Abstract
In this work, the thermo-sensitive materials N-isopropylacrylamide (NIPAM) and acrylic acid (AA) were crosslinked with carboxymethyl cellulose (CMC) (CMC/P (NIPAM-co-AA)) via a free radical polymerization method for the removal of U(VI) from aqueous solution. The L16 (45) orthogonal experiments were designed for the optimization of the synthesis condition. The chemical structures of the crosslinking hydrogel were confirmed by FTIR spectroscopy. The microstructural analyses were conducted though scanning electron microscopy (SEM) to show the pore structure of the hydrogel. The adsorption performance of the CMC/P (NIPAM-co-AA) hydrogel for the uptake of U(VI) from simulated wastewater was also investigated. The adsorption reached equilibrium within 1 h. Under the reaction of pH = 6 and a temperature of 298 K, an initial concentration of U(VI) of 5 mg·L−1, and 10 mg of the CMC/P(NIPAM-co-AA) hydrogel, the maximum adsorption capacity was 14.69 mg g−1. The kinetics fitted perfectly with the pseudo-second-order model, and the isotherms for the composite hydrogel adsorption of U(VI) was in accordance with the Langmuir model. The chemical modification confirmed that the acylamino group played an important role in uranium adsorption. The desorption and reusability study revealed that the resolution rate was still available at approximately 77.74% after five alternate heating cycles at 20 and 50 °C of adsorption-desorption.
Highlights
The technology of dissolution and leaching is widely used in uranium mining and metallurgy, and a large amount of low-concentration uranium-containing radioactive wastewater can be generated from these industrial processes, which could pose a serious potential risk to the environment and the health of those involved [1]
The adsorption method, which possesses the characteristics of a wide source of materials, low cost, high selectivity, fast treatment rate, and large capacity would provide a possibility for the efficient uptake of uranium-bearing wastewater [4]
These “smart” hydrogels are characterized by their high expansion capacity, biocompatibility, reversibility, and maneuverability compared with traditional methods [5,6]
Summary
The technology of dissolution and leaching is widely used in uranium mining and metallurgy, and a large amount of low-concentration uranium-containing radioactive wastewater can be generated from these industrial processes, which could pose a serious potential risk to the environment and the health of those involved [1]. Traditional methods such as reverse osmosis, ion exchange, and evaporation have the demerits of complexity, high energy consumption, and cumbersome operation [2,3]. The response characteristics of “smart” hydrogels are important parameters for their wide application in the fields of drug control release and separation, heavy metal adsorption, and biomedical treatments [5,12,13]
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