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Title: | Amino-Alkylphosphonate-Grafted TiO2: How the Alkyl Chain Length Impacts the Surface Properties and the Adsorption Efficiency for Pd | Authors: | Gys, Nick An, Rui PAWLAK, Bram Vogelsang, David Wyns, Kenny Baert, Kitty Vansant, Alexander Blockhuys, Frank ADRIAENSENS, Peter Hauffman, Tom Michielsen, Bart MULLENS, Steven Meynen, Vera |
Issue Date: | 2022 | Publisher: | AMER CHEMICAL SOC | Source: | ACS Omega, 7 (49) , p. 45409 -45421 | Status: | Early view | Abstract: | Amino-alkylphosphonic acid-grafted TiO2 materials are of increasing interest in a variety of applications such as metal sorption, heterogeneous catalysis, CO2 capture, and enzyme immobilization. To date, systematic insights into the synthesis- properties-performance correlation are missing for such materials, albeit giving important know-how towards their applicability and limitations. In this work, the impact of the chain length and modification conditions (concentration and temperature) of amino-alkylphosphonic acid-grafted TiO2 on the surface properties and adsorption performance of palladium is studied. Via grafting with aminomethyl-, 3-aminopropyl-, and 6-aminohexylphosphonic acid, combined with the spectroscopic techniques (DRIFT, 31P NMR, XPS) and zeta potential measurements, differences in surface properties between the C1, C3, and C6 chains are revealed. The modification degree decreases with increasing chain length under the same synthesis conditions, indicative of folded grafted groups that sterically shield an increasing area of binding sites with increasing chain length. Next, all techniques confirm the different surface interactions of a C1 chain compared to a C3 or C6 chain. This is in line with palladium adsorption experiments, where only for a C1 chain, the adsorption efficiency is affected by the precursor concentration used for modification. The absence of a straightforward correlation between the number of free NH2 groups and the adsorption capacity for the different chain lengths indicates that other chain-length-specific surface interactions are controlling the adsorption performance. The increasing pH stability in the order of C1 < C3 < C6 can possibly be associated to a higher fraction of inaccessible hydrophilic sites due to the presence of folded structures. Lastly, the comparison of adsorption performance and pH stability with 3-aminopropyl(triethoxysilane)-grafted TiO2 reveals the applicability of both grafting methods depending on the envisaged pH during sorption. | Notes: | Meynen, V (corresponding author), Flemish Inst Technol Res VITO NV, Sustainable Mat, B-2400 Mol, Belgium.; Meynen, V (corresponding author), Univ Antwerp, Dept Chem, Lab Adsorpt & Catalysis LADCA, B-2610 Antwerp, Belgium. vera.meynen@uantwerpen.be |
Document URI: | http://hdl.handle.net/1942/39115 | ISSN: | 2470-1343 | e-ISSN: | 2470-1343 | DOI: | 10.1021/acsomega.2c06020 | ISI #: | 000892638400001 | Rights: | 2022 The Authors. Published by American Chemical Society | Category: | A1 | Type: | Journal Contribution | Validations: | ecoom 2023 |
Appears in Collections: | Research publications |
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