A novel and sustainable process to recycle an environmentally injurious material rich in silica—waste bagasse bottom ash from the sugar industry—into mesoporous pure silica of high purity is reported. Bagasse bottom ash (BBA) is a major byproduct of the sugar industry, with very inadequate recycling possibilities due to environmentally detrimental pollutants, whose production is dramatically increasing. In this study, for the first time, more than 70% of the silica from the bottom ash could be extracted for the synthesis of mesoporous silica using a low-temperature alkaline dissolution method instead of the customary elevated-temperature process. Furthermore, the process of dissolution was thoroughly studied to obtain the essential insight into silica hydrolysis that is largely missing from the existing research literature. Under alkaline conditions, the hydrolysis of silica is hindered due to the formation of zeolites and protective layers around the etching particles. This layer becomes a protective barrier that hinders the mass transfer of silica monomers to the solution, thus halting the dissolution process. Therefore, sequential extractions with optimized conditions of 100 °C for 72 h were employed to attain maximum silica extraction efficiency.