Simulation study on remediation of acid mine drainage by in-situ injection of limestone based sustained release materials

Abstract

The karst area is widely distributed in China, and the ecological environment is fragile. Acid mine drainage (AMD) produced by mining activities in karst areas seriously threatens the safety of regional ecological environment. In this paper, carbonate rocks and corn cobs (biochar) widely distributed in karst areas were used as raw materials, and an alkaline sustained release material (ASRM) that could be used for in-situ injection and repair was prepared by means of modification, granulation and film coating. In addition, in-situ injection and repair experiments under alternating effects of wet and dry conditions were carried out in the laboratory, to verify and determine the ability and removal mechanism of ASRM in the in-situ remediation of heavy metals in acid mine wastewater. The results showed that ASRM can effectively improve the pH of water, and the pH of AMD can be increased from 2.8 to approximately 5-7, and it had a good removal effect on many harmful heavy metals, such as Fe2+, Mn2+, Zn2+, Cu2+, Cd2+, Pb2+ and Cr3+. XRD and SEM analyses showed that the reaction precipitates mainly existed in the form of FeOOH. The removal mechanism of heavy metals mainly includes: ①some metal ions were removed in the form of precipitation, such as hydroxides produced by the reaction; ②a large amount of FeOOH produced by the reaction system can adsorb and remove heavy metals. This experimental study provides a reliable theoretical and technical basis for the in-situ treatment of AMD in karst mountain mines with high efficiency by using slow-release materials.

Keywords

• sustained release materials
• karst mountainous area
• acid mine drainage(amd)
• in-situ injection
• heavy metal