Response surface optimization of the enzyme-based ultrasound-assisted extraction of acorn tannins and their corrosion inhibition properties.

Graphical abstract A highly efficient enzyme-based ultrasound-assisted method with a response surface methodology (RSM) was carried out to exctract the tannins from the acorns. Interestingly, the extracted tannins exhibited the good corrosion inhibition for the mild steel in the NaCl solution. Highlights • Highly efficient enzyme-based ultrasound-assisted extraction method was used to extract the tannins from acorns. • Response surface methodology (RSM) was carried out to optimize the extraction conditions. • The optimized conditions were obtained. • Corrosion inhibition property of the extracted tannins was demonstrated. Abstract In this work, a highly efficient enzyme-based ultrasound-assisted method for the extraction of tannins from acorns was demonstrated and optimized. Based on a three-level four-factor Box Behnken Design (BBD), response surface methodology (RSM) was carried out to optimize the extraction conditions, including the ultrasonic time, ultrasonic power, cellulose concentration, and extraction temperature. Additionally, a second-order polynomial fit was performed to fit the experimental data. The optimized conditions were obtained, including the ultrasonic time (2.51 h), ultrasonic power (97.92 W), cellulose concentration (3.44 g/L), and extraction temperature (38.00 °C). Furthermore, the experimental extraction yield was 63.16 ± 0.12% under the optimal extraction conditions, which was in good agreement with the predictive yield of 63.42%. Interestingly, the potentiodynamic polarization and electrochemical impedance spectroscopy demonstrated that the extracted tannins exhibited the good corrosion inhibition for the mild steel in the NaCl solution. The corrosion inhibition efficiency of tannins reached 86.0%. [ABSTRACT FROM AUTHOR]