Immobilization of U(VI) in wastewater using coal fly ash aerogel (CFAA) as a low-cost adsorbent

Coal fly aerogel (CFAA), as a low-cost, recyclable and highly efficient U(VI) adsorbent, was successfully prepared. Notably, the removal rate for U(VI) of CFAA was up to 94.5% (C0 = 10 mg L−1, m/V = 1.0 g L−1, T = 298 K, t = 24 h and pH = 3.0), which was much higher than previous studies. Meanwhile, the maximum removal capacity of U(VI) on CFAA was 110.73 mg g−1 (m/V = 1.0 g L−1, T = 298 K, t = 24 h and pH = 3.0), which was nearly twice as much as untreated coal fly ash. Notable, the removal rate of U(VI) by CFAA was more than 80% after five cycles, indicating that CFAA was a recyclable adsorbent. In addition, Pseudo-second-order and Langmuir model were more suitable to describe the adsorption behavior on the surface of CFAA, meaning that the rate limiting step might be chemical sorption or chemisorption involving valency forces through sharing or exchange of electrons between sorbent and sorbate. The conclusions of SEM, FT-IR, XRD as well as XPS further illustrated that adsorption behavior for U(VI) of CFAA was mainly depended on the groups on the surface of CFAA, such as OH-, SiO- and AlO-. In conclusion, CFAA could be considered as an excellent candidate for the capture of U(VI) from wastewater.