Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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REMOVAL OF LEAD FROM SOLID MATERIALS
FIELD
_
[0001] The present invention relates generally to a composition that
substantially removes lead from
solid materials, and a method of using said composition.
DESCRIPTION OF THE RELATED ART
[0002] As the world transitions to flat panel televisions and flat panel
computer monitors, more and
more cathode ray tubes (CRTs) are being discarded. The safe disposal of CRTs
present a serious
environmental challenge since they contain leaded glass (primarily in the
funnel, neck and frit) which
may be readily leached from a landfill by acidic water. The lead content in
the glass of a CRT can be
as high as 20%, which means that a single 34" television might contain more
than 1 kg of lead. Lead
is toxic and is known to damage the body's nervous and reproductive systems
and kidneys. It can
also cause high blood pressure and anemia. Lead is especially harmful to the
developing brains of
fetuses and young children and to pregnant women. As a result, lead has been
banned from fuel,
paint, pipes and all new electronics.
[0003] Recycling glass is manually intensive and expensive. This is so because
one vendor of glass
may use different concentrations of lead or other metals in their glass
products than another glass
vendor. Waste disposal facilities receive glass waste that is not separated,
and the waste disposal
facilities have no effective techniques for automatically separating different
glass wastes from one
another. Because of the expense and time consuming nature associated with
recycling glass waste,
many waste disposal facilities have resorted to the illegal disposal of glass
waste.
[0004] In the past, the most popular and legal technique for disposing of CRTs
is a smelting
technique, wherein the glass of the monitor is melted at an extremely high
temperature and the lead
extracted off the top of the liquid produced. A literature survey indicates
that smelting recovers only
50% of the lead in the glass, produces toxic vapors and a contaminated toxic
slag that is either
landfilled (at high cost) or used as a low-value aggregate. Therefore, the EPA
realizes that it cannot
permit the smelting process to continue indefinitely and is actively pursuing
and promoting research
to replace the process. Currently, CRT waste is the number two contributor to
hazardous lead waste
in the United States.
[0005] Since no truly viable solution to this problem exists, millions of tons
of waste glass are being
stockpiled by electronics recyclers looking for a solution. Reuse is not a
real option since relatively
few new CRTs are being manufactured. This problem will only get worse as
liquid crystal and/or
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plasma screen technology is integrated into the industry and the at least 1.9
billion CRTs still in use
worldwide are systematically disposed of
[0006] Accordingly, there is a need for improved techniques to extract heavy
metals from glass waste
products and other materials comprising said heavy metals. The techniques
should be environmentally
safe, efficient, and practical so that the techniques are readily embraced and
adopted by waste disposal
facilities.
SUMMARY
[0007] The present invention generally relates to a composition that
substantially removes lead from
solid materials, and a method of using said composition. Preferably, the
concentration of lead in the
solid materials following processing is low enough that the solid materials
can be reused and/or
disposed of at minimal cost to the processor. Preferably, the solid materials
comprise glass, such as
cathode ray tube glass.
[0008] In one aspect, a method of leaching lead or other heavy metals from
solid materials, said
method comprising:
pulverizing the solid materials to size in a range from about 10 microns to
about 3 mm;
introducing the pulverized solid materials into a chemical processing vessel
comprising a leaching
composition to form a slurry;
agitating the slurry to leach the lead or other heavy metals from the solid
material into the leaching
composition,
wherein the leaching composition comprises at least one oxidant, at least one
solvent, optionally at
least one metal chelator, optionally at least one accelerator/NO), (nitrogen
oxide) suppressor, and
optionally at least one etchant.
[0009] In another aspect, a leaching composition is described, said leaching
composition comprising
at least one oxidant, at least one solvent, optionally at least one metal
chelator, optionally at least one
accelerator/NO), (nitrogen oxide) suppressor, and optionally at least one
etchant.
[0010] Other aspects, features and advantages of the invention will be more
fully apparent from the
ensuing disclosure and appended claims.
DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS THEREOF
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[0011] The present invention generally relates to a composition that
substantially removes lead from
solid materials, and a method of using said composition to remediate lead from
said solid materials.
