Kinetics of silica dissolution from rice husk char

The effect of leaching time and temperature on the ash content of rice husk char and the resultant surface area development was investigated. Experiments on dissolution of rice husk char ash with 0.5 mol NaOH solution were conducted at 40 degrees C, 60 degrees C, 80 degrees C and 95 degrees C for different times up to 7200 s. The surface areas of the leached chars after drying were determined using Micromeritics 2200 surface area analyzer. The leaching data was analyzed using different models applicable for fluid-solid non-catalytic reactions. It was found that the data could be satisfactorily represented by diffusion-controlled mechanism as well as modified shrinking core models. The activation energies were in the range of 41.7s to 51.25 kJ/mole. The surface areas of the leached chars were found to depend linearly on the percentage of ash content in the chars.