Influence of hydrophilic groups and metal-ion adsorption on polymer-chain conformation of amidoxime-based uranium adsorbents

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:524

Article

Wiechert, Alexander I.¹  Liao, Wei-Po²  Hong, Eunice²  Halbert, Candice E.²  Yiacoumi, Sotira¹  Saito, Tomonori²  Tsouris, Costas^1,2 

[1] Georgia Inst Technol, Sch Civil & Environm Engn, Atlanta, GA 30332 USA

[2] Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA

关键词: Neutron reflectometry;    Amidoxime;    Polymer conformation;    Uranium;    Seawater;   

DOI  :  10.1016/j.jcis.2018.04.021

来源: Elsevier

【 摘 要 】

This study focuses on the influence of hydrophilic groups and metal-ion loading on adsorbent polymer conformation, which controls access to adsorption sites and may limit adsorption capacity. Gaining a better understanding of the factors that influence conformation may yield higher-capacity adsorbents. Polyamidoxime (PAO), deuterated-PAO polyacrylic acid diblock copolymers (d-PAO-b-PAA), and randomly configured copolymers (PAO-co-PAA) were synthesized and characterized by neutron reflectometry in air and D2O. For d-PAO-b-PAA, characterization was also performed after alkali conditioning and in simulated seawater. PAO and PAO-co-PAA, with similar molecular weight and grafting density, extended from 95-angstrom thickness in air to 180 and 280-angstrom in D2O, respectively. This result suggests that polymer swelling may cause the additional adsorption capacity observed when polymer hydrophilicity increases. Two d-PAO-b-PAA samples, A and B, with a d-PAO thickness of 55-angstrom swelled to 110-angstrom and 140-angstrom, respectively, with an overall thickness increase of similar to 160% in D2O. After alkali conditioning, molecular interactions increased the density of PAA near the PAO-PAA interface, while the d-PAO thickness only decreased by similar to 10 angstrom. The d-PAO thickness of both samples declined to similar to 90-angstrom after adsorption in simulated seawater due to polymer-chain crosslinking. These results are expected to aid in improving adsorbent synthesis to increase uranium capacity. (C) 2018 Elsevier Inc. All rights reserved.

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