Highly enhanced selectivity for the separation of rhenium and molybdenum using amino-functionalized magnetic Cu-ferrites

An effective method based on magnetic solid-phase extraction for the selective recovery of rhenium and molybdenum has been developed using diethylamine-functionalized magnetic CuFe₂O₄ (NH₂@CuFe₂O₄) as adsorbents. Various experimental parameters that could affect the extraction efficiency had been investigated in detail. NH₂@CuFe₂O₄ exhibited high adsorption ability and selectivity to \( {\text{ReO}}_{4}^{ - } \) and \( {\text{MoO}}_{4}^{2 - } \); selective separation of \( {\text{ReO}}_{4}^{ - } \) and \( {\text{MoO}}_{4}^{2 - } \) could be achieved by adjusting pH of the aqueous solution. The \( {\text{ReO}}_{4}^{ - } /{\text{MoO}}_{4}^{2 - } \) adsorption reaction was found to be fast, and the adsorption equilibrium was attained within 6.0 min following a pseudo-second-order model with an observed rate constant (k ₂) of 0.0215 mg·g⁻¹·min⁻¹/0.0496 mg·g⁻¹·min⁻¹ at 298 K. The adsorption data could be well interpreted by the Langmuir model. The maximum adsorption capacities for \( {\text{ReO}}_{4}^{ - } \) and \( {\text{MoO}}_{4}^{2 - } \) obtained from the Langmuir model are 41.667 and 62.893 mg g⁻¹, respectively. The extraction recovery of \( {\text{ReO}}_{4}^{ - } /{\text{MoO}}_{4}^{2 - } \) was more than 93 % from Mo–Re simulated industrial leach liquor.