Carbon fiber supported and N-doped carbon encapsulated nZVI for synergistically adsorbing and reducing uranium

Developing efficient, stable, and user-friendly adsorbents for removing uranium from radioactive wastewater is critical for ensuring the security of nuclear energy development. Here, a fixed adsorbent (nZVI@NC/CF), composed of in-situ derived N-doped carbon (NC) encapsulated nano zero-valent iron (nZVI) coated on carbon fiber (CF), was synthesized via carbonizing Prussian blue decorated CF, and used to synergistically adsorb and reduce UO22+ from contaminated water. The optimized nZVI@NC/CF exhibited an extremely high adsorption capacity of 2120.27 mg g−1 with a superior adsorption rate, and about 56.8 % fixed uranium was reduced into insoluble U(IV) species. This outstanding adsorption activity could be ascribed to the strong reducing property of nZVI and the package of NC that effectively prevented the agglomeration of nZVI and facilitated the adsorption and reduction of UO22+ due to the rich adsorption sites and good charge transport property. The nZVI@NC/CF also showed excellent anti-interference properties and regeneration performance that exhibited great potential in treating real uranium wastewater and extracting uranium from seawater. Mechanism study revealed that the fixation of UO22+ was mainly achieved through the synergistical adsorption by NC and reduction by nZVI, complexation by hydroxyl groups, and hydrolytic precipitation by local OH−. This study underscores the potential of nZVI@NC/CF as a highly effective adsorbent material, and provides valuable insights into developing efficient, stable, and easily manageable materials for uranium recovery.