Statistical optimization of nZVI chemical synthesis approach towards P and NO3- removal from aqueous solutions: Cost-effectiveness & parametric effects

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.

Preparation of covalently bonded silica-alginate hybrid hydrogels by SCHIFF base and sol-gel reactions

Organic-inorganic hybrid materials overcome drawbacks associated with alginate hydrogels. In this work, covalently coupled silica-alginate hybrids were prepared by Schiff base formation and sol-gel reaction using alginate dialdehyde (ADA), (3-Aminopropyl) triethoxysilane (APTES), and APTES/tetraethylorthosilicate (TEOS) precursors. The influence of the polysaccharide/inorganic ratio, the nature of the inorganic precursor and the ionic crosslinking ability are studied. Prepared hybrids were characterized by FT-IR, ¹³C and ²⁹Si NMR spectroscopies, SEM, and rheology. For ADA/APTES hybrids, at higher ADA content, Schiff base formation is predominant, but at lower ADA content, the sol-gel reaction is prevalent. However, the progress of the sol-gel reactions for ADA/(APTES+TEOS), is favored with higher ADA compositions. Introducing a posterior ionic crosslinking treatment was possible, increasing the moduli in ADA/(APTES+TEOS) hybrids from 86,207 Pa for 1.5 ADA/Si to 362,171 Pa for 1.5 ADA/Si-Ca. In-situ ADA-Silica hybrid hydrogels containing both ionic and covalent crosslinking can be successfully synthesized with the proposed method. CARBPOL-D-21-01042.