Preferably, the concentration of lead in the solid materials following
processing is low enough that the
solid materials can be reused and/or disposed of at minimal cost to the
processor. Preferably, the solid
materials comprise glass, such as cathode ray tube glass. It is also
contemplated that the compositions
described herein can be used to remove lead from soil, electronic equipment,
solder sludge, and paint
chips.
100121 As defined herein, "substantially devoid" corresponds to less than
about 2 wt. %, more
preferably less than 1 wt. %, and most preferably less than 0.1 wt. % of the
composition, based on the
total weight of said composition.
100131 "Substantially removed" is defined herein to mean that more than 95 wt.
% of the heavy metal
originally present is dissolved or otherwise solubilized, preferably more than
98 wt. %, more
preferably more than 99 wt. %, and most preferably more than 99.9 wt. %.
100141 As used herein, the term "leaches" corresponds to the complete removal
or extraction of the
lead or other metals from the material into the leaching composition or the
partial removal or
extraction of the lead or other metals from the material into the leaching
composition. The lead or
other metals is dissolved or otherwise solubilized in the leaching
composition, preferably dissolved.
100151 As defined herein, the "material" corresponds to any solid that
requires lead or other metal
remediation including, but not limited to, CRT glass waste, soil, paint chips,
electronic waste, and
solder sludge.
100161 As has been discussed in detail above, glass waste, particularly glass
waste associated with
CRT monitors or televisions, includes unacceptable levels of lead, or other
heavy metals (e.g.,
cadmium, mercury, selenium, arsenic, and the like), that need to be removed or
decreased to
acceptable levels before the glass waste can be disposed of in a landfill.
Using the composition and
method described herein, glass waste can economically and safely be disposed
of well within the
current EPA standards by safely and efficiently removing lead and other heavy
metals from the glass
waste. Alternatively, the glass can safely be recycled for reuse as glass or
for incorporation into other
products such as concrete or asphalt.
100171 The material, such as CRT glass waste, soil, paint chips, electronic
waste, and solder sludge,
can be pulverized using means suitable for crushing or grinding said materials
to variable particle
sizes. For example, CRT glass waste can be fed to a grinding device such as a
high-speed hammer
mill, grinder, or any other size reduction means. Preferably, the material is
pulverized to size in a
range from about 10 microns to about 3 mm. As the material leaves the grinding
means, preferably a
separation device classifies the material particles by size. For example, the
separation device can be
configured to classify the material particles into sizes between less than 3
mm and sizes greater than
approximately 10 microns. Material particles have a desired diameter size
between about 10 microns
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and about 3 mm or less, although it should be appreciated that diameters less
than 10 microns and
greater than 3 mm can be processed as well using the composition and method
described herein.
[0018] The pulverized material particles are then introduced into a chemical
processing vessel
comprising a leaching composition, which will be described below. The chemical
processing vessel
can be a drum set-up, a tumbler system, a mixing apparatus, or an equivalent
thereof. The leaching
composition in combination with the pulverized material particles results in
the formation of a slurry,
which can be agitated by stirring, mixing, tumbling, shaking, etc., in the
presence or absence of added
heat. Preferably, the temperature of the slurry during agitation is about 30 C
to about 150 C,
preferably about 30 C to about 70 C. The slurry can alternatively be
circulated using a pumping
system. In still another alternative, a feed-and-bleed system is contemplated
whereby some amount of
the leaching composition is removed for processing and fresh or recycled
leaching composition added
to the chemical processing vessel.
[0019] The slurry can be agitated for time in a range from about 5 min to 6
hr, depending on the
volume of leaching composition and the amount of pulverized material particles
added. Upon
completion of the leaching process, the leaching composition is removed from
the vessel and/or the
material particles are filtered from the leaching composition. Following
filtration, the material
particles are preferably rinsed with water to remove residual leaching
composition from the material
particles. Thereafter, the material particles can be filtered again. The
leaching composition can be
reused for another cycle of material particle treatment or treated for
disposal.
