Efficient Removal of UO22+ from Water Using Carboxycellulose Nanofibers Prepared by the Nitro-Oxidation Method

Carboxycellulose nanofibers (NOCNF) were extracted from untreated jute fibers using a simple nitro-oxidation method, employing nitric acid and sodium nitrite. The resulting NOCNF possessed high surface charge (−70 mV) and large carboxylate content (1.15 mmol/g), allowing them to be used as an effective medium to remove UO 2 2+ ions from water. The UO 2 2+ (or U(VI)) removal mechanism was found to include two stages: the initial stage of ionic adsorption on the NOCNF surface following by the later stage of uranyl hydroxide mineralization, as evidenced by the Fourier transform infrared, scanning electron microscopy with energy dispersive spectroscopy capabilities, transmission electron miscroscopy, and wide-angle X-ray diffraction results. Using the Langmuir isotherm model, the extracted NOCNF exhibited a very high maximum adsorption capacity (1470 mg/g), about several times higher than the most efficient adsorbent reported (poly(acrylic acid) hydrogel). It was also found that the remediation of UO 2 2+ ions by NOCNF was pH dependent and possessed the maximum adsorption at pH = 7. The removal efficiency of NOCNF was between 80 and 87% when the UO 2 2+ concentration was below 1000 ppm, while it decreased to 60% when the UO 2 2+ concentration was around 1250 ppm.