DBPapers
DOI: 10.5593/SGEM2014/B42/S18.005

BUFFERING CAPACITY OF SULFIDE MINE TAILING AMENDED WITH ALKALINE MATERIALS

A. Kastyuchik, A. Karam. M. Aider,A. Jaouich
Wednesday 1 October 2014 by Libadmin2014

References: 14th International Multidisciplinary Scientific GeoConference SGEM 2014, www.sgem.org, SGEM2014 Conference Proceedings, ISBN 978-619-7105-16-2 / ISSN 1314-2704, June 19-25, 2014, Book 4, Vol. 2, 35-42 pp

ABSTRACT
The ability of sulfide mine tailing (SMT) treated with alkaline materials to buffer or
neutralize anthropogenic acidity depends on several factors including the amount and
types of acid-neutralizing compounds present in SMT matrix. The main objective of this
laboratory experiment is to assess the acid buffering capacity of SMT samples after
their stabilization with chicken eggshell residue (CES), commercial cement rich in
calcareous products (CCM), dolomitic limestone (DOL), calcitic limestone (CAL) and
magnesium oxide (MGO). The treatments were as follows: SMT without alkaline
materials (AM); 2% CCM; 4% CCM; 10% CCM; 2% MGO; 2% DOL; 2% CAL; 2%
CES; 4% CES; 10% CES; 10% CES + 2% CCM; 10% CES + 2% DOL; 10% CES +
2% CAL; 10% CES + 2% MGO. Two days after the addition of 0.5 ml of 0.05 mol/l
sulfuric acid, the decrease in pH ranged over several orders of magnitude in SMT
treated with CES and CAL. In general, the lowest values of pH were recorded in SMT
amended with 2% and 4% CES (pH 3.3 and 3.5 respectively) and 2% CAL (pH 3.9).
The pH of all acidified aqueous SMT samples increased gradually over time. Chicken
eggshell residue mixed with MgO or cement was considerably more efficient in
neutralizing sulfuric acid than CES alone. At the end of the equilibration period (56
days), the pH values of aqueous SMT+ 2% AM suspensions (solid:liquid ratio of 1:20,
w/v) increased in the following order: SMT + 2% MGO (pH 9.0) ˃ SMT + 2% CCM
(pH 8.6) ˃ SMT + 2% limestone (CAL or DOL) (pH 7.3 – 7.5) ˃ SMT + 2% CES (pH
7.0). The study showed that sulfide mine tailing treated with magnesium oxide or
cement was stable and well buffered to acidifying input. The results suggested that
magnesium compounds and calcareous products rich in hydroxides, oxides and
carbonates present in limed SMT would provide long-term protection against acid
deposition or re-acidification of limed SMT.

Keywords: chicken eggshell, cement, calcareous materials, magnesium oxide,
acidification.

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