Synthesis of polyamide-based nanocomposites using green-synthesized chromium and copper oxides nanoparticles for the sorption of uranium from aqueous solution

Abstract

Utilization of the unmodified polyamides for the adsorption of pollutants is often unsatisfactory owning to their smaller surface areas and insufficient active sites on their surfaces. The objective of this work is to modify polyamide 6 (PA6) for enhancing its adsorption capability for uranium (VI). In this study, Cr2O3@PA6 (CrO@PA6) and CuO@PA6 as modified polyamides nanocomposites were successfully synthesized and applied, for the first time, as novel nano-adsorbents to efficiently remove U(VI) from aqueous solution. The nanocomposites were synthesized by the incorporation of green-synthesized CrO and CuO nanoparticles in PA6 matrices via melt compounding technique. The synthesized materials were characterized by various techniques such as UV-Vis, TEM, SEM, EDX, DLS, zeta potential, pHPZC, FTIR, BET, XRD, and TGA analysis. Thanks to their higher surface areas and available active sites, CrO and CuO nanoparticles embedded into PA6 contribute to enhancing the adsorption capacities of CrO@PA6 and CuO@PA6 (in comparison to unmodified PA6) toward U(VI). The TGA analysis confirms the thermal stabilities of the synthesized adsorbents for U(VI) removal from contaminated water. Additionally, the results showed that the adsorption process could be well described by the pseudo-second order kinetic and Sips isotherm models. The maximum adsorption capacities for CrO@PA6 and CuO@PA6 sorbents are 61.1 mg g−1 and 53.5 mg g−1, respectively, at a solution pH of 4.5. Thermodynamic parameters indicated that the sorption process was exothermic and energetically favored. Moreover, U(VI) adsorption was also confirmed through FTIR, SEM, and EDX analysis of U(VI)-loaded adsorbents. Different mechanisms for U(VI) adsorption onto CrO@PA6 and CuO@PA6 sorbents were tentatively proposed. The recycling experiments with five adsorption-desorption cycles indicated that CrO@PA6 sorbent showed excellent reusability. A good sorption performance for U(VI) at real waste solutions is also exhibited. Based on the findings of this study, the simple synthesis process and enhanced U(VI) adsorption performance, the CrO@PA6 and CuO@PA6 nanocomposites can be applied as attractive, highly effective, reusable, and cost-effective nano-adsorbents for the efficient treatment of radioactive wastewater.