Mining in focus
The Kansanshi copper mine in Zambia is one
of the biggest copper mines in Africa.
The plant also proved to be profitable
to an extent that the copper industry
became aware and interested in copper
L/SX/EW.
Improvement in L/SX/EW technology
was inevitable. In Kordasky’s paper,
he writes that “the first improvement
in copper SX reagents came when
LIX 64N was added as makeup to the
Ranchers plant in late 1968”. LIX 64N
had several advantages with greater
extractive strength, faster kinetics, faster
phase separation, and lower entrainment,
among others. Kordosky explained that
the benefits of LIX 64N resulted in
reagent properties that broadened the
range of copper leach liquors that could be
successfully treated by solvent extraction.
This had a knock-on effect on the SX
plant, as capital costs were reduced.
Decreased organic losses and tankhouse
bleeds lowered overall operating costs.
Adding LIX 860-1 to plants that were
already using LIX 64N enabled the
plants to upgrade plant performance and
flexibility quickly and conveniently.
Various companies with other
improvements to L/SX/EW technology
[40] MINING MIRROR SEPTEMBER 2018
were introduced to the market over
time, each with their unique benefits.
Among them was the reagent SME 529,
which was an alternative to LIX 64N.
Unfortunately, “the poor properties of
the side products from the manufacture
of this reagent overrode the very good
properties of the extractant molecule
widely used” — resulting in limited use
of the reagent in the market. LIX 65N,
SME 529, P-1, and LIX 84-1 were other
technologies introduced to the market.
From a leaching perspective, copper
producers felt that this method was an
important source of copper, especially
after seeing the cost-effectiveness of
purifying and concentrating copper
from leach liquors. The Thin Layer
(TL) acid cure leaching process was
one of the copper leaching processes
and in his paper, Kordosky explains
that Sociedad Minera Pudahuel (SM)
was the first plant to practice the TL
leaching for copper in 1978. Through
this process, the plant was able to
achieve “high copper recovery from both
the oxide and sulphuric portions of their
ore low soluble silica in the pregnant
leach liquor, and an overall water/acid
balance to give a zero-discharge plant”.
By leaching the tails from their TL
operation for an additional 45 days,
SMP was able to prove that total copper
recovery from the chalcocite/bornite
portion of their mixed oxide sulphide
ore could reach 85%. From then, the
significance of bacteria leaching metal
sulphides was recognised.
Kordosky mentions that in 1968,
Ranchers installed flotation cells to
remove entrained organic from the
pregnant electrolyte, resulting in
improved copper quality — which fell
into the category of electrowinning
(EW ). Seven years later, there was
a breakthrough in EW with the
registration of Baghdad cathode on the
Comex, followed by the registration of
Anamax cathode on the London Metal
Exchange several years later. One of
the methods of implementing cathode
through EW was a cathode press to
straighten two-day cathodes grown on
copper starter sheets. The results of this
process were higher current efficiencies
and improved copper quality.