Farklı fonksiyonel gruplara sahip polimerik nanofiberlerin arsenik gideriminde kullanılması
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Dosyalar
Tarih
2019
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Bursa Teknik Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Son yüzyılda hızlı nüfus artışı ile ortaya çıkan talep ve ihtiyaçların karşılanması için yapılan yoğun endüstriyel ve tarımsal faaliyetler su kaynaklarının kirlenmesine ya da tüketilmesine neden olmuştur. Bu nedenlerden dolayı yetersiz kalan su kaynaklarına alternatif olarak, yerkabuğunun yapısından gelen arsenik ve diğer ağır metaller gibi kirleticileri barındıran jeotermal bölgelerdeki yer altı suyu kullanımına yönelinmiştir. Kirleticiler içinde toksisitesi en yüksek metal olan arseniğin sulara doğal, endüstriyel ve tarımsal kaynaklı karışabilmesi sularda görülme sıklığını artırmış bunun sonucu olarak da arseğin sulardan uzaklaştırılmasını öncelikli hale gelmiştir. Yerkabuğunda en çok bulunan 20. element olan arsenik, element olarak düşük oksijenli ve düşük sülfürlü ortamlarda nadiren bulunur, buna karşın 10 tanesi yaygın olmakla birlikte 320'den fazla minerali bulunmaktadır. Bu mineraller elementel arsenik, arsenidler, arsenosülfitler, arsenitler ve arsenatlar olarak gruplandırılabilirler. Doğal sularda oksidasyon redüksiyon potansiyeline ve pH'a bağlı olarak farklı değerliklerde olmak üzere arsenit veya arsenat formunda bulunabilir. Arsenit formu arsenata göre çok daha zehirli olan arseniğin vücutta birikim yapabilme özelliği insan sağlığı için büyük bir tehdittir. Arsenik, insan sağlığı üzerinde düşük miktarlarda maruz kalınsa dahi uzun süreli kronik toksisiteye veya yüksek miktarlarda kısa süreli akut toksisiteye neden olabilir. Sulardan arsenik uzaklaştırma yöntemleri oksidasyon, koagülasyon, membran arıtma, iyon değişimi ve adsorpsiyon yöntemlerinden oluşur. Bu yöntemler içinde adsorpiyon diğerlerine göre daha ekonomik ve kullanışlı bir yöntemdir. Adsorpsiyon yönteminde adsorbent olarak aktif karbon, kil, zeolitler, kırmızı çamur, uçucu kül, kömür, bisorbentler ve polimerler gibi malzemeler kullanılır. Bu malzemeler arsenik gideriminde yeterince verimli olmadığı için daha yüksek yüzey alanına sahip nano malzemeler alanında araştırmalar yoğunlaşmıştır. Nanofiber membranlar arsenik giderimi sonrasında toksik atık oluşturmamaları, düşük maliyetli olmaları, verimli ve hızlı adsorpsiyon gerçekleştirme özellikleri mevcut arsenik giderme yöntemlerine üstünlük sağlamaktadır. Bu tez çalışmasında elektrospin yöntemi ile üretilen Poliakrilonitril (PAN), Polianilin (PANİ), Poliüretan (PU) nanofiber membranların sudan ağır metalleri giderme verimleri incelenmiştir. Hazırlanan nanofiberler SEM, TEM, FTIR ve TGA ile karekterize edilmiştir. Öncelikle farklı pH'lara sahip sulu arsenik çözeltileri hazırlanarak PAN ve PANİ için optimum pH 6,5, PU için optimum pH 7,5 değeri bulunmuştur. Daha sonra PAN, PANİ ve PU nanofiberlerin 0,25 mg/L, 0,5 mg/L, 1 mg/L, 2 mg/L, 3 mg/L arsenik derişimine sahip çözeltiler kullanarak 10 oC, 20 oC ve 30 oC sıcaklıklardaki adsorpsiyon kapasitesi tespit edilmeye çalışılmıştır. PAN, PANİ ve PU nanofiberler için 30 oC'de 0,25 mg/L arsenik derişimine sahip çözelti ile yapılan deneylerde bu değerler sırasıyla 49,18 mg As+5/g, 52,55 mg As+5/g, 28,73 mg/g As+5/g bulunmuştur. Sıcaklık artması ve başlangıç derişiminin azalması ile arsenik giderim veriminin arttığı tespit edilmiştir. Langmuir, Freundlich, Dubinin–Radushkevich (D-R) ve Temkin izoterm modellerinden PAN ve PU nanofiber Langmuir, PANİ nanofiber ise D-R izoterm modeline uygun adsorpsiyon gerçekleştirdiği tespit edilerek adsopsiyon mekanizmaları anlaşılmaya çalışılmıştır.
