{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,24]],"date-time":"2026-04-24T15:34:32Z","timestamp":1777044872834,"version":"3.51.4"},"reference-count":23,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2010,9,6]],"date-time":"2010-09-06T00:00:00Z","timestamp":1283731200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Microwave irradiation was used to obtain a di-Schiff base type crosslinked chitosan dibenzocrown ether (CCdBE) via the reaction between the \u2013NH2 and \u2013CHO groups in chitosan and 4,4\u2032-diformyldibenzo-18-c-6, respectively. The structure of the synthesized compound was characterized by elemental analysis, solid state 13C-NMR and FT-IR spectra analysis. The results showed that the mass fraction of nitrogen in the CCdBE derivative was much lower than those of chitosan. The FT-IR spectra of CCdBE revealed the expected chitosan-crown ether structure, as evidenced by the presence of the characteristic C=N and Ar peaks. The adsorption properties of CCdBE for Pd2+ and Hg2+ were investigated and the results demonstrated that the adsorbent has both desirable adsorption properties with a high particular adsorption selectivity for Hg2+ when in the presence of Pb2+ as well as selectivity coefficients for metal ions of KHg2+ \/Pb2+ = 8.00 and KHg 2+\/Pb2+ = 10.62 at pH values of 4 and 6, respectively. The reusability tests for CCdBE for Pb2+ adsorption showed that complete recovery of the ion was possible with CCdBE after 10-multiple reuses while CTS had no reusability at acidic solution because of its higher dissolution. The studied features of CCdBE suggested that the material could be considered as a new adsorbent. It is envisaged that the crosslinking of CTS into CCdBE would enhance practicality and effectiveness of adsorption in ion separation and removal procedures.<\/jats:p>","DOI":"10.3390\/molecules15096257","type":"journal-article","created":{"date-parts":[[2010,9,19]],"date-time":"2010-09-19T09:41:46Z","timestamp":1284889306000},"page":"6257-6268","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":33,"title":["Microwave Irradiation-Assisted Synthesis of a Novel Crown Ether Crosslinked Chitosan as a Chelating Agent for Heavy Metal Ions (M+n)"],"prefix":"10.3390","volume":"15","author":[{"given":"Awwad A.","family":"Radwan","sequence":"first","affiliation":[{"name":"College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia"},{"name":"Department of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Assiut University, Assiut-71527, Egypt"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fars K.","family":"Alanazi","sequence":"additional","affiliation":[{"name":"College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia"},{"name":"Department of Pharmaceutics, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ibrahim A.","family":"Alsarra","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutics, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia"},{"name":"Center of Excellence for Research in Engineering Materials, CEREM, Room 2A-138, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421, Saudi Arabia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2010,9,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1016\/j.chemosphere.2003.10.034","article-title":"Adsorption of Cu and Mn on covalently crosslinked alginate gel beads","volume":"55","author":"Gotoh","year":"2004","journal-title":"Chemosphere"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1016\/j.chemosphere.2003.11.016","article-title":"Preparation of alginate-chitosan hybrid gel beads and adsorption of divalent metal ions","volume":"55","author":"Gotoh","year":"2004","journal-title":"Chemosphere"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2558","DOI":"10.1016\/j.biortech.2009.10.069","article-title":"Novel complex gel beads composed of hydrolyzed polyacrylamide and chitosan: An effective adsorbent for the removal of heavy metal from aqueous solution","volume":"101","author":"Cao","year":"2010","journal-title":"Bioresource Technol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"348","DOI":"10.1016\/j.jhazmat.2009.11.034","article-title":"Adsorption of Cu(II), Hg(II), and Ni(II) ions by modified natural wool chelating fibers","volume":"176","author":"Monier","year":"2010","journal-title":"J. Hazard. Mater."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"613","DOI":"10.1016\/S0043-1354(00)00307-9","article-title":"Kinetic modeling of liquid-phase adsorption of reactive dyes and metal ions on chitosan","volume":"35","author":"Wu","year":"2001","journal-title":"Water Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"995","DOI":"10.1016\/j.jhazmat.2008.04.078","article-title":"Characteristics of equilibrium, kinetics studies for adsorption of Hg(II), Cu(II), and Ni(II) ions by thiourea-modified magnetic chitosan microspheres","volume":"161","author":"Zhoua","year":"2009","journal-title":"J. Hazard. Mater."