I have some flyash and want to leach out Al2O3 and SiO2 using NaOH. IS there any additive which can help me to improve rate of leaching or dissolution .
Try Increasing temperature, NaOH concentration and stirring speed to find at what value of these operating parameters the leaching rate is maximum. Add H2O2 and check whether the leaching rate improves, if it does optimize the H2O2 dose.
Under some circumstances there are a few organic acid ions such as oxalate, glycolate that marginally assist in silicate leaching but I am not sure if they would work in your case. However, if you find nothing else, they might be worth investigating.