[0020] With regards to additional cycles, the leaching composition can be
reused until the leaching
composition is saturated with lead and other metals and no longer efficiently
solubilizes lead into the
leaching composition. Ion-exchange resins selective to lead can be used in
combination with the
leaching composition to further extend the life of the bath. Moreover, as will
be discussed below, the
leaching composition can be recycled using diffusion dialysis and reused. With
regards to disposal
procedures, when no longer viable, the leaching composition can be rendered
essentially non-toxic by
electrowinning or precipitating the Pb and neutralizing the excess acidity.
[0021] At this point, particles consisting of glass (e.g., CRT glass) are
substantially devoid of lead
and other heavy metals on their surface due to the mixing cycles with the
leaching composition.
Moreover, any lead or heavy metal remaining within the filtered glass
particles cannot be extracted
from the filtered glass particles because of the size of the glass particle
and the fact that the remaining
heavy metals are sequestered in the core. Products, such as road materials and
others, can include the
filtered glass particles with assurance that lead or other heavy metals (e.g.,
cadmium, mercury,
arsenic, selenium, and others) will not be released. Therefore, the particles
consisting of glass can be
used for other products such as foundations for roads, mixtures for concrete,
etc.
[0022] Preferably, all of the lead is removed from the material. For example,
when the material
comprises soil or some other amorphous solid, the leaching composition can
penetrate the entire
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material and the lead can be substantially removed from the material. When the
material comprises
glass, only the lead on the surface of the glass is removed. This is
advantageous because the lead in
the core of the particle is sequestered and not easily removed if disposed of
in a landfill. That said, it
is theorized that if the leaching composition can solubilize the glass
particle then substantial removal
of the lead can be effectuated and substantially lead-free glass re-
precipitated and sold for reuse. As
defined herein, "substantially lead-free" corresponds to a concentration of
lead in the material less
than about 5 wt%, preferably less than about 2 wt%, and even more preferably
less than 1 wt%, based
on the total weight of the solid glass.
[0023] The leaching composition is formulated to oxidize and sequester the
lead thereby removing
same from the material. The leaching composition comprises, consists of, or
consists essentially of at
least one oxidant, at least one solvent, optionally at least one metal
chelator, optionally at least one
accelerator/NO. (nitrogen oxide) suppressor, optionally at least one etchant.
In one embodiment, the
leaching composition comprises, consists of, or consists essentially of at
least two oxidants, at least
one solvent, and at least one accelerator/NO. (nitrogen oxide) suppressor. In
another embodiment, the
leaching composition comprises, consists of, or consists essentially of at
least one oxidant, at least one
solvent, at least one metal chelator, and at least one accelerator/NO.
(nitrogen oxide) suppressor.
[0024] The components of the leaching composition comprising, consisting of,
or consisting
essentially of at least two oxidants, at least one solvent, and at least one
accelerator/NO. (nitrogen
oxide) suppressor can be present in the following amounts, based on the total
weight of the leaching
composition:
Component weight %
oxidizing agent(s) about 6 wt% to about 85 wt%
