Efficient Adsorption of Multi-Heavy Metal Ions at Trace-Levels from Groundwater Using UiO-66 and Activated Carbon Nanocomposites for Safe Drinking

A composite of UiO-66 and activated carbon was synthesized by using a solvothermal method to efficiently remove heavy metal ions from synthetic water and groundwater at trace levels. The adsorbents were characterized for their physicochemical properties using FE-SEM, EDX, XRD, BET, TGA, FT-IR, and XPS. FE-SEM and EDX analyses confirmed the octahedral structure of nanoparticles, along with a homogeneous distribution of activated carbon on UiO-66. XRD patterns revealed that the samples were crystalline, with an average crystalline size of 39 nm. Under optimum operating conditions, the adsorbents exhibited maximum capacities for Cd(II), Cr(VI), Pb(II), and Se(IV) ions, determined to be 431.1, 351.8, 499.3, and 380.8 mg/g, respectively. In contrast, the adsorbent's meaningful adsorption capacity against the permissible metal ion concentration in drinking water was calculated to be 1.12, 21.54, 25.26, and 37.94 mg/g. These values surpass those of the most similar MOFs and other porous materials. The thermodynamic study revealed that the adsorption of these metal ions was spontaneous and endothermic within the temperature range of 288.15–318.15 K. Notably, the presence of competitive coexisting ions had a minimal impact on the removal efficiency of heavy metal ions, emphasizing the selectivity of the adsorbent. The adsorbent demonstrated excellent performance in effectively removing metal ions from synthetic water and groundwater within the allowable limits for drinking water. The material showed good regeneration capability for up to 5 studied cycles, emphasizing the robust adsorption performance of the composite and highlighting its potential application in water treatment.