Bioengineering for Soil Remediation: Nanocomposite Based on Iron Nanoparticles with Biopolymer on Bentonite

Zero-valent iron nanoparticles and based on them nanocomposites are being used in the purification of environment, epcially for waste water and soils decontamination from persistent organic pollutants (POPs). The main cause of the limited use of these materials is the toxicity of iron nanoparticles with respect to soil microorganisms. Design of a functional composite exhibiting reactivity in pesticide degradation and simultaneously having a positive influience on the soil microflora is an actual problem. We elaborated a nanocomposite based on bentonite of grade (ERBSLÖH, PORE-TEChnologie) exposed to a biopolymer and iron nanoparticles precipitated during the reduction of simple iron salts.

The fabricated nanoparticles were characterized by X-ray powder diffraction (XRD) analysis, scanning electron microscopy (SEM), and FTIR spectroscopy. XRD analysis of the iron nanoparticles and nanocomposite powder was conducted on a PANalytical Empyrean X-ray diffractometer (q–2q, CuK_a1+a2 radiation, l = 1.54184 Å). The XRD pattern of Fe⁰ nanoparticles with the diffraction peak at 2θ = 44.8° was recorded.The avarage particle size, which was calculated by the Debye–Scherrer formula, was 4 nm. The observed diffraction peaks at 2Q =35,81°, 41.2 4°, 44.81°, 46.05°, 54.80°, and 63.04 were attributed to both bentonite and iron nanoparticles.

Ecotoxicity of the nanocomposite was studied on microorganisms Alternaria sp. 4D and P.viride. The obtained results confirm that Fe(0) nanoparticles can act as both stimulators and inhibitors of growth of micellar fungi. The stimulating effect of Fe(0) nanoparticles was observed in three of the five strains of micromycetes, namely 1LD, 5D, and 8D. The growth of strains Alternaria sp. 4D and P.viride was significantly maintained in the presence of the nanocomposite (AI of 26.88% and 13.91%, respectively). At the same time, Fe(0) nanoparticles, in common with magnetite Fe₃O₄ nanoparticles, have a stimulating effect on the formation and maturation of spores in micromycetes. Thus, the proposed nanocomposite provides a decrease in the toxic effect on the soil “microsociety”, while maintaining the ability to degrade some POPs, such as DDT, DDD, and DDE, provide an effective tool for soil decontamination.