Adsorption of neodymium(III) from aqueous solutions using a phosphorus functionalized adsorbent

Separation of neodymium(III) from aqueous solutions is investigated using an phosphorus based sol-gel adsorbent. This adsorbent has been formed by the sol-gel synthesis method. The speciation diagram of Nd(III) in an aqueous phase with varying pH is studied by analyses of the equilibria equations. Batch adsorption equilibrium studies show an increase in neodymium uptake capacity with increase in pH in the range from pH 0.5 to pH 6.5, and the maximum uptake capacity at pH 6 is observed to be 1.13 mmol/g (160 mg/g). The equilibrium adsorption isotherm gives a satisfactory fit of the adsorption data. A kinetics study conducted with different concentrations and particle sizes of neodymium(III) in a batch reactor shows a high rate of adsorption. The adsorbent shows a capability of selectivity toward Nd(III) and other rare earths. Adsorption tests in a fixed bed column show a sharp breakthrough curve. Stripping of the neodymium-loaded column bed is achieved using 1 M HNO ₃. The material also has sustainable stability over repeated metal loading and stripping in a column. In addition to the experimental studies, the adsorption processes in batch and packed column systems are successfully modeled by using a pore diffusion model, and the results are presented. The organophosphorus functionalized adsorbent is demonstrated to be an effective sorbent material for the separation of neodymium(III) from aqueous solutions.