Statistical optimization of nZVI chemical synthesis approach towards P and NO₃^- removal from aqueous solutions:...

This study aims to conduct statistical optimization of nZVI synthesis parameters towards the removal efficiency of phosphorus (P) and nitrate (NO₃^-), considering for the first time the cost-effectiveness index. The detailed statistical analysis was implemented to evaluate the main effects and interactions of eight synthesis parameters, including reductant concentration (R_C), reductant delivery rate (R_DR), reductant liquid volume (R_LV), pH, aging time (AG_T), mixing speed (M_S), temperature (T), and precursor concentration (P_C). Results revealed that the experimental optimization of the synthesis factors improved the removal efficiency of NO₃^- and P by 27 and 9%, respectively, with respect to that before the optimization. ANOVA statistical results indicated the significance of R_P (%) and [Formula: see text] (%) models with F-values of 4.480 × 10⁸ and 23,755.08, respectively. Moreover, the p-values of all the eight main linear effects were less than 0.05 in both two models of R_P (%) and [Formula: see text] (%). However, most of the interaction parameters were not statistically significant (higher than 0.05) in the case of [Formula: see text] (%), which is unlike R_P (%) where all interaction parameters were statistically significant (less than 0.05). The normal probability plots of factors effects provided significant evidence of the significance of the investigated parameters R_C had the highest positive statistically significant effect on R_P (%) followed by R_LV, R_DR, M_S and T. In case of [Formula: see text] (%), R_LV had the highest positive significant effect, followed by AG_T > R_DR > pH > T > M_S. The cost-effective optimal constraints in this study resulted in the best economically optimized values of the nZVI synthesis parameters in terms of higher reactivity and reduced synthesis cost.