Role of pH in the Aqueous Phase Reactivity of Zerovalent Iron Nanoparticles with Acid Orange 7, a Model Molecule of Azo Dyes

Table 1

BET specific surface area (SSA) values as obtained by N₂ sorption isotherms at −196°C and calculated phase composition (% by weight) as obtained by Rietveld refinement.

Sample	BET SSA (m^2 g^−1)	Phase composition (% by weight)	Phase composition after reaction; (% by weight)
Fe_fresh	60	α-Fe; 80.08 ± 0.13	α-Fe; 77.06 ± 0.19
		Fe3O4; 19.92 ± 0.76	Fe3O4; 22.41 ± 0.80
Fe_fresh-HCl	93	α-Fe; 87.09 ± 0.14	α-Fe; 26.59 ± 0.61
			Fe3O4; 3.54 ± 0.99
		Fe3O4; 12.91 ± 0.82
			γ-FeOOH; 69.87 ± 0.45
Fe_aged	56	α-Fe; 76.23 ± 0.17	—
		Fe3O4; 23.77 ± 0.69	—