accelerator/NO. suppressor(s) about 0.1 wt% to about 10 wt%
solvent(s) about 5 wt% to about 93.9 wt%
[0025] The components of the leaching composition comprising, consisting of,
or consisting
essentially of at least one oxidant, at least one solvent, at least one metal
chelator, and at least one
accelerator/NO. (nitrogen oxide) suppressor can be present in the following
amounts, based on the
total weight of the leaching composition:
Component weight %
oxidizing agent(s) about 5 wt% to about 20 wt%
metal chelator(s) about 10 wt% to about 65 wt%
accelerator/NO. suppressor(s) about 0.2 wt% to about 10 wt%
solvent(s) about 5 wt% to about 84.8 wt%
[0026] Oxidizing agents are included in the leaching composition to oxidize
the metals to be
removed into an ionic form and accumulate highly soluble salts of dissolved
metals. Oxidizing agents
contemplated herein include, but are not limited to, ozone, nitric acid
(HNO3), bubbled air,
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cyclohexylaminosulfonic acidõ hydrogen peroxide (H202), oxone (potassium
peroxymonosulfate,
2KH505.KH504.K2SO4), ammonium polyatomic salts (e.g., ammonium
peroxomonosulfate,
ammonium chlorite (NH4C102), ammonium chlorate (NH4C103), ammonium iodate
(NH4I03),
ammonium perborate (NH4B03), ammonium perchlorate (NH4C104), ammonium
periodate (NH4I03),
ammonium persulfate ((NH4)2S208), ammonium hypochlorite (NH4C10)), sodium
polyatomic salts
(e.g., sodium persulfate (Na25208), sodium hypochlorite (NaC10)), potassium
polyatomic salts (e.g.,
potassium iodate (KI03), potassium permanganate (KMn04), potassium persulfate,
potassium
persulfate (K2 S208), potassium hypochlorite (KC10)), tetramethylammonium
polyatomic salts (e.g.,
tetramethylammonium chlorite ((N(CH3)4)C102), tetramethylammonium chlorate
((N(CH3)4)C103),
tetramethylammonium iodate ((N(CH3)4)I03), tetramethylammonium perborate
((N(CH3)4)B03),
tetramethylammonium perchlorate ((N(CH3)4)C104), tetramethylammonium periodate
4N(CH3)4)I04),
tetramethylammonium persulfate ((N(CH3)4)5208)), tetrabutylammonium polyatomic
salts (e.g.,
tetrabutylammonium peroxomonosulfate), peroxomonosulfuric acid, urea hydrogen
peroxide
((C0(NH2)2)H202), peracetic acid (CH3(C0)00H), sodium nitrate, potassium
nitrate, ammonium
nitrate, sulfuric acid, and combinations thereof. Although not oxidizing
agents per se, for the sake of
the present disclosure, oxidizing agents further include alkanesulfonic acids
(e.g., methanesulfonic
acid (MSA), ethanesulfonic acid, 2-hydroxyethanesulfonic acid, n-
propanesulfonic acid,
isopropanesulfonic acid, isobutenesulfonic acid, n-butanesulfonic acid, and n-
octanesulfonic acid).
The oxidizing agents can include a combination of the any of the species
defined herein as oxidizing
agent. The oxidizing agent may be introduced to the first composition at the
manufacturer, prior to
introduction of the leaching composition to the particles, or alternatively in
situ. Preferably, the
oxidizing agent comprises methanesulfonic acid, nitric acid, or a combination
of methanesulfonic acid
and nitric acid.
[0027] When present, it is thought that an effective amount of nitric acid
serves as an accelerator of
the leaching process. Accordingly, in some embodiments, the oxidizing agent in
the leaching
composition preferably comprises an alkane sulfonic acid (e.g., MSA) and
nitric acid, wherein the
alkane sulfonic acid is present in an amount ranging from 0.1 to 85 wt%, more
preferably from 5 to 45
wt%, and the nitric acid is present in an amount of about 0.1 to 80 wt%,
preferably from about 1 to 40
wt%.
[0028] Metal chelators are included to complex the metal ions generated by the
oxidizing agent.
