Perlite

Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is an industrial mineral, suitable "as ceramic flux to lower the sintering temperature", and a commercial product useful for its low density after processing.[1] It is also used as a soil conditioner in horticulture.

## Contents

* 1 Properties
* 2 Typical analysis
* 3 Sources and production
* 4 Uses
* 4.1 Construction and manufacturing
* 4.2 Aquatic filtration
* 4.3 Biotechnology
* 4.4 Agriculture
* 4.5 Cosmetics
* 4.6 Substitutes
* 5 Occupational safety
* 5.1 United States
* 6 See also
* 7 References
* 8 External links

## Properties

Perlite boulders with fireweed in foreground

Perlite softens when it reaches temperatures of 850–900 °C (1,560–1,650 °F). Water trapped in the structure of the material vaporises and escapes, and this causes the expansion of the material to 7–16 times its original volume. The expanded material is a brilliant white, due to the reflectivity of the trapped bubbles. Unexpanded ("raw") perlite has a bulk density around 1100 kg/m3 (1.1 g/cm3), while typical expanded perlite has a bulk density of about 30–150 kg/m3 (0.03–0.150 g/cm3).[2]

## Typical analysis

* 70–75% silicon dioxide: SiO2
* 12–15% aluminium oxide: Al2O3
* 3–4% sodium oxide: Na2O
* 3–5% potassium oxide: K2O
* 0.5-2% iron oxide: Fe2O3
* 0.2–0.7% magnesium oxide: MgO
* 0.5–1.5% calcium oxide: CaO
* 3–5% loss on ignition (chemical / combined water)[3]

## Sources and production

Perlite mine in Owens Valley, California.

Perlite is a non-renewable resource. The world reserves of perlite are estimated at 700 million tonnes.[4]

The confirmed resources of perlite existing in Armenia amount to 150 million m3, whereas the total amount of projected resources reaches up to 3 billion m3.[5] Considering specific density of 1.1 ton/m3 confirmed reserves in Armenia amount to 165 million tons.

Other reported reserves are: Greece - 120 million tonnes, Turkey, USA and Hungary - about 49-57 million tonnes.[6][7]

Perlite world production, led by China, Turkey, Greece, USA, Armenia and Hungary, summed up to 4.6 million tonnes in 2018.[6][7]

Osham hills of Patanvav, Gujarat, India are the only source of mineral Perlite in India.

The largest landslide in Icelandic history (the Loðmundarskriður in Loðmundarfjörður) was assisted by the mountain's high perlite composition. Plans to mine and export the perlite in the mid 20th century fell through.

## Uses

Because of its low density and relatively low price (about US$150 per tonne of unexpanded perlite), many commercial applications for perlite have been developed.

### Construction and manufacturing

In the construction and manufacturing fields, it is used in lightweight plasters, concrete and mortar, insulation and ceiling tiles.[8] It may also be used to build composite materials that are sandwich-structured[9] or to create syntactic foam.[10]

Small quantities of perlite are also used in foundries, cryogenic insulation, and ceramics (as a clay additive).[11] It is also used by the explosives industry.[12]

### Aquatic filtration

Perlite is an excellent filtration aid and is used extensively as an alternative to diatomaceous earth. The popularity of perlite usage as a filter medium is growing considerably worldwide. Several products exist in the market to provide perlite based filtration. Several perlite filters and perlite media have met NSF-50 approval (Aquify PMF Series and AquaPerl), which standardizes water quality and technology safety and performance. Perlite can be safely disposed of through existing sewage systems, although some pool operators choose to separate the perlite using settling tanks or screening systems to be disposed of separately.{{citation needed|date=September 2021

### Biotechnology

Due to thermal and mechanical stability, non-toxicity, and high resistance against microbial attacks and organic solvents, perlite is widely used in biotechnological applications. Perlite was found to be an excellent support for immobilization of biocatalysts such as enzymes for bioremediation and sensing applications.[13]

### Agriculture

Perlite mixed into potting compost

In horticulture, perlite can be used as a soil amendment or alone as a medium for hydroponics or for starting cuttings. When used as an amendment, it has high permeability and low water retention and helps prevent soil compaction.[14]

### Cosmetics

Perlite is used in cosmetics as an absorbent and mechanical exfoliant.[15][16]

| Estimated perlite consumption
in the U.S. by application[17]

Fraction | Use[18]
53% | building construction products
14% | horticultural aggregate
14% | fillers
8% | filter aid
11% | other

| Cost of unexpanded perlite[19]

End of
year | Price in the U.S.
$ per metric ton
2001 | $36.30
2002 | $36.50
2003 | $38.20
2004 | $41.80[8]
2005 | $40.50[8]
2006 | $42.90
2007 | $45.30
2008 | $48.00
2009 | $49.00

### Substitutes

Perlite can be replaced for all of its uses. Substitutes include:[20]

* Diatomite, used for filter-aids
* Expanded clay, an alternative lightweight filler for building materials
* Shale
* Pumice
* Slag
* Vermiculite \- many expanders of perlite are also exfoliating vermiculite and belong to both trade associations

## Occupational safety

As perlite contains silicon dioxide, goggles and silica filtering masks are recommended when handling large quantities.

