Mübeccel Ergun

Application of a statistical technique to the production of ethanol from sugar beet molasses by Saccharomyces cerevisiae.

In this work, a statistical model which can be used to describe the rate of ethanol production from sugar beet molasses by Saccharomyces cerevisiae was developed. Total sugar concentration, pH, and ammonium dihydrogen phosphate (NH4H2PO4) concentration were chosen as a 23-factorial experimental design and the effects of these factors on ethanol production were examined in repeated shake flask cultures according to the Box–Wilson experimental design method. With the use of the developed model a maximum ethanol production of 1.06 g dm−3 h−1 was obtained when sugar concentration, pH, ammonium dihydrogen phosphate concentration, were 1.6 g dm−3, 4.51, 0.72 g dm−3, respectively.

The prediction of corrosion rates of reinforcing steels in concrete

Abstract The effect of chloride and acetate ions on corrosion of steel in concrete was studied. The reinforcement corrosion was evaluated by measuring the corrosion potentials and corrosion current density using linear polarization resistance technique. The initial corrosion rates (io) of reinforcing steel in concrete containing either chloride or acetate ion were found to be higher as compared to concrete without admixture. The corrosion rate is very high at early days and decreases by time.The corrosion rate vs time curves for reinforcements in all three types of concrete blocks follow the same pattern. The following exponential quantitative relation between the corrosion rate (icor) and time (Θ) was proposed: icor = i0 exp(-CΘ) where C was termed as concrete corrosion constant having a value of 1.1 × 10−3 day−1 for the types of concrete samples under consideration.

PITTING POTENTIAL AND PROTECTION POTENTIAL OF CARBON STEEL FOR CHLORIDE ION AND THE EFFECTIVENESS OF DIFFERENT INHIBITING ANIONS

Abstract The pitting potential, E p , and protection potential, E pp , have been determined for carbon steel using a potentiodynamic method. Increasing Cl − concentrations shift these potentials to more active values. The pitting potential, E pp , and protection potential, E pp , depend on the concentration of CI according to the equations: E p = a + b log [Cl − ] and E pp = a + b log [Cl − ]. The pitting potential is shifted to more noble values by the presence of other anions which do not themselves cause pitting, e.g. HPO 2− 4 , benzoate, CO 2− 3 , acetate, citrate. Sufficient concentrations of these anions act as pitting inhibitors. The following relationship has been determined between the minimum anion concentration [ l ] necessary to inhibit pitting of carbon steel and Cl − ion concentration: log [Cl − ] = a + b log[ l ]. From these equations obtained for the anions, the effectiveness of the inhibitors used in preventing pitting corrosion was in the order as listed. These results are interpreted in terms of competitive adsorption of Cl − and other anions for sites on the metal surface.

Improved Ethanol Production by Saccharomyces cerevisiae with EDTA, Ferrocyanide and Zeolite X Addition to Sugar Beet Molasses

The influence of ethylenediaminetetra acetic acid (EDTA), potassium ferrocyanide and zeolite X on ethanol production from sugar beet molasses by Saccharomyces cerevisiae was studied. For all of the three substances used, the effect was more pronounced when added to the fermentation medium rather than to the growth medium; 1·9 mmol dm−3 potassium ferrocyanide caused an increase in the final ethanol concentration of about 16·4% and 47·5% with respect to control culture on addition to growth and fermentation media respectively. The greatest stimulation in product yield was obtained with zeolite X introduced during the fermentation stage; 8·0 g dm−3 zeolite X increased ethanol concentration by 53·3%.

Mathematical model for pitting potential of Fe-16% chromium steel

Abstract The effects of chloride concentration, temperature and pH value on the pitting potential, E p , of Fe-16 Cr steel in aqueous solutions were studied by a potentiodynamic method. It was observed that the pitting potential depends linearly on the logarithm of the chloride ion concentration, decreases as the temperature increases and increases linearly with increase in pH. By taking the individual effects of these variables into consideration a mathematical model that correlates the pitting potential with simultaneous variations of Cl − concentration, temperature and pH was offered. Model parameters were found by the use of experimental data. The resultant expression is: E p = 1622 - 5.70 T - 0.004 T - 0.488 T log [Cl − ] where E p is expressed in mV, the temperature T in degrees K and the chloride concentration [Cl − ] in mol l 1 .

Investigation of pitting potential of carbon steel using experimental design method

Abstract The dependence of the pitting potential Ep of 1018 carbon steel on chloride concentration, pH and the temperature of the solution was studied by the potentiodynamic method in accordance with a statistical experimental design. The parameters of the empirical pitting potential model determined on the basis of Box-W ilson ex perimental design method were evaluated using the experimental data. Comparison of the predicted values from the model with the observed values showed that the model is a good fit. From the model equation the most noble pitting potential value of -225 mV (SCE) was obtained when the Cl- ion concentration, temperature and pH of the solution were 205 ppm, 25°C, and 6·4, respectively. The Box-Wilson experimental design technique was proved to be applicable in modelling the pitting potential of carbon steel.

Saccharomyces cerevisiae İLE REMAZOL SARI (RR) BOYASININ KESİKLİ SİSTEMDE BİYOSORPSİYONU

DOI: Bu çalışmada Remazol Sarı (RR) tekstil boyasının giderimi ısıl işlemle ölü forma getirilmiş Saccharomyces cerevisiae ile kesikli sistemde pH, sıcaklık, başlangıç boya ve biyosorbent konsantrasyonu gibi çeşitli parametrelere bağlı olarak incelenmiştir. pH=2; C0= 400 ppm; Cb= 2 g/L; T=25°C; karıştırma hızı=140 rpm koşullarında maksimum %88 giderim ve 163 mg/g biyosorpsiyon kapasitesine ulaşılmıştır. Biyosorbente EtOH ve NaCl ile ön işlem yapılarak biyosorpsiyon deneyleri gerçekleştirilmiş ve ön işlemin biyosorpsiyon performansı üzerinde olumlu bir etkisi gözlenmemiştir. Desorpsiyon çalışmaları sonucunda 0,5 M NaOH ile %36,5 ve pH değeri 8’e ayarlı su ile %1,5 desorpsiyon verimine ulaşılmıştır. Elde edilen deneysel veriler Langmuir, Freundlich, Temkin ve Harkins-Jura izoterm modellerine uygulanarak sistemi en iyi Langmuir izoterm modelinin tanımladığı belirlenmiştir. Biyosorpsiyon kinetiği ise ikinci derece kinetik model ile uyumludur. Biyosorpsiyon prosesine ait termodinamik parametreler ΔH=25,3 kj/mol ve ΔS=52 j/molK olarak bulunurken biyosorpsiyon prosesinin endotermik olduğu belirlenmiştir. Karakterizasyon çalışmaları kapsamında Saccharomyces cerevisiae için biyosorpsiyon öncesi ve sonrası FTIR ve SEM analizi yapılarak biyosorpsiyon mekanizmasındaki fonksiyonel gruplar incelenmiş ve biyosorpsiyon sonrası oluşan yapısal değişikliklerin varlığı görülmüştür. 10.17341/gazimmfd.278452