Ntwampe OI, Waanders FB and Bunt JR
Acid mine drainage (AMD) from decant in Krugersdorp (South Africa) was dosed with acid-free polyferric chloride (af- PFCl) of CaOH2 or MgOH2 (PFCl-Ca(OH)2 or-Mg(OH)2). A 200 mL sample was poured into five 500 mL glass beakers and the flocculent was added in a jar test respectively using different methods of mixing and dosing. The mechanism tests were performed employing two methods of dispersing reagents throughout the colloidal suspension, i.e., rapid mixing and shaking in order to find the removal mechanism of mineral salts and relationship between the removal and characteristics of flocculent/pollutants. The results showed that the turbidity removal efficiency exhibited by FeCl3, PFCl-Ca(OH) 2 or Mg(OH)2, and hydroxides of Ca or Mg is identical, all above 90%. It also revealed that the effective AMD treatment is not necessarily dependent upon the pH, but the ability of the coagulant to destabilize the double layer (high electronegativity) of an aqua-colloid and optimal hydrolysis. The residual turbidity of the AMD samples at 15, 25 and 35°C does not exhibit significant deviations. The turbidity removal of the samples with low temperature shows that dynamic viscosity of the colloidal suspension has an influence in the destabilization-hydrolysis reaction.
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