Advances in Acid Rock Drainage (Ard) Characterisation of Mine Wastes

Abstract

Research was carried out to improve acid rock drainage (ARD) prediction methodologies, focussing on resolving uncertainties in acid base accounting (ABA) methods. Advancements, their application, and interpretation are reported. Consideration of both net acid production potential (NAPP) and net acid generation (NAG) test results provide a more reliable routine screening technique than either test alone, increasing confidence in acid potential classification and identifying apparent conflicts requiring further investigation. Techniques such as sequential NAG, modified organic carbon NAG, modified ANC methods to account for siderite and acid buffering characteristic curve (ABCC) testing can be used to help resolve these conflicts in a relatively short time frame. Samples with abundant siderite require complex modified ANC methods, involving excess addition of H 2 O 2 to ensure all dissolved ferrous ion is oxidised before completion of the back titration step. It is demonstrated that at siderite abundances of less than 15 wt %, standard ANC methods are sufficient, improving the efficiency of ANC assessment by reducing the number of modified ANC tests required. Comparison of ABCC profiles with the developed set of standard carbonate curves provides an indication of the relative reactivity of the ANC measured in waste rock samples, something not evident in ANC test results alone. A relationship was established between kinetic NAG and leach column test results, which provides an indication of lag times without the need to carry out leach columns on all samples. This has the great advantage of allowing kinetic prediction on a broad sample set in a short time frame. The test refinements and developments described in this paper improve the reliability of ARD prediction from short duration tests, provide information on relative reactivity of acid forming and neutralising phases, and improve predictions of acid forming potential.

Prediction of acid mine drainage generation potential of various lithologies using static tests: Etili coal mine (NW Turkey) as a case study

“…The solution was left under a fume hood for at least 2 h while reactions continued (until no further bubbles or gas were released) and then placed in a 70°C water bath. The heating procedure served to remove excess peroxide and to reveal the current neutralizing ability of the sample (Stewart et al 2006). The solution was left in the bath for at least 2 h or until the reactions were complete, then removed and left to cool.…”

Comprehensive utilization of lead–zinc tailings, part 1: Pollution characteristics and resource recovery of sulfur

“…The ABA test predicts the acid production ability of the tailings based on the net acid production potential (NAPP). The NAPP is the difference between the acid neutralizing capacity (ANC) and the maximum potential acidity (MPA) [17,18]. The ANC was determined as follows: approximately 1.0 g of sample reacted with 25 mL of 0.2 mol/L HCl at 90 C for 3 h, then excess HCl was titrated with 0.2 mol/L NaOH.…”

“…To ensure reliable results and to avoid the shortcomings of the two different methods for predicting AMD, the AMD classification plot was used [18]. Table 1 displays the guidelines for classifying AMD prediction test results.…”

Revue de littérature détaillée sur les tests statiques et les essais cinétiques comme outils de prédiction du drainage minier acide

“…Pour prendre en considération la génération de l'acidité par le Fe et le Mn (voire l'Al des silicates) lors de la détermination du PN avec le test statique de Sobek, Skousen et al (1997), Jambor et al (2003), Stewart et al (2006) ont proposé l'ajout du peroxyde d'hydrogène (H 2 O 2 ) lors de la titration de la pulpe (en plus du NaOH) pour forcer l'oxydation et l'hydrolyse des éléments chimiques hydrolysables en libérant ainsi l'acidité qui sera considérée lors de la titration. L'ajout du H 2 O 2 permet d'obtenir une estimation plus correcte du PN.…”