*2.1. Synthesis of nZVI Particles*

*Synthesis of nZVI particles using FeSO4*·*7H2O and NaBH4*: For nZVI synthesis, 4.17 g of FeSO4·7H2O in 150 mL of water and 3.72 g of EDTA in 100 mL of water were mixed with 2.87 g of NaBH<sup>4</sup> in 100 mL of distilled water in a stirred closed flask for 60 min and purged with nitrogen to achieve black color precipitates. These particles were filtered, washed with ethanol thrice, and filtered again [20].

*Synthesis of nZVI particles using neem and mint leaves*: Synthesis using *Azadirachta indica* (neem) and *Mentha longifolia* (mint) leaves was identical for each kind of leaf and involved the following procedure: (i) 10 g of leaves were cleaned, washed, dried, chopped and grounded; (ii) the leaves were then heated to 50 ◦C within 20 mL of distilled water for 10 min; (iii) 20 mL of each leaf extract was mixed with 20 mL of 0.001 M FeCl3·6H2O in a stirred closed flask for 60 min and purged with nitrogen. During this stage, 1% of polyvinyl alcohol and 1% of chitosan were added to stabilize the particles; (iv) the obtained black color particles were filtered and (v) dried at 50 ◦C for 12 h [25].
