Fig. 7. UV-Vis spectra for the reduction of (a–c) 4-NP and (e–g) 2-NP in aqueous solution recorded every 1 min using different amounts of Ni/CNF: (a, e) 0.3 mg, (b, f) 0.6 mg and (c, g) 0.9 mg, and plots of ln[C_t/C₀] versus reaction time for reduction of (d) 4-NP and (h) 2-NP with NaBH₄ over Ni/CNFs.