Simulation of Grain size Distribution & pH effect on metals reactive transport in Porous Media

Many environmental problems associated with the mining industry, involve the understanding and analysis of the contaminant transport processes and results. Both experimental work and numerical models can provide the necessary information to understand and solve any problem. The long term pyrite oxidation, acid mine drainage generation and transport of the oxidation products and heavy metals are noted to be the most important problems that can be modeled in order to predict the transport of the contaminants through groundwater and river flow systems to interpret the geochemistry and achieve a better understanding of the process involved. This study investigated the effects of the initial pH and the grain size distribution on the reactive transport of three metals (Cd, Ni and Mn) from Zanjan Zinc leaching plant tailings. The migration of these metals was simulated using a multicomponent reactive transport model (PHREEQC) in a 30 days period. Not surprisingly, lower pH, and smaller effective particle size increased metal transport. The simulation results generally agreed well with results from a previously conducted column study. We conclude that different grain size distribution and pH values induce variable metal speciation and suggest accounting site-specific risk assessments for the above mentioned issues.

Keywords:

Metals Reactive transport modeling , PHREEQC , Grain size distribution , pH , Zanjan mine tailings