Fabrication of Zn-MOF-74/polyacrylamide coated with reduced graphene oxide (Zn-MOF-74/rGO/PAM) for As(III) removal

Contamination of drinking water with heavy metals, particularly arsenic (As), is a persistent problem with serious public health implications worldwide. In this study, we present a zinc based metal-organic framework (Zn-MOF-74) and polyacrylamide polymer (PAM) coated on reduced graphene oxide (rGO) as an effective adsorbent for the removal of arsenite (As(III)) from water. Zn-MOF-74 nanoparticles were prepared by room-temperature precipitation and these were immobilized on rGO surface grafted PAM by a free-radical polymerization method, (Zn-MOF-74/rGO/PAM nanocomposites). The experimental data correlates well with the pseudo-second-order kinetic model and Langmuir isotherm, and the maximum adsorption capacity (qmax) was 282.4 mg g−1 at pH 10, 298 K. The removal efficiency was rapid, removing more than 99.8% of As(III) from a 0.2 mg L−1 solution and achieving drinkable levels in 15 min. Thermodynamic data revealed that the process was spontaneous and endothermic. Furthermore, the adsorbent revealed high stability in pH range 4–10 and could be reused at least four times. Adsorption mechanism involved a synergistic combination of chemisorption and physisorption. FTIR and XPS analyzes revealed that the amide group (–NH2) and hydroxyl group (–OH) on Zn-MOF-74/rGO/PAM dominate in their adsorption. [Display omitted] •A novel adsorbent Zn-MOF-74/rGO/PAM was successfully synthesized.•Excellent adsorption properties with maximum capacities of 282.4 mg g−1 at pH 10, 278 K•Surface complexation and hydrogen bonding are the main contribution for As(III) adsorption.•Zn-MOF-74/rGO/PAM exhibited good reusability at least four cycles.