Intense industrial and agricultural activities to meet the demands and requirements arising from rapid population growth in the last century have caused pollution or depletion of water resources. Therefore using of groundwater that contains arsenic and other heavy metals in geothermal regions as an alternative to insufficient water resources from inside of geothermal regions of the Earth's crust was pursued. Arsenic, which has the highest toxicity among pollutants, can contaminate water sources via natural, industrial, and agricultural means, herewith, the existence of the arsenic in the water have been increased, hence, it has become a priority to remove arsenic from water. Arsenic, which is the 20th most common element in the Earth's crust, is rarely found as an element in low-oxygen and low-sulfur environments. Though it has more than 320 minerals, 10 of which are commonly encountered. These minerals can be grouped into elemental arsenic, arsenides, arsenosulfites, arsenites and arsenates. It can be seen as arsenite and arsenate forms in varying atomic valency values depend on the oxidation-reduction potential and pH of natural waters. Ability of the arsenic, whose arsenite form is more toxic than arsenate, to be accumulated in the body poses a significant threat to human health. Arsenic may lead to long-term chronic toxicity even if one is exposed to low amounts of it, or short-term acute toxicity with exposure of high quantities. Metods for removing arsenic from water consist of oxidation, coagulation, membrane purification, ion exchange and adsorption. Among these, adsorption is more cost-efficient and useful. In the adsorption method activated carbon, clay, zeolites, red mud, fly ash, coal, bisorbents and polymers are used as adsorbents. Since these materials are not efficient enough for arsenic removal, research has been focused on nanomaterials that have larger surface area. Nanofiber membranes are superior from available arsenic removal methods regarding some properties such as creating no toxic waste after arsenic removal, low costing, efficiency and fast adsorption. In this study, the efficiencies removing heavy metals from water of polyacrylonitrile (PAN), polyaniline (PANI), polyurethane (PU) nanofiber membranes with electrospinning method were investigated. The nanofibers were characterized by SEM, TEM, FTIR and TGA. Firstly, arsenic solutions in different pHs were prepared and optimum pH were found as 6.5 for PAN and PANI and 7.5 for PU. Then, adsorption capacity of PAN, PANI and PU nanofibers at 10 oC, 20 oC ve 30 oC temperatures was determined using arsenic solution at 0,25 mg/L, 0,5 mg/L, 1 mg/L, 2 mg/L, 3 mg/L concentrations. The values of PAN, PANI and PU nanofibers at 30 oC temperature and 0,25 mg/L concentrations were found 49,18 mg As+5/g, 52,55 mg As+5/g, 28,73 mg/g As+5/g, respectively. It has been found that arsenic removal efficiency was increased with rising the temperature and decreasing the initial concentration. The adsorption mechanisms have been clarified by determined that PAN ve PU nanofiber execute the adsorption fit in with Langmuir, whereas PANI nanofiber execute the adsorption fit in with D-R isotherm model among Langmuir, Freundlich, Dubinin – Radushkevich (D-R) and Temkin isotherm models.
Intense industrial and agricultural activities to meet the demands and requirements arising from rapid population growth in the last century have caused pollution or depletion of water resources. Therefore using of groundwater that contains arsenic and other heavy metals in geothermal regions as an alternative to insufficient water resources from inside of geothermal regions of the Earth's crust was pursued. Arsenic, which has the highest toxicity among pollutants, can contaminate water sources via natural, industrial, and agricultural means, herewith, the existence of the arsenic in the water have been increased, hence, it has become a priority to remove arsenic from water. Arsenic, which is the 20th most common element in the Earth's crust, is rarely found as an element in low-oxygen and low-sulfur environments. Though it has more than 320 minerals, 10 of which are commonly encountered. These minerals can be grouped into elemental arsenic, arsenides, arsenosulfites, arsenites and arsenates. It can be seen as arsenite and arsenate forms in varying atomic valency values depend on the oxidation-reduction potential and pH of natural waters. Ability of the arsenic, whose arsenite form is more toxic than arsenate, to be accumulated in the body poses a significant threat to human health. Arsenic may lead to long-term chronic toxicity even if one is exposed to low amounts of it, or short-term acute toxicity with exposure of high quantities. Metods for removing arsenic from water consist of oxidation, coagulation, membrane purification, ion exchange and adsorption. Among these, adsorption is more cost-efficient and useful. In the adsorption method activated carbon, clay, zeolites, red mud, fly ash, coal, bisorbents and polymers are used as adsorbents. Since these materials are not efficient enough for arsenic removal, research has been focused on nanomaterials that have larger surface area. Nanofiber membranes are superior from available arsenic removal methods regarding some properties such as creating no toxic waste after arsenic removal, low costing, efficiency and fast adsorption. In this study, the efficiencies removing heavy metals from water of polyacrylonitrile (PAN), polyaniline (PANI), polyurethane (PU) nanofiber membranes with electrospinning method were investigated. The nanofibers were characterized by SEM, TEM, FTIR and TGA. Firstly, arsenic solutions in different pHs were prepared and optimum pH were found as 6.5 for PAN and PANI and 7.5 for PU. Then, adsorption capacity of PAN, PANI and PU nanofibers at 10 oC, 20 oC ve 30 oC temperatures was determined using arsenic solution at 0,25 mg/L, 0,5 mg/L, 1 mg/L, 2 mg/L, 3 mg/L concentrations. The values of PAN, PANI and PU nanofibers at 30 oC temperature and 0,25 mg/L concentrations were found 49,18 mg As+5/g, 52,55 mg As+5/g, 28,73 mg/g As+5/g, respectively. It has been found that arsenic removal efficiency was increased with rising the temperature and decreasing the initial concentration. The adsorption mechanisms have been clarified by determined that PAN ve PU nanofiber execute the adsorption fit in with Langmuir, whereas PANI nanofiber execute the adsorption fit in with D-R isotherm model among Langmuir, Freundlich, Dubinin – Radushkevich (D-R) and Temkin isotherm models.
Açıklama
Anahtar Kelimeler
Çevre Mühendisliği, Environmental Engineering
