Preliminary Study on the Use of Reverse Osmosis Brine and Mine Tailings as Cement Paste Mixtures for Mine Backfilling Application

The processing of low-grade gold ores generates a significant volume of tailings and wastewater that impacts the environment. The treatment of wastewater using reverse osmosis (RO) produces brine as a by-product with high salinity levels. Improper disposal of mine wastes can significantly pollute water bodies and soils. A novel and sustainable method for managing, disposing, and handling these wastes is vital. The use of RO brine and mine tailings to produce cement paste mixtures for backfilling applications has been investigated. Sulfide gold mine tailings and RO brine were characterized, and cement paste backfill (CPB) mixtures were prepared by mixing varying proportions of cement and RO brine. The CPB cubes were cured for a specified number of days, and their physical and mechanical properties were determined. The results indicate a decrease in slump value with increasing cement content, whilst the slump increased with RO brine content. The compressive strength at 28 days increased with binder content reaching a maximum of 1.83 MPa using 50% RO brine. The CPB cubes produced with 50% RO brine and 12 wt.% cement possessed the required combination of fluidity and strength for mine backfilling applications.