The Effect of Sodium Chloride On the Rate of Calcite Dissolution and Acid Mine Drainage

Elaine Langone Center, Terrace Room

Open limestone channels are a common method for treating acid mine drainage. The Swank open limestone channel in Reade Township, Cambria County has been monitored over the past 3 years, measuring pH, alkalinity, dissolved oxygen, and conductivity. In 2011, the inflow of the channel had an average pH of 3.3 and an outflow average pH of 4.4. Currently, there is less pH increase than when the channel was originally installed. This is due to the buildup of precipitates on the limestone rocks which slows dissolution rates. In order to fix this problem, a new method of regeneration needs to be discovered. The purpose of this experiment was to observe the effect of salt (sodium chloride) on the speed of calcite dissolution and acid mine drainage by testing the pH, conductivity, and alkalinity every 3 hours for 2 days under controlled laboratory conditions. Based on the data collected, the pH increased faster with salt than without. By adding salt, the conductivity raised drastically, allowing the pH to change faster. Future treatment plans could include adding salt to increase calcite dissolution rates and possibly regenerate channel performance.