressure drying. The silica source was obtained from the gold mine waste by alkali fusion method instead of using pure and expensive silica sources such as tetraethyl orthosilicate. The synthesized aerogels were used in the production of insulating plaster with different mass percentages (1, 5, 10, and 20%) and characterized by XRD, FT-IR, contact angle measurement, TG/DTA and N2 adsorption/desorption analysis. In addition, the thermal conductivity of the aerogel-based plaster was determined by using TCi thermal conductivity analysis. The results show that addition of aerogel to plaster was decreased the thermal conductivity and when the mass percentage was 20% the thermal conductivity decreases of 63% as compared to the natural plaster without aerogel.

Determination of lemon and carbonate effects on caffeine content of various teas and investigation of daily caffeine intakes / Çeşitli çayların içerdikleri kafein miktarlarına limon ve karbonatın etkisi ve günlük alım miktarlarının incelenmesi

Abstract Objective: Tea (Camellia sinensis), has been used for health field in thousands of years. Caffeine is one of the key component in tea and investigation of caffeine is a popular working subject among the researches. The novelty of this study is not only the determination of the caffeine contents of the teas, but also how addition of lemon and carbonate effects the caffeine contents. Another aim of the study is the investigation of the daily caffeine intakes from teas. Methods: Tea infusions were prepared and caffeine contents were extracted by using chloroform and determined by UV-Vis Spectrophotometer. For lemon and carbonate addition experiments, lemon was added before the caffeine analysis and carbonate was added at the beginning. Results: Maximum caffeine contents from highest to lowest were seen in black, earl grey and green in classic teas; fennel, mint and sage in herbal teas; lemon, apple and rosehip in fruit teas. With lemon addition caffeine contents were increased except green tea and with carbonate addition caffeine contents were decreased except black and fennel tea. Daily caffeine intakes are found between 32.10% (green tea with carbonate) - 77.20% (black tea with lemon), 1.85% (sage tea with carbonate) - 4.05% (fennel tea with lemon) and 2.10% (rosehip with carbonate) - 4.00% (lemon tea with lemon) in classic, herbal and fruit teas, respectively. Conclusion: The significance of this study indicates that herbal and fruit teas contain caffeine, which is assumed zero in literature. The caffeine amount of herbal teas (20.79±0.36-30.68±0.63 ppm) were found barely higher than the fruit teas (22.87±0.54-28.54±0.75 ppm) but daily maximum caffeine intakes were found less than 5%. The daily maximum caffeine intakes were found in the teas as 525.36±2.84-20.79±0.36 ppm, where lemon addition increased to 617.90±3.54-22.97±0.58 ppm and carbonate addition decreased to 488.54±2.05-16.84±0.28 ppm. Özet Amac: Çay (Camellia sinensis) binlerce yıldır sağlık alanında kullanılmaktadır. Kafein, cayın içerisindeki önemli bileşenlerden biri olup araştırmacılar arasında popüler bir calışma konusudur. Bu çalışmanın yenilikçi yönü sadece cayların icerdikleri kafein miktarlarının belirlenmesi değil aynı zamanda kafein içeriğine limon ve karbonatın nasıl etki ettiğinin incelenmesidir. Ayrıca bu çalışmanın diğer bir amacı da çaylardan alınan günlük kafein alım miktarlarının hesaplanmasıdır. Metod: Çaylar demlenip kafein miktarları kloroformla ekstrakte edilmiş ve UV/Vis spektrofotometresiyle belirlenmiştir. Limon ve karbonat eklemeli deneylerde limon, kafein analizinden önce, karbonat ise başlangıçta eklenmiştir. Bulgular: Maksimum kafein içeriği çoktan aza doğru klasik çaylardan siyah, bergamut ve yeşil çayda; bitki çaylarından rezene, nane ve ada çayında; meyve çaylarından limon, elma ve kuşburnu çayında belirlenmiştir. Limon eklenmesi yeşil çay hariç kafein miktarını arttırmış. Günlük kafein alımları %32.10 (karbonatlı yeşil çay) - %77.20 (limonlu siyah çay), %1.85 (karbonatlı ada çayı) - %4.05 (limonlu rezene çayı) ve %2.10 (karbonatlı kuşburnu çayı) - %4.00 (limonlu limon çayı) olarak sırasıyla, klasik, bitki ve meyve çaylarında bulunmuştur. Sonuç: Bu çalışmada, literatürde sıfır olarak kabul edilen kafein içeriğinin bitki ve meyve çaylarında bulunduğu gösterilmektedir. Bitki çaylarının kafein miktarları (20.79 ±0.36-30.68 ±0.63 ppm), meyve caylarına (22.87 ±0.54-28.54 ±0.75 ppm) kıyasla daha düşük olarak bulunmuş ama günlük maksimum alımlarının %5’ten duşuk olduğu belirlenmiştir. Günlük maksimum kafein alımları klasik çaylarda ve meyve çaylarında bulunmuş (525.36 ±2.84-20.79 ±0.36 ppm) olup limon eklenmesi tum cayların kafein miktarını yukseltirken (617.90 ±3.54- 22.97 ±0.58 ppm), karbonat eklenmesi tum çaylarda kafein miktarını azaltmıştır (488.54 ±2.05-16.84 ±0.28 ppm).