Ham ve asit aktif killer ile çinko-siyanür [Zn(CN)4]2- kompleksi adsorpsiyonu

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 Zn2+ 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 Zn2+ 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. Anahtar Kelimeler: Zeolit, sepiyolit, çinko-siyanür [Zn(CN)4]2- kompleksi, adsorpsiyon.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 Zn2+ 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. Zn2+ adsorption is characterised by Freundlich isotherm which represents physical adsorption whose energy changes logarithmically.  Maximum Zn2+ adsorption capacities were 4.6 meq/g for raw zeolite, 2.4 meq/g for acid-activated 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 Zn2+ 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. Keywords: Zeolite, Sepiolite, Zinc-cyanide complex [Zn(CN)4]2-, Adsorption

Electrokinetic and Sedimentation Properties of Simectic Suspensions in Some Electrolite and Polymer Solutions

Kil içeren atıkların susuzlaştırılması tüm maden işleme tesislerinde önemli bir problemdir. Bentonit simektit gurubu bir kil mineralidir ve maden atıklarında yaygın olarak bulunmaktadır. Na bentonit, ara tip bentonit (Na, Ca bentonit) ve Ca bentonit olarak sınıflandırılır. Onların varlığı susuzlandırma işlemlerinde, düşük verime, yüksek flokülant sarfiyatına neden olmaktadır. Bu çalışmanın amacı , ara tip bentonit mineral süspansiyonlarının sedimantasyon ve elektrokinetik özellikleri üzerine koagülasyon ve flokülasyon yöntemlerinde kullanılan inorganik elektrolitler ve polimerlerin etkisinin belirlenmesidir. Çalışmada koagülant olarak Al2 (SO4)3, FeCl3, NaCl, MgCl2 ve CaCl2 ; flokülant olarak anyonik, katyonik ve noniyonik polimerler kullanılmıştır. Performans, süspansiyonun zamana bağlı ara yüzey yüksekliği değişimi ile deneysel çalışmalar sonucu oluşan temiz suyun bulanıklık verileri kullanılarak değerlendirilmiştir. Koagülasyonda, 250 mg/l konsantrasyonda Al2(SO4)3 (% 99 verim-5,3 mm/dakika sedimantasyon hızı); Flokülasyonda 6,25 mg/l konsantrasyonda anyonik flokülant (% 97 verim- 47 mm/dakika sedimantasyon hızı) en iyi sonucu vermiştir. Koagülasyon+Flokülasyon deneylerinde NaCl+Anyonik flokülant daha düşük kimyasal konsantrasyonlarında (12,5 mg/l NaCl+3,75 mg/l anyonik flokülant) yaklaşık aynı oranda sedimantasyon(%97 verim- 39 mm/dakika sedimantasyon hızı) sağlamıştır.Dewatering of tailings containing clay is an important problem in all mineral processing plants. Bentonite is a smectite group clay and commonly present in the tailings of minerals industry. Bentonites are classified as Na bentonite, mixed type bentonite (Na-Ca bentonite) and Ca bentonite. Their presence can cause very difficult dewatering, high flocculant demand, low settling rates and poor supernatant clarity. In this study, the efficiency of inorganic electrolytes and polymers used in coagulation and flocculation methods onto sedimentation and electokinetic properties of mixed type bentonite mineral suspensions is investigated. Al2(SO4)3, FeCl3, NaCl, MgCl2 and CaCl2 were used as the coagulant and anionic, cationic, nonionic polymers were used as the flocculant. The performances of the coagulant in the experimental studies were assessed with the change in the interface height during sedimentation resultant and turbidity values of treated water. Best results were obtained with Al2(SO4)3 (99% efficiency with 5,3 mm/min settling rate) at 250 mg/l concentration and anionic flocculat (97% efficiency with 47 mm/min settling rate)at 6,25 mg/l concentration in coagulation and flocculation, respectively. In combined coagulation and flocculation experiments NaCl+Anionic flocculant showed a similar efficiency (97%) and settling velocity (39 mm/min) at a lower chemical concentration (12,5 mg/l NaCl+3,75 mg/l anionic flocculant)

Performance of natural zeolite and sepiolite in the removal of free cyanide and copper-complexed cyanide ([Cu(CN)3]2-)

The chemical and biological methods employed to date in the removal of free cyanide (CN) and metal-cyanide complexes from aqueous fluids have proved expensive and problematic. A simpler and more economical approach was attempted in the present study using zeolite and sepiolite. The effectiveness of zeolite from Manisa-Gördes (Turkey) and of sepiolite Eskişehir-Sivrihisar (Turkey) at removing free and Cu-complexed cyanide, [Cu(CN)] was investigated. For removal of CN, the system performance was examined in terms of concentration, particle size, and retention time. Material with smaller particle sizes (<0.106 mm) performed better, particularly in the case of sepiolite. The maximum CN removal capacities of zeolite and sepiolite were calculated as 571 and 695 meq/100 g for free CN adsorption, and 455 and 435 meq/100 g for Cu-complexed CN adsorption, respectively. The time to reach equilibrium was calculated as 1050 min. Acid activation, a simple cation adsorption removal method, did not improve the process, instead leading to reduced CN adsorption. Hydroxylated surfaces of metal oxides at the edges of zeolite develop charges and exchange with anions in water. Mg ions located at the edges of the octahedral sheet can create complexes with CN anions. Moreover, hydrogen bonding with anions (CN in this case) and H of zeolitic water bonded to coordinated water molecules can also create complexes. These two complexes are considered to be effective mechanisms for sepiolite. The effects of both acid activation and CN adsorption were clearly observed in the Fourier-transform infrared spectra. Removal of CN was characterized by the Langmuir isotherm, indicating monolayer coverage with chemical bonding to the surface, which deteriorated during acid activation. The study indicated that zeolite and sepiolite can be used efficiently and easily for removal of free and Cu-complexed CN