This study aimed to screen and optimized the biosynthesis of iron nanoparticles (FeNPs) by utilizing watermelon rind extract (WMR) as the reducing and stabilizing agent. To determine the significant characteristics in terms of attaining a high yield of FeNPs, the screening of the factor influencing the biosynthesis FeNPs was then analyzed using a two-level factorial design with Design-Expert Software version 11. The factors were reactant concentration, incubation time, and incubation temperature, as well as the response, which was the yield of FeNPs. This response refers to the main target of this study which is to improve the yield of production FeNPs. The findings indicated that among all the factors investigated, reactant concentration, incubation time, and incubation temperature were the significant contributing factors impacting the yield of FeNPs with a p-value < 0.05. The experimental domain factors were effectively collected from the ANOVA analysis with a good linear regression; thus, these data could be augmented and to be used as the optimized condition. The optimal condition suggested by the Design Expert for the biosynthesis of FeNPs was 1 M of reactant concentration, 3 h of incubation time, and 30 °C of incubation temperature.
