The principle of treating cyanide-containing sewage with bleaching powder (CaOCl 2 ) and liquid chlorine (Cl 2 ) is the same, and is collectively referred to as alkali chlorination.
The pH of the solution above 9.5, a chlorine bleach and hypochlorite silver almost completely hydrolyzed to a strong root oxidation of ClO - so that oxidative decomposition of cyanide, cyanide toxicity elimination. The chemical reactions in the cyanide chlorination process are as follows:
1. Hydrolysis of bleaching powder or liquid chlorine:
2CaOCl 2 +2H 2 O→2HClO+Ca(OH) 2 +CaCl 2
Cl 2 +H 2 Oâ†â†’HClO+H + +Cl -
HClOâ†â†’H + +ClO -
2HClO+ Ca(OH) 2 →CaClO 2 +2H 2 O
2. Local oxidation stage Chemical reaction of hypochlorite oxidized cyanide:
CN - +ClO - +H 2 O→CNCl+OH -
CNCl+2OH - →CNO - +Cl - +H 2 O
In this stage oxidation process, pH value should be 10 or more, since the reaction intermediate is CNCl volatiles, which is quite toxic and HCN, in an alkaline solution greater, and can CNCl OH - reaction CNO -, so Should maintain a high alkaline.
If the solution is acidic, the CNCl is very stable and will cause secondary pollution with the discharge of sewage. When pH < 9.5, the chemical reaction between CNCl and OH - is incomplete and the rate is very slow, sometimes for several hours or more. Only when the pH is >10, the reaction speed is fast, and it takes only 10 to 15 minutes to complete the reaction.
3. Although the complete reaction phase isocyanato CNO - of toxic cyanide only 1 ‰, only the fully oxidized at this stage to completely remove toxicity. This stage can be achieved by increasing the amount of oxidizing agent (bleach or liquid chlorine). The chemical reaction formula is as follows:
2CNO - +3ClO - →CO 2 ↑+N 2 ↑+3Cl - +CO 3 2-
In this reaction, the bond between carbon and nitrogen in the cyanate root is completely destroyed. The pH of this reaction should be controlled to be most effective between 7.5 and 8.5, and complete oxidation takes only 30 minutes.
Thermoforming is a manufacturing process used to shape plastic sheets into various custom design products. It involves heating a plastic sheet until it becomes pliable, then using a mold or a vacuum to form it into the desired custom shape.
Thermoforming and vacuum forming are both processes used to shape plastic sheets into specific forms. However, there are some differences between the two techniques:
1. Process: In thermoforming, a plastic sheet is heated until it becomes pliable, and then it is pressed against a mold using pressure or a vacuum. Vacuum forming, on the other hand, relies solely on the use of a vacuum to draw the heated plastic sheet onto the mold.
2. Mold complexity: Thermoforming is typically used for more complex shapes and intricate molds, as it allows for greater detail and precision. Vacuum forming, on the other hand, is better suited for simpler shapes and molds that do not require as much detail.
3. Material thickness: Thermoforming is often used for thicker plastic sheets, typically ranging from 0.030 to 0.250 inches in thickness. Vacuum forming is more commonly used for thinner plastic sheets, typically ranging from 0.005 to 0.060 inches in thickness.
4. Production volume: Thermoforming is generally more suitable for high-volume production due to its faster cycle times and ability to handle larger sheets of plastic. Vacuum forming is better suited for low to medium volume production, as it has slower cycle times and is limited by the size of the vacuum forming machine.
5. Cost: Thermoforming typically requires more expensive equipment and molds, making it a more costly process compared to vacuum forming. Vacuum forming, on the other hand, is a more cost-effective option for smaller production runs or prototypes.
Overall, thermoforming is a more advanced and versatile process that offers greater precision and complexity, while vacuum forming is a simpler and more cost-effective option for less complex shapes and smaller production volumes.
Thermoforming is a versatile process that is widely used in industries such as packaging, automotive, aerospace, and medical. It offers advantages such as cost-effectiveness, quick turnaround times, and the ability to produce complex shapes with high precision.
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