Effects of modulus and dosage of sodium silicate on limestone flotation

Sodium silicates are probably one of the oldest and most widely used industrial chemicals. Among a wide variety of applications, an important one is as a depressant in flotation. In this investigation, the effectiveness of sodium silicates of different values of modulus (silica-to-soda ratio) and dosage was investigated on a low-grade siliceous limestone sample having CaO = 45.10%, SiO2 = 15.60% and LOI = 36.03% from Jayantipuram mine of Andhra Pradesh, India. Direct flotation (flotation of carbonate minerals) was adopted to reduce the silica content and enrich CaO using laboratory-scale flotation process batch tests. The analysis of variance (ANOVA) statistical tool was used for evaluation of the influence of operating parameters, viz. the modulus and dosage of sodium silicate, on the flotation. The study indicated that a modulus of 2.19 and a dosage of 0.6 kg/ton is optimum for the flotation for the low-grade siliceous limestone sample.