AnodizingRI
Chemical
Hello everyone! I've been having some troubles in waste treatment here in RI and was looking for some wisdom. An Etch bath (containing mostly sodium hydroxide, sodium aluminate, and aluminum hydroxide) was recently dumped into a waste tank and my infinite genius decided to neutralize the pH of this dump with more waste from an anodize bath (containing mostly sulfuric acid, aluminum, and small amounts of various other metals from various alloys (Cu, Mg, Mn, Si (I know Si isn't a metal))). After the pH reached ~7, I was happy, walked away, and came back the next day to find a pH of ~3... I believe this is a cause of the Ka of the second acidic proton on H2SO4 being so much lower than the firsty and it needed time to react. So obviously I started to add sodium hydroxide to bring the pH back up, but it seems that the pH does not really want to go above 5.3. A lifer here at the plant is trying to convince me that NaOH is just too concentrated in the bath and no more will go into solution. Regardless of whether this is true or not, a bigger problem is the fact that the waste has the consistency of last thanksgivings mashed potatoes. Every time we try to send it through the press it just coats the filter plates and won't let any water flow through (imagine the floods of acidic mashed potatoe milk all over your shoes). So I implore some wisdom from all of you regulars here at Eng-Tips... any tips?
