Box-Behnken Design Approach to Optimize the Extraction and Characterization of Neem (Azadirachta indica) Seed Oil

Abstract

This study introduces a novel and efficient optimization strategy for the solvent extraction of neem (Azadirachta indica) seed oil, a promising non-edible feedstock for biodiesel production, using a three-factor Box-Behnken Design (BBD) under Response Surface Methodology (RSM). The innovation lies in the systematic integration of statistical modeling with conventional Soxhlet extraction using n-hexane, focusing on the interactive effects of reaction temperature (50–80 °C), extraction time (40–60 min), and particle size (0.14–0.20 mm). A highly significant quadratic model (F-value = 21.21, p = 0.0003, R² = 0.9646) was developed, revealing temperature as the dominant linear factor and strong quadratic effects for all variables. The optimized conditions yielded a maximum oil extraction of 39.93% (predicted), closely validated by confirmatory experiments (relative error < 2.5%). The extracted oil exhibited a high acid value (172 mg KOH/g), confirming its suitability as a low-cost, non-edible biodiesel precursor after acid pre-treatment, while FTIR analysis verified the presence of characteristic triglyceride functional groups. This work represents a significant advancement by providing a scalable, cost-effective, and statistically robust protocol for valorizing abundant neem seeds in resource-limited settings. It bridges the gap between conventional extraction techniques and modern optimization tools, offering a replicable model for enhancing oil yield while supporting sustainable biofuel development.