Ham ve Asit Aktif Killer ile Çinko-Siyanür (Zn(CN)_4)(2-) Kompleksi Adsorpsiyonu
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Tarih
2006
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info:eu-repo/semantics/openAccess
Özet
Bu çalışma, çeşitli endüstriyel faaliyetlerden ve madencilik çalışmalarından açığa çıkan (Zn(CN)_4)(2-) kompleksi içeren atıklardan, bu kompleksin giderilebilmesi için daha bol bulunabilen materyallerle ve kolay uygulanabilir bir yöntem arayışı çerçevesinde yapılmıştır. Çalışmada, Eskişehir- Sivrihisar yöresine ait sepiyolit minerali ile Manisa-Gördes yöresine ait zeolit minerali kullanılarak (Zn(CN)_4)(2-) kompleksinin gideriminde en başarılı uygulamanın tesbitine çalışılmıştır. Ham mineralin yanısıra asit aktivasyonun kompleksin adsorpsiyonu üzerine etkileri araştırılmıştır. Konsantrasyon, tane boyutu ve bekleme süresi deneysel değişkenler olarak belirlenmiş ve bu faktörlerinin adsorpsiyon performansı üzerine etkileri incelenmiştir. Yürütülen deneysel çalışma sonucunda mineralin, kompleksi tek bir iyon halinde değil de bileşimini oluşturan Zn(2) ve CN- iyonları halinde ayrı ayrı adsorpladığı belirlenmiştir. Asit aktivasyon minerallerin fiziksel ve kimyasal yapısında değişime sebep olmakla birlikte bu değişimin komplekslerin gideriminde dikkate değer bir etkisi olmamıştır. Ham ve asit aktif zeolitte ulaşılan maksimum Zn(2) tutma kapasiteleri sırasıyla 4.6 mek/g ve 2.4 mek/g iken aynı koşullardaki sepiyolitte sırasıyla 1.4 mek/g ve 1.5 mek/g olarak bulunmuştur. Benzer şekilde, CN- tutma kapasiteleri ham ve asit aktif zeolitte sırasıyla 11.5 mek/g ve 1.1 mek/g ve aynı koşullardaki sepiyolitte sırasıyla 23.1 mek/g ve 15.4 mek/g olarak belirlenmiştir. Adsorpsiyonda etkin izoterm metal için Freundlich, CN- için ağırlıklı olarak Langmuir olarak belirlenmiştir. Tane boyutunun sistem performansı üzerine dikkate değer bir etkisi olmamakla birlikte 0.106-0.300 mm önerilen tane boyutudur.
Metal-cyanide complexes are environmentally important anions including metal and cyanide ions together in their structure. Whether in their complex form or after their degradation into metal and cyanide in the structure, their removal is considerably important, especially considering high quantities of wastes of industries like mineral processing, electroplating etc. which include high quantities of various weak and strong metal-cyanide complexes. Studies on anion removal with sepiolite and zeolite are very limited in the literature, and none about adsorption of cyanide and its compounds onto these minerals. This study was conducted to propose a method for the removal of zinc-cyanide (Zn(CN)_4)(2-) complex from aqueous solutions. The purpose was to remove the complex by using cheap, achievable minerals, sepiolite from Eskişehir-Sivrihisar (Turkey) region, and zeolite from Manisa-Gördes (Turkey) region. XRD patterns showed that, structure of zeolite was hyrated sodium, potasium, calcium alumina silicate and 85-98 % clinoptilolite; structure of sepiolite was magnesium silicate hydroxy hydrate. The main purpose was to determine the effectiveness of these minerals on (Zn(CN)_4)(2-) adsorption. Mineral samples were crashed, grinded and sieved to different sizes, and three of these were used in the study: -0.106 mm, 0.106-0.300 mm and 0.300- 0.600 mm. In batch systems, 0.05 g sepiolite or zeolite minerals were added into the synthetic (Zn(CN)_4)(2-) solutions of different