Recovery of molybdenum from the sea nodule leach liquor by solvent extraction using Alamine 304-I

Separation and recovery of molybdenum was investigated from the sea nodule leach liquor containing 0.505 kg/m3 Mo(VI), 0.212 kg/m3 Fe(III),12.08 kg/m3 Cu(II), 2.012 kg/m3 Co(II) and 15.16 kg/m3 Ni(II). The recovery process was carried out in two key steps: (i) Solvent extraction of Mo(VI) from the leach liquor using Alamine 304-1 dissolved in kerosene and (ii) Preparation of MoO3 from stripped solution by crystallization followed by thermal decomposition of ammonium polymolybdate crystals. In the solvent extraction study, the effects of several operational factors like contact time, pH, extractant concentration and different stripping reagents were examined to establish suitable conditions for effective extraction and stripping of molybdenum. The number of stages required for extraction and stripping were determined from a McCabe Thiele diagram and confirmed by a counter current simulation study. Enrichment of approximately 6.05 kg/m3 Mo(VI) into the loaded organic phase was achieved with 10% (v/v) Alamine 304-1, at equilibrium pH 1.62, and A:O = 12:1. The McCabe Thiele diagrams at A:O = 1:16 with 5 M NH4OH + 2.5 M (NH4)2CO3 showed two theoretical stages needed for quantitative stripping of molybdenum. Ammonium polymolybdate was crystallized from the stripped solution (96.79 kg/m3 Mo) and molybdenum trioxide was obtained by thermal decomposition at 400 °C with purity of 99.9%.