Expanded vermiculite-reached product obtained from mining waste: the effect of roasting temperature on the agronomic properties

This article explores the possibility of using the vermiculite-lizardite granular product with 30% of vermiculite content for the potential agronomic application. The vermiculite-lizardite product was obtained by beneficiation of phlogopite mining waste (Kovdor, Murmansk region, Russia). The beneficiation scheme included a hydro separator, a spiral separator, and concentrating tables. The output of vermiculite-lizardite product was about 35%. The effect of roasting temperature on the hydrophysical and agrochemical properties of the vermiculite-lizardite material and the mono-mineral vermiculite was studied. Heat treatment of materials was performed in the laboratory shaft furnace. Based on the differential thermal analysis results, a temperature of 700℃ was selected as the upper limit and the temperature of 400℃ - as the lower limit of the temperature range in order to obtain an expanded vermiculite-reached product containing lizardite. For samples obtained in this temperature range with a step of 25℃, a set of data such as bulk density, water saturation, surface area, volume and average pore diameter, Eh, pH suspensions in water and KCl solution, chemical resistance in ammonium acetate solution buffered at pH 4.65 were obtained. The temperature range of 500-600℃ of the vermiculitelizardite granular product was determined as favorable for agronomic application.