الفهرس 
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Abstract
The recovery of strategic metals such as rare earth elements (REEs) requires the development of new sorbents with high sorption
capacities and selectivity. The bi-functionality of sorbents showed aremarkable capacity for the enhancement of binding properties. This
work compares the sorption properties of magnetic chitosan (MC,
prepared by dispersion of hydrothermally precipitated magnetite
microparticles (synthesized through Fe(II)/Fe(III) precursors) into
chitosan solution and crosslinking with glutaraldehyde) with those of the
urea derivative (MC-UR) and its sulfonated derivative (MC-UR/S) for
cerium (as an example of REEs). The sorbents were characterized by
FTIR, TGA, elemental analysis, SEM-EDX, TEM, VSM, and titration. In
a second step, the effect of pH (optimum at pH 5), the uptake kinetics
(fitted by the pseudo-first-order rate equation), the sorption isotherms
(modeled by the Langmuir equation) are investigated. The successive
modifications of magnetic chitosan increases the maximum sorption
capacity from 0.28 to 0.845 and 1.25 mmol Ce g−1 (MC, MC-UR, and
MC-UR/S, respectively). The bi-functionalization strongly increases the
selectivity of the sorbent for Ce(III) through multi-component equimolar
solutions (especially at pH 4). The functionalization notably increases the
stability at recycling (for at least 5 cycles), using 0.2 M HCl for the
complete desorption of cerium from the loaded sorbent. The bi-
functionalized sorbent was successfully tested for the recovery of cerium
from pre-treated acidic leachates, recovered from low-grade cerium-
bearing Egyptian ore.