Ultralight carbon aerogel composites derived from MOFs and cross-linked chitosan: Synthesis, characterization, and U(VI) adsorption

An environmentally friendly and cost-effective adsorbent for removing U(VI) from radioactive wastewater is of significant importance for protecting the environment. In this work, we successfully prepared an ultralight carbon aerogel material (CUCA/MPCs) derived from chitosan and MOFs, and synthesized an adsorbent (CUCA/MPCs-PO4) with a high chelation ability to U(VI) through phosphorylation modification. Various characterization techniques were used to characterize the microscopic morphology and crystallographic structure of the adsorbents. During the batch experiments, it was determined that the optimum pH for the adsorbents for U(VI) was 6.5. According to the linear Langmuir isotherm model and pseudo-second-order kinetic model, U(VI) adsorption on the adsorbent is a monolayer chemisorption reaction. The fitted maximum adsorption capacities of CUCA-PO4, CUCA/1MPCs-PO4, and CUCA/2MPCs-PO4 for U(VI) were 357.1 mg/g, 526.3 mg/g, and 592.0 mg/g, respectively. Furthermore, the three adsorbents showed good recyclability, maintaining 79.0 %, 77.4 %, and 82.2 % of the initial adsorption capacity after eight cycles, respectively. The results of actual U(VI) waste adsorption experiments showed that CUCA/2MPCs-PO4 achieved 92.2 % removal of U(VI), showing good potential for practical applications. Finally, the possible adsorption mechanism between U(VI) and adsorbent was discussed in the context of experimental and characterization results. Overall, this study provides a valuable research idea for the treatment of radioactive wastewater containing U(VI).