Layered Double Hydroxides Modified with Carbon Quantum Dots as Promising Materials for Pharmaceutical Removal

Pharmaceutical contaminants such as ibuprofen are increasingly detected in water sources due to widespread use and insufficient removal by conventional treatment processes. Given its persistence and adverse effects on human health and aquatic ecosystems, efficient removal technologies are needed. This study reports the synthesis of a Mg/Al-layered double hydroxide (LDH) hybridized with carbon quantum dots (CQDs) via in situ co-precipitation to enhance adsorptive performance. The hybrid (LDH-CQD) was characterized by FTIR, XRD, DSC, TGA-DTG, SEM-EDS, BET, and pH in the point of zero charge (pHPZC) analysis. Results indicated a marked increase in surface area (2.89 to 66.9 m2/g), a shift in surface charge behavior (pHpzc from 8.57 to 6.21), and improved porosity. Adsorption experiments using ibuprofen as a model contaminant revealed superior performance of the hybrid compared to pristine Mg/Al-LDH, with a maximum capacity of 22.13 mg·g−1 (% Removal = 88.53%) at 25 ppm, and in lower concentrations (5 and 10 ppm), the hybrid showed 100% removal. Kinetic modeling followed a pseudo-second-order mechanism, and the isotherm was the SIPS model (maximum adsorption capacity = 24.150 mg.g−1). These findings highlight the potential of LDH-CQD hybrid as efficient and tunable adsorbents for removing emerging pharmaceutical pollutants from aqueous media.