Remediation of contaminated soils by the coupled action of microorganisms and metallic oxide nanoparticles

In this work, it was developed an active "microorganism-nanoparticle" couple for soils bioremediation. The nanoparticles used in this work are iron oxide nanoparticles encapsulated in a silica matrix, called Fe2O3/SiO2 xerogel catalysts. The latter were synthesized by hydrolysis and condensation of tetraethoxysilane (TEOS) and 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS), which is able to form a chelate with iron ions. Characterization of Fe2O3/SiO2 catalysts showed that two parameters strongly influence the gels texture: (i) the EDAS/TEOS molar ratio and (ii) the thermic treatments. The species of iron was determined by Mössbauer spectroscopy and only Fe3+ ions were observed in xerogel catalysts. In parallel, biphenyl degradation tests were achieved in the presence of micro-organisms and different sources of iron (salts or nanoparticles). Tests on the evolution of biphenyl concentration in aqueous medium were also performed alone to determine if the biphenyl undergoes degradation or evaporation in the test conditions. In this way, these tests have identified evaporation and abiotic degradation of biphenyl in the working conditions. Changes of these conditions have been suggested so that in future tests, the degradation of biphenyl by microorganisms and the potential impact of catalysts can be assessed more accurately.