The use of Bauxsol™ technology in mine site management and remediation

CIM Montreal 2003
Malcolm Clark, Gregory Maddocks, Fiona Davies-McConchie, Sarah Pope, Will Caldicott, ,
Abstract The use of Bauxsol™ (physically and chemically
modified alumina refinery residues) to treat acid
rock drainage (ARD), and sulphidic waste rock and
tailings, provides new options for managing some
intractable environmental problems at both
derelict and active mine sites.

Treatment of ARD waters using the Bauxsol
technology shows that the effectiveness of raw
Bauxsol material can be enhanced by including
modest amounts of selected industrial minerals or
common chemical additives. The type and amount of
additive required and the amount of the blend
needed to treat the water depends on the initial
composition of the water and the target water
quality; for some ARD waters, optimum treatment
may require one or more changes in the type or
amount of additive used. Maximum treatment
efficiency can be achieved only when a balance is
maintained between the rate of trace metal binding
and the rate of change in water pH; adding
treatment reagents faster than can be accommodated
by the reaction kinetics will not result in more
rapid water treatment. This paper presents the
results for treating several ARD waters to
illustrate the importance of blend selection and
treatment procedure.

Although treating ARD water is often necessary,
this strategy treats the symptoms rather than the
cause. The best permanent solution is to treat
the sulphidic waste rock or tailings such that
they do not continue to oxidise and produce acidic
metal-rich leachates; sulphide oxidation needs to
be stopped or slowed to a rate that can be
accommodated by normal environmental processes.
Capping lined impoundments is not a solution
because all caps and linings will inevitably fail
some time in the future creating a nasty surprise
for some future generation. Adding lime is also
less than ideal because the lime leaches from the
treated material; treatment often appears to be
effective for a few years and then fails. Bauxsol
technology offers effective alternatives to
conventional liming and capping procedures and
Bauxsol blend application rates and procedures can
be planned to ensure that no acidic or metal-rich
water can ever escape from the site. Bauxsol can
be physically mixed with the sulphidic mine wastes
or it can used to form subsurface permeable
reactive barriers, or both. Bauxsol treated waste
rock and tailings can be immediately and
effectively revegetated. In this paper we present
leachate quality and plant growth rate data for
several sulphidic waste rock and ta

Keywords: Sulphides, Acid rock drainage
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