Assessment and Modeling of Nanofiltration of Acid Mine Drainage

The main objective of the present investigation was to analyze, evaluate, and model the behavior in the treatment of real acid mine drainage (AMD) with commercial spiral-wound nanofiltration membranes (NF270 and NF90). Both membranes showed operational differences regarding the effect of pH, temperature, continuous operation, concentration polarization, and fouling. Both NF90 and NF270 presented a high rejection of divalent ions (similar to 100%); however, NF90 showed a greater fouling with AMD. Adjustment of pH in the continuous tests reduced the precipitation of aluminum, and gypsum was identified as the main compound generating a significant decrease in the permeate flow in the membrane. The Spliegler-Kedem model was used to represent rejection and permeate flows, identifying the contribution of convective and diffusive transport in both membranes with a good fit of the model. The results obtained represent important information for a future industrial application to the treatment of AMD by means of commercial NF membranes.