Hi, I have read that lime neutralization is the most common treatment for acidic mine drainage.The process involves neutralization and precipitation of a metal hydroxide - gypsum sludge using a flocculant, generally Percol. In short term the sludge is stable however in long term any tendency of pH to drop can re dissolve metal hydroxides and contaminate the surrounding area and groundwater.

Therefore,the use of activated silica sol, an inorganic silicate polymer used in municipal water treatment, as a replacement to Percol is investigated to improve long term stability of sludge.

Silica sol is an effective flocculant. It has neutralization potential and forms metal - silica bonds which is more resistant to pH variation than metal hydroxides.

You can read this journal " Use of activated silica sol as a flocculant in the treatment of Acid Mine Drainage to Promote Sludge  Stability"  for  more  details information  or

email  isabelle.demers@uqat.ca  since she was the one who published that journal.

I attach 6 very useful papers in which you will read:

The split treatment of AMD with limestone and lime may offer some advantages in cost and improved sludge characteristics. It might also be used on ferrous iron AMD. A two-step process is required. First, the AMD is treated with limestone to a pH of 4.0 to 4.5 to take advantage of the pH range when limestone is most effective, The water then passes to a second reactor where lime is applied to raise the pH range to the desired level. This process may have a cost advantage over lime alone and the desired sludge characteristics of the limestone process.

We have years of experiences and great success using engineered membranes to clean up AMD/ARD waters in copper mining operations for reuse and/or discharge to ground.