Kinetic and Thermodynamic studies on the Microwave-Assisted Extraction of Bioactive Compounds from Cashew Nut Shell wastes using Batch Mode

In the present study, Microwave-Assisted Extraction (MAE) was employed to recoverbioactive compounds from cashew nut shell (CNS) waste. The effects of extraction time,temperature, and microwave power on extraction kinetics, thermodynamics, diffusionbehaviour, mass transfer coefficients, and Biot number were systematically investigated.Extractions were carried out using 5 g of CNS in 100 mL of water at temperatures rangingfrom 95 to 98 °C, microwave powers of 200–500 W, and extraction times of 30–180 min.Kinetic analysis revealed an activation energy of 243.4 kJ mol 1 for microwave-supportedleaching, with extraction rate constants increasing from 0.008 to 0.05 mL mg 1 s 1 astemperature rose from 95 to 98 °C. Thermodynamic parameters indicated an endothermic andspontaneous process, with ΔH = 31.57 kJ mol 1, ΔS = 0.131 kJ mol 1 K 1, and negativeGibbs free energy values (−7.37 to −8.01 kJ mol 1). An empirical diffusion model showedthat diffusion coefficients (3.0 × 10 1 to 11.0 × 10 1 m2 s 1), mass transfer coefficients(0.23 to 1.5 m s 1), and Biot numbers increased with temperature, confirming enhanced masstransfer under MAE conditions.