{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,21]],"date-time":"2026-09-21T15:03:01Z","timestamp":1790002981832,"version":"4.0.1"},"reference-count":27,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2026,9,19]],"date-time":"2026-09-19T00:00:00Z","timestamp":1789776000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan","award":["BR27101179"],"award-info":[{"award-number":["BR27101179"]}],"id":[{"id":"https:\/\/ror.org\/05tyne317","id-type":"ROR","asserted-by":"crossref"}]},{"award":["BR27101179"],"award-info":[{"award-number":["BR27101179"]}],"id":[{"id":"https:\/\/ror.org\/05tyne317","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Selective recovery of critical metals such as gallium and scandium from dilute, multicomponent process streams remains challenging due to their low concentrations and complex matrices. Here we investigate a remotely interacting intergel system based on crosslinked poly(acrylic acid) (hPAA) and poly(4-vinylpyridine) (hP4VP) hydrogels across seven mass ratios (6:0\u20130:6) for sorption of Ga(III) and Sc(III) from binary sulfate solutions. Inductively coupled plasma optical emission spectroscopy shows that mutual activation of the weak polyacid\/polybase pair markedly enhances metal uptake, with maximum sorption degrees of 73.17% for Ga(III) at hPAA:hP4VP = 3:3 and 56.00% for Sc(III) at 2:4, corresponding to distribution coefficients up to 2726.7 mL g\u22121 and Ga\/Sc selectivity factors \u03b2 up to 6.41. Sorption is well described by Langmuir-type isotherms, and desorption with 2 wt.% HNO3 reveals an inverse sorption\u2013release relationship, indicating stronger binding at compositions of maximal mutual activation. FTIR spectroscopy evidences inner-sphere complexation through bidentate carboxylate coordination in hPAA and M\u2190N dative bonding in hP4VP, while TGA\/DSC shows that metal-loaded hydrogels retain their structural integrity up to approximately 320\u2013340 \u00b0C, with the onset of significant decomposition occurring at ~350 \u00b0C for hP4VP-containing samples. The composition-dependent magnitude of Ga(III)-over-Sc(III) preferential uptake\u2014with selectivity coefficients \u03b2 = Kd(Ga)\/Kd(Sc) remaining greater than 1 across all seven compositions studied\u2014is rationalized using Hard\u2013Soft Acid\u2013Base considerations and demonstrates that hPAA:hP4VP intergels constitute a composition-tunable platform for enhancing Ga(III) recovery and partial Ga\/Sc separation from simplified sulfate media, motivating future validation in real hydrometallurgical liquors and in the presence of competing multivalent cations.<\/jats:p>","DOI":"10.3390\/molecules31183324","type":"journal-article","created":{"date-parts":[[2026,9,21]],"date-time":"2026-09-21T14:12:09Z","timestamp":1789999929000},"page":"3324","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Synergistic Sorption of Gallium(III) and Scandium(III) Ions by the Interpolymer System of Poly(Acrylic Acid)\/Poly(4-vinylpyr-idine) Hydrogels: Kinetics, Selectivity, and Mechanism"],"prefix":"10.3390","volume":"31","author":[{"given":"Bakytgul","family":"Totkhuskyzy","sequence":"first","affiliation":[{"name":"Bekturov Institute of Chemical Sciences, 106 Valikhanov Str., Almaty 050010, Kazakhstan"},{"name":"Department of Biotechnology and General Chemical Technology, School of Pharmacy, Asfendiyarov Kazakh National Medical University, 94 Tole bi Str., Almaty 050012, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Talkybek","family":"Jumadilov","sequence":"additional","affiliation":[{"name":"Bekturov Institute of Chemical Sciences, 106 Valikhanov Str., Almaty 050010, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5138-5997","authenticated-orcid":false,"given":"Khuangul","family":"Khimersen","sequence":"additional","affiliation":[{"name":"Bekturov Institute of Chemical Sciences, 106 Valikhanov Str., Almaty 050010, Kazakhstan"},{"name":"Department of Chemistry, Institute of Natural Sciences and Geography, Abai Kazakh National Pedagogical University, 13 Dostyk Ave., Almaty 050010, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"given":"Arailym","family":"Akhmetova","sequence":"additional","affiliation":[{"name":"School of Chemical Engineering, Kazakh-British Technical University, 59 Tole bi Str., Almaty 050000, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6377-7050","authenticated-orcid":false,"given":"J\u00f3zef","family":"Haponiuk","sequence":"additional","affiliation":[{"name":"Department of Polymer