Metal chelators contemplated herein include, but are not limited to: f3-
diketonate compounds such as
acetylacetonate, 1 ,1 ,1 -trifluoro -2,4 -pentanedione, and 1,1,1,5,5,5 -
hexafluoro -2,4 -p entanedione ;
carboxylates such as formate and acetate and other long chain carboxylates;
and amides (and amines),
such as bis(trimethylsilylamide) tetramer. Additional chelating agents include
amines and amino
acids (i.e. glycine, serine, proline, leucine, alanine, asparagine, aspartic
acid, glutamine, valine, and
lysine), citric acid, acetic acid, maleic acid, oxalic acid, malonic acid,
succinic acid, phosphonic acid,
phosphonic acid derivatives such as hydroxyethylidene diphosphonic acid
(HEDP), 1-hydroxyethane-
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1,1-diphosphonic acid, nitrilo-tris(methylenephosphonic acid),
nitrilotriacetic acid, iminodiacetic acid,
etidronic acid, ethylenediamine, ethylenediaminetetraacetic acid (EDTA), and
(1,2-
cyclohexylenedinitrilo)tetraacetic acid (CDTA), uric acid, tetraglyme,
pentamethyldiethylenetriamine
(PMDETA), 1,3,5-triazine-2,4,6-thithiol trisodium salt solution, 1,3,5-
triazine-2,4,6-thithiol
triammonium salt solution, sodium diethyldithiocarbamate, disubstituted
dithiocarbamates
(R1(CH2CH20)2NR2CS2Na) with one alkyl group (R2 = hexyl, octyl, deceyl or
dodecyl) and one
oligoether (Ri(CH2CH20)2, where RI = ethyl or butyl), ammonium sulfate,
monoethanolamine
(MEA), Dequest 2000, Dequest 2010, Dequest 2060s, diethylenetriamine
pentaacetic acid,
propylenediamine tetraacetic acid, 2-hydroxypyridine 1-oxide, ethylendiamine
disuccinic acid
(EDDS), N-(2-hydroxyethyl)iminodiacetic acid (HEIDA), sodium triphosphate
penta basic, sodium
and ammonium salts thereof, ammonium chloride, sodium chloride, lithium
chloride, potassium
chloride, ammonium sulfate, hydrochloric acid, sulfuric acid, and combinations
thereof Preferably,
the metal chelator comprises ammonium chloride, sodium chloride, lithium
chloride, potassium
chloride, ammonium sulfate, hydrochloric acid, sulfuric acid, and combinations
thereof, most
preferably sodium chloride, sulfuric acid, or a combination of sodium chloride
and sulfuric acid.
[0029] When nitric acid is included in the leaching composition, nitrogen
oxides (NO.) are
generated. Accordingly, NO suppressors are preferably included when the
leaching composition
includes nitric acid. Surprisingly, however, the NO. suppressors are also
accelerators of the metal
etch rates so they can be added even if the leaching composition does not
include nitric acid. NO.
suppressors/accelerators contemplated include, but are not limited to,
ascorbic acid, adenosine, L(-0-
ascorbic acid, isoascorbic acid, ascorbic acid derivatives, citric acid,
ethylenediamine, gallic acid,
oxalic acid, tannic acid, ethylenediaminetetraacetic acid (EDTA), uric acid,
1,2,4-triazole (TAZ),
triazole derivatives (e.g., benzotriazole (BTA), tolyltriazole, 5-phenyl-
benzotriazole, 5-nitro-
b enzotriazole, 3 -amino -5 -mercapto -1,2,4-triazole, 1-amino -1,2,4-
triazole, hydroxybenzotriazole, 2-(5 -
amino -p enty1)-b enzotriazole, 1 -amino -1,2 ,3 -triazole, 1-amino-5-methyl-
1,2,3 -triazole, 3-amino -1,2,4-
triazole, 3-mercapto-1,2,4-triazole, 3-isopropy1-1,2,4-triazole, 5-phenylthiol-
benzotriazole, halo-
benzotriazoles (halo = F, Cl, Br or I), naphthotriazole), 4-amino-1,2,4-
triazole (ATAZ), 2-
mercaptob enzimidazole (MBI), 2-
mercaptobenzothiazole, 4-methyl-2-phenylimidazole, 2-
mercaptothiazoline, 5-aminotetrazole (ATA), 5-amino-1,3,4-thiadiazole-2-thiol,
