I have done water absorption test for chemical treatment rice husk . It has seen, the absorption of water rises gradually during the time for sample. I know, Any cellulosic material has a tendency to absorb fluid due to its chemical structure and the hydroxyl groups available in their chain. The hydrogen and oxygen bonds are at the outer surface and immediately absorb any amount of water present forming a hydrogen bond. But I am looking for the reason for, why the water absorption is lower at the beginning, and enhanced at increasing the time.
I think, Silica contents of rice husks cause lower water absorption.
When the rice husks are very dry, the water is in a monolayer. Adding water is thermodynamically less favorable than when there is more water, and it fills capillaries. "Moisture sorption isotherm" is a good search phrase for further literature.You are likely to find publications in food science and seed science, where they are particularly concerned with dry materials
You can demonstrate the phenomenon by seeing water droplets bead up on dry coir, peat moss, or cellulose sponges.
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