3/23/2023 0 Comments Chromium sources![]() ![]() ![]() Īccording to the latest update of the European Pollutant Release register, a total of 512 facilities from EU countries are registered as they release chromium compounds into air and water. Particularly, in the last two minerals, the Mn (IV) reduction provides the most free energy for Cr (III) oxidation. Other Mn (IV) minerals involved in Cr (III) oxidation are asbolane, lithiophorite, hausmannite, and manganite. This mineral is associated with the Cr (VI) formation from natural Cr (III) in the environment. Birnessite is a Mn (IV) oxide-containing mineral, which commonly forms a coat onto weathered grains and fractures in Cr-rich ultramafic rocks. For example groundwaters proximal to ultramafic rocks and sediments in La Spezia province, Italy, have a Cr (VI) content ranging from 5 to 73 µg L −1 exceeding the Italian limit for drinking water set at 5 µg L −1 as well as the World Health Organization limit for drinking water of 50 µg L −1. Īlthough to a lesser extent than human activities, some geogenic processes also have an impact on the soil and groundwater Cr (VI) content, such as the weathering of ultramafic igneous and metamorphic rocks in several European countries (Greece, Italy, France, Serbia and Poland). Their improper use is the main cause of chromium pollution in agricultural areas. Moreover, phosphate amendments produced from sewage sludge ashes or tannery sludge are rich in hexavalent chromium which can be leached. The latter is finely porous with exposed chromite particles on the outer and inner surfaces, which tend to leach from all exposed surfaces. The residue material is a mixture of finer particulate waste matter and fused material. For example, the improper disposal of chromite ore processing residues, that is stocking them in open dump sites, results in a rapid migration by leaching of soluble contaminants into surface waters and groundwater. Industrial use and urban source in fact are closely related to Cr (VI) accumulation in sediments and waters. However, levels of Cr (VI) exceeding 70–90 µg L −1 in groundwater and water have been frequently measured as a result of man-made pollution. In the environment kinetic and several other factors, that is, pH and organic matter, mean that Cr (III) species dominate in nature. At industrial level the process involved in the Cr (VI) extraction from chromite has been known since the 19th century as oxidative roasting. This work critically presents their advantages and disadvantages, suggesting a site-specific and accurate evaluation for choosing the best available recovering technology.Ĭhromite represents the main commercial form of chromium for industrial application. ![]() ![]() Remediation strategies commonly used for Cr (VI) removal include physico-chemical and biological methods. Risks for human health range from skin irritation to DNA damages and cancer development, depending on dose, exposure level, and duration. Public concerns with chromium are primarily related to hexavalent compounds owing to their toxic effects on humans, animals, plants, and microorganisms. Once in water, chromium mainly occurs in two oxidation states Cr (III) and Cr (VI) and related ion forms depending on pH values, redox potential, and presence of natural reducing agents. Chromium discharge in European Union (EU) waters is subjected to nationwide recommendations, which vary depending on the type of industry and receiving water body. Moreover, Cr (VI) pollution is largely related to several Cr (VI) industrial applications in the field of energy production, manufacturing of metals and chemicals, and subsequent waste and wastewater management. Microbial interaction with mafic and ultramafic rocks together with geogenic processes release Cr (VI) in natural environment by chromite oxidation. Chromium is a potentially toxic metal occurring in water and groundwater as a result of natural and anthropogenic sources. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |