NATURAL%20ZEOLITES%20AS%20MULTIFUNCTIONAL%20ENVIRONMENTAL%20FRIENDLY%20MATERIALS%20%20%20THEIR%20APPLICATION%20FOR%20REMOVAL%20OF%20Pb%20AND%20Zn%20FROM%20BINARY%20SOLUTIONS

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NATURAL ZEOLITES AS MULTIFUNCTIONAL ENVIRONMENTAL
FRIENDLY MATERIALS THEIR APPLICATION FOR
REMOVAL OF Pb AND Zn FROM BINARY SOLUTIONS
2nd Slovenian-Croatian Symposium on
Zeolites Ljubljana, 2009

• Marina Trgo
• Faculty of Chemistry and Technology
• University of Split
• Croatia

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NATURAL ZEOLITES - deposits and properties

• natural aluminosilicate minerals with crystal
  three-dimensional structure
• hydrated cations are located inside framework
  structure and weakly bound with structure
• advantages of these natural minerals are their
  large deposits on the Earth, easiness of
  exploitation and mostly unnecessary treatment for
  practical application
• the most important deposits are in the United
  States, Mexico, Ukraine, Slovakia, Italy, Greece,
  Turkey, Russia, Serbia, Romania, Bulgaria,
  Georgia, Armenia, Cuba and Croatia
• discovered more than 260 years ago by the Swedish
  mineralogist A.A.F. Cronstedt, commercial
  exploitation started 30 years ago
• the end of 70-ties is proclaimed as "new
  discovery" of natural zeolites
• about 50 different minerals of zeolites are
  discovered in nature, but some of them have
  commercial valuable
• currently, the worlds annual production of
  natural zeolite is about 4 million tons

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NATURAL ZEOLITES - physical and chemical
properties

• many natural zeolites are synthesized in
  laboratory
• difference between natural zeolite minerals is
  manifested in content of hydrated cations which
  occupied pores and channels, ratio of Si/Al in
  structure and number of water molecules
• zeolites have different dimensions of pores and
  channels responsible for their physical and
  chemical properties
• each examined sample is mineralogical
  heterogeneous, and quantification of its
  mineralogical composition in mostly complex
  procedure.

