Recovery of Nd(III) in coexistence with Fe(III) ions from aqueous phase using functionalized multiwalled carbon nanotubes: An environmental benign approach

The present paper reports an environmental benign process for the selective adsorption of Nd(III) in presence of Fe(III) on functionalized multiwalled carbon nanotubes (MWCNT) from a synthetic aqueous solution, which can be utilized for the rare earth recovery from scraps or end of life products. Effects of metal ion concentration, aqueous phase acidity (pH), weight of MWCNT, temperature, complexing agents and contact time on the adsorption of Nd(III) and Fe(III) over MWCNT have been studied in detail. The Nd(III) adsorption followed Langmuir isotherm in presence of Fe(III)and showed favourable adsorption at pH 3. The maximum adsorption capacities for Nd(III) and Fe(III) were found to be 44 mg/g and 30.8 mg/g respectively. Pseudo second order kinetics was followed by both Nd(III) and Fe(III) adsorption on MWCNT. For selective adsorption, ascorbic acid was found to be the best among different complexing with a selectivity coefficient of 120 for Nd(III) with respect to Fe(III). The adsorbed ions could be fully desorbed with 0.2 M HCl, indicating the process feasibility in terms of ease of recovery of loaded metal ions as well as regeneration of functionalized MWCNT. This process eliminates the use of hazardous organic solvents for the recovery of rare earths.