×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Anodizing: Treatment of Combined Etch and Anodize Bath Wastes?

Anodizing: Treatment of Combined Etch and Anodize Bath Wastes?

Anodizing: Treatment of Combined Etch and Anodize Bath Wastes?

(OP)
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?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources