Development and adsorption performance of Ag2O/ZnO/MWCNTs nanocomposites for effective removal of selected heavy metal ions from irrigation water

High volumes of untreated wastewater are discharged into various water bodies worldwide, leading to the distortion and deterioration of the aquatic environment. The use of untreated wastewater to irrigate food crops often results in food poisoning-related deaths due to high levels of pollutants, including heavy metals. Herein, bimetallic oxides (Ag 2 O/ZnO) were incorporated on the surface of multiwall carbon nanotubes (MWCNTs) by wet impregnation at different mixing ratios to design Ag 2 O/ZnO/MWCNTs nanocomposites (AZM X ), which were used for the removal of Cr, Pb and Zn ions from irrigation water. The synthesized nanocomposites were characterized by BET, XRD, TEM, and SEM/EDS to confirm the successful incorporation of Ag 2 O/ZnO on the surface of MWCNTs. The characterization results confirmed the formation of highly crystalline materials with enhanced surface area, which can be attributed to the improved dispersion and interfacial interaction between Ag₂O/ZnO and MWCNTs. This synergistic effect increases the effective surface area regardless of the mixing ratios relative to individual nanoparticles. Among the tested heavy metals, Pb showed the highest removal efficiency (98.62%) using the AZM 2:1:1 nanocomposite under optimum conditions of dosage (0.8 g) and contact time (25 min). The adsorption data fitted well with the Langmuir isotherm model, suggesting that the heavy metals adsorbed to the surface of AZM X in a monolayer fashion. The adsorption kinetics revealed that the adsorption process was better explained by pseudo-second-order kinetics. Thermodynamic studies demonstrated that the metal ion adsorption by AZM X was spontaneous, feasible, and endothermic. The desorption study revealed that hydrochloric acid was the most effective desorbing agent. The AZM 2:1:1 nanocomposite maintains more than 90% removal rate of Pb after five regeneration cycles. This study suggested that the developed novel bimetallic oxides–MWCNTs nanocomposites are capable of efficiently removing metal ions from aqueous environments. • A novel AZMx composites was designed for effective metal ions removal. • Characterization confirmed successful incorporation of Ag 2 O/ZnO on MWCNTs surface. • Adsorption followed pseudo-second-order kinetics and Langmuir isotherm. • Thermodynamic analysis showed the process is endothermic and spontaneous. • AZM2:1:1 showed better adsorption performance toward Cr(VI), Pb(II), and Zn(II). • The AZM2:1:1 retained 90% of Pb removal even after 5 reuse cycles.