The present invention provides a simple, facile and clean process route for the production of industrially and commercially important valuable alkali metal silicates from spent foundry sand by amenable synthetic depolymerization mechanism through hydrothermal method. The synthetic process route involves the dissolution of silica mass of waste foundry sand using alkaline solution over a period of 3 hours and at 250°C. Further, the obtained sodium silicate and potassium silicate were converted into corresponding aluminosilicates using aluminium foil and aluminium metal scrap at ambient temperature over a period of 30 and 180 minutes respectively. The production of alkali metal silicates and aluminosilicates were characterized using different modern analytical techniques. The synthetic process route developed in the present work for the preparation of alkali metal silicates and aluminosilicates possesses number of special features with regard to concentration of alkalies used, reaction time, temperature, workup methodology and percentage yield. The value added alkali metal silicates obtained in the present work from spent foundry sand can be used as a source material for the manufacture of different industrial products viz., binding materials, additives, fillers, raw materials, admixtures, molecular sieves, catalysts, masonry products and geopolymer concrete, etc, This invention is considered to be the novel method of waste utilization and effective approach for industrial solid waste management.