Mathematical analysis of compound release during microwave assisted retting of flax stems

Microwave-assisted retting was conducted at various power levels (1, 1.5 and 2 W g⁻¹) on pre-soaked flax stems (12, 24 and 36 h). The retted flax stems were dried and the fibres were separated. The amount of cellulose, hemicellulose and lignin presented in the flax fibres was established by NIR (near infrared) spectroscopy. Based on the rate of change of cellulose, hemicellulose and lignin at various levels of treatments, a kinetic model was developed and the model was validated by analysing the compositions of hemp fibres obtained from pre-soaked hemp stems at various microwave power levels. The rate of change of cellulose percentage in the model fitted with the observed values of cellulose percentage with an average R² value of 0.87 and an average RMSE (root-mean-square error) value of 0.0130. But in hemicellulose, the R² value was 0.936 and average RMSE value was 0.0135, and for lignin, R² value was 0.92 and RMSE value of 0.0181. The rate coefficient for all the treatments was increasing within the treatment limit, which indicated the increased reaction rate with an increase in microwave power. Validation of the model was successfully conducted by analysing the components of hemp fibres at various levels of microwave powers.