Abstract:
In response to the challenges of high difficulty and low comprehensive utilization rate when conventionally using ultrafine molybdenum tailings for the preparation of building materials, a technical approach combining alkali activation and hydrothermal method to prepare soil conditioners has been proposed. Molybdenum tailings are used as the main raw material, with quicklime, KOH, and others as activators to prepare soil conditioners under hydrothermal conditions. The study investigated the impact of factors such as the mass concentration of KOH, the mass ratio of tailings to lime, the mass ratio of straw to tailings, the mass−volume ratio of mixed dry materials to alkaline solution, hydrothermal reaction time, and hydrothermal reaction temperature on the production of soluble Si and K elements. The results showed that under the conditions of a KOH concentration of 0.5 mol/L, a mass ratio of tailings to lime of 1 : 0.8, a mass ratio of straw to tailings of 1 : 70, a mass−volume ratio of mixed dry materials to alkaline solution of 100g : 300mL, a hydrothermal reaction time of 9 hours, and a hydrothermal reaction temperature of 180 ℃, the prepared soil conditioner had soluble Si and K contents of 8.9 % and 6.85 %, respectively, meeting the requirements for Si and K elements in "Silicon−Calcium−Potassium−Magnesium Fertilizer" (GB/T36207—2018). Under the combined action of alkali activation and hydrothermal method, the silicate minerals in the tailings undergo depolymerization and condensation reactions, activating the reactivity of elements such as Si, K, and Al. The prepared soil conditioner samples meet the national standard requirements for soluble Si and K elements; they form a network structure with strong adsorption capacity. This research outcome will be of great significance to the reduction, resource utilization of molybdenum tailings in China, and the sustainable development of agricultural production.