Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 2Citation - Scopus: 4Use of Electrospun Fiber Mats for the Remediation of Hypersaline Geothermal Brine(Desalination Publications, 2017) Çelik, Aslı; Koç, Gonca; Erdoğan, Emre; Shahwan, Talal; Baba, Alper; Demir, Mustafa MuammerGeothermal brines display high contents of various metal ions that can adversely affect surface and groundwater resources. Nevertheless, it is possible to sequestrate these metals and use some of them in certain engineering applications. The aim of this study was to fabricate electrospun chitosan fiber mats and remove heavy metal cations from geothermal brine of the Tuzla geothermal field (TGF) by employing these mats. TGF is located on the Biga Peninsula in the northwestern part of Turkey. The brine of TGF has high salinity (EC > 91 mS/cm) and high temperature (reservoir temperature is 173°C). The brine is rich in terms of metal cations. For instance, the concentration of lithium ion in geothermal fluid ranges from 17 to 35 mg/L, with little seasonal variations. A horizontal electrospinning setup was employed to obtain a non-woven mat comprising submicron diameter chitosan fibers at 2.0 kV∙cm−1. This material was then utilized as a stable membrane for the removal of metal ions present in the brine through sorption at 25°C overnight. The results showed that the chitosan fiber mats sequestrate various ions in the brine. Under the studied conditions, the material was capable of removing 46%, 44%, 50%, 44%, 40%, 67% and 48% of Li+, Mg2+, Ba2+, Sr2+, Mn2+, Ca2+ and K+ from the geothermal brine, respectively.Article Citation - WoS: 23Citation - Scopus: 23Use of Polyethylene Glycol Coatings for Optical Fibre Humidity Sensing(Springer Verlag, 2008) Açıkgöz, Sabriye; Bilen, Bukem; Demir, Mustafa Muammer; Menceloğlu, Yusuf Z.; Skarlatos, Yani; Aktaş, Gülen; İnci, Mehmet N.Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystalline structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed.