in the spotlight
During my eight weeks
of vacation
work, I learnt to appreciate the value of
experience. A requirement for third year
chemical engineering is six weeks of
vacation work experience. Although these
six weeks are compulsory, many students
find it difficult to find companies willing to
take them on. Therefore, I was very fortu-
nate to be given the opportunity to work
for such a first-class team of engineers.
I worked for two separate months for the
BIOX® department of Gold Fields Group
Ltd which has subsequently branched
off from Gold Fields and formed a new
company BIOMIN, South Africa. BIOMIN
focuses on technologies in gold refining
with particular focus on refractory gold
processing. The majority of my vacation
work revolved around biotechnology and
its use within gold processes.
BIOMIN owns technologies such as
BIOX®, ASTER™ and HiTech™ which are
all technologies that focus on improving
gold processing either by improving recov-
eries or by decreasing effluent concentra-
tions.
BIOX® is a biological oxidation process
which pre-treats refractory gold ores
and concentrates by destroying sulphide
minerals thus liberating the gold for
subsequent leaching in CIL tanks. It is
an alternative technology to conventional
technologies such as roasting and pres-
sure oxidation. BIOX® is an environmen-
tally friendly process, has low capital and
operating costs and improves rates of gold
recovery. This was my first exposure to the
use of micro-organisms for the improve-
ment of mineral processing.
ASTER™ (Activated Sludge Tailing Ef-
fluent Remediation) is the use of micro-
organisms to substantially decrease the
thiocyanate and cyanide concentrations
in the effluent from the CIL process. The
process consists of an aerated biological
reactor followed by a sludge settler. The
settler separates the solution from the
reactor into a clear degraded solution and
a thickened sludge. The sludge is recycled
to the reactor to improve the activity of the
bacteria within the reactor.
HiTech™ is a high temperature opti-
mization of the CIL process in order to
increase recovery of gold from double
refractory ores. Double refractory ores
contain both sulphide minerals and car-
bonaceous materials. Sulphide minerals
encapsulate the gold ore and therefore
the BIOX® process is used to destroy
Using biotechnology to improve mineral processes
by Tiega Alberts, SASTech award winner, fourth year chemical engineering student at the University of the Witwatersrand.
sulphide minerals thus liberating the gold
for leaching. Carbonaceous materials, on
the other hand, inhibit gold recovery and
such ores or concentrates are termed
preg-robbing. The carbonaceous materials
in preg-robbing concentrates essentially
compete with the activated carbon in
the CIL process. Gold adsorbs onto the
carbonaceous material rather than the ac-
tivated carbon thus resulting in lower gold
dissolution and higher cyanide consump-
tion. Hi-Tech™ combats the preg-robbing
nature of double refractory concentrates
by utilising a hot, caustic process. The
availability of non-refractory ores is low
and therefore technologies to improve the
recovery of gold from refractory ores are
in demand.
In my first month of vacation work
in June 2012, my primary focus was to
put together a preliminary design for a
HiTech™ process linked to a CIL process.
Although similar to a CIL process, the
HiTech™ differs in terms of operating
temperatures, size of equipment and resi-
dence times. For the design, a mass and
energy balance, preliminary equipment
sizing and a cost analysis of the process
was required.
During my second month of vacation
work in January 2013, my primary focus
was to analyse the current models used to
size the ASTER™ reactor and settler, with
focus on determining the sensitivity of the
model to changes in sludge, thiocyanate
and cyanide concentration. I enjoyed this
project because of the mathematical
aspects of the project, as well as learning
about the ASTER™ process itself.
With environmental issues at the
forefront of engineering, being able to
research a simple, cost-effective and ef-
ficient biotechnology capable of meeting
environmental standards was fascinat-
ing. As being environmentally conscious
becomes not only the right thing to do, but
the economical thing to do, technologies
such as ASTER™ will become crucial to
the profitability of a plant.
These two projects were not the only
things that I was exposed to. I attended
the daily morning meetings which were
30-minute meetings aimed to delegate
tasks, discuss various projects and dis-
cuss upcoming deadlines. As a student,
this system was foreign to me, but it
taught me the importance of meetings.
For the success of any project or company,
“business savvy” and effective interac-
tion in the workplace is just as important
as being “book smart”. At the core of
any business or industry are people and,
therefore, being able to deal with and mo-
tivate people to achieve your objectives is
critical for personal and project success.
I was also afforded the opportunity to
visit the Barberton gold processing plant.
The Barberton mining complex represents
the birthplace of BIOX® and ASTER™.
The first BIOX® plant was commissioned
at the Fairview Mine and the first com-
mercial ASTER™ plant is installed at the
Consort plant. Both the Consort and
Fairview plants form part of the Barberton
mining complex.
The team I was working with was also
always willing to help and give me advice.
I was encouraged to chat to engineers
from different departments and spent lots
of time with my more experienced superi-
ors and learnt a great deal from them dur-
ing my time there. These interactions also
helped me to assess the type of work I
would like to do when I graduate because
an engineer can be anything from a min-
ing manager to a banker.
South Africa has a scarcity of engineers
and there is a drive to change this. How-
ever, more than this, third year students
heading to graduation need to be given
vacation work. The learning and growth
that occurs in six weeks of practical work
experience is crucial to the quality of
engineer at graduation. Industry should
find ways to offer effective mentorship
programs, learnerships and experience
opportunities to the final year students.
Increasing the number of graduate
students is important, but ensuring the
quality of engineering graduates is equally
important.
Tiega Alberts at the Fairview gold processing
plant. She is standing next to a BIOX® sludge
tank for the pre-treatment of refractory gold
ores prior to the carbon-in-leach process.
35
Chemical Technology • September 2013
