acpeacemaker
Well-known member
Since I didn't see it in the comments.... The addition of water to acid will not neutralize it. It's just a creation of a larger volume of waste thats still going to be an acid.
Andrew
Andrew
Need to recover a significant amount of gold from 25l of neutralised Aqua Regia Solution
- Thread starter goldkron
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Geo
Well-known member
acpeacemaker said:
It's true that it doesn't neutralize it but it does raise the PH value by dilution to neutral PH. Diluting an acid makes it weaker. You can dilute acid in enough water that the acid is not detectable. It does create a lot of waste solution. It will need to be condensed and evaporated. The energy cost will need to be factored in to any profit.
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So are we getting pictures or did I miss them?
kurtak
Well-known member
anachronism said:
It may be that he has not figured out how to post pics - thats a common problem with new members
goldkron - if you don't know how to post pics - ask & we will help you get it figured out
the pics I asked for are important to helping you with this - with out us SEEING those test results we are working "blind" in trying to help you solve your problem
Kurt
To change the pH one step closer to 7 you need to dilute the liquid about 10 times, more so if you are close to 7. You can never neutralize acid or base by dilution, only getting it closer to neutral.Geo said:
So if you have 1 liter of acid at pH 2, to get to pH 5 you need to dilute it at least to 1000 liters.
Dilute 1 liter of pH6 to 10 liter gets you to pH 6.72, not pH 7.
Göran
Geo
Well-known member
Thank you Göran. I understand the mechanics better than the chemistry.
goldenchild
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g_axelsson said:
While I agree with your math (and maybe this is a bit nit picky), adding water will eventually get a solution to 7. Or at least undetectable. For instance if I were to put a drop of nitric in an ocean sized body of water (water is pH7). The water would still be 7. But for our purposes 7-8 is good for disposal of waste solutions.
kurtak
Well-known member
Seems the discussion has shifted from helping goldkron solve his problem to one of general discussion 
but then again we can't really help goldkron solve his problem --- until he post the pics of his test results I & Jon have asked for :roll:
That said - lets go with the general discussion this thread has turned to
There is a big difference from neutralizing an acid & diluting an acid (at least as I understand it)
When you adjust the Ph of an acid with a base (such as sodium hydroxide or baking soda as example) you are causing a "change" in the Ph by way of a chemical reaction - which is why it fizzles &/or foams up & if adding enough base at one time it also heats up - so you are actually "changing" the chemical composition of the acid from more acidic to less acidic because you are "killing" acid as you add the base to it until you have added enough base to make the acid neutral --- in other words - you have gotten "rid" of the acid - leaving you with a by product of salt water --- you have dis-associated the chemical (salt) bonds that made it an acid - to there (un-bonded) salts = salt water - the acid is no longer an acid
When you change the Ph of an acid by diluting it with water- in effect - what you are actually doing is changing the Ph of the water - in other words - there is no chemical reaction - the chemical bonds (salts) that make it an acid are not dis-associated/changed - it is still an acid - its a question of the ratio of acid to water (drop of water in gallon of acid) or water to acid (drop of acid in gallon of water) --- in other words the acid is still an acid - you have changed nothing other the volume of the acid in relation to the volume of water added
Why is that important ? --- because both "strong" bases & "strong" acids are considered hazardous (above Ph 8 or below Ph 6) so strong bases &/or acid - in & of them selves - can be made non hazardous by adjusting there Ph to between 6 - 8 --- whether doing it chemically or diluting them
However - when you start dissolving metals with acids you end up with solutions that are not only hazardous - but solutions that are toxic as well - And all though diluting an acid that has metal dissolved in it will cause SOME metals to drop out (as salts/oxides) but not all metals --- in other words - diluting an acidic solution (to PH 7) with metals dissolved in it "may" cause a "portion" of "some" dissolved metal to drop out - the diluted (weaker) acid will allow "some" of that metal to stay dissolved in the solution - & as well some metals do not drop out at all by diluting to Ph 7
In other words - you can not simply make a TOXIC solution of acid dissolved metals safe for dumping down the drain by diluting it to a Ph of 7 --- doing so only dilutes the toxins going down the drain - but the toxins are still going into the environment - & the environment doesn't always deal with these toxins in a friendly way - but rather they "build up" in the organisms that take them in --- fish are a good example of this - fish that take in (water dissolved) mercury - the mercury builds up in their system & then when you eat the fish - the mercury builds up in you - which is why in certain waters the Dept. of fish & game will advise you should only eat X number of fish caught in those waters over X amount of time
