Elaboration of bentonite-carbide slag composite for mineralization and immobilization of Cu2+ in acid mine drainage

Abstract

In this study, a series of bentonite-carbide slag (BCS) mineral composites were developed by modifying bentonite with carbide slag using Na2CO3 as activator, to achieve acid neutralization and mineralized immobilization of Cu2+ in acid mine drainage (AMD). The main factors that affect the structure-activity relationship of the BCS particle, such as material ratio, Na2CO3 dosage, calcination temperature, and calcination time, were investigated in detail to determine the influence rules of each factor and the structure-activity relationship of the BCS particle on the immobilized mineralization of Cu2+ via spontaneous film formation. The results indicated that the optimal preparation parameters for BCS particle were as follows: bentonite/carbide slag mass ratio of 3:7, Na2CO3 amount of 10 wt%, calcination temperature of 500℃ and calcination time of 60 min. During the calcination process, Na2SiO3 and C-S-H were formed under the action of the Na2CO3 activator, which were conducive to bonding between the raw material in BCS particle. The mechanism of OH- alkalinity release of endophytic crystal ions in BCS particle, and the mechanism of spontaneous film formation and immobilization mineralization of Cu2+ in AMD were also proposed with the help of SEM, XRD and FT-IR analysis. This study can provide theoretical guidance for the preparation of composite mineral particle material with endophytic crystal ions, as well as the prevention and control of AMD and the recovery of valuable metals from AMD.