Amidoximes potentials in the bioremediation of heavy metal and organic pollutants

Abstract

This review explores the bioremediation potential of amidoximes, organic ligands with the -C(=NOH)-NH₂ group, valued for their strong chelating and catalytic properties. Amidoximes are synthesized efficiently through nucleophilic addition of hydroxylamine to nitriles, using sustainable methods like microwave-assisted or solvent-free synthesis. These compounds form stable complexes with heavy metals such as U(VI), Cu(II), and Pb(II), enabling selective removal from wastewater, soil, and seawater, thus reducing bioaccumulation and toxicity. Characterization techniques, including FT-IR (showing C=N bands at 1680–1620 cm⁻¹), Nuclear Magnetic Resonance (NMR), X-ray diffraction, UV-Visible spectroscopy, and solubility studies, confirm their structural integrity, metal-binding mechanisms, coordination geometries, and tautomeric forms. In bioremediation, amidoxime-based materials, such as poly(amidoxime)-grafted polymers, demonstrate high adsorption capacities (e.g., 886.73 mg/g for U(VI)) and catalyze organic pollutant degradation via Fenton-like reactions. They also enhance microbial activity by serving as enzyme cofactors. Their tunable properties allow customization for specific pollutants, and integration with nanomaterials or microbial systems improves efficiency. Amidoxime-based materials offer high selectivity, reusability, and alignment with green chemistry principles, making them sustainable alternatives to conventional remediation methods. Applications include uranium extraction from seawater and radionuclide capture, addressing critical environmental challenges. However, scalability and long-term environmental impacts pose challenges requiring further research. This review underscores amidoximes’ chemical versatility and sustainability in tackling heavy metal and organic pollution, emphasizing the need for continued exploration to optimize their practical deployment in global pollution management, particularly in advancing bioremediation strategies.