That is why we talk (not enough IMO) about "proper" waste treatment of our chemical waste - often by cementing with iron first - then with "actual" Ph adjustment --- & it is important here to fully understand Ph adjustment - not all metals simply drop out at Ph 7 - some metals will drop out under Ph 7 but "start" to go back into solution "around" Ph 7 while other metals will only start to drop out around Ph 7 so need to go higher then Ph 7 --- in other words - once adjusted to PH 7 & after filtering out the sludge - you need to test the filtered solution by raising &/or lowering the Ph to what else may drop out
Bottom line - diluting acid does not in anyway make it neutral - it only changes the Ph of the acid/water according to the acid/water ratio - & diluting metal acid dissolved solutions in NO WAY makes them safe for disposal by dumping down the drain
Kurt
but then again we can't really help goldkron solve his problem --- until he post the pics of his test results I & Jon have asked for :roll:
That said - lets go with the general discussion this thread has turned to
There is a big difference from neutralizing an acid & diluting an acid (at least as I understand it)
When you adjust the Ph of an acid with a base (such as sodium hydroxide or baking soda as example) you are causing a "change" in the Ph by way of a chemical reaction - which is why it fizzles &/or foams up & if adding enough base at one time it also heats up - so you are actually "changing" the chemical composition of the acid from more acidic to less acidic because you are "killing" acid as you add the base to it until you have added enough base to make the acid neutral --- in other words - you have gotten "rid" of the acid - leaving you with a by product of salt water --- you have dis-associated the chemical (salt) bonds that made it an acid - to there (un-bonded) salts = salt water - the acid is no longer an acid
When you change the Ph of an acid by diluting it with water- in effect - what you are actually doing is changing the Ph of the water - in other words - there is no chemical reaction - the chemical bonds (salts) that make it an acid are not dis-associated/changed - it is still an acid - its a question of the ratio of acid to water (drop of water in gallon of acid) or water to acid (drop of acid in gallon of water) --- in other words the acid is still an acid - you have changed nothing other the volume of the acid in relation to the volume of water added
Why is that important ? --- because both "strong" bases & "strong" acids are considered hazardous (above Ph 8 or below Ph 6) so strong bases &/or acid - in & of them selves - can be made non hazardous by adjusting there Ph to between 6 - 8 --- whether doing it chemically or diluting them
However - when you start dissolving metals with acids you end up with solutions that are not only hazardous - but solutions that are toxic as well - And all though diluting an acid that has metal dissolved in it will cause SOME metals to drop out (as salts/oxides) but not all metals --- in other words - diluting an acidic solution (to PH 7) with metals dissolved in it "may" cause a "portion" of "some" dissolved metal to drop out - the diluted (weaker) acid will allow "some" of that metal to stay dissolved in the solution - & as well some metals do not drop out at all by diluting to Ph 7
In other words - you can not simply make a TOXIC solution of acid dissolved metals safe for dumping down the drain by diluting it to a Ph of 7 --- doing so only dilutes the toxins going down the drain - but the toxins are still going into the environment - & the environment doesn't always deal with these toxins in a friendly way - but rather they "build up" in the organisms that take them in --- fish are a good example of this - fish that take in (water dissolved) mercury - the mercury builds up in their system & then when you eat the fish - the mercury builds up in you - which is why in certain waters the Dept. of fish & game will advise you should only eat X number of fish caught in those waters over X amount of time
That is why we talk (not enough IMO) about "proper" waste treatment of our chemical waste - often by cementing with iron first - then with "actual" Ph adjustment --- & it is important here to fully understand Ph adjustment - not all metals simply drop out at Ph 7 - some metals will drop out under Ph 7 but "start" to go back into solution "around" Ph 7 while other metals will only start to drop out around Ph 7 so need to go higher then Ph 7 --- in other words - once adjusted to PH 7 & after filtering out the sludge - you need to test the filtered solution by raising &/or lowering the Ph to what else may drop out
Bottom line - diluting acid does not in anyway make it neutral - it only changes the Ph of the acid/water according to the acid/water ratio - & diluting metal acid dissolved solutions in NO WAY makes them safe for disposal by dumping down the drain
Kurt
