Enhanced lanthanum adsorption by amine modified activated carbon

Rare earths are one of the most critical raw materials group. In an effort to develop an effective adsorbent for aqueous rare earths recovery, activated carbon (AC) was modified with pentaethylenehexamine. Both raw AC and modified activated carbon (MAC) were characterized by X-ray diffraction (XRD), FT-IR and surface area analyses. The set of experiments was carried out with lanthanum, selected as representing of rare earths family, and the impacts of reactive time and concentrations of lanthanum were evaluated. The aqueous lanthanum adsorptive kinetics and capacity were also determined. The strong improvement in the efficiency values detected by using modified carbons (uptake 100% until initial concentrations of about 2600 ppm and release over 95%) demonstrated that the coordination mechanism due to modifying agent is effective. MAC presented lower kinetics and more than double adsorptive capacity as compared with AC. Furthermore, the adsorbent can be used successfully at least four times after regeneration for the removal of lanthanum and seems to show a selective behaviour in equimolar solutions with copper as competitive ions. The overall results demonstrated the potential utility of modification for enhancement of performances of AC-based materials for rare earths removal from aqueous solutions.