ZnAl/LDH@CQD: Synthesis, Characterization and Use as Adsorbent

This work aimed to evaluate the synthesis of the ZnAl/layered double hydroxides (LDH) composite with carbon quantum dots (CQD) and its application in water treatment. The synthesis of the ZnAl/LDH@CQD composite was carried out by the co‐precipitation method, being characterized by XRD, FTIR, pHZCP, SEM, EDX, TG, and N2 adsorption/desorption. The results presented a composite with a mesoporous structure, satisfactory values of surface area (18.72 m2 g‐1), and pore size (14.78 nm). Preliminary adsorption tests were carried out, and the composite was efficient in removing some dyes and drugs. The kinetic and equilibrium data for the adsorption study for methylene blue fit best the General Order and Liu models, respectively, with maximum adsorption capacity occurring at 30°C (12.11 mg g‐1). Thermodynamic analysis indicated that the adsorption of MB was exothermic and spontaneous, governed mostly by physical processes. The regeneration of the adsorbent was carried out by oxidation with hydrogen peroxide (250 mmol), showing a 20.93% reduction in the percentage of removal after the first cycle and remaining practically constant until the sixth cycle. These results present an efficient way of using CQD composite as an adsorbent material, with potential application in water purification for human and environmental use.