Catalytic activation of persulphate with Mn3O4 nanoparticles for degradation of acid blue 113: process optimisation and degradation pathway.

The performance of the persulphate/Mn₃O₄ nanoparticles (PS/Mn₃O₄) oxidation process was investigated for the degradation of acid blue 113 (AB113) azo dye. XRD, N₂ adsorption-desorption analysis, FE-SEM and EDX confirmed the successful synthesis of Mn₃O₄ nanoparticles. The effect of three independent variables including PS concentration, Mn₃O₄ dosage and solution pH on the system response was optimised by genetic algorithm (GA) and central composite design (CCD) techniques. The results of ANOVA and fit statistics (P-value < 0.0001, R a d j 2 = 0.9772) showed that the proposed quadratic model can predict the AB113 removal efficiency with high confidence. The optimum points for PS concentration, Mn₃O₄ dosage and solution pH were predicted to be 61.46 mg/L, 57.69 and 3.00, respectively, by CCD method. Under these conditions, after 60 min of reaction, the maximum experimental removal efficiency of AB113 in the PS/Mn₃O₄ oxidation system and separate application of PS and Mn₃O₄ were obtained 96.70%, 18.0% and 7.0%, respectively. The pseudo-first-order rate constants of AB113 degradation the PS/Mn₃O₄ oxidation system and separate application of PS and Mn₃O₄ were 0.0597, 0.0029 and 0.0015 min⁻¹, respectively. In this way, the synergistic effect for degradation of AB113 in the PS/Mn₃O₄ was determined 92.6%. Oxalic acid, naphthalen-1-ol and acetic acid were the major identified intermediates due to AB113 degradation. [ABSTRACT FROM AUTHOR]