Optimization and stability analysis of TiO₂-palm olein nano-biolubricants using one-factor-at-a-time

This study investigates the formulation, stability, and optimization of titanium dioxide (TiO 2 )–reinforced palm olein nano-biolubricants using a two-step method coupled with ultrasonication. Palm olein, selected for its renewable origin, high oxidative stability, and favorable tribological profile, was blended with 21 nm TiO 2 nanoparticles to enhance nano-biolubricants and functional properties. Stability was systematically evaluated through visual sedimentation, UV–Vis spectrophotometry, and zeta potential analysis over 30 days. Among various ultrasonication durations (30–80 min), the 60-minute treatment produced the most homogeneous dispersion, retaining high absorbance ratios (A208/A308 = 0.95/0.91) and strong electrostatic repulsion (zeta potential = –121.5 mV), indicating excellent resistance to agglomeration. Statistical modeling employing Box-Cox transformation and cubic response surface analysis, supported by ANOVA, demonstrated high predictive accuracy (R 2 = 0.9947, adjusted R 2 = 0.9894, p < 0.0001), with ultrasonication duration emerging as the dominant factor. The findings highlight that controlled ultrasonication not only prevents nanoparticle aggregation but also strengthens molecular interactions between TiO 2 and palm olein, yielding superior nano-biolubricants stability. This work demonstrates a reproducible, eco-friendly strategy to develop nanolubricants with optimized performance, offering scalable pathways for next-generation sustainable lubrication in agricultural machinery and related molecular-liquid applications. • Ultrasonication for 60 min maximizes TiO₂ dispersion and minimizes aggregation. • Cavitation shear breaks clusters and enhances particle–oil interactions, yielding steric and electrostatic stabilization. • Zeta potential values confirm strong electrostatic stabilization and long-term colloidal stability. • Box-Cox transformation enhances model accuracy, validating reproducibility of dispersion results.