The effect of alkali treatment on rice husk moisture content and drying kinetics

The utilization of rice husks for energy production is often problematic due to their high ash content. A simple method for silica ash removal is the treatment of the husks with sodium hydroxide solutions. The alkali treatment can induce other changes to the husks which need to be investigated. Here, the effects of alkali treatment on the moisture content and drying kinetics of the samples were investigated. The alkali treatment is shown to result in an increase in moisture retention by the as-prepared biomass. Response surface methodology (RSM) using a BoxeBehnken design (BBD) is employed to investigate the effects of various input parameters, namely reaction temperature, duration, and alkali mass ratio on moisture uptake of the rice husk. In addition, the drying kinetics of the as-prepared samples are modeled and compared to raw husk prior to treatment. The results show a small increase in the effective diffusivity and a significant decrease in the activation energy required for drying the treated samples. (C) 2014 Elsevier Ltd. All rights reserved.