Geopolymers are inorganic materials that form long-range, covalently bonded networks. They have been used to immobilize hazardous secondary wastes from incineration plants by encapsulating the waste. The document describes a study where geopolymers were synthesized from fly ash or metakaolin, mixed with waste ash, and cured. Analysis found the waste was successfully solidified in the geopolymer matrix. Metakaolin-based geopolymers solidified faster than fly ash-based ones. The study demonstrates geopolymers can highly immobilize compounds in incineration waste like heavy metals.

2. Introduction
What are the Geopolymers????

3.  Geopolymers are inorganic, typically
ceramic, materials that form long-range,
covalently bonded, non-crystalline
networks.
For example:
 Obsidian is an example of naturally
occurring geopolymer.

5. Background
 Incineration plants has been used to burn the solid
waste by combustion process
 Secondary products (heavy metals and dioxins) are also
formed due to burning activity
 Geopolymers has been used to immobilize the
secondary waste by encapsulating the waste; resulted
due to combustion

6. Material and methods
1. Collection of the secondary waste (ash) from
incineration plant
2. Synthesis of the geopolymers
3. Mixing of the waste into synthesized geopolymer

7. Designing of the geopolymers
 Geopolymers were made from
a. Fly ash from bituminous coal combustion
a. Metakaolin (Coal fly ash)

8. Methodology
 Metakaolin ws mixed with the waste from
incineration plant
 Preparation of the alkaline solution
 Aqueous solution of sodium silicate was poured over the
solid sodium hydroxide.
 Solution was thoroughly mixed and paste was obtained

10. Cont…
 Paste was poured into cubic molds and was let be
solidified
 Molds were heated for 24 hours at 75o°C, cooled to the
ambient temperature
 Material was taken out of the molds and stored for 28
or 90 days.

11. Cont…
 Certain properties of waste were analyzed e.g.
 Chemical composition
 Dioxin content
 Size and morphology of particles.

12. Analysis of the sample
 Particle size distribution was determined by laser
diffraction wet-dispersion method
 The morphologies of the samples were examined by
means of the scanning electron microscope
 The oxide content was measured by means of the
spectrometer
 The content of dioxins was determined using gas
chromatography coupled with mass spectrometry

14. Results
 The secondary waste from the incineration plant and
solidified in the geopolymer
 Matrix made from fly ash, the desirable values of
compressive strength are obtained after 90 days of
curing
 In the case of metakaolin-based geopolymers it takes
only 28 days

18. Conclusion
 It was proved that geopolymerization process allows
for the high-level immobilization of such compounds
and elements as: chlorides, sulfates, fluorides, barium
and zinc
 Metakoilen was proved t be better stabilizer than flysh
 Pretreatment (e.g. washing) of the secondary waste is
recommended for future studies