Simultaneous extraction of molybdenum and silicon from sulphate leach solution of spent catalyst using trialkylamine (N235) and recovery of pure ammonium molybdate

Abstract

Spent catalyst of molybdenum with silicon dioxide, commonly used as the carrier, is an important secondary resource for recovery of molybdenum. This work proposes a process to recycle molybdenum and remove silicon simultaneously by solvent extraction. The sulfuric acid leachate of the spent catalyst was contacted with the trialkylamine N235 (R₃N, R = C₈–C₁₀), to extract molybdenum and silicon. Several vital parameters were investigated to explore the influence on extraction and stripping. The extraction efficiencies of molybdenum and silicon were up to 99.6% and 77.1% after three-stage countercurrent extraction under optimized condition. The extraction reactions were determined by maximum loading capacity and FT-IR. The peak at 802.1 cm⁻¹ was caused by the stretching vibration of Si-O-Si, indicating the co-extraction of silicon. Molybdenum and silicon in the loaded organic phase can be stripped by the mixture of solution containing 7.00 mol/L NH₄OH and 0.80 mol/L (NH₄)₂CO₃, and the stripping efficiencies were >99.0%. Ammonium molybdate was prepared by removing silicon and evaporating, and the purity was 99.9%.