David
Yes, there is no significant dissolution of lead in low pH liquids, so
an acid leaching will be very small. But think of high pH leaching. At
pH 7, lead glass is already dissolving, albeit slowly. At pH 10, the
rate may be 4-8 times higher.
Don't believe me? Put your best lead crystal glassware in a domestic
dishwasher and pass it through a washing cycle a few tens of times
(preferably with a cation exchanger on the waste pipe). Then admire the
lack of sparkle.
Brian
Thompson, David wrote:
> Brian:
>
> In the US we are routinely monitoring landfill leachate. Even unlined
> landfills that date back to 1930s show no evidence of lead leaching.
> Modern landfills have leachate collection systems.
>
> We also have a mandated EPA test called the Toxic Leachate
> Characteristic Procedure (TCLP), where leaded glass is ground up into
> particles that will pass through a 9 mm sieve, and then subjected to a
> strong acidic solution for 18 hours. Typically monochrome CRTs do not
> fail this test for lead, suggesting that CRTs are safe for disposal in
> landfills. (I doubt that CRTs will be ground up so finely in a
> real-life landfill environment.)
>
> Color CRTs typically fail the TCLP because of the solder glass that
> joins the faceplate and the funnel, but this hardly suggests that the
> funnel, which contains almost all of the lead in CRTs, will fail or that
> a landfill will not contain them properly.
>
> I say all of this not to suggest that CRTs should be landfilled, but
> only that we do not face the crisis that the greens would have us
> believe.
>
> We advocate that CRTs be collected and recycled. Technology is
> available to reclaim and reuse both the funnel and the faceplate glass,
> although the faceplate likewise will not fail the TCLP test.
>
> Dave
>
> -----Original Message-----
> From: Brian Ellis [mailto:[log in to unmask]]
> Sent: Monday, December 11, 2006 11:15 AM
> To: TechNet E-Mail Forum; Thompson, David
> Subject: Re: [TN] The 'poisonous'- computer reports
>
> I disagree about the bioavailabilty. In a landfill, the lead glass is
> inevitably crushed into small particles the total surface area is
> therefore very large. As lead glass is slightly water soluble, the lead
> can enter into run-off over a matter of years. What happens to this
> water is the nux of the problem.
>
> I agree that the quantity of lead in a modern computer is small, but
> what about the zillions of CRT monitors still in use?
>
> Brian
>
> Thompson, David wrote:
>> Glen / Ingemar: CRTs do not contain layer of lead coating inside the
>> tube. The lead is contained in the glass and is not readily
>> bioavailable in a landfill environment.
>>
>> Today's computers probably do not contain 1/2 pound of lead.
>> Panasonic's current line up of laptops contain about 5 mg, a long way
>> from 1/2 pound.
>>
>> David Thompson
>> Panasonic
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Glen Herzog
>> Sent: Monday, December 11, 2006 10:15 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] The 'poisonous'- computer reports
>>
>> Ingemar, possibly this article is suspicious because it was written
> in
>> 1996, long before LCD screens and long before the introduction of RoHS
> &
>> WEEE. CRTs have a heavy layer of lead in coating the inside of the
>> envelope. I'll bet that todays lead weight in a desktop would not
>> exceed
>> 1/2 pound.
>>
>> Table presented in: Microelectronics and Computer Technology
> Corporation
>> (MCC). 1996. Electronics Industry Environmental Roadmap. Austin, TX:
>> MCC.
>>
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