initial concentrations. Besides raw form, sepiolite and zeolite minerals were utilized also in acid-activated form. For activation, HNO3 of various normalities were applied in 70 0C, and so, several acid activated zeolite and sepiolite samples were obtained. Reactors of 100 ml liquid volume and 0.05 g mineral were operated in the shaker until equilibrium and change of concentration against time was followed. Preliminary trials indicated that 4 hours was sufficient to achieve equilibrium. Sepiolite and zeolite can adsorb (Zn(CN)_4)(2-) to varying extent. CN- can be adsorbed in higher performance (19 to 92 %) than Zn (18 to 38 %), which is the first indication of removal of the complex after separation into its ions. Acid activation causes certain structural changes onto mineral surface properties but these were not effective in improving the performance of the mineral for both sepiolite and zeolite. Raw minerals showed slightly better performances than acid activated minerals. Although surface area increases with decreasing particle size, particle size has no considerable effect on adsorption in the studied particle size range. Therefore, it was difficult to specify any mineral condition which best adsorbs (Zn(CN)_4)(2-). For isotherm and capacity calculations, one of the conditions which best characterized the achieved removal results was selected and further isotherm studies were performed in these conditions. The selected particle size for isotherm studies was 0.106-0.300 mm, which is the average of the studied range. The reason was simply economy of obtaining larger particle size than -0.106 mm. Adsorption of (Zn(CN)_4)(2-) onto zeolite and sepiolite was modelled with single-layer-two parameter isotherm models Freundlich, Langmuir and Tempkin. Isotherm studies indicated that Zn(2) uptake can be interpreted by means of Freundlich equation while CN- removal data fits Langmuir isotherm better. Having different isotherms in two ions is the second indication of separate ions removal instead of the whole complex. anion. Zn(2) adsorption is characterised by Freundlich isotherm which represents physical adsorption whose energy changes logarithmically. Maximum Zn(2) adsorption capacities were 4.6 meq/g for raw zeolite, 2.4 meq/g for acidactivated zeolite while they were 1.4 meq/g and 1.5 meq/g for raw and acid-activated sepiolite, respectively. Whereas CN- adsorption was interpreted by means of Langmuir isotherm, a two parameter adsorption which represents a single layer chemical bonding occurring on the mineral surface sites, with uniform energy. CN- removal capacities were higher for most minerals as compared to Zn(2) ion such that, they were 11.5 meq/g for raw zeolite, 1.1 meq/g for acid-activated zeolite, 23.1 meq/g for raw sepiolite and 15.4 meq/g for acid-activated sepiolite. Here the effect of acid-activation can be seen more clearly. It did not improve adsorption, instead, acid activation decreased adsorption performance since acid changes chemical adsorption sites. These calculated capacities were high enough as compared to known adsorbents. (Zn(CN)_4)(2-) is a weak acid dissociable complex and dissociates easily in aqueous systems. It was removed from the system after dissociation into its components with different adsorption performances of each. All studies were performed in approximately neutral pH (7-8) which makes this application more favorable in field applications.
