Yerli selestit konsantresinden hidrometalurjik süreçler yardımıyla stronsiyum karbonat üretimi
Strontium carbonate production from local celestite concantrate via hydrometallurgical processes
Yazar: AYŞEGÜL BİLEN
Danışman: PROF. DR. CÜNEYT ARSLAN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı / Üretim Metalurjisi ve Teknolojileri Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2017
Konu: Metalurji Mühendisliği = Metallurgical Engineering

Özet:
Bu tez çalışmasının ana amacı, stronsiyum cevheri olan selestitten (SrSO4), basit proses adımları uygulayarak ticari değeri yüksek stronsiyum karbonat (SrCO3) üretmektir.
Tez konusu kapsamında, selestit konsantresi, asidik baryum klorür (BaCl2) çözeltisinde liç işlemine tabi tutulmuş ve elde edilen stronsiyum yüklü çözeltiden, sodyum karbonat (Na2CO3) vasıtasıyla stronsiyum karbonat (SrCO3) çöktürülmüştür. 
Dünyada selestit rezervleri, İspanya, Kanada, ABD, Meksika, İngiltere, İran ve Türkiye'de bulunmaktadır. Türkiye, Barit Maden A.Ş tarafından işletilen selestit rezervlerinden yıllık yaklaşık 2 milyon ton selestit minerali üretim kapasitesine sahiptir. Sarsıntılı masa ve jig işlemleri sonrasında elde edilen cevher konsantresi %95-96 SrSO4 içeriğinin yanı sıra ticari üründe yaklaşık %3 CaSO4, %0,5 BaSO4, %0,5 SiO2 ve %0,5 Fe2O3 oranlarında empürite içermektedir. İşletimi yapılan selestit mineralinin yüksek tenörlü olduğu ifade edilebilir. Türkiye'de selestitin stronsiyum karbonata dönüşeceği bir tesis bulunmamaktadır. Stronsiyum karbonat yurtdışından ithal edilmektedir. Selestitin ton fiyatı 90-100 $ olup, stronsiyum karbonatın ton fiyatı ise 400-500 $'dır. Stronsiyum karbonat, renkli televizyon tüplerinin camları dışında, sert seramik magnet üretimi başta olmak üzere, seramik ve cam endüstrisinde kullanılabilmektedir. Ayrıca özel camların üretiminde ve çinko elektrolizinin rafinasyonunda kurşun giderilmesi için kullanılabilmektedir. Bunların dışında alev ile kırmızı renk oluşturabildiğinden havai fişek endüstrisinde de tercih edilmekte olup, makine sanayinde, mil yataklarında yağlayıcı olarak kullanılmaktadır. 
Tez kapsamında yapılan çalışmalarda asıl amaçlanan, daha basit ve az yatırım maliyeti gerektiren proses adımlarıyla yüksek konsantrasyonlu SrCO3 üretebilmektir.
Deneysel çalışmalarda Barit Maden Türk A.Ş'den temin edilen selestit minerali kullanılmıştır. Deneysel çalışmaların ilk bölümünü kapsayan liç deneylerinde, sürenin, katı sıvı oranının, sıcaklığın, hidroklorik asit (HCl) konsantrasyonunun ve sodyum klorür (NaCl) konsantrasyonunun liç verimi üzerindeki etkisi incelenmiştir. Deneysel tasarım programı MİNİTAB kullanılmış ve sonuçlar karşılaştırılmıştır. En yüksek liç veriminin alındığı deney koşulları, 1/300 katı sıvı oranının kullanıldığı, 0,5M HCl ve 1M NaCl içeren ve 65°C'de gerçekleştirilen deney olmuş, liç verimi %91,17 olarak hesaplanmıştır. 
Deneysel çalışmaların ikinci kısmında stronsiyum klorür (SrCl2) yüklü stok çözeltiden, SrCO3 çöktürülme koşulları incelenmiştir. HSC programında alınan datalar değerlendirilmiştir. Sıcaklığın ve sürenin etkisi üzerinde durulmuştur. En verimli sonuç 75°C'de stokiyometrinin gerektirdiğinin iki katı Na2CO3 kullanılan deneyde elde edilmiş ve çöktürme verimi %99,52 olarak hesaplanmıştır.
Kullanılan konsantre ve deney numunelerinin karakterizasyonu için AAS ve XRD analiz cihazları kullanılmıştır. Deneylerde elde edilen veriler MİNİTAB programında hesaplanan datalarla karşılaştırılmıştır.

