Hemp seed nanoparticle composites for removing lead, methylene blue, and ibuprofen from an aqueous solution and their antimicrobial towards Escherichia coli and Staphylococcus aureus

The WHO considers lead (Pb(II)), methylene blue (MB) and ibuprofen (IBU) as priority pollutants. At the same time, pathogenic Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in contaminated water, kills millions of people annually. Removing these pollutants from water are necessary for human health and environmental concerns. This study aimed to use nanocomposites of hemp seeds as green adsorbents for multi-applications in water treatment and as anti-microbial agents. Binary nanoparticles (MnO/CuO and MnO/ZnO) were deposited on the surface of hemp seeds (HS). The composites were characterized by SEM, EDX, XRD, FTIR, TEM and BET. Isotherm studies indicated that the Freundlich model best described the adsorption based on heterogeneous surfaces involved in multilayer adsorption uptake and formation. The highest adsorption capacities were obtained with HS-MnO/CuO with, uptakes of 66.58, 68.95 and 21.50 mg/g for Pb(II), MB and IBU respectively. The contact time effect revealed that the process had two phases; phase 1, a rapid adsorption rate and phase 2, a slow increment due to the saturation of the active sites as contact time progressed. ΔHo values were (<40 kJ/mol) suggesting that the adsorption was controlled by physisorption which include π-π, electrostatic interactions and dipole-dipole (Van der Waals) forces. Furthermore, the ΔHo values were positive for Pb(II) and MB and negative for IBU. The adsorption trends for Pb(II) and MB increased with temperature increases while that of IBU decreased, indicating that the adsorption was endothermic for Pb(II) and MB and exothermic for IBU. The agar well diffusion showed that HS-MnO/CuO and HS-MnO/ZnO inhibited the growth if E. coli and S. aureus. The minimum inhibition concentration (MIC) values of HS-MnO/ZnO showed effectiveness at 6.25 and 1.56 μg/mL for both E. coli and S. aureus. The hemp-based composites were more effective than a commercial antibiotic (neomycin) which showed effectiveness at 12.5 and 6.25 μg/mL for E. coli and S. aureus.