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The Geosphere and Geochemistry
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Weathering is an important process for releasing trace levels of elements, including nutrients and toxic substances, into water and into soil. Fulvic acids, a form of humic material, chelate iron in the weathering of iron-rich minerals and may be responsible for maintaining levels of this micronutrient high enough in water to support the growth of algae. Bacterially mediated weathering of mineral pyrite, FeS2, can release sulfuric acid and excessive levels of soluble iron into water. The acid is toxic to aquatic life as is soluble iron at higher levels. The dissolution of aluminum-containing minerals by acidic water, such as that from acid rainwater, can raise levels of dissolved Al3+ high enough to be phytotoxic (toxic to plants). Some toxic elements are released by weathering. One of these is radioactive radium, a harmful water pollutant released in the weathering of some kinds of shale. Another is toxic arsenic, commonly associated with iron-rich minerals. Lead leached from mineral galena, PbS, can be toxic in water consumed by humans and animals.
Chemistry of Acid Mine Drainage Formation
Published in Geoffrey S. Simate, Sehliselo Ndlovu, Acid Mine Drainage, 2021
Galena is a sulphide mineral with a chemical composition of PbS. The mineral occurs in igneous and metamorphic rocks in medium to low temperature hydrothermal veins (Ogwata and Onwughalu, 2019). In sedimentary rocks, it exits as veins, breccia cements, isolated grains, and as replacements of limestone and dolostone. Galena is also commonly associated with acid-generating minerals, such as pyrite and pyrrhotite (Blowes et al., 2003).
Extraction of Metals
Published in Alan Cottrell, An Introduction to Metallurgy, 2019
The extraction of lead provides a simple example of sulphide metallurgy. Galena ore, PbS, is widely distributed, the main sources being the U.S.A., Australia, Spain, Mexico and Germany. The initial PbS content is about 1–10 per cent and flotation is used to concentrate it to 60–80 per cent and also to separate ZnS. Very rich concentrates are sometimes converted directly to lead by roast-reduction but the presence of FeS2 impurities makes this process hard to control. Complete roasting to oxide, followed by reduction with carbon, is generally preferred. A small blast furnace is used, running at about 900°C, using coke as fuel and reducing agent and CaO and FeO to flux the SiO2.
Chelate assisted phytoextraction for effective rehabilitation of heavy metal(loid)s contaminated lands
Published in International Journal of Phytoremediation, 2023
Akshaya Prakash Chengatt, Nair G. Sarath, Delse Parekkattil Sebastian, N. Shibin Mohanan, E. S. Sindhu, Satheesh George, Jos T. Puthur
Lead is one of the early discovered metals known to humans and one of the most dangerous heavy metals present in nature (Acuña et al.2020). In nature, a pure form of lead is rare in occurrence. It is found in ores, of which galena (PbS) is the most abundant ore of lead. Radioactive disintegration of thorium and uranium results in the formation of lead naturally. Lead has been used in the radiation shielding, production of lead acid batteries, petrol, paint, and stabilizer in the plastic industry (Acharya 2013). Therefore, all these are anthropogenic sources of lead pollution in the environment.