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CARBONLETT, vol. 24, no. 1, pp.62-72, 2017

DOI: http://dx.doi.org/I:10.5714/CL.2017.24.062

Relationships between dielectric properties and characteristics of impregnated and activated samples of potassium carbonate- and sodium hydroxide-modified palm kernel shell for microwave-assisted activation

Norulaina Alias1, Muhammad Abbas Ahmad Zaini1,2,♠ and Mohd Johari Kamaruddin2

Affiliation: 1Centre of Lipids Engineering and Applied Research (CLEAR), Ibnu-Sina Institute for Scientific and Industrial Research (ISI-SIR), Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia
2Faculty of Chemical & Energy Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia

Abstract: The aim of this work was to evaluate the dielectric properties of impregnated and activated palm kernel shells (PKSs) samples using two activating agents, potassium carbonate (K2CO3) and sodium hydroxide (NaOH), at three impregnation ratios. The materials were characterized by moisture content, carbon content, ash content, thermal profile and functional groups. The dielectric properties were examined using an open-ended coaxial probe method at various microwave frequencies (1-6 GHz) and temperatures (25, 35, and 45°C). The results show that the dielectric properties varied with frequency, temperature, moisture content, carbon content and mass ratio of the ionic solids. PKSK1.75 (PKS impregnated with K2CO3 at a mass ratio of 1.75) and PKSN1.5 (PKS impregnated with NaOH at a mass ratio of 1.5) exhibited a high loss tangent (tan δ) indicating the effectiveness of these materials to be heated by microwaves. K2CO3 and NaOH can act as a microwave absorber to enhance the efficiency of microwave heating for low loss PKSs. Materials with a high moisture content exhibit a high loss tangent but low penetration depth. The interplay of multiple operating frequencies is suggested to promote better microwave heating by considering the changes in the materials characteristics.

Keyword: ctivation, dielectric properties, impregnation, palm kernel shell, penetration depth