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Re: Glass Etchants



Ric:
I am responding to the part of your question that asks about HF
regeneration.  A while back, I researched using membrane technologies to
maintain HF etches.  Can be done, but it is very tricky, and only justified
by very, very expensive products and/or large volume uses.  Even then, the
worker safety issues are pretty darn important, and if they have an
acceptable product now that is not directly HF-based, they probably should
stick with it.  We used to accidentally generate HF fumes now and then when
we ran our fluoboric acid + tin/lead solution too hot, and it was scary. 


>All,
>I'm looking for any information or leads on the topic of etching glass
>(information in the archives was obtained).  Specific issues being
>investigated include:
>1) Hydrofluoric acid management
>2) Alternatives to HF including non-corrosive etching methods
>3) Wastewater treatment (fluoride and ammonia/nitrates seem to be the
>main issues)
>4) Waste reduction technologies (HF regeneration (is it possible?),
>closed-loop rinse systems, sludge management, formal wastewater treatment
>systems that might allow effluent re-use))
>
>Thanks, Ric
>Illig.richard@dep.state.pa.us <mailto:Illig.richard@dep.state.pa.us>
>PADEP
>Fax: 570-327-3565      Office of
>Pollution Prevention
>Call: 570-327-3568      208 W. Third
>Street, Suite 101
> 
>Williamsport, PA  17701
>        ATTN: Ric
>Illig
>
>If you would like more information about the specific case...
>A company is frosting wine bottles (flint glass).  Rather than use
>hydrofluoric acid (directly) they decided to use a product called LERITE.
>LERITE contains ammonium bifluoride and barium sulfate (we're not sure what
>role the barium plays in the process) and is mixed with concentrated
>muriatic acid.  Waste rinse water is discharged to the local treatment
plant
>after pH adjustment.  The frosting bath is used for an extended period of
>time.
>It appears the LERITE+muriatic acid generates HF for etching AND creates
>numerous problems in the process.  The redeeming quality of LERITE appears
>to be ease of handling relative to storage and management of HF.  Finished
>product quality is excellent so there is resistance to change BUT the POTW
>accepting the waste requires the ammonia/nitrate levels to be GREATLY
>reduced.
>Problems observed include:
>1) Ammonia/nitrate, fluoride, and barium levels are very high in the
>discharge (correction required)
>2) Total suspended solids (TSS) are also high
>3)  Barium is expected in tank sludges (for the frost bath, rinse
>tanks, and wastewater treatment tanks)
>4) Removal of rinse water dragout from the etch solution generates a
>corrosive hazardous wastewater.  The wastewater requires either on-site
>treatment prior to discharge or off-site shipment and disposal.
>
>We're weighing the direct use of HF against the issues of using LERITE.
>Using HF could eliminate the muriatic acid but may present greater handling
>problems.  HF is also a HAP.  Alternative technologies appear to be too
slow
>or non-existent.  Elimination of the barium seems to be a major improvement
>if HF is used directly.  HF would also seem to allow for reducing
>ammonia/nitrate and fluoride levels in the discharge possibly without the
>need for a formal wastewater treatment system.
>
><> 
><>
><>
><>
>Pennsylvania is "Growing Greener" 
>



Terry Foecke, Managing Partner
Materials Productivity LLC
1821 University Avenue, Suite S-219
St. Paul, MN   55104
(p) 651-603-8282
(f) 651-603-8286
tfoecke@matprod.com