Effects of High-Temperature Oxidative Roasting and Acid Type on the Selective Solubility of Rare Earth Elements

Abstract

This study comparatively evaluates direct leaching and leaching following oxidative roasting for the recovery of rare earth elements (REEs) from the complex ore of Eskişehir-Beylikova. Within the scope of the study, both direct leaching and leaching following a roasting process were carried out, and the effect of two different acid types (HCl and H2SO4) on leaching efficiencies was investigated at each stage. One of the original aspects of the study is that the high-temperature total oxidative roasting applied provides selectivity in the dissolution of REEs and impurities. When direct leaching and leaching following roasting at 900 °C were compared, a significant increase (40-60%) in leaching efficiencies was observed after roasting. Another original aspect of the study is that the type of acid used in the leaching process also provides selectivity between REEs and impurities. Following the roasting step, REE recovery reached 70-90% with HCl acid leaching, whereas with H2SO4 this ratio was 5-10% lower, particularly for the light REE group. When the effect of the two different acid types on impurities after roasting was examined, impurity recoveries were <5% with HCl, while recovery values were at the level of 20-30% in the H2SO4 medium. In this respect, the use of H2SO4 had a negative effect on selectivity compared to HCl. In conventional REE process applications, numerous purification stages are applied following leaching to remove impurities. The high-temperature roasting process applied in this study provides selective REE leaching while reducing the number of purification stages, such as solvent extraction, precipitation, or ion exchange, required in subsequent steps. The findings obtained reveal that both oxidative thermal pretreatments and appropriate acid selection are determinative factors in terms of leaching efficiency and selectivity in the processing of complex-structured REE ores.

Keywords

• REE
• Leaching
• Selective dissolution
• Oxidative roasting

Ethical Statement

Bu araştırmada hayvanlar ve insanlar üzerinde herhangi bir çalışma yapılmadığı için etik kurul onayı alınmamıştır.

Yüksek Sıcaklıklı Oksitleyici Kavurma ve Asit Türünün Nadir Toprak Elementlerinin Seçimli Çözünmesine Etkileri

Abstract

Bu çalışma, Eskişehir-Beylikova kompleks cevherinden nadir toprak elementleri(NTE)nin kazanımına yönelik doğrudan liç ile oksitleyici kavurmayı takiben liç uygulamasını karşılaştırmalı olarak değerlendirmektedir. Çalışma kapsamında doğrudan liç ve kavurma işlemini takiben liç uygulanmış olup, her bir aşamada iki farklı asit türünün (HCl ve H₂SO₄) liç verimlerine etkisi incelenmiştir. Çalışmanın özgün yanlarından biri, uygulanan yüksek sıcaklıktaki total oksitleyici kavurmanın NTE ve safsızlıkların çözünmesinde seçicilik sağlamasıdır. Doğrudan liç ve 900 °C sıcaklıkta gerçekleştirilen kavurmayı takiben liç uygulamaları kıyaslandığında, kavurma sonrası liç verimlerinde önemli oranda (%40-60) artış gözlemlenmiştir. Çalışmanın bir diğer özgün yanı ise liç işleminde kullanılan asit türünün de NTE ve safsızlıklar arasında seçicilik sağlamasıdır. Kavurma adımını takiben uygulanan HCl asit liçi sonucunda NTE verimleri %70-90 seviyesine ulaşırken, H2SO4 kullanımında bu oran özellikle hafif NTE grubunda %5-10 daha düşüktür. Kavurma işleminin ardından iki farklı asit türünün safsızlıklar üzerindeki etkisi incelendiğinde, HCl kullanımında safsızlıkların verimleri <%5 iken, H2SO4 ortamında verim değerleri %20-30 düzeyindedir. Bu durumda H2SO4 kullanımı, seçicilik açısından HCl ile kıyaslandığında olumsuz bir etki yaratmıştır. Geleneksel NTE proses uygulamalarında safsızlıkların uzaklaştırılmasında liç işleminin ardından birçok saflaştırma kademesi uygulanmaktadır. Bu çalışmada uygulanan yüksek sıcaklıklı kavurma işlemi, seçici NTE liçi sağlarken, ilerleyen aşamalarda uygulanması gereken solvent ekstraksiyon, çöktürme veya iyon değiştirme gibi saflaştırma kademelerinin azaltılmasını sağlamaktadır. Elde edilen bulgular, kompleks yapılı NTE cevherlerinin işlenmesinde hem oksitleyici termal ön işlemlerin hem de uygun asit seçiminin liç verimi ve seçicilik açısından belirleyici olduğunu ortaya koymaktadır.

Keywords

• NTE
• Liç
• Seçici çözündürme
• Oksitleyici kavurma

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