2.1. Test Nanomaterials and Characterization

Commercial GO (catalog #763713, Sigma-Aldrich, St. Louis, MO, USA) were purchased in flakes and rGO (catalog #777684, Sigma-Aldrich) in powder. The GO flakes were suspended in deionized water (10 mg/mL) and sonicated in an ultrasonic bath for 30 min immediately prior to use. The characterization data of the commercial GBNs are available on the supplier’s webpage and have also been previously assessed [12,13]. Briefly, the tested GO was composed of carbon (42–52 wt %) and oxygen (≥36 wt %), and exhibited the size of 219 nm (performed using dynamic light scattering and zeta potential of −14.13 ± 11.1. Reduced GO was composed of carbon (≥75 wt %), nitrogen (>5 wt %) and oxygen (≤22 wt %), and exhibited a BET surface area of 450 m²/g. Further characterization of the size and zeta potential of rGO was not possible as it was added to the soil as a dry powder (not water-dispersed).