The relationship between pH adjustment and the amount of alkali added
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How many kilograms of alkali (on a percent basis) are needed per hour to raise the pH of 1 m3/h of sodium chloride solution with a pH of 2 (300 g/l) to pH 5, by adding alkali in the form of sodium hydroxide? Please list the calculation steps. Thank you!
Why is sodium chloride acidic? What other components are there inside? For example: if there are other substances that can form a precipitate with hydroxide, it’s difficult to calculate.
Calculate it yourself; the approach is as follows: start with pH=2.0 and proceed with neutralization until pH=7.0, to obtain the theoretical amount of alkali required, m1. In the second step, start with pH=5.0 and continue neutralizing until pH=7.0, to get the theoretical amount of alkali required, m2. The amount of alkali needed is m1 minus m2. However, since the H+ concentration at pH=5.0 is very low, m2 is also small, so it can be ignored in rough calculations – in that case, use m1. For an accurate calculation, use m1 minus m2
As for this portion of alkali consumption associated with hydrolyzable metal cations, it can also be calculated using the hydrolysis equation. Is it a hydrolysis purification process?
Thank you!!! I found an EXCEL spreadsheet online; the calculation formulas have already been entered, and once the data is inputted, the results are obtained right away. :) It’s quite convenient.
A pH value of 2 corresponds to an acid value of 0.01 N for the solution; when the pH is adjusted to 5, the acid value becomes 0.00001 N. The amount of sodium hydroxide required is therefore (0.01 – 0.00001) * 40/1 = 3.996 kg/m3. It seems to be a process for purifying brine from wells and mines, right? Shouldn’t acidity occur in the two-alkali method? Either it’s the lime-flue gas method, where excess carbon dioxide is introduced; it’s not cost-effective to use caustic soda to adjust the levels, so using lime milk is the most convenient option.
Could the original poster share their Excel file? I need it. Why can’t I find it?
The calculation itself is not complicated; the simplest method is to consult an acidity-Ph table. Check the table showing the relationship between acidity and pH values; it shows the acidity levels corresponding to pH values of 2 and 5. The acidity value indicates the amount of sodium hydroxide required to neutralize every 100 grams of the sample.