### United States

The Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for perlite exposure in the workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 10 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday.[21]

## See also

* Biochar
* Foam glass
* Industrial minerals
* Mortar (firestop)
* Vermiculite

## References

1. ↑ Reka, Arianit A.; Pavlovski, Blagoj; Lisichkov, Kiril; Jashari, Ahmed; Boev, Blažo; Boev, Ivan; Lazarova, Maja; Eskizeybek, Volkan et al. (24 October 2019). "Chemical, mineralogical and structural features of native and expanded perlite from Macedonia" (in en). Geologia Croatica 72 (3): 215–221–215–221. doi:10.4154/gc.2019.18. ISSN 1333-4875. http://www.geologia-croatica.hr/index.php/GC/article/view/gc.2019.18. Retrieved 4 January 2020.
2. ↑ Maxim, L. Daniel; Niebo, Ron; McConnell, Ernest E. (2014-04-01). "Perlite toxicology and epidemiology – a review". Inhalation Toxicology 26 (5): 259–270. doi:10.3109/08958378.2014.881940. ISSN 0895-8378. PMID 24601903. Bibcode: 2014InhTx..26..259M.
3. ↑ Md Arifuzzaman and H. S. Kim, "Prediction and evaluation of density and volume fractions for the novel perlite composite affected by internal structure formation", Construction and Building Materials, Vol 141, 2017, 201–215.
4. ↑ Celik, Atila Gurhan; Kilic, Ahmet Mahmut; Çakal, Gaye Ö. (2013-02-27). "Expanded perlite aggregate characterization for use as a lightweight construction raw material". https://www.researchgate.net/publication/278069817.
5. ↑ "General Information - Mining Resources - www.minenergy.am". http://www.minenergy.am/en/page/472.
6. ↑ 6.0 6.1 M. Bennett, Shawnna. "USGS Mineral Commodity Summaries - PERLITE". https://prd-wret.s3-us-west-2.amazonaws.com/assets/palladium/production/atoms/files/mcs-2019-perli.pdf.
7. ↑ 7.0 7.1 "Perlite Statistics and Information". https://www.usgs.gov/centers/nmic/perlite-statistics-and-information.
8. ↑ 8.0 8.1 8.2 Wallace P. Bolen Perlite USGS 2009 Minerals Yearbook
9. ↑ Md Arifuzzaman and H. S. Kim, Novel flexural behaviour of sandwich structures made of perlite foam/sodium silicate core and paper skin, Construction and Building Materials, Construction and Building Materials, Vol 148 2017, pp 321–333.
10. ↑ Dipendra Shastri and H. S. Kim, “A new consolidation process for expanded perlite particles”, Construction and Building Materials, Vol 60, June, 2014, pp.1–7.
11. ↑ Moradi, L.; Mirzaei, M. (2019). "Immobilization of Lewis acidic ionic liquid on perlite nanoparticle surfaces as a highly efficient solid acid catalyst for the solvent-free synthesis of xanthene derivatives". RSC Advances 9 (35): 19940–19948. doi:10.1039/c9ra03312b. PMID 35514727. Bibcode: 2019RSCAd...919940M.
12. ↑ Emulsion explosive composition containing expanded perlite United States Patent 4940497
13. ↑ Torabi, Seyed-Fakhreddin; Khajeh, Khosro; Ghasempur, Salehe; Ghaemi, Nasser; Siadat, Seyed-Omid Ranaei (2007-08-31). "Covalent attachment of cholesterol oxidase and horseradish peroxidase on perlite through silanization: Activity, stability and co-immobilization". Journal of Biotechnology 131 (2): 111–120. doi:10.1016/j.jbiotec.2007.04.015. PMID 17658643.
14. ↑ "ISU Extension News Release". iastate.edu. http://www.extension.iastate.edu/newsrel/2004/feb04/feb0429.html.
15. ↑ "Perlite". L'Oréal. https://www.lorealparisusa.com/ingredient-library/perlite.aspx.
16. ↑ Winter, Ruth (2009-10-20) (in en). A Consumer's Dictionary of Cosmetic Ingredients, 7th Edition: Complete Information About the Harmful and Desirable Ingredients Found in Cosmetics and Cosmeceuticals. Potter/Ten Speed/Harmony/Rodale. pp. 402. ISBN 978-0-307-45986-2. https://books.google.com/books?id=3hLmyma2-MsC&q=perlite&pg=PA402.
17. ↑ Perlite , USGS Mineral Commodity Summaries 2011
18. ↑ "PERLITE : (Data in thousand metric tons unless otherwise noted)". https://minerals.usgs.gov/minerals/pubs/commodity/perlite/mcs-2008-perli.pdf.
19. ↑ "Perlite". U.S. Geological Survey Mineral Commodity Summaries: 122–123. January 2006. https://minerals.usgs.gov/minerals/pubs/commodity/perlite/perlimcs06.pdf. Retrieved 2006-09-11.
20. ↑ USGS Mineral Commodity Summaries, 2013, https://minerals.usgs.gov/minerals/pubs/commodity/perlite/mcs-2013-perli.pdf
21. ↑ "CDC – NIOSH Pocket Guide to Chemical Hazards – Perlite". https://www.cdc.gov/niosh/npg/npgd0491.html.

## External links

* The Perlite Institute
* Mineral Information Institute – perlite
* "That Wonderful Volcanic Popcorn." Popular Mechanics, December 1954, p. 136.
* CDC – NIOSH Pocket Guide to Chemical Hazards

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