High-surface-area activated carbon - Iron oxide nanocomposite for enhanced arsenic remediation: Performance optimization and adsorption dynamics

Arsenic is a widely occurring geogenic contaminant in groundwater in many places around the globe. The incorporation of high-adsorption iron oxides into activated carbon is an important area of research for arsenic removal. The present study describes an activated carbon-based iron-oxide nanocomposite (AC-IONC) synthesized via co-precipitation and evaluated for the removal of arsenic from aqueous systems. The characterization of AC-IONC using BET, SEM-EDS, FTIR, FESEM, and XRD confirmed the successful integration of iron oxide nanoparticles onto the porous activated carbon matrix, yielding a high surface area (947.97 m²/g), structural stability, and abundant functional groups, all of which are favorable for adsorption. Batch adsorption experiments were conducted to assess the influence of pH, adsorbent dosage, kinetics, and initial arsenic concentration. The kinetics of adsorption at various pH levels were investigated. The modeling studies using kinetic adsorption models revealed that the adsorption process followed a pseudo-second-order kinetics model (R² = 0.98, NAPE = 2.6%). The adsorption equilibrium datasets were best fit by the Langmuir isotherm model (R² = 0.99, NAPE = 2.81), suggesting monolayer adsorption on a homogeneous surface, with a maximum adsorption capacity of 8.08 mg/g. The combined adsorption kinetic and equilibrium (CAKE) model was used to predict the adsorption kinetics and equilibrium at various initial concentrations and times. The regeneration studies showed a modest decrease in adsorption capacity after repeated adsorption-desorption cycles, indicating the AC-IONC’s moderate regeneration efficiency. A spiked study conducted with real water samples showed a marked reduction in adsorption capacity, which suggested that adsorption was reduced in the presence of other co-existing ions. In summary, the AC-IONC demonstrated strong potential as an efficient method for arsenic remediation in water treatment applications.