APPLICATION of natural zeolites is based on or
more of the following properties - cation
exchange - adsorption and related molecular
sieving - dehydration and rehydration -
biological activity - catalytic All of these
properties have been intensively investigating.
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Cation exchange - the ability to exchange
inherent cations for other cations on a basis of
ion selectivity - high cation exchange capacity
for heavy metal cations that can be removed from
liquid effluents through the process of
ion-exchange. These cations include lead, silver,
cadmium, cobalt, zinc, copper, mercury,
magnesium, iron, aluminium, chromium and others.
Some natural zeolites are applicable in
industries such as mining, electroplating and
electronics. Giant industrial houses, like IBM,
have deployed this application for treatment of
wastewater containing heavy metals.
-selectivity for ammonium cations, the natural
zeolites lower the level of ammonium in
wastewaters and sewages to non-toxic, acceptable
levels. The zeolite beds can be regenerated and
recycled indefinitely.
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Adsorption and related molecular sieving
The adsorption process is fully reversible and of
purely physical nature. The structure of the
zeolite is unchanged during the adsorption
process and its later regeneration.
The adsorption on molecular sieves is therefore
dependent on the following physical molecular
properties - Size and Shape molecules or ions
larger than the pore opening of the zeolite can
not be adsorbed, smaller molecules or ions can.
-Molecular Polarity due the charge on outer and
inner zeolitic surface particle, molecules with
large polarity or polarisability can be adsorbed
preferentially under identical conditions.
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Adsorption and related molecular sieving
- this property is used for selective absorption
of organic molecules and for absorption of
radioactive ions (absorber of Sr and Cs
radioisotopes in the nuclear industry and for
clean up of nuclear accidents - applied in the
Chernobyl disaster).
- adsorption process on zeolite is used to remove
polar H2O, H2S, and CO2 from natural gas and
developed a zeolite-adsorption process for
purifying methane produced in a landfill.
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Dehydration and rehydration
Natural zeolites may hold water up to 60 of
their weight due to a high porosity of the
crystalline structure. Water molecules in the
pores could be easily evaporated or reabsorbed
without damage to such structures. Zeolites
assure a permanent water reservoir, providing
prolonged moisture during dry periods they also
promote a rapid rewetting and improve the lateral
spread of water into the root zone during
irrigation. This results in a saving in the
quantity of water needed for irrigation.
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Biological activity
- natural zeolite has been shown to exhibit
diverse biological activities and has been used
successfully for the treatment in medical therapy
- promotes better plant growth by improving the
value of fertilizer, helps preventing the plant
from burning, that can be caused by over use of
fertilizer, by trapping and slowly releasing
valuable nutrients - as additive in
concentrated animal growing facilities improve
feed conversion, reduce airborne ammonia up to
80, act as a mycotoxin binder, and improve bone
density, it can be used in general odour
elimination for all animal odours
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Surface modification of natural zeolites
- modifying the surface of clinoptilolite with
long-chain quaternary amines allowed it to adsorb
benzene, toluene, and xylene in the presence of
water -surface modified natural zeolites remove
toxic compounds from animal food - natural
zeolite can be treated further with additional
amine to produce anion exchangers capable of
taking up chromate, arsenate, selenate, and other
metal oxyanions from aqueous solutions
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Natural zeolite - clinoptilolite
- is one of the most investigated natural
zeolites - unit cell formula is (Na,
K)6Si30Al6O72 20H2O - high silica zeolite,
Si/Al4, HEU type framework topology - Croatia
has deposits of natural zeolite with content of
30-50 of clinoptilolite - recent investigations
in Croatia have done with Serbian zeolite which
contain 80 clinoptilolite
Physical characteristics of some naturally
occurring zeolites
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Clinoptilolite Examinations on Faculty of
Chemistry and Technology University of Split
- removal of Cu, Zn and Pb on natural and
pre-treated zeolite using batch method - study
of kinetic and thermodynamic of Zn on natural
zeolite - removal of Pb or Zn on natural and
pre-treated zeolite using column method -
removal Pb and Zn from binary solution on natural
and pre-treated zeolite using column
method -recent examinations are directed on
removal of metal ions on iron coated zeolite
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Removal Pb and Zn from binary solution on
zeolite-clinoptilolite using column method
SERVICE CYCLE - experiments were performed in
glass columns, d12mm, H40mm - binary aqueous
solutions of lead and zinc ions have been
prepared by dissolving of Pb(NO3)2 and
Zn(NO3)2 in doubly distilled water - flowrate
was 1 ml/min
Concentrations of metal ions in binary solutions
for each service cycle.
Concentration ratio co(Pb)/co(Zn) co(PbZn) mmol/l co(Pb) mmol/l co(Zn) mmol/l
0.19 1.031 0.165 0.866
0.71 1.149 0.478 0.671
0.95 1.062 0.516 0.546
1.37 1.060 0.612 0.448
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Removal Pb and Zn from binary solution on
zeolite-clinoptilolite using column method
breakthrough points
exhaustion points
BVV/VS
c/co c(PbZn)/co(PbZn)
Pb/Zn co(Pb)/co(Zn)
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c/co c(Pb or Zn)/co(Pb or Zn)
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Concentration ratio Pb/Zn in influent VB, BV VE, BV qB, mmol/g qB, mmol/g qB(Pb)/qB(Zn) qE, mmol/g qE(Pb)/qE(Zn)
0.19 218.9 564.0 PbZn 0.336 0.189 0.545 0.174
0.19 218.9 564.0 Pb 0.053 0.189 0.080 0.174
0.19 218.9 564.0 Zn 0.281 0.189 0.460 0.174
0.71 206.8 583.9 PbZn 0.337 0.714 0.521 1.012
0.71 206.8 583.9 Pb 0.140 0.714 0.260 1.012
0.71 206.8 583.9 Zn 0.196 0.714 0.257 1.012
0.95 221.2 614.8 PbZn 0.336 0.942 0.509 1.980
0.95 221.2 614.8 Pb 0.163 0.942 0.396 1.980
0.95 221.2 614.8 Zn 0.173 0.942 0.200 1.980
1.37 209.0 572.8 PbZn 0.312 1.364 0.581 2.010
1.37 209.0 572.8 Pb 0.180 1.364 0.388 2.010
1.37 209.0 572.8 Zn 0.132 1.364 0.193 2.010
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Removal Pb and Zn from binary solution on
zeolite-clinoptilolite using column method
REGENERATION CYCLE - experiments were performed
in glass columns, d12mm, H40mm - regeneration
solution has been prepared by dissolving of NaNO3
in doubly distilled water - flowrate was 1
ml/min
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REGENERATION CURVES for particular ions
Regeneration was completed with 100 BV of
solution.
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CONCLUSIONS
Removal of lead and zinc on zeolite using column
method is applicable in practice. CEC of zeolite
doesn't depend of concentration ratio in feeding
solution. The quantity of regenerated zinc is
significantly lower compared to the lead. The
only exception is the binary solution with a
small Pb/Zn ratio. This confirms that lead was
mostly bound onto zeolite, possible due to
replacement of zinc ions with lead ions during
the service cycle. This replacement is due to
higher selectivity of natural zeolite for lead
ions. Lower radius of the hydrated Pb2 ion in
comparison to Zn2 provides for its better
mobility through the framework structure. Advanta
ge of column method is regeneration of zeolite
what enables unlimited use of the same bed.
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Presented investigations are part of the
scientific project "Natural zeolites in water
protection" which has been financing by Ministry
of Science, Education and Sports of the Republic
of Croatia
Researchers on the project Jelena Peric, full
professor - senior researcher Marina Trgo -
assistant professor Nediljka Vukojevic
Medvidovic- assistant professor Ivona Nuic -
assistant Marin Ugrina - assistant
Thank you!
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• Thank you!