Microscopic properties and neutralization mechanism of steel slag in acid mine drainage (AMD) remediation process

Abstract Steel slag has been proven to be an effective environment remediation media for acid neutralization, and a potential aid to mitigate acid mine drainage (AMD) in passive treatment process. But its acid neutralization capacity (ANC) is frequently inhibited by precipitate after a period of time, while the characteristic of the formation process are unclear yet. In this work, ANC of the SS sample was tested using simulated AMD (H 2 SO 4 , 0.1M) and real AMD. Steel slag and AMD has been characterized on pH, ANC, as well as Ca, Mg, Al, Mg-bearing ingredients. Microscopic properties characterization and neutralization experiment results shown that Ca-bearing constitutes leaching and sulfate formation were the two main categories reactions throughout the neutralization process. A prominent transition point of the two kind reactions was selected at 40 % of the neutralization process. Microscopic properties characterization indicated Ca 3 SiO 5 (C 3 S) played a dominant role among Ca-bearing components in alkaline releasing stage for the present sample. Morphology, pore distribution, composition, surface area and other microscopic properties of the neutralized slag were significantly changed by the crystallized CaSO 4 precipitates in sulfate formation stage, which hindered the alkaline releasing behaviors gradually. Neutralization experiments conducted by real AMD suggested that the steel slag ANC property was also influenced by the contained high concentration metal ion due to the precipitate reactions except for sulfate formation reactions.