Separation and Extraction of Niobium from H ₂SO ₄ Solution with Highly Concentrated Titanium Using a Fluoride-Free Method

Niobium consumption increases rapidly due to its application in critical industries such as the aerospace, nuclear, and materials. Conventional metallurgical and separation technologies for niobium use highly concentrated HF, however, it results in many problems. A fluoride-free method for niobium separation in leached sulfuric mother liquor of ilmenorutile is proposed in this paper. The solvent extraction system comprising trioctyl tertiary amine (N235) and 4-methyl-2-pentanone (MIBK) demonstrated good extraction efficiency and selectivity of niobium over titanium and iron impurities in sulfuric acid–oxalate solutions. This study demonstrates its practical effectiveness in both batch and multi-stage simulated counter-current modes. The sulfuric mother liquor contains a lot of titanium and iron impurities, thus, details of extraction, scrubbing, and stripping processes were investigated. Over 73.8% niobium was extracted at an organic-to-aqueous phase ratio of 1.0, an oxalic acid-to-niobium molar ratio of 5.0, and the H+ concentration of 8.17 mol/L using an organic phase with 50 vol% N235 and 50 vol% MIBK as the extractants at 20 °C, and only 2.8% titanium and 1.7% iron were co-extracted. The recovery of niobium reached 99.1% in the four-stage simulated counter-current extraction tests. In the three-stage simulated counter-current stripping tests, the stripping efficiency of niobium reached 99.7% with 2.0 mol/L HNO3.