Carbon-Dot-Decorated Layered Double Hydroxide Nanocomposites as a Multifunctional Environmental Material for Co-immobilization of SeO42- and Sr2+ from Aqueous Solutions

Co-immobilization of cationic and anionic radionuclides is highly desirable for total remediation of radioactive wastewater. Carbonaceous nano materials have received much attention in the field of water remediation and pollution control in recent years. However, the handling of these nano materials is challenging due to increased bioavailability and toxicity. In this work, MgAl-NO3 layered double hydroxide (LDH) was synthesized and modified using carbon nanodots (C-dot). The prepared materials were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), zeta potential, and transmission electron microscopy (TEM) observation. Adsorption of SeO42- and Sr2+ on MgAl-NO3-LDH/C-dot composites showed that the Sr2+ immobilization capacities increased with an increase in the amount of C-dot. The mechanism of Sr2+ adsorption on these composites occurs via coordination with the -COO- group of C-dot, whereas that of SeO42- occurs through ion exchange with NO3- in the interlayer galleries of LDH. The adsorption of Sr2+ and SeO42- was enhanced in both bicomponent (Sr2+ + SeO42-) and tricomponent systems (Sr2+ + SeO42- + M+/M2+ = coexisting cations or A(n-) = coexisting anions) with the presence of other anion and cations. The MgAl-NO3-LDH/C-dot composites demonstrated that the high adsorption efficiency of Sr2+ and SeO42- than most of other materials reported. These results demonstrate that MgAl-NO3-LDH/C-dot composites are an effective adsorbent for total remediation of anionic and cationic radioactive nuclides from wastewater.