Abstract:
The main objective of this thesis is to produce strontium carbonate (SrCO3) with high commercial value by applying simple process steps to celestite (SrSO4), the strontium ore.
Within the scope of the thesis, the celestite concentrate is leached in the acidic barium chloride solution and the strontium-loaded solution obtained is precipitated with sodium carbonate to form strontium carbonate.
Strontium is an alkali metal with an atomic number of 38 found between calcium and barium in group 2A of the periodic table. Atomic weight of strontium is 87.62, melting point is 770˚C, and density is 2.6 g/cm3. 
Strontium metal is obtained from the naturally found celestite (SrSO4) and strontianite (SrCO3) minerals. Strontium percentage is higher in the strontianite but the high calcium content limits its industrial usage. Hence, despite the lower strontium percentage of celestite, it has higher commercial value. Selestite ore, a strontium sulphate mineral, is the main raw material source for many strontium compounds such as strontium nitrate, strontium chloride, strontium hydroxide, especially strontium carbonate.
In the world, selestit reserves are located in Turkey, Spain, Canada, USA, Mexico, England, Iran, and Turkey. Turkey has an annual production capacity of about 2 million tons of celestite reserves operated by Barit Maden Türk A.Ş.. The ore concentrate obtained after shaky table and jig operations contains in the ratio of about 95-96% SrSO4, 3% CaSO4, 0.5% BaSO4, 0.5% SiO2 and 0.5% Fe2O3. It can be said that the activated celestite is high-grade. There is no facility in Turkey where selestite will convert into strontium carbonate. Strontium carbonate is imported from abroad. The tonnage of celestite is $ 90-100 and the tonnage of strontium carbonate is $ 400-500. Strontium carbonate can be used in ceramics and glass industries, especially in the production of hard ceramic magnets, the windows of color television tubes. It can also be used for lead refining in the production of special glasses and in zinc electrolysis. Since they can produce red color with flame, they are also preferred in fireworks industry and used as lubricant in machine bearings. The main aim of the thesis is to produce high concentration of SrCO3 by process steps which require less investment cost.
Solubility of the celestite in water, acidic or basic chemicals is very low, and thus it is difficult to dissolve it by direct hydrometallurgical method. Because of that, in experiments, HCl is used to lower the pH and NaCl will be used as an auxiliary activator because of the increase in ionic strength. 


In the experimental works, selestite mineral obtained from Barit Maden Türk A.Ş. was used. MINITAB experimental design program is used and the data obtained in the experiments are compared with the data calculated in the MINITAB program. In experimental work, barium chloride (BaCl2) is used as chloride agent and sodium chloride (NaCl) and hydrochloric acid (HCl) are used to increase dissolution efficiency. Experiments were carried out to determine the effects of solid/liquid ratio (1/300-3/300 w/v), temperature (25-65°C), HCl concentration (0-1M), NaCl concentration (0.5-1.5M), and time (30-180 min). Reaction in leaching processes;
SrSO4  +BaCl2(aq)→SrCl2(aq)  + BaSO4
In this reaction, the propellant is the difference in solubility between BaSO4 (1.1 × 10-10) and SrSO4 (3.2 × 10-7). Thus, the solution of the strontium-loaded solution as well as the refining of the solution will be provided. 
Strontium dissolved as a chloride salt more efficiently at 1/300 solid to liquid ratio. The reason for this is the reaction that occurs when the strontium is dissolved. As a result of this reaction, BaSO4 grains are deposited on SrSO4 grains, which are in the dissolution phase. The increase in solid-liquid ratio leads to the increase of this layer and the efficiency decreases.
When the test results at different temperatures are evaluated, as the temperature increases, efficiency increases. Therefore, the best efficiency results were obtained at 65°C.
The increase in acid concentration first increases the yield of strontium dissolution and then decreases. Therefore, the most efficient result was obtained at 0.5 M acid concentration. This situation is also supported by experimental design.
The increase in NaCl concentration first increases the yield of strontium dissolution and then decreases. Therefore, the most efficient result was obtained at 1 M acid concentration. This situation is also supported by experimental design.
The increase in dissolution period strontium efficiency is increased.  Therefore, the most efficient result was obtained at 180th minute. And also according to MINITAB experimental design that the calculated strontium solubility efficiency values are compatible with the experimental design model. An the highest yield was calculated as 91.17%
Before proceeding to the second part of the experiments, the best conditions were determined based on the AAS and XRD results at the end of the first part, and 5 liters of strontium chloride solution was formed according to these conditions. However, because of the excessive amount of barium chloride required due to excessive use, the amount of barium remaining in the solution is desired to be removed. For this, the amount of sulfuric acid required to precipitate the barium was calculated from the results of AAS, and the solution was removed in the form of barium sulfate.
In the second part of the experiments, the modeling of the experimental results in the Spana named program has shown that the pH required for strontium carbonate precipitation is between 6 and 8. For this reason, sodium carbonate was used in excess of stoichiometry to adjust the pH of the strontium-loaded acidic solution. After the pH is brought to the desired level, the required amount of sodium carbonate solution will be added to precipitate SrCO3. In the SrCO3 precipitation experiments, the effect of temperature (25, 50, 75 ° C) and precipitation period (15, 30, 60, 90, 120 min) was investigated. Reaction in leaching processes;
〖SrCl〗_(2(aq))  + 〖Na〗_2 〖CO〗_3→〖SrCO〗_3  + 2NaCl(aq)
As the temperature increased, the sprecipitation efficiency increased first, then decreased slightly. The most efficient result was obtained at the 75°C.
With the increase in the precipitation period, the rate of strontium in the solution decreases. However, there is no significant difference between the results at 90th and 120th minutes. The highest efficiency was calculated as 99.52%.