In-Depth Analysis of Silica Rejection From Low-Grade Dolomite Fines Using Dry and Wet Processing Methods

Abstract

Dolomite is an important raw material for refractory and steelmaking industries; however, large quantities of low-grade dolomite fines are discarded as mine waste because of their high silica content. The present study presents a systematic mineralogy-guided beneficiation strategy for valorizing low-grade dolomite fines by integrating detailed characterization with process flowsheet development. The scientific novelty lies in establishing the relationship between mineral liberation characteristics and the selection of an optimum beneficiation route through the comparative evaluation of three alternative flowsheets: (i) gravity separation-flotation, (ii) dry air classification-flotation, and (iii) two-stage reverse-direct flotation. Mineralogical investigations revealed quartz as the dominant siliceous gangue, with significant interlocking that necessitated controlled fine grinding for effective liberation. Although the hybrid dry classification-flotation route reduced water consumption and produced a concentrate containing approximately 4.2% SiO2, its separation efficiency was limited by the narrow density contrast between dolomite and gangue minerals. Among the three alternatives, the two-stage reverse-direct flotation flowsheet proved to be the most effective, producing a high-grade dolomite concentrate containing 0.8% SiO2 with 96.9% silica rejection at an overall mass recovery of 32.2%. The proposed mineralogy-driven flowsheet demonstrates an effective approach for upgrading low-grade dolomite fines into metallurgical-grade feedstock while simultaneously improving resource utilization, supporting circular economy principles, and reducing environmental impacts through sustainable process design.