Exploration of the effects of electrolytic manganese residue on the environmental, economic, and engineering performance of magnesium oxychloride cement: A possible utilization method of electrolytic manganese residue

The widespread use of magnesium oxychloride cement (MOC) can effectively solve the waste problem in the potash industry. However, its poor water resistance limits its practical application. Electrolytic Manganese Residue (EMR), as a solid waste from manganese metal smelting, requires an effective utilization method. In this work, we have attempted to incorporate EMR into MOC after its treatment in order to improve the water resistance of MOC and increase the utilization rate of EMR. The addition of EMR to MOC increased the density of MOC. The incorporation of EMR did not significantly reduce the strength of the MOC samples. The incorporation of EMR reduced the relative content of magnesium oxide in the specimens and EMR can be used as a source of soluble Al, Si and Fe to produce insoluble amorphous gels. The combined effect resulted in an effective improvement in the water resistance of the samples. The 28-day water immersion strength of the EMR100 can reach 38.3 MPa, and its water resistance coefficient was 82.10%. The appropriate doping of EMR can improve the pore structure of the specimens, reduce the porosity and refine the pore size distribution. Carbon emission per unit compressive strength and cost per unit compressive strength were used as evaluation indices of environmental and economic benefits. A high dosage of EMR-incorporated MOC resulted in low cost and carbon emission, especially the strength of the specimen after water immersion as a strength index. Taking into account the strength after 14 days of air curing and 28 days of water immersion, the advantages of cost per unit compressive strength and carbon emission per unit compressive strength of EMR100 were further extended and reduced by 86.23% and 22.15% respectively compared to the benchmark group. The heavy metal curing of EMR was evaluated by ion leaching test, and the result showed that MOC effectively cured the heavy metal ions in EMR and reduced the environmental risk of EMR. The good performance of EMR in MOC systems not only provides an effective breakthrough for the efficient utilization of EMR and its heavy metal curing, but also effectively improves the performance of MOC and reduces the production cost.