Defense of the dissertation of Rakisheva Saniya for the degree of Doctor of Philosophy (PhD) in the educational program «8D07140 - Nanomaterials and nanotechnologies»

The defense of the dissertation for the degree of Doctor of Philosophy (PhD) by Rakisheva Saniya Renatovna on the topic «Development of the MOF-based composite track etched membranes for adsorptive removing of uranyl ions» under the educational program «8D07140- Nanomaterials and Nanotechnology» will be held at the L.N. Gumilev Eurasian National University.

The dissertation was carried out at the «Nuclear physics, new materials and technologies education department» of L.N. Gumilyov Eurasian National University.

The language of defense is russian

Official reviewers:

Efremov Sergey Anatolyevich – Doctor of Chemical Sciences, Professor, Professor of the Department of Analytical, Colloidal Chemistry and Technology of Rare Elements of the NJSC "KazNU named after al-Farabi", (Almaty, Republic of Kazakhstan);

Melnikova Galina Borisovna – Candidate of Physical and Mathematical Sciences, Associate Professor, Scientific Secretary of the Department of Physical and Technical Sciences of the National Academy of Sciences of Belarus, (Minsk, Republic of Belarus).

Temporary members of the Dissertation Council:

Vinogradov Ilya Igorevich – PhD, Head of the Sector of the Center for Applied Physics of the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research (Dubna, Russian Federation);

Klivenko Alexey Nicolayevich – PhD, Associate Professor, Director of Shakarim Lab (Ust-Kamenogorsk, Republic of Kazakhstan);

Amitova Aigul Amantayevna – PhD, Leading Researcher at Kazakhstan Oil group LLP (Aktau, Republic of Kazakhstan).

Scientific advisors:

Mashentseva Anastassiya Aleksandrovna – PhD, Professor, Practitioner of the Department of Nuclear Physics, New Materials and Technologies, L.N. Gumilyov Eurasian National University (Astana, Republic of Kazakhstan)

Murat Barsbay – PhD, Professor of the Department of Chemistry, Faculty of Science, Hacettepe University (Ankara, Türkiye)

The defense will take place on June 09, 2026, at 02:00 PM in the Dissertation Council for the training direction «8D071 – Engineering and engineering trades» in the specialty «8D07140 – Nanomaterials and nanotechnologies» of L.N. Gumilyov Eurasian National University. The dissertation council meeting will be held in a mixed (offline and online) format.

Link: https://clck.ru/3TS9bD  

Address: Astana, Kazhymukan Street 13, Room 309.

