Activity of Electrolytic Manganese Residue under High Temperature Calcination-mechanical Coupling and the Solidification Mechanism of Heavy Metals

Abstract

The effects of calcination temperature and mechanical ball milling on the physicochemical properties of electrolytic manganese residue (EMR), mineral phase transition, pozzolanic activity, and pore structure were studied. The experimental results show that the strength activity index (SAI) of 20% EMR mixed mortar at 28 days is 90.54%, 95.40%, and 90.73%, respectively, after pretreatment with EMR at 800 °C calcined for 3, 5, and 8 min. This is mainly attributed to the high temperature decomposition of gypsum dihydrate to form activated calcium oxide. In addition, high temperature and mechanical force destroys the Si-O chemical bond and promotes the formation of calcium silicate gel structure. Due to the existence of a large number of gypsum phases in EMR mixed mortar, a large number of ettringite, C-S-H, aluminosilicate, C-A-S-H, and AFm are formed, which strongly verifies the volcanic activity of EMR. The leaching test shows that high temperature calcination has a significant effect on the stabilization of NH₃-N. However, the curing effect of Mn²⁺ is significant only in the calcination at 1 000 °C, but both Mn²⁺ and NH₃-N in the calcined EMR are higher than the emission standard. The encapsulation effect of EMR composite mortar provided by hydration products, and the buffering capacity of the Si-Al system for solidification of heavy metals and strong alkalis are conducive to the stability of Mn²⁺ and NH₃-N. After the EMR mixed mortar is aged for 3 days, Mn and NH₃-N are completely lower than the emission standard. In general, the EMR mixed mortar can meet the requirements for green building use.

Keywords

electrolytic manganese residue / calcination / grinding / pozzolanic activity / leaching / curing mechanism

RIGHTS & PERMISSIONS

Wuhan University of Technology and Springer-Verlag GmbH Germany, Part of Springer Nature