Resistance to Sulfate Attack Under Drying–wetting Cycles of Reactive Magnesia–microbial Cured Electrolytic Manganese Residue

Abstract

The reactive MgO (r-MgO)-microbial curing technology can not only effectively improve the strength of electrolytic manganese residue (EMR) but also repair heavy metal ions. By conducting unconfined compressive strength (UCS) test, heavy metal leaching test, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP), the effects of the type and concentration of sulfate on the strength and repair of heavy metals of the cured EMR under drying–wetting (DW) cycles were studied, and the strength and the evolution mechanism of heavy metal remediation is elucidated. The results indicate the following: With the increase in the number of DW cycles, the dry density of the samples in high concentration of MgSO₄ first increased slightly and then decreased gradually and became stable. The dry density of the samples in Na₂SO₄, low concentration of MgSO₄, and water generally showed a downward trend. The pH of the soaking solution slightly decreased, and the leaching concentration of heavy metal Mn²⁺ ions always remained at a low level. The UCS of the samples in MgSO₄ first increased slightly and then decreased gradually, and then became stable. The amount of cured products first increased and then decreased, and the size of internal pores first decreased and then increased. The UCS of the samples in Na₂SO₄ and water gradually decreased and became stable. The amount of cured products gradually decreased, and the size of internal pores gradually increased. The research results provide a theoretical basis for the evaluation of resistance against the sulfate corrosion of cured EMR under DW cycles.

Keywords:

• Drying–wetting cycles
• electrolytic manganese residue
• reactive MgO–microbial curing
• resistance
• sulfate attack

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was financially supported by National Natural Science Foundation of China [No. 51978103] and Chongqing Technology Innovation and Application Development Special Key Project [Take the lead, No. cstc2021jscx-jbgsX0005].