Abstract (English): ANNOTATION The dissertation of Rakisheva Saniya on the topic «Development of the MOF-based composite track etched membranes for adsorptive removing of uranyl ions», submitted for the degree of Doctor of Philosophy (PhD) in the educational program «8D07140 – Nanomaterials and nanotechnologies» General characteristics of the work. The dissertation work is devoted to the development of a method for modifying track membranes based on polyethylene terephthalate (PET TeM) with metal-organic frameworks (MOF) of the MIL-101(Cr) type, including doping with nanoparticles, and exploring the possibility of using these composite materials in the sorption removal of uranium U(VI) ions. Relevance of the work. An analysis of current directions in the development of the global economy shows that in conditions of increasing energy demand and limited fossil resources, the importance of nuclear energy will constantly increase. Uranium is the main fuel for nuclear reactors, but its reserves in terrestrial ores are limited, which stimulates the search for alternative sources and effective methods of its extraction. At the same time, uranium, being a heavy natural radionuclide, poses a serious environmental danger, since wastewater from the nuclear industry and ore mining can pollute the aquatic environment. Given the significant reserves of uranium in the bowels of the Republic of Kazakhstan and the country's leading position in its extraction, the development of effective methods for extracting uranium from aqueous solutions is an urgent and sought-after objective. In recent years, various methods have been proposed for the extraction of U(VI) from solutions, including ion exchange, solvent extraction, co-precipitation, and flotation. Among them, adsorption is considered one of the most effective and economical ways to remove uranium from the aquatic environment. Of particular interest are organometallic frameworks (MOFs), which have a high surface area, an adjustable porous structure, and the possibility of post-synthetic modification, which makes them promising materials for the selective adsorption of uranium ions. This paper proposes the development of membrane sorbents based on PET track-etched membranes (PET TeM) and metal-organic frameworks (MOF), combining high mechanical and chemical stability of membranes with a developed surface. To increase the sorption capacity and selectivity, it is planned to carry out post-synthetic modification of the scaffolds using "click chemistry" methods. It is no coincidence that it was for the development of click chemistry that Caroline Bertozzi, Barry Sharpless, and Morten Meldal were awarded the Nobel Prize in Chemistry in 2022 [1]. This strategy is based on highly selective reactions that occur quickly and with minimal formation of by-products, which makes it one of the most effective tools for modifying functional materials. Using this approach will make it possible to create promising sorption materials for the efficient extraction of uranium ions from aqueous solutions. The purpose of the dissertation research. Experimental development of new effective and highly selective sorbents of uranium (VI) ions based on PET TeMs modified with chromium-based metal-organic frameworks (MOF) of the MIL-101 series, including those with impregnated metal nanoparticles, as well as a comprehensive study of the properties of the obtained composite track membranes in the processes of sorption removal of uranium (VI) ions in model systems. Achieving this goal involves solving the following objectives: - Investigation of the specific features of the processes of directed modification of PET TeM with poly(N-vinyl formamide) (PNVF) by RAFT-initiated polymerization, followed by condensation to saturate samples with alkyne fragments. - Investigation of the possibility of using "click chemistry" techniques to immobilize MOF MIL-101(Cr) on the surface of modified PET TeM. - Investigation of the kinetics and mechanism of sorption removal of uranium (VI) ions in the presence of MOF @PET TeM composites. - Investigation of the effect of the nature of the reducing agent on the structure and sorption properties of azide-modified MIL-101(Cr) MOF modified with silver nanoparticles. - Investigation of the effect of the MOF modification MOF@PET TeM nanoparticles of silver and iron oxide for their sorption characteristics in the processes of selective removal of uranium (VI) ions. Research object. Composite materials based on microporous polymer TeMs based on PET modified with functional monomers and organometallic frameworks (MOFs) based on MIL101 (Cr) and with immobilized silver Ag and iron oxide Fe3O4 nanoparticles. The relationship of the work with the plan of the state scientific programs. This work was carried out within the framework of the grant financing project of the Ministry of Education and Science of the Republic of Kazakhstan "MOF decorated track membranes for selective and effective sorption of uranium (IV) ions: theoretical calculations and experimental verification" (IRN AP19676626, implementation period 2023-2025) and the JINR CIS Research and Development Center project "Synthesis of composite Sorbents based on Cr(azide)@MOF-PET track etched membranes modified with iron oxide nanoparticles" (contract № 25-112, implementation period 05.12.2025-12.10.2025). Scientific novelty. For the first time, optimal conditions for the modification of PET TeM by RAFT-mediated graft polymerization with N-vinyl formamide (NVF) and subsequent hydrolysis have been determined, ensuring a high conversion of NVF to polyvinylamine (PVA), which makes it possible to synthesize alkyne@PET TeM by condensation. For the first time, composite TeMs modified with MIL-101(Cr) type of MOFs were synthesized using "click