Abstract
Background: Rare earth elements, REEs, are used for many high-tech applications; the rarefaction of the resource requires developing methods for their recovery from low-grade sources and their recycling from waste materials. Sorption processes, including biosorbents, represent an interesting method for their recovery from dilute effluents.
Objective: This work investigates the sorption of 3 REEs using a cheap, renewable biosorbents: microcrystalline cellulose (considered as a reference material for on-going research on chemically modified materials). Methods: Sorption properties are studied considering the effect of pH, the uptake kinetics, the sorption isotherms, the thermodynamic parameters, the recycling of the material and its reuse for successive sorption/desorption cycles. Results: Metal sorption increases with pH, uptake kinetics are relatively fast with an equilibrium reached within 3-4 hours. The kinetic profiles are well fitted by the pseudo-second order rate equation. Maximum sorption capacity reaches 31-53 mg metal g-1, and the Langmuir equation fits well sorption isotherms. The reaction is endothermic and spontaneous. Metal ions can be readily desorbed with 0.5 M HNO3 solutions and the sorbent can be recycled for at least 4 cycles of sorption/desorption with limited decrease in performance (less than 3 %). FTIR and XRD analyses contribute to the characterization of the material and the interpretation of sorption mechanism. Conclusion: Microcrystalline cellulose has low sorption capacities for La(III), Nd(III), and Er(III); however, this renewable resource with high effectiveness in terms of recycling and re-use is a promising support for metal recovery.Keywords: Cellulose, sorption isotherms, uptake kinetics, rare earth metal ions, metal desorption, sorbent recycling, sorption thermodynamics.
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