Gold mining
The removal of gold minerals via mining is known as gold mining. However, as gold mining has expanded
to include ores that are not visible on the surface, more complex extraction procedures such as gold
cyanidation and pit mining have emerged. There are four main ways to mine gold: hard byproduct
mining, rock mining, placer mining, and processing. In processing it uses sodium cyanide chemical to
extract gold from ore. Cyanide is a fast-acting, possibly lethal molecule of one carbon atom and one
nitrogen atom CN. It reacts quickly with live organisms since it is organic. It separates metals like gold
from their ore since it reacts with a wide range of metals. There are two forms of leaching: acid leaching
and alkaline leaching.
Heap leaching: cyanide mixture is sprayed in the open over massive mounds of crushed ore distributed over
massive collection pads. As the cyanide trickles through the heap, it melts the gold from the ore into the
solution. The pad collects now the metal-impregnated mixture, which is then stripped of the gold and
sprayed back onto the heap till the ore is exhausted. The ore is combined with solvent in big tanks for vat
(or tank) leaching. Although spills are less likely since the leaching process is better regulated, the waste
produced, known as tailings, is held behind huge dams (tailings impoundments), which can and often do
fail catastrophically.
To form a slurry, the ore is pulverized and crushed. The gold is subsequently treated with sodium cyanide,
which causes the following reaction:
Au + 2CN2 Au(CN)2 Au(CN)2 Au(CN)2 Au(CN)2 Au(CN)2 Au
The gold is now soluble in this state. Leaching is the term for this procedure. This reaction is usually done
at a pH of 10-11 to avoid the cyanide ion being transformed to hydrogen cyanide, which would happen if
the pH was lower. Leaching can be done by heaps leaching or in leaching tanks, which involves dripping
sodium cyanide over a heap of gold ore and allowing it to percolate through the heap.
Now it's time to separate and collect the soluble gold in the form of the complex. This can be accomplished
by a process known as absorption. When dissolved or gaseous organisms connect to a solid surface, this is
called absorption. The gold is absorbed via a material called activated carbon. Wood, peat, coal, and other
organic materials are used to make activated carbon. It has been treated to allow gold to absorb into its
surface. This activated carbon will absorb the most of the gold. After that, the activated carbon is rinsed
with water.
Because gold in this form is soluble, it can now be separated from the rest of the insoluble ore. Leaching is
the term for the process of dissolving gold using cyanide. Other valuable metals, such as platinum, can
sometimes be leached along with the gold like silver. The gold is then refined further by electro winning,
which uses electricity, after the activated carbon has been washed with air or water on a screen. It's then
fine-tuned until it's ready to use. The cyanide that remains in the slurry must now be recycled or disposed
of in some way.
Cyanide is harmful and should not be released into the environment. It can be removed by a variety of
natural methods. The following items are included in this list: Volitisation occurs when CN is converted to
HCN at low pH levels and subsequently becomes gaseous. Absorption, when carbon monoxide (CN) is
spontaneously absorbed onto solid surfaces, such as soil particles. Microbial decomposition, cyanide is
spontaneously decomposed by some bacteria. All of these processes can occur in holding pools, which are
used to store slurry following gold extraction. There are also certain chemical processes that can be used.
The international mining community uses highly poisonous sodium cyanide to extract gold as well as other
precious metals by heap leaching low-grade ores and grinding high-grade ores (Korte et al. 2000). In the
1970s, the gold industry adopted the procedure, and heap leaching quickly became the industry standard
for gold mining (Da Rosa and Lyon 1997). The milling ores and heap leach, which entail spraying dilute
cyanide solutions, dewatering gold-bearing ores, on absolutely enormous heaps of ores, or comprising low
concentrations of gold with cyanide and subsequent recovery of the gold-cyanide complex, have caused a
slew of serious environmental issues that have impacted wildlife and water management.
Chemical sodium cyanide is harmful to our health. The small-scale miners operated for an average of 10.3
years, were 36 years old, and had a total of 18,564 hours of mining work throughout their lives.
All participated in tunneling work and a great percentage were involved in cyanide mixing with the ore (44
percent). During the mining operation, a significant number (35 percent) were hurt, and an alarming number
(35 percent) had increased blood cyanide levels. Exposure to chemicals, notably nitric acid, and cyanide,
which were commonly dealt with bare hands, was the most common hazard.
Milling and heap leaching necessitate the recycling of billions of liters of alkaline water carrying significant
levels of NaCN, free cyanide, metal cyanide, and complexes, all of which are accessible to the biosphere
(Eisler 2000). Tailings ponds of 150 ha and greater are the product of some milling operations. Solutions
processing ponds of around 1 ha surface area are required for heap leach operations that drip cyanide
or spray solution onto the leveled top of the ore heap. On the tops of piles, where the largest amounts of
NaCN are found, puddles of varying sizes may form.
The small-scale gold miners are a group of people who are nearing the end of their working lives. The task
of mining gold from underneath, on the other hand, is a long and arduous procedure that exposes miners to
numerous risks, including cyanide, with no personal protection. The study revealed that small-scale gold
miners suffer from health problems.
To conclude, use of cyanide in gold mining poses an environmental health and occupational risk to these
miners. Measures to protect the miners' and their families', and the environment's health must be
implemented. These include rigorous cyanide use regulations and the possibility of relocating cyanide
leaching ponds away from residential areas. These include rigorous cyanide use regulations, the possibility
of moving cyanide leaching ponds away from residential areas, and health programs and promotion for
miners and their families.