Chromium extracted from chromite is used on a large scale in many industries, including metallurgy, electroplating, paints, tanning, and paper production. Environmental contamination with hexavalent chromium is a major health and environmental concern. Chromium is most stable in its
trivalent (Cr(III)) form, seen in stable compounds such as natural ores. Cr(III) is an essential nutrient, required for
lipid and
glucose metabolism in animals and humans. In contrast, the second most stable form,
hexavalent chromium (Cr(VI)), is generally produced through human activity and rarely seen in nature (as in
crocoite), and is a highly toxic carcinogen that may kill animals and humans if ingested in large doses.
Health effects When chromite
ore is mined, it is aimed for the production of
ferrochrome and produces a chromite
concentrate of a high chromium to iron ratio. It can also be crushed and processed. Chromite concentrate, when combined with a
reductant such as
coal or
coke and a high temperature furnace can produce
ferrochrome. Ferrochrome is a type of
ferroalloy that is an
alloy in between chromium and iron. This ferroalloy, as well as chromite
concentrate can introduce various health effects. Introducing a definitive control approach and distinct mitigation techniques can provide importance related to the safety of human health. When chromite ore is exposed to surface conditions,
weathering and
oxidation can occur. The element chromium is most abundant in chromite in the form of trivalent (Cr-III). When chromite
ore is exposed to aboveground conditions, Cr-III can be converted to
Cr-VI, which is the hexavalent state of chromium. Cr-VI is produced from Cr-III by means of dry
milling or grinding of the ore. This is due to the moistness of the milling process as well as the
atmosphere in which the milling is taking place. A wet environment and a non-oxygenated atmosphere are ideal conditions to produce less Cr-VI, while the opposite is known to create more Cr-VI. Production of
ferrochrome is observed to emit
pollutants into the air such as
nitrogen oxides,
carbon oxides and
sulfur oxides, as well as dust
particulates with a high concentration of
heavy metals such as
chromium,
zinc,
lead,
nickel and
cadmium. During high temperature
smelting of chromite
ore to produce
Ferrochrome, Cr-III is converted to Cr-VI. As with chromite ore, Ferrochrome is
milled and therefore produces Cr-VI. Cr-VI is therefore introduced into the dust when the
Ferrochrome is produced. This introduces health risks such as inhalation potential and
leaching of toxins into the environment. Human exposure to chromium is ingestion, skin contact, and inhalation. Chromium-III and VI will accumulate in the tissues of humans and animals. The excretion of this type of chromium from the body tends to be very slow which means that elevated concentrations of chromium can be seen decades later in human tissues. As a result of leaching of soils and the explicit discharge from industrial activities,
weathering of rocks that contain chromium will enter the water column. The route of chromium uptake in plants is still ambiguous, but because it is a nonessential element, chromium will not have a distinct mechanism for that uptake which is independent from chromium speciation. Plant studies have shown that toxic effects on plants from chromium include things such as wilting, narrow leaves, delayed or reduced growth, a decrease in
chlorophyll production, damage to root membranes, small root systems, death and many more. Chromium's structure is similar to other essential elements which means that it can impact the mineral nutrition of plants. During industrial activities and production things such as sediment, water, soil, and air all become polluted and contaminated with chromium. Hexavalent chromium has negative impacts towards soil ecology because it decreases soil micro-organism presence, function, and diversity. Chromium concentrations in soil diversify depending on the different compositions of the sediments and rocks that the soil is made from. The chromium present in soil is a mixture of both Cr(VI) and Cr(III). Certain types of chromium such as
Chromium-VI has the capability to pass into the cells of organisms. Dust particles from industry operations and industrial wastewater contaminate and pollute surface water, groundwater, and soils. In aquatic environments, chromium could experience things such as
dissolution,
sorption,
precipitation,
oxidation,
reduction, and
desorption. In aquatic ecosystems chromium
bioaccumulates in invertebrates, aquatic plants, fish, and algae. These toxic effects will operate differently because things such as sex, size, and the development stage of an organism may vary. Things such as the temperature of the water, its alkalinity, salinity, pH, and other contaminants will also impact these toxic effects on organisms. == Applications ==