ELİF YILMAZ, FIRAT AHLATCI, ERSİN YENER YAZICI, OKTAY CELEP, Hacı DEVECİ

KARBON DİOKSİT İLE ATIK ÇÖZELTİLERDEN SİYANÜR GERİ KAZANIMI

Siyanür liçi işlemleri sonucu üretilen atık çözeltiler, siyanür içeriğinin yasal sınırlara indirilebilmesi için arıtma işlemine tabi tutulmaktadır. Siyanür geri kazanımı ekonomik ve çevresel nedenlerden dolayı, özellikle siyanür tüketimi yüksek cevherler için en çok tercih edilen seçenektir. Bu çalışmada, alkali çözeltilerde hidrojen siyanürün (HCN(g)) absorpsiyonu/geri kazanımı öncesinde siyanür çözeltilerinin asitleştirilmesi amacıyla karbon dioksit (CO2) kullanılmıştır. Yapılan kinetik testler, reaksiyon süresinin siyanür geri kazanımında önemli bir rol oynadığını göstermiştir (90 dk.’da %89,1 siyanür geri kazanımı). Siyanür konsantrasyonu (0,5-1,5 g/L NaCN), karbon dioksit akış debisi (0,38-1,15 L/dk. CO2) ve süre’nin (30-90 dk.) siyanür geri kazanımı (%) üzerindeki etkisi iki seviyeli tam faktöriyel deney tasarımı kullanılarak araştırılmıştır. Verilerin istatistiksel analizi karbon dioksit akış hızı ve süre’nin istatistiksel olarak anlamlı parametreler olduğunu göstermiştir. Siyanür konsantrasyonunun prosesin etkinliği üzerinde bir etkisinin olmadığı belirlenmiştir. Elde edilen sonuçlar, uygun koşullarda %93,1’e varan yüksek siyanür geri kazanımlarına ulaşılabileceğini göstermiştir. Karbon dioksit kaynağı olarak hava (1,15 L/dk.) kullanılmanın etkin olmadığı ve yüksek verimler için daha uzun süre gerektiği bulunmuştur (15 dk.’da kazanım sıfır iken 24 saatte %95,4 olmuştur). Gerçek bir yüklü liç çözeltisinden yapılan testte %49,7 verim elde edilmiştir. Elde edilen bulgular karbon dioksitin siyanürlü atık çözeltilerin asitleştirilmesinde ve siyanürün geri kazanımında kullanılabileceğini göstermiştir.

Anahtar Kelimeler:

Siyanür geri kazanımı, Karbon dioksit, Asitleştirme, Deney tasarımı

RECOVERY OF CYANIDE FROM EFFLUENTS USING CARBON DIOXIDE

Cyanidation effluents are treated in order to reduce the cyanide level down to regularity limits. Cyanide recovery is the most desired route for treatment of effluents of high cyanide consuming ores, in particular, due to economic and environmental incentives. In this study, carbon dioxide (CO2) was utilised as an alternative for acidification of cyanide solutions prior to absorption/recovery of hydrogen cyanide (HCN(g)) in alkaline solutions. Kinetic tests have indicated that reaction time is an important parameter for the recovery of cyanide, which reached 89.1% over a period of 90 min. Effects of concentration of cyanide (0.5-1.5 g/L NaCN), flow rate of carbon dioxide (0.38-1.15 L/min. CO2) and time (30-90 min.) on the recovery of cyanide (%) were investigated in detail by a two-level full factorial design (23). The statistical evaluation of the data showed that flow rate of carbon dioxide and time were statistically significant parameters. Efficiency of the process was not affected by the concentration of cyanide. The results demonstrated that high recoveries of cyanide up to 93.1% could be achieved under suitable conditions. Introduction of air (1.15 L/min.) as a carbon dioxide source was found to be inefficient and require longer reaction periods for high recoveries i.e. no recovery at 90 min. vs. 95.4% at 24 h. A separate test performed using a real pregnant leaching solution (PLS) yielded a cyanide recovery of 49.7%. These finding demonstrated that using carbon dioxide can be used for acidification of cyanide solutions for cyanide recovery.

Keywords:

Cyanide recovery, Carbon dioxide, Acidification, Experimental design,

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