Need help with COD values
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Dear experts: I would like to ask what the COD value is for methanol with a concentration of 0.02%. This post was last edited by wudi700209 on 2009-3-19 at 13:57
Bro, isn’t there a method for determining COD? It seems that the books also provide COD values for various pure organic substances, and you will need to look them up. Who can remember that much! Practice makes perfect! This post was last edited by lyhh9024 on 2009-3-17 12:40.]
It can be calculated. The COD value refers to the amount of oxidizing agent required to oxidize the reducing substances in one liter of water sample under certain conditions; this is known as chemical oxygen demand. Your concentration is 0.02%, so it depends on what oxidizing agent you’ve used; the unit is generally expressed in mg/L, which is quite simple.
COD 1.5 g/g methanol
In practical work, measurement methods are commonly used; I would appreciate guidance on how to calculate the expected values.
1.05mg/g, is that correct?
This specific value needs to be measured; for the detailed method, please refer to http://bbs.hcbbs.com/viewthread.php?tid=193318&page=2#pid2069977
It’s possible to calculate it based on the definition of COD; by using the heat of combustion of methanol, one can determine how much oxygen is required to completely oxidize methanol into carbon dioxide and water, and this is calculated based on the mass ratio of methanol to oxygen
You can go and calculate it, or determine it
The theoretical value is 300 mg/L; the actual measured value should be slightly lower than that. Last edited by Shui Sui Yuan Bo on 2009-3-18 at 11:52.]
Such issues can only be determined through actual measurement; the two concepts need to be distinguished: the theoretical COD value and the actual measured COD value
I’m talking about a theoretical calculated value. I remember an old mage saying whether it was CODcr1000 or 10000; I can’t remember exactly. Additionally, there is a certain discrepancy between these data and THOD; those who are aware of this please advise
The theoretical value can be calculated, based on the complete oxidation of methanol to carbon dioxide and water. Then, the amount of oxygen required is calculated, which represents the theoretical COD value. The following set of data is the COD conversion table for organic substances that I found on the Internet at that time. But I did not verify the data: (Serial number, Compound name, Structural formula, Compound concentration (mg), CODcr, BOD5) 1 Methanol CH3OH 1000 1420～1440 1020～1120
2CH3OH + 3O2 = 2CO2 + 4H2O 64 96 1 X X = 1.5 Theoretical COD value for a 0.02% methanol solution: 300 mg/L
There will be a certain difference between calculation and measurement, but you can compare them.
Haha, COD can be calculated!
The specific algorithm is: establish an equation for the complete reaction of ethanol with oxygen to produce water and carbon dioxide, and balance it. Then it’s possible to calculate the amount of oxygen consumed per unit volume of ethanol, and that’s it!
It seems like they are all measured; I’ve never seen any calculations done. Looking forward to learning about it in class.
It can be calculated based on complete oxidation, but there is a deviation. The reflux method yields more accurate results. 19# shi-jun1981
Under normal circumstances, actual measurement provides more accurate results, and there are **standard methods** for measuring COD. The figures obtained through calculations under fairly ideal conditions are meaningless. There is a significant discrepancy between theoretical concepts and actual data, making it impossible to even draw any insights from them.