Statistical Optimization of Nzvi Chemical Synthesis Approach Towards P and No3- Removal from Aqueous Solutions : Cost-Effectiveness & Parametric Effects

The aim of this study is 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 8 synthesis parameters, including reductant concentration (RC), reductant delivery rate (RDR), reductant liquid volume (RLV), pH, aging time (AGT), mixing speed (MS), temperature (T) and precursor concentration (PC). 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 RP (%) and RNO3- (%) models with F-values of 4.480×10 8 and 23755.08, respectively. Moreover, the p-values of all the 8 main linear effects were less than 0.05 in both two models of RP (%) and RNO3- (%). However, most of the interaction parameters were not statistically significant (higher than 0.05) in case of RNO3- (%), which is unlike RP (%) where all of the interaction parameters were statistically significant (less than 0.05). The normal probability plots of factors effects provided great evidence on the significance of the investigated parameters RC had the highest positive statistically significance effect on RP (%) followed by RLV , RDR , MS and T. In case of RNO3- (%), RLV had the highest positive significant effect, followed by AGT > RDR > pH > T > MS . The cost-effective optimal constrains in this study resulted in the best economically optimized values of the nZVI synthesis parameters in terms of higher reactivity and reduced synthesis cost