2,4-diamino-6-
methy1-1,3,5-triazine, thiazole, triazine, methyltetrazole, 1,3-dimethy1-2-
imidazolidinone, 1,5-
pentamethylenetetrazole, 1-pheny1-5-mercaptotetrazole, diaminomethyltriazine,
imidazoline thione,
mercaptobenzimidazole, 4 -
methy1-4H -1,2,4 -triazole-3 -thiol, 5-amino -1,3 ,4 -thiadiazo le -2 -
thiol,
benzothiazole, tritolyl phosphate, imidazole, indiazole, benzoic acid, boric
acid, malonic acid,
ammonium benzoate, catechol, pyrogallol, resorcinol, hydroquinone, cyanuric
acid, barbituric acid
and derivatives such as 1,2-dimethylbarbituric acid, alpha-keto acids such as
pyruvic acid, adenine,
purine, phosphonic acid and derivatives thereof, glycine/ascorbic acid,
Dequest 2000, Dequest 7000,
p-tolylthiourea, succinic acid, phosphonobutane tricarboxylic acid (PBTCA),
sodium molybdate,
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ammonium molybdate, salts of chromate (e.g., sodium, potassium, calcium,
barium), sodium
tungstate, salts of dichromate (e.g., sodium, potassium, ammonium), suberic
acid, azaleic acid,
sebacic acid, adipic acid, octamethylene dicarboxylic acid, pimelic acid,
dodecane dicarboxylic acid,
dimethyl malonic acid, 3,3-diethyl succinic acid, 2,2-dimethyl glutaric acid,
2-methyl adipic acid,
trimethyl adipic acid, 1,3-cyclopentane dicarboxylic acid, 1,4-cyclohexane
dicarboxylic acid,
terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 2,7-
naphthalene dicaroxylic
acid, 1,4-naphthalene dicarboxylic acid, 1,4-phenylenedioxy diacetic acid, 1,3-
phenylenedioxy
diacetic acid, diphenic acid, 4,4'-biphenyl dicarboxylic acid, 4,4'-
oxydibenzoic acid,
diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic
acid, decamethylene
dicarboxylic acid, undecamethylene dicarboxylic acid, dodecamethylene
dicarboxylic acid,
orthophthalic acid, naphthalenedicarboxylic acid, paraphenylenedicarboxylic
acid, trimellitic acid,
pyromellitic acid, sodium phosphates (e.g., sodium hexametaphosphate), sodium
silicates, amino
acids and their derivatives such as 1-arginine, nucleoside and nucleobases
such as adensosine and
adenine, respectively, and combinations thereof. Most preferably, the NO
suppressor/accelerator
comprises ATAZ, TAZ, triazole derivatives, or combinations thereof, most
preferably ATAZ.
[0030] Solvents contemplated herein include water, preferably deionized water,
as well as organic
solvent such as alcohols, glycol ethers, glycols, and carbonates, including,
but not limited to,
methanol, ethanol, isopropanol, butanol, and higher alcohols (including diols,
triols, etc.), ethylene
glycol, propylene glycol, butylene carbonate, ethylene carbonate, propylene
carbonate, dipropylene
glycol, diethylene glycol monomethyl ether, triethylene glycol monomethyl
ether, diethylene glycol
monoethyl ether, triethylene glycol monoethyl ether, ethylene glycol
monopropyl ether, ethylene
glycol monobutyl ether, diethylene glycol monobutyl ether (i.e., butyl
carbitol), triethylene glycol
monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl
ether, ethylene
glycol phenyl ether, propylene glycol methyl ether, dipropylene glycol methyl
ether (DPGME),
tripropylene glycol methyl ether, dipropylene glycol dimethyl ether,
dipropylene glycol ethyl ether,
propylene glycol n-propyl ether, dipropylene glycol n-propyl ether (DPGPE),
tripropylene glycol n-
propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl
ether, tripropylene glycol n-
butyl ether, propylene glycol phenyl ether, and combinations thereof, and
combinations thereof
Preferably, the solvent comprises water.
