The study of drying of red alga (Gelidium sesquipedale, Rhodophyta), with initial sample masses varying from 1 to 10 g, was carried at different temperatures 30 -80 °C. The experimental drying curves show a slight effect of the initial mass. Two types of curves are obtained: those at temperatures below 50 °C are fitted into straight line according to an interfacial progression process in cylindrical symmetry. Those of high-temperature drying (50 < θ < 80 °C), are perfectly parabolic and show that the kinetic regime is controlled by the three-dimensional diffusion according to the Jander equation. The two types of water molecules identified were also highlighted during the drying kinetics process. The apparent activation energy of the strongly bounded water (20%) is about 36.25 kJ·mol -1 , and that of the wetting water is in the range of 47.68 kJ·mol -1 .

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Microwave technology is currently very interesting because it offers, in many industrial processes, a new alternative energy for drying and treatment of various materials. In this context, the drying of the Gelidium sesquipedale (Rhodophyta), which is a red algae, is carried out under microwave irradiation in the aim to optimize the energy consumption in the drying process and the quality of the extracted products. The drying process of Gelidium sesquipedale under microwave irradiation is carried out by studying the thermal and kinetic aspects of drying under different irradiation conditions. The experiments were performed on samples of different initial masses ranging from 2 to 30 g. The samples are irradiated in an experimental device combining a gravimetric balance and microwave assembly that may impose different power microwave ranging from 50 to 200 W.The analysis of the experimental curves of the drying process shows that the initial mass of the sample has little influence and the applied microwave power has a significant effect on the drying kinetics. The comparative study of the drying of Gelidium sesquipedale by conventional heating and under electromagnetic field shows that the controlling kinetic mechanism depends on the way in which the sample is dried. The action of the electromagnetic field allows faster heat transfer leading to the rapid evacuation of water molecules from the seaweed.