Synthesis, characterization and application of nanoscale zero-valent iron in the degradation of the azo dye Disperse Red 1

•Application of surface response methodology to optimize synthesis of NZVI with Fe2+ and sodium borohydride.•The interaction of the reducing agent addition rate and the pH was very significant.•Significant dependence between BET surface area and reactivity.•NZVI yielded high color removal in fairly short time (around 98% in 10 min).•The combination with H2O2 allowed high mineralization.

In this work, a multivariate response surface methodology (RSM), was applied to analyze the effects of the synthesis variables that affect the reactivity of nanosized zero valent iron particles (NZVI), obtained by chemical reduction with sodium borohidride on the decoloration of azo dye Disperse Red 1 (DR1). Statistical analysis and data interpretation revealed that the generated model showed significant regression and fitting. The conditions that generated NZVI with higher reactivity correspond to [Fe 2+]:[BH4−] molar ratio = 1:3, higher rates of reducing agent addition and lower pH (2-3). NZVI particles synthesized under the optimal conditions were characterized via XRD, BET surface area and electron microscopy. The results showed that the nanostructured material had composition, morphology and crystallinity typical of zero-valent iron, with BET surface area of ​​45 m2 g−1 and an average particle size of 60 nm. NZVI yielded high color removal in fairly short time (around 98% in 10 min). Latter combination with H2O2 allowed high mineralization.