Hello, I hope I picked the right forum. So I'm currently trying to follow the instructions given in a post called "dealing with waste" but I'm having trouble raising the pH to 2.5 so i can add my iron. My memory serves me right it says slowly raise the ph to 2.5 over a day or two. So I've been adding soda ash over 2 or 3 days and I've yet to get the ph up to zero or one according to my pH meter. I even tried to add a little sodium hydroxide and still know bump up in the pH am I doing something wrong?
Trouble raising pH on waste
- Thread starter Rreyes097
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Have you already cemented on copper?
Yes
I think you have plenty acid left in solution.
Just keep adding NaOH, but it might be easier to control it, if you make a strong solution and add it in smallish increments under strong stirring.
You have to remember that pH is logarithmic. A ton of the work is just getting the pH to 1. If there's a fair amount of free acid, it's going to take a while. I usually like to take a small representative sample and increase it's pH knowing that if I screw up I'm not screwing up the whole batch. Then once I have the volume base I need to add, I can just multiply accordingly.
Ok thank you so much. My container is only a gallon, so not very big. And should I be mixing these ( soda ash or sodium hydroxide?) with water then pour it in? Cuz if so I'll need to up the size on my container.
It is definitely better to use dissolved stuff - when intermediary precipitate of BM hydroxides forms, it has much larger surface area and thus is re-dissolved much quicker. For rough pH adjustment to cross the 0, with good mechanical stirrer, it is also possible to use solid NaOH. But mixing should be fairly aggresive to break up the hydroxide coating, which immediately forms on granules in the solution. Fine pH adjustment is also possible with sodium bicarbonate, as it is usually very fine powder and thus forms smaller "BM hydroxide coated" particles, which re-dissolve/equilibrate much more quickly.
I have done this few times, but now we use slaked lime for processing waste. Hard to filter the hydroxide cake, but we stick with little suction and plenty of time
Cost of reagents is very low, and one small aliexpress vacuum pump with 15W power consumption and pressure regulator costs below 50euros.
You get oxohydroxides cake with residual calcium hydroxide and gypsum (from sulfates contained in the waste), and mainly calcium chloride solution. As we recover copper from the waste, BM consist mainly of nickel, iron and little bit of nearly every metal imaginable Relatively harmless in terms of storage.
It is also doable to adjust pH to 1 or 2 with sodium hydroxide/carbonate/bicarbonate and then left the solution evaporate - obtaining sludgy mixture of BM chlorides and nitrates/sulfates + leftover salts from neutralization. If you do not want to undergo another hassle with hydroxide formation, and you can dispose waste for fair price, then this is also the way how to do it. Requires only time and one fan blowing air over the drum. But logically, you pay for disposing "chloride part" as well
I have done this few times, but now we use slaked lime for processing waste. Hard to filter the hydroxide cake, but we stick with little suction and plenty of time
Cost of reagents is very low, and one small aliexpress vacuum pump with 15W power consumption and pressure regulator costs below 50euros. You get oxohydroxides cake with residual calcium hydroxide and gypsum (from sulfates contained in the waste), and mainly calcium chloride solution. As we recover copper from the waste, BM consist mainly of nickel, iron and little bit of nearly every metal imaginable
Relatively harmless in terms of storage.It is also doable to adjust pH to 1 or 2 with sodium hydroxide/carbonate/bicarbonate and then left the solution evaporate - obtaining sludgy mixture of BM chlorides and nitrates/sulfates + leftover salts from neutralization. If you do not want to undergo another hassle with hydroxide formation, and you can dispose waste for fair price, then this is also the way how to do it. Requires only time and one fan blowing air over the drum. But logically, you pay for disposing "chloride part" as well
