Hexavalent chromium is an ingestive poison/inhalation extreme poison, and skin contact may cause sensitivity; It is more likely to cause genetic defects, and inhalation may cause cancer, which is a lasting danger to the environment. But these are the characteristics of hexavalent chromium, and chromium metal, trivalent or tetravalent chromium do not have these toxicity.
Hexavalent chromium is easily absorbed by human body, which can invade human body through digestion, respiratory tract, skin and mucosa. It has been reported that there are different degrees of hoarseness, atrophy of nasal mucosa, perforation of nasal septum and bronchiectasis when the air contains different concentrations of chromic anhydride through breathing. Invasion through the digestive tract can cause vomiting and abdominal pain. Dermatitis and eczema can occur when it is invaded through the skin. The most harmful thing is the risk of cancer caused by long-term or short-term contact or inhalation.
Excessive (more than 10ppm) hexavalent chromium is lethal to aquatic organisms. Experiments show that hexavalent chromium in polluted drinking water can cause cancer. Hexavalent chromium compounds are often used in electroplating, tanning and other animals. After drinking water containing hexavalent chromium, hexavalent chromium will be absorbed by cells in many tissues and organs in the body.
[Edit this paragraph] Forbidden range
In the European Union, hexavalent chromium, which can cause cancer or mutation, is not allowed to be sold publicly. However, chromic acid is reduced to CrO state (zero valence) in electrochemical industry, and CrO2 in tape industry. So it does not affect the electrochemical industry or the tape industry.
RoHS: The electrical and electronic equipment regulated by this directive shall not contain hexavalent chromium since 2008.
Except for the following, the cooling system of absorption refrigerator uses hexavalent chromium corrosion inhibitor TCO'0 1- Mobile Phones: at present, there is no control standard for hexavalent chromium.
Chromium is a silvery hard metal. There are bivalent, trivalent and hexavalent compounds.
All chromium compounds are toxic, among which hexavalent chromium is the most toxic.
Chromium has a wide range of industrial uses, mainly in metal processing, electroplating and tanning industries. The wastewater and waste gas discharged from these industries are the main pollution sources in the environment.
ROHS directive of the European Union clearly stipulates that the content of hexavalent chromium should not exceed 0.1%(1000 ppm, meaning: one in a million).
In the electronic industry and various metal processing industries, hexavalent chromium generally exists in the solvent used for treatment.
Therefore, although China has started to implement the "China ROHS" plan which is compatible with the EU directive, in practice, it is a temporary solution rather than a permanent cure.
Because the sewage and waste treated by hexavalent chromium are still discharged in China.
Technically, the treated product can completely achieve the effect of no hexavalent chromium residue.
However, the self-discipline and self-discipline awareness of these metal processing, electroplating and tanning industries are very poor.
If we really follow the treatment process of wastewater discharge, this kind of wastewater and waste gas treatment needs a lot of money.
In the current economic environment where short-term benefits are the first priority, it is simply an idiotic dream to require self-discipline in the industry.
There are many so-called big international companies. Although they have responded to the call of the environmental protection movement in the world, in practice, they have adopted a method of avoiding the heavy and neglecting the light, using products that meet international standards, but designating the use of technologies with serious pollution. Shouldn't this be a shame?
As a government, enterprises with serious pollution are allowed to discharge industrial wastewater around residential areas without any supervision.
Is this kind of government for the people?
Where have all our civil servants gone? !
[Edit this paragraph] Source
Chromium slag is sodium dichromate, the waste residue discharged from the production of metallic chromium. The appearance of chromium slag is yellow, black and ochre, and most of them are powder. The slag contains magnesium, calcium, silicon, iron, aluminum and unreacted chromium trioxide, as well as water-soluble sodium chromate (Na2Cr207) and acid-activated calcium chromate (CaCr04). Its chemical composition is: SiO: (4%-30%), A12O 3: (5%-10%), CaO(26％%-44%), MgO (8%-36%), Fe 203 (2%-1. The main minerals in chromium slag are periclase (Mg0), calcium silicate (2CaO．Si02), brucite (4Ca0.A 1203.Fe2O3) and1%-0/0% residual chromite.
[Edit this paragraph] Chemical production will produce hexavalent chromium.
Every ton of sodium dichromate is produced, and 3-3.5 tons of chromium slag is produced at the same time. At present, about 200,000-300,000 tons of chromium slag are discharged from domestic metallurgical and chemical industries every year. The harmful components in chromium slag are mainly hexavalent chromium ions such as soluble sodium chromate and acid-soluble calcium chromate. These hexavalent chromium and its loss and diffusion constitute pollution hazards to the ecological environment. Secondly, the strong alkaline hazard of chromium slag. When chromium slag is stored in the open air, a large number of hexavalent chromium ions are leached, lost and infiltrated into the surface with the rain after long-term rain, thus polluting groundwater, rivers and lakes, and further endangering farmland, aquatic products and human health. Hexavalent chromium ions are very harmful to human health. Its compounds have strong oxidation and are harmful to human digestive tract, respiratory tract, skin and mucosa. What's more, chromium has carcinogenic effect, and the part of chromium that causes cancer is mainly the lung.