<p>The pollution issue of uranium-containing wastewater generated from the rapid development of the nuclear energy industry has attracted widespread attention. To efficiently remove uranium from wastewater, six types of SiO₂ modified with g. lycine, β-alanine, γ-aminobutyric acid, 6-aminocaproic acid, 8-aminocaprylic acid, and 11-aminoundecanoic acid, with different carbon chain lengths and terminal amino groups, were successfully prepared via the sol–gel method. The materials were characterized using XPS, FTIR, BET, XRD, and SEM. Amino groups are important functional groups for efficient coordination with uranyl ions. The effects of chain length on the properties of amino acids and uranium adsorption capacity were investigated through batch experiments. The results indicate that the introduction of amino acids can effectively enhance the uranium adsorption capacity of SiO₂. Notably, SiO₂/6-aminocaproic acid demonstrates the fastest adsorption rate (<i>k</i>_id = 56.42&#xa0;mg·g⁻¹·min^−0.5) and a maximum adsorption capacity of 221&#xa0;mg·g⁻¹, surpassing that of unmodified SiO₂ (<i>q</i>_e = 50.25&#xa0;mg·g⁻¹). The chain length of SiO₂/6-aminocaproic acid aligns with the size of uranyl ions, while the terminal amino groups maintain coordination. Grafting amino acids onto the SiO₂ surface can combine the hydrophobic effect of the chain length and the benefits of multidentate coordination to achieve a synergistic effect. The elution rate remains excellent after five adsorption–desorption cycles, indicating recyclable and reusable capabilities. This research offers valuable ideas for materials modified with amino groups or other functional groups (like phosphate and sulfonic acid groups).</p>