The use of halloysite functionalized with isothiouronium salts as an organic/inorganic hybrid adsorbent for uranium(VI) ions removal

• Published in: Journal of hazardous materials Vol. 354; pp. 133 - 144
• Main Authors: Gładysz-Płaska, A., Majdan, M., Tarasiuk, B., Sternik, D., Grabias, E.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.07.2018
• Subjects: Adsorption; Halloysite; Isothiouronium salts; Uranium; Isothiouronium salts; Uranium; Adsorption; Halloysite
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2018.03.057

[Display omitted] •Halloysite sorbents with isothiouronium groups are synthesized for U(VI).•The maximum sorption capacity of sorbent 157 mg U/g.•The sorption of U(VI) from acidic aqueous solutions with 12–20% efficiency.•[R-S-C(=NH)(NH2)]n = 1-2(UO22+) complexes interacting with silanols.•Oligomeric hydroxy complexes (UO2)3(OH)5+ and (UO2)4(OH)7+ in the sorbent interior. Elimination of U(VI) from nuclear wastes and from the underground water near the uranium mines is the serious problem. Therefore search for new sorbents for U(VI) is still a big challenge for the scientists. This paper investigates of U(VI) ions sorption on halloysite modified with the isothiouronium salts: S-dodecaneisothiouronium bromide (ligand 1), S,S'-dodecane-1,12-diylbis(isothiouronium bromide) (ligand 2), S-hexadecaneisothiouronium chloride (ligand 3), S,S'-naphthalene-1,4-diylbis(methylisothiouronium) dichloride (ligand 4), and S,S'-2,5-dimethylbenzene-1,4-diylbis(methylisothiouronium) dichloride (ligand 5). It was established that halloysite modified by the ligands with four nitrogen atoms in their structure (ligand-5, 2 and 4) was characterized by higher sorption capacity compared with that modified by the ligands with two donor nitrogens (ligand-1 and 3). The maximum sorption capacity of halloysite-5 toward U(VI) was 157 mg U/g and this places the modified mineral among the most effective sorbents for U(VI) removal from wastes. As follows from ATR, XPS and thermal degradation spectra of the sorption products [R-S-C(NH)(NH2)]n = 1-2(UO22+) complexes are formed on the external surface of the halloysite whereas oligomeric hydroxy complexes (UO2)3(OH)5+ and (UO2)4(OH)7+ are present in the interior of halloysite structure and interact predominantly with aluminols.