[0031] When present, the at least one etchant can include at least one
carbonate species, at least one
hydroxide species and/or at least one fluoride species. Carbonates include,
but are not limited to,
sodium carbonate, potassium carbonate, sodium hydrogen carbonate, and
combinations thereof
Hydroxides contemplated include, but are not limited to, alkali hydroxides,
alkaline earth metal
hydroxides, metal ion-free hydroxides, and combinations thereof such as Li0H,
NaOH, KOH, RbOH,
Cs0H, Mg(OH)2, Ca(OH)2, Sr(OH)2, Ba(OH)2, NR4OH, wherein R can be the same as
or different
from one another and include H, C1-C6 alkyl (e.g., methyl, ethyl, propyl,
butyl, pentyl, hexyl) or C6-
C10 aryl (e.g., benzyl), and combinations thereof The at least one fluoride
species may comprise a
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species selected from the group consisting of xenon
difluoride; HF ;
pentamethyldiethylenetriammonium trifluoride; ammonium bifluoride;
triethylaminogallate
trihydrofluoride; alkyl hydrogen fluoride (NRH3F), wherein each R is
independently selected from
hydrogen and C1-C4 alkyl (e.g., methyl, ethyl, propyl, butyl); dialkylammonium
hydrogen fluoride
(NR2H2F), wherein each R is independently selected from hydrogen and C1-C4
alkyl;
trialkylammonium hydrogen fluoride (NR3HF), wherein each R is independently
selected from
hydrogen and C1-C4 alkyl; trialkylammonium trihydrogen fluoride (NR3:3HF),
wherein each R is
independently selected from hydrogen and C1-C4 alkyl; ammonium fluorides of
the formula R4NF,
wherein each R is independently selected from hydrogen, C1-C4 alkyl, and C1-C4
alkanol (e.g.,
methanol, ethanol, propanol, butanol) such as ammonium fluoride,
tetramethylammonium fluoride,
triethanolammonium fluoride, tetraethylammonium fluoride; and combinations
thereof. Preferably,
the fluoride source comprises HF, ammonium fluoride, or combinations thereof
When present the
amount of etchant is preferably in a range from about 0.01 wt% to about 10
wt%, based on the total
weight of the composition.
[0032] It is also contemplated herein that the combination of low energy
sonication or megasonics
with leaching formulations also can accelerate lead removal from CRT glass.
[0033]
Advantageously, an easily recyclable leaching composition can be employed in a
closed-
loop process generating minimal waste. For example, when the leaching
composition includes MSA,
the MSA is easily recycled using diffusion dialysis.
[0034] Most
preferably, the leaching composition comprises, consists or consists
essentially of
MSA, nitric acid, and ATAZ. In another preferred embodiment, the leaching
composition comprises,
consists of, or consists essentially of MSA, sulfuric acid, ATAZ, and NaCl.
[0035] In
another aspect, the leaching composition and the pulverized CRT glass can be
placed
into a high pressure autoclave for the leaching process. Water is known to
have very strong oxidizing
properties at hydrothermal (>100 C and >100 psi) conditions and near critical
conditions (>300 C and
>3000 psi). Accordingly, at these hydrothermal conditions, water alone may be
strong enough to
oxidize the lead so that the chelator can extract the lead. Suitable chelators
include chloride, iodide,
hydroxide, or sulfate salts (e.g., as described herein), wherein hydroxide or
sulfate are preferred
because they will not corrode steel vessels required for high pressure
applications and they will
readily precipitate from solution upon cooling and depressurizing of the
vessel.
[0036] The resulting lead-free glass may be remelted for reuse (e.g., bricks,
tiles, foam), mixed into,
for example, asphalt or cement as a filler, or sent to a landfill for safe
disposal. Lead can be removed
from the solution in the form of an oxide or salt and may be resold. The
system is closed so that no
vapors escapes and all of the chemistry and the rinse water are recycled for
reuse in the process.
Small amounts of rinse water are discharged, but it is first neutralized and
has less than part-per-
million trace metals and no organics.
9
CA 02869431 2014-10-01
WO 2013/152260
PCT/US2013/035379
[0037] Although the invention has been variously disclosed herein with
reference to illustrative
embodiments and features, it will be appreciated that the embodiments and
features described
hereinabove are not intended to limit the invention, and that other
variations, modifications and other
embodiments will suggest themselves to those of ordinary skill in the art,
based on the disclosure
herein. The invention therefore is to be broadly construed, as encompassing
all such variations,
modifications and alternative embodiments within the spirit and scope of the
claims hereafter set
forth.
