SYNTHESIS AND CHARACTERISATION OF NANO-BIOCOMPOSITES AND INVESTIGATION OF THEIR USE IN THE RECOVERY OF RARE EARTH ELEMENTS
Project no. 24045 · Status: Kapanmış · 2022
Summary
<p>In this doctoral dissertation, the development, characterization, and application potential of environmentally friendly, biodegradable nanobiocomposites with high surface area were investigated for the recovery of rare earth elements. The study specifically focused on the adsorption of lanthanide group elements, such as lanthanum (La) and neodymium (Nd), from aqueous solutions using carboxymethyl cellulose (CMC)-based biopolymers. For this purpose, nanocrystalline cellulose (NCC) derived from textile waste was composited with a CMC matrix to synthesize CMC/NCC bionanocomposites, which were analyzed using advanced characterization techniques including FTIR, SEM, XRD, DLS, and XPS.</p><p><br></p><p>Adsorption experiments were conducted by considering parameters such as pH, temperature, initial ion concentration, contact time, and adsorbent dosage to evaluate their effects on performance. The results demonstrated that CMC/NCC bionanocomposites exhibited a high capacity for La(III) and Nd(III) adsorption, and the optimum adsorption conditions were determined. Experimental data showed a strong fit with the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models, while the calculated thermodynamic parameters indicated that the adsorption process was endothermic and spontaneous. Kinetic studies revealed that the adsorption closely followed the pseudo-second-order model, indicating that ion retention on the surface was primarily governed by chemical interactions and that the adsorption rate was controlled by chemisorption mechanisms.</p><p><br></p><p>Additionally, selectivity experiments were carried out to evaluate the adsorption behavior in the presence of different competing metal ions. The results indicated that although the CMC/NCC composites displayed high adsorption capacity, they did not exhibit pronounced selectivity for lanthanide ions. Nonetheless, owing to the hydrogel structure rich in functional groups, the materials effectively removed various metal ions from solution.</p><p><br></p><p>One of the innovative aspects of this study is the integration of nanocellulose derived directly from textile waste into functional composite structures without the need for additional chemical additives. This approach offers an environmentally friendly solution for sustainable waste management while also providing economic advantages in adsorbent production.</p><p><br></p><p>In conclusion, this dissertation demonstrates that nanocellulose-based biocomposites present a promising alternative for the recovery of rare earth elements. With their eco-friendly nature, high adsorption capacity, favorable kinetic behavior, applicability, and cost-effectiveness, these new-generation biopolymer-based adsorbents are strong candidates for both industrial and environmental applications. Furthermore, the study contributes significantly to the utilization of national resources by offering an approach to recover lanthanides, which are by-products of thorium deposits in Türkiye.</p>