Technology, Gdansk University of Technology, 11\/12 Gabriela Narutowicza, 80-233 Gdansk, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Juozas","family":"Grazulevicius","sequence":"additional","affiliation":[{"name":"Department of Polymer Chemistry and Technology, Kaunas University of Technology, 73 K. Donelai\u010dio Street, 44249 Kaunas, Lithuania"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,19]]},"reference":[{"key":"ref_1","first-page":"1","article-title":"Electronic Waste and Semiconductor-Related Residues as Secondary Sources of Gallium: Occurrence, Processing Routes, Separation Challenges, and Circular Supply Perspectives","volume":"13","author":"Pereira","year":"2026","journal-title":"REMUNOM"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"e27869","DOI":"10.1002\/adfm.202527869","article-title":"Gallium-Based Semiconductor Integrated Circuits: Past, Present, and Future for Emerging Optoelectronic Devices","volume":"36","author":"Zhuang","year":"2026","journal-title":"Adv. Funct. Mater."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"103906","DOI":"10.1016\/j.oregeorev.2020.103906","article-title":"Scandium: Ore Deposits, the Pivotal Role of Magmatic Enrichment and Future Exploration","volume":"128","author":"Wang","year":"2021","journal-title":"Ore Geol. Rev."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"9","DOI":"10.52228\/JRUB.2021-34-1-2","article-title":"Need of Gallium Recovery from Waste Samples: A Review","volume":"34","author":"Swami","year":"2021","journal-title":"J. Ravishankar Univ. PART-B"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Shoppert, A., Loginova, I., Napol\u2019skikh, J., Kyrchikov, A., Chaikin, L., Rogozhnikov, D., and Valeev, D. (2022). Selective Scandium (Sc) Extraction from Bauxite Residue (Red Mud) Obtained by Alkali Fusion-Leaching Method. Materials, 15.","DOI":"10.3390\/ma15020433"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"108","DOI":"10.1080\/07366299.2024.2447483","article-title":"Recent Advances in Solvent Extraction for the Efficient Recovery of Scandium: A Review","volume":"43","author":"Yoshida","year":"2025","journal-title":"Solvent Extr. Ion Exch."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1237","DOI":"10.1002\/jctb.2655","article-title":"Separation and Purification of Scandium by Solvent Extraction and Related Technologies: A Review","volume":"86","author":"Wang","year":"2011","journal-title":"J. Chem. Technol. Biotechnol."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Salman, A.D., Juzsakova, T., Mohsen, S., Abdullah, T.A., Le, P.-C., Sebestyen, V., Sluser, B., and Cretescu, I. (2022). Scandium Recovery Methods from Mining, Metallurgical Extractive Industries, and Industrial Wastes. Materials, 15.","DOI":"10.3390\/ma15072376"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Jumadilov, T., Khimersen, K., Malimbayeva, Z., and Kondaurov, R. (2021). Effective Sorption of Europium Ions by Interpolymer System Based on Industrial Ion-Exchanger Resins Amberlite IR120 and AB-17-8. Materials, 14.","DOI":"10.3390\/ma14185402"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Talkybek, J., Khuangul, K., and Jozef, H. (2023). Influence of Initial States on the Electrochemical Behavior of Industrial Ionites in the Interpolymer System Lewatit CNP LF-AB-17-8. Advanced Polymer Structures, Apple Academic Press.","DOI":"10.1201\/9781003352181-9"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"21","DOI":"10.31643\/2026\/6445.37","article-title":"Study of the Kinetics of Sorption of Praseodymium and Neodymium Ions Using Interpolymer Systems Based on KU-2-8 and AB-17-8 in Salt Forms","volume":"339","author":"Jumadilov","year":"2026","journal-title":"Kompleks. Ispolzovanie Miner. Syra"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Dyussembayeva, G., Jumadilov, T., Gra\u017eulevicius, J., Mukatayeva, Z., Khimersen, K., and Totkhuskyzy, B. (2025). Selective Gold Ion Sorption from Iron-Containing Solution Using an Interpolymer System of Industrial Ion Exchangers. Polymers, 17.","DOI":"10.3390\/polym17202808"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"7","DOI":"10.23939\/chcht16.01.007","article-title":"Anomalous Sorption of Neodymium and Praseodymium Ions by Intergel System Polyacrylic Acid Hydrogel\u2013Poly-4-Vinylpyridine Hydrogel","volume":"16","author":"Jumadilov","year":"2022","journal-title":"Chem. Chem. Technol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"47","DOI":"10.31489\/2021Ch4\/47-56","article-title":"Abnormal Activity of Functional Groups during Uranyl Ions Sorption by Polymethacrylic Acid\u2013Poly-4-Vinylpyridine Intergel System","volume":"104","author":"Jumadilov","year":"2021","journal-title":"Bull. Karaganda Univ. Chem. Ser."