ABSTRACT

In this work, five nanoparticles (zinc oxide, magnetite, bio-ZnO, biomagnetite and graphene oxides) and two nanocomposites (magnetite/graphene oxides and magnetite/chitosan) were synthesized and applied for the removal of emerging pollutants (pharmaceutical compounds, pesticides and PAH), heavy metals (As, Cd, Cr, Pb, Hg), anions (NO₃^-, (PO₄)^3-, Cl^-) and oil and grease from three different industrial effluents. The prepared nanoparticles were characterized by Powder-X-ray diffraction (Powder-XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission - Scanning electron microscopy (FE-SEM) and Energy dispersive X-ray (EDX). Results confirmed successful nanoscale syntheses of the nanoparticles and composites. Most of the target emerging contaminants and heavy metals were detected in the effluents. Batch adsorption experiments were conducted with the seven different nanoparticles on the three industrial effluents in order to determine their removal efficiencies on emerging contaminants and heavy metals. Results showed a significant decrease in the final concentration values of the various anions and oil and grease in effluents, with the biologically synthesized magnetite (biomagnetite) and chitosan-magnetite composite (chit-mag) exhibiting the highest adsorption efficiencies. GC-MS analysis results showed that the nano-adsorbents all removed the PAHs to an extent, although some of them like the bio-magnetite and chitosan-magnetite performed quite better than the others, except in the effluent collected from cosmetics industry, where graphene oxide showed better removal efficiency than biomagnetite.  GC-MS analysis of pesticides was carried out only in the agrochemical effluent; all the target pesticide compounds were detected, although in low concentrations. A poor overall and negative removal pattern of pesticides by most of the nanoparticles was observed, despite the very low concentrations of pesticide residues in this effluent. The biocomposites:  chit-mag and biomagnetite gave the highest % total removal of 98.45 % and 95.22 %. A poor and negative removal pattern was recorded for nanoparticles treatment with amoxicillin, HPLC analysis showed significant removal of paracetamol and ascorbic acid in the pharmaceutical effluent. ZnO and biomagnetite were noted to have relatively high removal efficiencies (64.71 % and 48.92 %) for these bioactive components. pH and kinetics parameters were studied in order to determine the time and conditions required to attain equilibrium for the heavy metals adsorption. Although all the nanoadsorbents demonstrated significant removals of heavy metals, higher removal capacities were observed for bioadsorbents and nanocomposites. Also, the adsorption processes for heavy metals fitted better into the pseudo-second order kinetic model with very high R² values, indicating that adsorption followed chemisorption processes. On the basis of these findings, it can be inferred that the treatment of industrial effluents under investigation with synthesized nanoparticles was very effective, especially with the bio-adsorbents which enhance environmental friendliness and sustainability.