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"3219","DOI":"10.1016\/S0043-1354(02)00044-1","article-title":"Kinetics of cadmium uptake by chitosan-based crab shells","volume":"36","author":"Evans","year":"2002","journal-title":"Water Res."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"503","DOI":"10.1016\/j.jhazmat.2008.05.073","article-title":"Chitosan selectivity for removing cadmium (II), copper (II), and lead (II) from aqueous phase: pH and organic matter effect","volume":"162","author":"Shirai","year":"2009","journal-title":"J. Hazard. Mater."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"469","DOI":"10.1016\/0043-1354(92)90047-8","article-title":"Uptake of Pb2+ and Cu2+ by novel biopolymers","volume":"26","author":"Deans","year":"1992","journal-title":"Water Res."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"511","DOI":"10.1002\/app.1979.070230221","article-title":"Studies on Chitin. VI. Binding of Metal Cations","volume":"23","author":"Kurita","year":"1979","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"E756","DOI":"10.1208\/aapsj080485","article-title":"In vitro evaluation of chitosan-EDTA conjugate polyplexes as a nanoparticulate gene delivery system","volume":"8","author":"Loretz","year":"2006","journal-title":"AAPS J."},{"key":"ref_12","first-page":"483","article-title":"Removal of metallic ions by partially polyamine polymers","volume":"19","author":"Masri","year":"1978","journal-title":"Polym. Preprints-Am."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"9765","DOI":"10.1021\/la025917l","article-title":"Mechanisms of lead adsorption of chitosan\/PVA hydrogel beads","volume":"18","author":"Jin","year":"2002","journal-title":"Langmuir"},{"key":"ref_14","first-page":"1","article-title":"Adsorption of Cu(II) and Cr(VI) ions by chitosan: kinetics and equilibrium studies","volume":"27","author":"Schmuhl","year":"2001","journal-title":"Water SA"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"591","DOI":"10.1021\/la00002a039","article-title":"Enhancement of metal ion sorption performances of chitosan: effect of the structure on the diffusion properties","volume":"11","author":"Guibal","year":"1995","journal-title":"Langmuir"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"580","DOI":"10.1021\/jf00087a002","article-title":"Crawfish chitosan as a coagulant in recovery of organic compounds from seafood processing streams","volume":"37","author":"No","year":"1989","journal-title":"J. Agric. Food Chem."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"425","DOI":"10.1016\/S0144-8617(03)00104-8","article-title":"Preparation of new crosslinked chitosan with crown ether and their adsorption for silver ion for antibacterial activities","volume":"53","author":"Yi","year":"2003","journal-title":"Carbohydr. Polym."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"2150","DOI":"10.1016\/j.carres.2005.06.028","article-title":"Salt-assisted acid hydrolysis of chitosan to oligomers under microwave irradiation","volume":"340","author":"Xing","year":"2005","journal-title":"Carbohydr. Res."},{"key":"ref_19","first-page":"102","article-title":"Application of microwave irradiation in the synthesis of heterocyclic compounds","volume":"21","author":"Sha","year":"2001","journal-title":"Chin. J. Org. Chem."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1473","DOI":"10.1246\/bcsj.53.1473","article-title":"New applications of crown ethers. II. Synthesis of 4\u2032-Formylbenzocrown Ethers","volume":"53","author":"Wada","year":"1980","journal-title":"Bull. Chem. Soc. Jpn."},{"key":"ref_21","first-page":"1081","article-title":"Solid-state characterization of the structure of chitosan films","volume":"19","author":"Samuels","year":"1981","journal-title":"J. Polym. Sci. Part B: Polym. Phys."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1016\/j.carbpol.2008.06.006","article-title":"Physicochemical characterization of chitin and chitosan from crab shells","volume":"75","author":"Yen","year":"2009","journal-title":"Carbohydr. Polym."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1886","DOI":"10.1002\/app.2316","article-title":"Study of the synthesis of chitosan derivatives containing benzo-21-crown-7 and their adsorption properties for metal ions","volume":"83","author":"Tang","year":"2001","journal-title":"J. Appl. Polym. Sci."}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/15\/9\/6257\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T22:03:19Z","timestamp":1760220199000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/15\/9\/6257"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2010,9,6]]},"references-count":23,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2010,9]]}},"alternative-id":["molecules15096257"],"URL":"https:\/\/doi.org\/10.3390\/molecules15096257","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2010,9,6]]}}}