Isotherm moisture sorption of composite desiccant made from rice husk biomass

Abstract

The behavior of isotherm moisture sorption form rice husk-CaCl2 composite desiccants was studied. The desiccant composite in various treatments was tested for its isotherm sorption using gravimetric method. Saturated solution of LiCl, CH3COOK, MgCl, K2CO3, NaBr, NaNO2, NaCl, KCl, and K2SO4 were used to obtain the moisture of 11 %, 22 %, 32 %, 44 %, 56 %, 64 %, 75 %, 84 % and 97 %. Water activity produced from these saturated salt solutions was measured using aw meter. The equilibrium moisture data was then fitted into several isothermal equation models that have been used and tested in several literature including the model of Courie, Oswin and Chen Clayton. This rice husk composite desiccant had exposed a J shape curve of equilibrium water content with a boundary zone A of aw 0.2 and zone B of aw 0.67. Based on the isothermic absorption curve, the Oswin equation model was able to predict the results of research with R2 of 0.96, 0.89 and 0.97, respectively for temperature of 30, 40 and 50°C. This rice husk desiccant was able to absorb water vapor at low RH. It means that this desiccant is promising to be used for low water content or hygroscopic product such as flour based product, food flavor powder, chili powder, palm sugar and other products.