Nd Recovery from Wastewater with Magnetic Calcium Alginate ((1,4)-β-d-Mannuronic Acid and α-L-Guluronic Acid) Hydrogels

Abstract

In this study, a magnetic adsorbent material was produced, by environmentally friendly and inexpensive precursor materials, to clean wastewater that may result from primary and secondary rare earth metal (REM) production. Then, the absorption of Nd 3+ ions from wastewater was done and this process's kinetic and isotherm models were developed. Thus, the removal of Nd 3+ from wastewater with magnetic materials was accomplished, and then, this precious metal was recovered by using different acid media. First, Fe sub-micron particles were successfully produced by the polyol method. To increase the stability of Fe-based particles, their surfaces were covered with an oxide layer, and the average thickness was determined as 16 nm. The synthesized Fe particles were added into the calcium alginate beads and then coated with chitosan to increase the pH stability of the gels. The chemical composition of the gels was determined by Fourier transform infrared spectroscopy, the thermal properties were determined by differential scanning calorimetry, and the magnetic properties were determined by vibrating-sample magnetometer analysis. The magnetic saturation of the hydrogels was 0.297 emu/g. After the production of magnetic calcium alginate hydrogels, Nd 3+ ion removal from wastewater was done. Wastewater was cleaned with 94.22% efficiency. The kinetic models of the adsorption study were derived, and isotherm studies were done. Adsorption reaction fitted different kinetic models at different time intervals and the Freundlich isotherm model. The effect of pH, temperature, and solid−liquid ratio on the system was determined and the thermodynamic constants of the system were calculated. After the adsorption studies, Nd 3+ ions were regenerated in different acid environments and achieved an 87.48% efficiency value. The removal of Nd 3+ ions from wastewater was carried out with high efficiency, the gels obtained as a result of adsorption were regenerated with high efficiency by using acid media, and it was predicted that the gels could be reused. This study is thought to have reference results not only for the removal of REM from wastewater by magnetic adsorption materials but also for the adsorption of heavy metals from wastewater.

Development of a Near-Zero-Waste Valorization Concept for Waste NdFeB Magnets: Production of Antimicrobial Fe Alginate Beads via Adsorption and Recovery of High-Purity Rare-Earth Elements

“…The FTIR spectrum of CaAlg and FeAlg gel obtained from the adsorption process is shown in Figure . The peak at 3242 cm –1 in the CaAlg spectrum refers to the vibration of OH bonds, the peak at 930 cm –1 refers to the vibration of the C–O bond, the peaks at 1592 and 1415 cm –1 refer to the symmetric and asymmetric carboxyl group vibrations at 3242 cm –1 , and the peak at 1031 cm –1 refers to the pyranose ring. ,, The FTIR spectrum of the CaAlg gels obtained as a result of the adsorption process demonstrates that the chemical structure of alginate is preserved. It was observed that the carboxylate peaks at 1592 and 1415 cm –1 (shifted to 1590 and 1411 cm –1 ) shifted to the right; furthermore, the pyranose ring bond peak at 1031 cm –1 (shifted to 1029 cm –1 ) also shifted to the right.…”

“…Equaions and estimated the Gibbs free energy change (Δ G °) of adsorption studies; eq calculated Δ H ° and Δ S ° …”

“…Equaions and estimated the Gibbs free energy change (Δ G °) of adsorption studies; eq calculated Δ H ° and Δ S ° normalΔ G ° = italicRT 0.25em ln ( 55.5 × K normald ) K d = Q e / C e ln ( K normald ) = normalΔ S ° R − normalΔ H ° RT …”