## 4 Conclusions  
The main objective of this study was the creation and characterization of a novel class of multifunctional hybrid membranes combining modified chitosan, functionalized multi-walled carbon nanotubes (MWCNTs), and rare earth element ion-imprinted polymers (REEIIPs), designed for selective adsorption and separation of lanthanide ions (Nd\({}^{3+}\), Pr\({}^{3+}\), Gd\({}^{3+}\)) from coal fly ash extracts. To evaluate potential future applications of proposed hybrid adsorptive membranes in industry, characterization of their magnetic, chemical, structural, mechanical, rheological, and thermal properties was conducted. The obtained membranes exhibit tunable magnetic properties through precise adjustment of MWCNT content, their functionalization, and the magnetic casting method (even a 10-fold increase in magnetic saturation and coercivity decrease with the rise in MWCNT addition). The proposed polymer matrix modifications and incorporation of REEIIP-functionalized MWCNTs simultaneously enhanced mechanical properties, like tensile strength and Young's modulus (2-fold increase), and thermooxidative stability (Gd-sensitive membranes stable even up 730 \({}^{\circ}\)C). Performed structural (SEM and XRD) analysis confirmed homogeneous dispersion, phase compatibility, network integration, and formation of a complex 3D microstructure. While TGA and DMA analysis (almost a 2-fold increase in storage E\({}^{\prime}\) and loss E\({}^{\prime\prime}\) modules) indicated improved operational stability of created hybrid membranes, which is significant for their future applications. Synthesized hybrid membranes showed a high rejection of matrix components and an increase in retention ratio with rising MWCNT-REEIIP addition, ultimately reaching 94.35%, 92.12%, and 90.11% for Nd, Pr, and Gd, respectively. This paper presents biopolymer-based, magnetically responsive, and REE selective and specific hybrid membranes that address the current need for sustainable, reusable, and high-performance materials applied in critical metal recovery and environmental protection. The studied properties of the newly synthesized adsorption membranes were extremely important in terms of their use for the recovery of Nd, Pr, and Gd from coal fly ash extracts with a rich composition, a complex matrix, and extreme pH ranges.  
**Author Contributions:** Conceptualization, A.R. ([PERSON]), A.R. ([PERSON]), S.B. and S.D.K.; methodology, A.R. ([PERSON]), A.R. ([PERSON]), W.K., S.B. and A.K. ([PERSON]); analysis, A.R. ([PERSON]), A.R. ([PERSON]), W.K., S.B., A.K., M.N., R.M. and J.J.; software, A.R. ([PERSON]) and A.R. ([PERSON]); writing--original draft preparation, A.R. ([PERSON]), A.R. ([PERSON]), W.K., S.B., A.K., M.N., R.M., J.J. and S.D.K. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by Norway Grants 2014-2021 via the National Centre for Research and Development, grant number NOR/SGS/MOHMARER/0284/2020-00. SD Kolev is grateful for the financial support of the European Union-NextGenerationEU, through the National Recovery and Resilience Plan of the Republic of Bulgaria, project No. BG-RRP-2.004-0008.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.  
**Conflicts of Interest:** There are no conflicts to declare.