Copper oxide is formed when copper is exposed to oxygen and oxidizes. There are two types of copper oxide: copper (I) oxide and copper (II) oxide. Copper (I) oxide is referred to as cuprous oxide, while copper (II) oxide is known as cupric oxide.
What Is Copper Oxide?
Copper oxide is formed when copper is exposed to oxygen and oxidizes. There are two types of copper oxide: copper (I) oxide and copper (II) oxide. Copper (I) oxide is referred to as cuprous oxide, while copper (II) oxide is known as cupric oxide. Both are used as pigments and can be used as semiconductors. Even though they have the same components, they each have slightly different characteristics.
Cuprous oxide has the chemical formula Cu2O. It is red in color and does not dissolve in water or any organic solvents. In nature, this copper oxide is commonly found in rocks as the mineral cuprite. However, the production of cuprous oxide in the natural world takes a while to happen. Therefore, it can be manufactured artificially at high temperatures or under high oxygen pressure.
Cuprous oxide can also be used as a pigment, as a fungicide, and as an anti-fouling agent for marine paint. It is also used as a catalyst. However, exposure to this type of copper oxide can be dangerous. If inhaled, it can cause shortness of breath, coughing as well as ulceration and perforation of the respiratory tract. If ingested, it can cause irritation of the gastrointestinal tract, vomiting, pain, and diarrhea.
Cupric oxide (CuO), on the other hand, is a black material that melts above 2192°F (1200°C). This copper oxide is used as a pigment in clay glazes. Several colors, including red, blue, and green, can be derived from it. It is also used to produce cuprammonium hydroxide, a material that is used to make rayon. Some also give this form of copper oxide to animals as a copper supplement.
Exposure to this type of copper oxide can also be dangerous. If inhaled, cupric oxide can cause irritation to the lungs. Cupric oxide, as well as cuprous oxide, can also cause metal fume fever. Symptoms of the fever are flulike and temporary. Cupric oxide can also cause skin discoloration and can cause vision problems. Like cuprous oxide, it is also toxic when ingested, causing symptoms like vomiting and pain.
Copper (II) oxide or cupric oxide (CuO) is the higher oxide of copper. As a mineral, it is known as tenorite.
It is red in color and does not dissolve in water or any organic solvents. In nature, this copper oxide is commonly found in rocks as the mineral cuprite. However, the production of cuprous oxide in the natural world takes a while to happen. This means that such a component has to possess the ability to conduct an electric current, which is not as good as a conductor, but better than an insulator. The most common type of metal rectifiers included copper oxide and vacuum tube rectifiers. Starting in the 1930s, some companies began manufacturing rectifiers using selenium, a chemical element that is actually not a metal.
It is a black solid with an ionic structure which melts above 1200 °C with some loss of oxygen. It can be formed by heating copper in air:
2 Cu + O2 → 2 CuO
Here, it is formed along with copper(I) oxide as a side product; thus, it is better prepared by heating copper(II) nitrate, copper(II) hydroxide or copper(II) carbonate:
2 Cu (NO3)2 → 2 CuO + 4 NO2 + O2
Cu (OH) 2 (s) → CuO (s) + H2O (l)
CuCO3 → CuO + CO2
Copper(II) oxide is a basic oxide, so it dissolves in mineral acids such as hydrochloric acid, sulfuric acid or nitric acid to give the corresponding copper(II) salts:
CuO + 2 HNO3 → Cu (NO3)2 + H2O
CuO + 2 HCl → CuCl2 + H2O
CuO + H2SO4 → CuSO4 + H2O
It reacts with concentrated alkali to form the corresponding cuprate salts:
2 XOH + CuO + H2O → X2[Cu (OH) 4]
It can also be reduced to copper metal using hydrogen or carbon monoxide:
CuO + H2 → Cu + H2O
CuO + CO → Cu + CO2
A laboratory method for preparing copper (II) oxide is to electrolyze water containing sodium bicarbonate at a moderate voltage with a copper anode, collect the mixture of copper hydroxide, basic copper carbonate, and copper carbonate produced, and heat it.
Copper (II) oxide belongs to the monoclinic crystal system, with a crystallographic point group of 2/m or C2h. The space group of its unit cell is C2/c, and its lattice parameters are a = 4.6837(5), b = 3.4226(5), c = 5.1288(6), α = 90°, β = 99.54(1) °, γ = 90°. The copper atom is coordinated by 4 oxygen atoms in an approximately square planar configuration.
Copper (II) oxide is an irritant. It also can cause damage to the endocrine and central nervous system. Contact to the eyes or skin can cause irritation. Ingesting cupric oxide powder can result in a metallic taste, nausea, and vomiting and stomach pain. In more severe cases, there may be blood in vomit or black or tarry stools, jaundice and enlarged liver. Blood cells rupture resulting in circulatory collapse and shock. Inhalation can lead to damage to the lungs and septum. Inhalation of fumes during smelting of cupric oxide powder can lead to a disease called metal fume fever, which can result in flu like symptoms. Copper (II) oxide can cause a toxic build-up of copper in a small subset of the population with Wilson's disease. Handling copper (II) oxide powder should be done in well ventilated area, and care should be taken to avoid contact with the skin or eyes. However copper is an essential trace element for the normal function of many tissues, including the nervous system, immune system, heart, skin and for the formation of capillaries as well as copper being extremely well metabolized by humans. Copper oxide is used in vitamins supplements as a safe source of copper and over-the-counter treatments. Copper oxide is also used in consumer products such as pillowcases and socks, due to its cosmetic and anti-microbial properties. The risk of dermal sensitivity to copper is considered extremely minimal.
Cupric oxide is used as a pigment in ceramics to produce blue, red, and green (and sometimes gray, pink, or black) glazes. It is also used to produce cuprammonium hydroxide solutions, used to make rayon. It is also occasionally used as a dietary supplement in animals, against copper deficiency. Copper (II) oxide has application as a p-type semiconductor, because it has a narrow band gap of 1.2 eV. It is an abrasive used to polish optical equipment. Cupric oxide can be used to produce dry cell batteries. It has also been used in wet cell batteries as the cathode, with lithium as an anode, and dioxalane mixed with lithium perchlorate as the electrolyte. Copper (II) oxide can be used to produce other copper salts. It is also used when welding with copper alloys.
Another use for cupric oxide is as a substitute for iron oxide in thermite. This can turn the thermite from an incendiary to a low explosive.
Use in disposal
Cupric oxide can be used to safely dispose of hazardous materials such as cyanide, hydrocarbons, halogenated hydrocarbons and dioxins, through oxidation.
Here are equations depicting the decomposition of phenol and pentachlorophenol, respectively, with copper oxide:
C6H5OH + 14CuO → 6CO2 + 3H2O + 14Cu
C6Cl5OH + 2H2O + 9CuO → 6CO2 + 5HCl + 9Cu