chemistry" techniques, and optimal process conditions were determined. During the study of sorption removal of uranium (VI) ions in the presence of MOF@PET TeM composites has been established that the sorption kinetics is best described by the pseudo-second-order model and the adsorption of U(VI) on MOF@PET TM is probably caused by chemisorption involving interactions between U(VI) ions and specific active sites such as carboxylate or azide triazole groups. Among the tested models, the Freundlich isotherm provided the best match (R2=0,997), which indicates that adsorption occurs on a heterogeneous MOF@PET TeM surface with a different range of binding energies. When studying the modification process of an azide derivative of MOF type MIL-101(Cr) with silver nanoparticles, it was found that the use of hydrazine hydrate and sodium borohydride makes it possible to synthesize silver nanoparticles with a dimension of about 50,22±2,1 nm and provides the highest sorption capacity of samples during removing uranyl ions. When studying the effect of the method of immobilization of silver and iron oxide nanoparticles in the MOF@PET TeM structure has been found that the preliminary modification of the modified MOF type MIL-101(Cr) with these nanoparticles not only improves the efficiency of composite sorbents, but also reduces the time to achieve sorption equilibrium by 2,5 times. The main provisions of the dissertation submitted for defense. RAFT-mediated grafting polymerization with N-vinyl formamide (NVF) (10% monomer, 4 hours, butanol) leads to a maximum grafting rate of 14.0%. Subsequent hydrolysis is accompanied by an increase in the concentration of amino groups to 26.87 nmol/cm2, which leads to the formation of a grafted layer of polyvinylamine on the surface of PET TeM. The immobilization of MIL-101(Cr) type MOF in the presence of a DCC catalyst ensures MOF loading of about 2.3% (at.wt) for 72 hours of the reaction, while a further increase in reaction time does not affect the increase in the degree of MOF loading. The composite MOF @PET TeM provides effective sorption of uranium (VI) ions at pH=6.3, equal to 418.0 mg/g, the time to reach equilibrium is 96 hours. The kinetics of the sorption process correspond to a pseudo-second-order model with a rate constant of 4.38×10-4 g/mg×min, and the sorption mechanism can be described by the Freundlich isotherm with a coefficient of determination of R2=0.99. At the same time, MOF@PET TeM composite has a high selectivity for uranyl ions with a distribution coefficient of 7.97 × 10⁷ mL/g. The use of an environmentally friendly reducing agent, sodium borohydride, in the immobilization of silver nanoparticles on an azide derivative of MOF type MIL-101(Cr) increases its sorption capacity by more than 91.57% compared with the initial MOF and by more than 71.47% and 81.57% compared with samples reduced with DMAB and ascorbic acid, respectively. Modification of the composite MOF@PET TeM with Fe3O4 nanoparticles makes it possible not only to increase the sorption capacity by more than 20%, but also to significantly reduce the time to reach sorption equilibrium from 96 hours to 48 hours. Practical significance of the work. The composite sorbents of the MOF@PET TeM type obtained as a result of the conducted research can be successfully used for testing in real-world enterprises and become the basis for the development of high-tech products. Based on the research results, a patent application for a utility model has been filed (application № 2026/0638.2). Personal contribution of the author consists in analyzing literary sources, conducting experimental and computational work, interpreting, theoretically substantiating, summarizing, discussing the results obtained, preparing and arranging schedules, and preparing the manuscript of the article. Approbation of the work. The main provisions, conclusions and scientific results of the dissertation were reported and discussed at international conferences: NANOTR-18. (Istanbul, 2024); V International Scientific Forum, Nuclear Science and Technologies. (Almaty, 2024); INESS 13th International Conference on Nanomaterials & Advanced Energy Storage Systems, (Astana, 2025); XVI International Scientific Conference "Mmembranes-2025" (Minsk, 2025). Publications. The main results of the dissertation research are reflected in 10 published papers, including 2 articles in scientific publications included in the first and/or second quartile of impact factor according to the Journal Citation Reports of Clarivate Analytics; 3 articles in publications recommended by the authorized body and 5 papers in materials of national and international conferences: In one publication in a scientific publication included in the first quartile of the impact factor according to the Journal Citation Reports, the applicant is the first author: Rakisheva S.R., Mashentseva A.A., Yessengaliyeva N.B., Barsbay M., Abuova F.U., Zheltov D.A. MOF-decorated track-etched membranes for the U(VI) ions sorption removal. // Scientific Reports. – 2025 – Vol.15. – P. 36454 (Web of Science: Q1 - Multidisciplinary sciences; Scopus: 89% – Multidisciplinary). Mashentseva A.A., Sütekin D.S., Rakisheva S.R., Barsbay M. «Composite Track-Etched Membranes: Synthesis and Multifaced Applications//Polymers– 2024. – Vol. 16. – P.2616. // Polymers. – 2022. – Vol.16. – P. 2616. (64 p.), (Web of Science: Q1 - Polymer Science, Q1 – Polymers and Plastics; Scopus: 78% – Materials Science (Polymers and Plastics), 76% - Chemistry (General Chemistry). 1 Bauer D. и др. Click chemistry: a transformative technology in nuclear medicine // Nat. Protoc. 2023. Т. 18, № 6. С. 1659–1668.

Dissertation

List of Scientific Works

Consultant's Review

Foreign Consultant's Review

Conclusion of the Research Ethics Committee