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Jumadilov, T., Dyussembayeva, G., Mukatayeva, Z., Gra\u017eulevicius, J., and Khimersen, K. (2026). Selective Sorption of Gold and Iron Ions in the PMAA-P4VP Intergel System. Molecules, 31.","DOI":"10.3390\/molecules31101583"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"100497","DOI":"10.1016\/j.sctalk.2025.100497","article-title":"Novel Material Innovations for the Efficient Extraction and Separation of Critical Elements","volume":"16","author":"Protsak","year":"2025","journal-title":"Sci. Talks"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2005","DOI":"10.1039\/C5GC02225H","article-title":"Recovery of Scandium from Leachates of Greek Bauxite Residue by Adsorption on Functionalized Chitosan\u2013Silica Hybrid Materials","volume":"18","author":"Roosen","year":"2016","journal-title":"Green Chem."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"146869","DOI":"10.1016\/j.ijbiomac.2025.146869","article-title":"Hydroxamic Acid-Functionalized Chitosan Hydrogel Beads for Sustainable and Continuous Gallium Recovery","volume":"322","author":"Lv","year":"2025","journal-title":"Int. J. Biol. Macromol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"109980","DOI":"10.1016\/j.micromeso.2019.109980","article-title":"Bisphosphonate Modified Mesoporous Silicon for Scandium Adsorption","volume":"296","author":"Thapa","year":"2020","journal-title":"Microporous Mesoporous Mater."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"12549","DOI":"10.1021\/acs.est.1c01877","article-title":"Phosphate Polymer Nanogel for Selective and Efficient Rare Earth Element Recovery","volume":"55","author":"Zhang","year":"2021","journal-title":"Environ. Sci. Technol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"154468","DOI":"10.1016\/j.cej.2024.154468","article-title":"Enhanced Selective Extraction of Indium and Gallium Using Mesoporous Sorbents","volume":"498","author":"Protsak","year":"2024","journal-title":"Chem. Eng. J."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"23805","DOI":"10.1039\/C7TA08127H","article-title":"Titanium Alkylphosphate Functionalised Mesoporous Silica for Enhanced Uptake of Rare-Earth Ions","volume":"5","author":"Zhang","year":"2017","journal-title":"J. Mater. Chem. A"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Baishibekov, A., Fischer, D., Jumadilov, T., Temirova, S., Yulusov, S., Altaibayev, B., and Karim, D. (2025). Structural, Sorption, and Regeneration Properties of Poly(Methacrylic Acid): Poly(4-Vinylpyridine) Interpolymer Systems for the Recovery of Rhenium and Molybdenum. Polymers, 17.","DOI":"10.3390\/polym17223054"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"52","DOI":"10.23939\/chcht17.01.052","article-title":"Anomalous Sorption of Yttrium Ions by the Mutual Activated Hydrogels in the Interpolymer System of Poly(Methacrylic Acid) and Poly(4-Vinylpyridine)","volume":"17","author":"Jumadilov","year":"2023","journal-title":"Chem. Chem. Technol."},{"key":"ref_25","first-page":"1482","article-title":"Selective Sorption of Gold Ions from Iron-Rich Solutions Using a Dual-Phase Interpolymer System","volume":"35","author":"Jumadilov","year":"2025","journal-title":"Eng. Sci."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"3533","DOI":"10.1021\/ja00905a001","article-title":"Hard and Soft Acids and Bases","volume":"85","author":"Pearson","year":"1963","journal-title":"J. Am. Chem. Soc."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"84","DOI":"10.1016\/j.apsusc.2003.12.033","article-title":"The HSAB Concept as a Means to Interpret the Adsorption of Metal Ions onto Activated Carbons","volume":"228","author":"Alfarra","year":"2004","journal-title":"Appl. Surf. Sci."}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/18\/3324\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,21]],"date-time":"2026-09-21T14:19:12Z","timestamp":1790000352000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/18\/3324"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,19]]},"references-count":27,"journal-issue":{"issue":"18","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["molecules31183324"],"URL":"https:\/\/doi.org\/10.3390\/molecules31183324","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,19]]}}}