Metal-cyanide complexes are environmentally important anions including metal and cyanide ions together in their structure. Whether in their complex form or after their degradation into metal and cyanide in the structure, their removal is considerably important, especially considering high quantities of wastes of industries like mineral processing, electroplating etc. which include high quantities of various weak and strong metal-cyanide complexes. Studies on anion removal with sepiolite and zeolite are very limited in the literature, and none about adsorption of cyanide and its compounds onto these minerals. This study was conducted to propose a method for the removal of zinc-cyanide (Zn(CN)_4)(2-) complex from aqueous solutions. The purpose was to remove the complex by using cheap, achievable minerals, sepiolite from Eskişehir-Sivrihisar (Turkey) region, and zeolite from Manisa-Gördes (Turkey) region. XRD patterns showed that, structure of zeolite was hyrated sodium, potasium, calcium alumina silicate and 85-98 % clinoptilolite; structure of sepiolite was magnesium silicate hydroxy hydrate. The main purpose was to determine the effectiveness of these minerals on (Zn(CN)_4)(2-) adsorption. Mineral samples were crashed, grinded and sieved to different sizes, and three of these were used in the study: -0.106 mm, 0.106-0.300 mm and 0.300- 0.600 mm. In batch systems, 0.05 g sepiolite or zeolite minerals were added into the synthetic (Zn(CN)_4)(2-) solutions of different initial concentrations. Besides raw form, sepiolite and zeolite minerals were utilized also in acid-activated form. For activation, HNO3 of various normalities were applied in 70 0C, and so, several acid activated zeolite and sepiolite samples were obtained. Reactors of 100 ml liquid volume and 0.05 g mineral were operated in the shaker until equilibrium and change of concentration against time was followed. Preliminary trials indicated that 4 hours was sufficient to achieve equilibrium. Sepiolite and zeolite can adsorb (Zn(CN)_4)(2-) to varying extent. CN- can be adsorbed in higher performance (19 to 92 %) than Zn (18 to 38 %), which is the first indication of removal of the complex after separation into its ions. Acid activation causes certain structural changes onto mineral surface properties but these were not effective in improving the performance of the mineral for both sepiolite and zeolite. Raw minerals showed slightly better performances than acid activated minerals. Although surface area increases with decreasing particle size, particle size has no considerable effect on adsorption in the studied particle size range. Therefore, it was difficult to specify any mineral condition which best adsorbs (Zn(CN)_4)(2-). For isotherm and capacity calculations, one of the conditions which best characterized the achieved removal results was selected and further isotherm studies were performed in these conditions. The selected particle size for isotherm studies was 0.106-0.300 mm, which is the average of the studied range. The reason was simply economy of obtaining larger particle size than -0.106 mm. Adsorption of (Zn(CN)_4)(2-) onto zeolite and sepiolite was modelled with single-layer-two parameter isotherm models Freundlich, Langmuir and Tempkin. Isotherm studies indicated that Zn(2) uptake can be interpreted by means of Freundlich equation while CN- removal data fits Langmuir isotherm better. Having different isotherms in two ions is the second indication of separate ions removal instead of the whole complex. anion. Zn(2) adsorption is characterised by Freundlich isotherm which represents physical adsorption whose energy changes logarithmically. Maximum Zn(2) adsorption capacities were 4.6 meq/g for raw zeolite, 2.4 meq/g for acidactivated zeolite while they were 1.4 meq/g and 1.5 meq/g for raw and acid-activated sepiolite, respectively. Whereas CN- adsorption was interpreted by means of Langmuir isotherm, a two parameter adsorption which represents a single layer chemical bonding occurring on the mineral surface sites, with uniform energy. CN- removal capacities were higher for most minerals as compared to Zn(2) ion such that, they were 11.5 meq/g for raw zeolite, 1.1 meq/g for acid-activated zeolite, 23.1 meq/g for raw sepiolite and 15.4 meq/g for acid-activated sepiolite. Here the effect of acid-activation can be seen more clearly. It did not improve adsorption, instead, acid activation decreased adsorption performance since acid changes chemical adsorption sites. These calculated capacities were high enough as compared to known adsorbents. (Zn(CN)_4)(2-) is a weak acid dissociable complex and dissociates easily in aqueous systems. It was removed from the system after dissociation into its components with different adsorption performances of each. All studies were performed in approximately neutral pH (7-8) which makes this application more favorable in field applications.
Açıklama
Anahtar Kelimeler
Zeolit, sepiyolit, çinko-siyanür [Zn(CN)4] 2- kompleksi, adsorpsiyon, Zeolite, Sepiolite, Zinc-cyanide complex [Zn(CN)4] 2-, Adsorption
Kaynak
İTÜ Dergisi Seri E: Su Kirlenmesi Kontrolü
WoS Q Değeri
Scopus Q Değeri
Cilt
16
Sayı
01.Mar
Künye
Tarlan, E., Önen, V., Yılmaz, Z., (2006). Ham ve Asit Aktif Killer ile Çinko-Siyanür (Zn(CN)_4)(2-) Kompleksi Adsorpsiyonu. İTÜ Dergisi Seri E: Su Kirlenmesi Kontrolü, 16(1-3), 35-44.
