Alternative plant extracts were examined as raw materials for the synthesis of nZVI from ferric solutions. Four plants were selected for evaluation, i.e. Camellia sinensis (green tea, GT), Syzygium aromaticum (clove, CL), Mentha spicata (spearmint, SM) and Punica granatum (pomegranate, PG). Based on the results obtained, it was concluded that the reduction of Fe(III) with the herb extracts is not complete. Using the GT extract, approximately 28 mM of the initial 66 mM of Fe (42.4 %) are reduced to the elemental state Fe(0). The highest reduction of Fe(III), about 53 %, was achieved with PG and the lowest, only 15.6 %, with the SM extract. Additional batch experiments have been carried out to evaluate the effectiveness of nZVI, synthesized with GT, CL, SM and PG, for the removal of hexavalent chromium from a 0.96 mM solution. The highest reduction of Cr(VI) (96 %) was obtained using the nZVI suspension produced with PG juice. The other three nZVI suspensions, i.e. CL-nZVI, GT-nZVI, and SM-nZVI, had a comparable effectiveness corresponding to 70 % reduction of chromate.

Nano zero valent iron (nZVI) is highly reactive, targets a wide range of contaminants and is considered as a promising material for the in situ remediation of contaminated aquifers. Injection of nZVI suspension is a remedial option for the in-situ reduction and immobilization of pollutants in aquifers. The goal of the present study was to evaluate the efficiency of iron nanoparticles (GT-nZVI), synthesised by a green synthesis route, for Cr(VI) removal in a pilot scale application. A tank with dimensions 2.5 m (width) × 3.75 m (length) × 1.5 m (height) was constructed and filled with 24 tons of soil. Firstly 3 m GT-nZVI suspension was injected and then the supply of contaminated water containing 5 mg/L Cr(VI) was initiated. Samples were analysed for pH, redox potential and electric conductivity, as well as Fe and Cr(VI). The reactive zone operated efficiently for the treatment of contaminated water for 1 year.