Pure copper (Cu) is red or purplish red, and copper oxide is black. One is metal simple substance, and the other is oxide.

the way to distinguish

A small amount of sample shall be put into two dry and clean test tubes respectively, and then appropriate amount of dilute sulfuric acid shall be added into the test tubes respectively. The solution gradually turns blue from colorless, the solid gradually dissolves copper oxide, and the copper without phenomenon;

A small amount of samples shall be put into two dry and clean test tubes respectively, and then an appropriate amount of silver nitrate solution shall be added into the test tubes respectively. Copper is separated from the silver white substance, and the solution turns from colorless to blue, and copper oxide is free from any phenomenon.

Copper oxide is an alkaline oxide, which can react with acid. According to this principle, copper oxide reacts with sulfuric acid

CuO+H?SO?====CuSO?+H?0

Basic oxides can also react with acid oxides. Copper oxide and sulfur trioxide react:

CuO+SO?====CuSO?

Sulfuric acid process

Copper powder is calcined at 600~700 ℃, oxidized to copper oxide, decomposed and clarified by sulfuric acid to remove insoluble impurities, and then cooled, crystallized, filtered and dried to obtain copper sulfate finished products;

Electrolyte recovery method

The waste electrolyte (containing Cu50 ～ 60g/L, H2SO4180 ～ 200g/L) reacts with calcined copper mud to produce fine copper powder. After separation and sedimentation of the reaction solution, the clear solution is cooled, crystallized, separated and dried to produce copper sulfate products;

Chemical concentration crystallization method

The low-grade oxidized copper ore is crushed to a certain particle size, impregnated with sulfuric acid, added with copper dissolving and iron precipitating agent to obtain copper sulfate solution with a copper iron ratio of more than 100, and then concentrated with chemical concentration agent to drain 70%~90% of the water. Finally, the finished copper sulfate product is prepared through evaporation, cooling crystallization, separation and air drying;

Put copper sulfate pentahydrate in a porcelain dish, heat it on a sand bath with good ventilation, and the temperature is not higher than 220 ℃. Keep stirring until the blue disappears. Grinding the white powder obtained (if the product is grayish white, it indicates excessive heating) is anhydrous copper sulfate;

Recovery method

When recovering the ammonia synthesis feed gas in the nitrogen fertilizer plant, the copper compound precipitate (customarily referred to as copper pollution) in the acetic acid copper ammonia solution in the copper washing tower is calcined at 700 ℃, oxidized to copper oxide, and then reacted with sulfuric acid to produce copper sulfate.

The best way to prevent copper oxidation in daily life

1. Antirust oil can be coated on copper to prevent copper from reacting with oxygen. It is difficult to clean the antirust oil when it is used

2. The reaction between copper and oxygen can also be blocked by coating the copper through the wire tube

3. Antirust agent can also be sprayed on copper in the way of antirust agent, which can form a relatively lightweight protective film on the copper surface to prevent copper from reacting with oxygen

4. Antirust agent can also be sprayed on copper in the way of antirust agent, which can form a relatively lightweight protective film on the copper surface to prevent copper from reacting with oxygen

Treatment method of copper surface oxidation

The anti-oxidation working solution penetrates into the pores on the copper ion surface, and then the anti-oxidation working solution on the copper surface is washed clean, and the moisture on the copper surface can be dried. The anti-oxidation solution forms a uniform protective film between the copper ion pores, which can effectively isolate the oxygen in the nature and prevent copper from oxidation discoloration.

The advantages of this process are: long anti oxidation time, low cost, bright color, no influence on conductivity, welding performance and tin coating performance.

The basic principle is: effectively isolate copper ions from oxygen in the nature, which can solve the oxidation problem of copper and copper alloys, such as electroplating, oil spraying, painting, passivation, film protection and other treatment methods can better solve the oxidation problem of copper products after processing.

Source: Changjiang Nonferrous Network