Phosphonic Acid-functionalized Silica Magnetic Microspheres (PA-SMMs) were synthesized for U(VI) adsorption from aqueous solutions. PA-SMMs were characterized by using various methods such as SEM, XRD, FTIR, and VSM. PA-SMMs exhibited a higher adsorption capacity for U(VI) when compared to unmodified silica magnetic microspheres due to the high affinity of phosphonic acid groups with U(VI). The adsorption was dominated by inner-sphere surface chelation, as evidenced by the slight influence of ionic strength. The adsorption isotherms fitted well to the Langmuir model, with the maximum adsorption capacity of 76.9 mg/g at 298 K and pH 5.0. PA-SMMs could be successfully regenerated using 0.2 M EDTA-0.5 M HNO_3 as the eluent.
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