Mineral-based gas adsorbents: the halloysite example

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Published: Friday, 27 June 2014

Halloysite has found niche applications in a variety of industries, and one such example is the use of halloysite nanotubes for gas component adsorption.

By Joachim Schomburg, Tom Conway, Gary Nelson

Different technologies have been developed to remove harmful or foul-smelling gas components from polluted air or industrial gas streams. Physisorption, or physical adsorption, effects of inorganic or organic porous material are widely used within these technologies.

Industrial used inorganic adsorbents are:

- zeolites (synthetic, natural)

- activated smectites (acid activated, organophile)

- diatomaceous earth

Additionally, iron hydroxides (goethite, limonite), titanium oxide (anatase, rutile) and vermiculite are known as adsorbents from the patent literature.

The major properties of mineral adsorbents are:

- pore diameter (0.3 nm-400 nm)

¥ porosity (25-60%)

- specific surface (100-800 m²/g)

- pore volume (0.3-0.7 cm²/g)

Their advantages comparing with organic adsorbents are:

- normally cheaper

- not flammable

- lower temperatures of regeneration (< 300 ºC)

- no or low costs for reusing or deposition of loaded mineral adsorbents




Halloysite granulates as gas adsorbents

In developing the potential of halloysite nanotubes (HNT) for gas component adsorption, several laboratory and pilot plant studies were performed with different types of halloysite materials.

The halloysite materials were used as granulates (1-6 mm), which can be prepared by sieving or compaction of powdered material.

Halloysite reactivity differences depend on the single tube morphology (length, outer and inner diameter), the content and type of accompanying minerals, and the content and type of heavy and trace elements (separate catalytic activity).

In some cases the hydration stage (ratio 10 A - and 7 A - halloysite) seems to be of importance.

The HNT-granulates can be used as single adsorbent material or in combination with low Temperature Plasma Technology for treatment of gas streams or polluted air (WO 2009/125004; WO 2011/128073).

Depending on the type of the adsorbed harmful gas component, three ways of regeneration of loaded HNT-granulates were successfully tested:

- thermal treatment (heating up to 300 ¡C)

- low temperature plasma treatment (up to 80 ¡C)

- oxygen flushing (very short time)

Industrial applications

Halloysite nanotubes can act as an interesting new adsorbent for several gas components. The first industrial scale application has already been put into use.

HNT-adsorbent production will be a part of I-Minerals’ product portfolio based on the Helmer-Bovill Halloysite source located in North-Idaho, USA.





Further reading

[1] MULLER; S.; K. SAULICH & J. SCHOMBURG:

Plasmaregeneration mineralischer Adsorbentien zur Formaldehydabscheidung aus Abgasen von Biogas-Motoren.-

Proc. 7. Bioenergieforum, Rostock 21./22.06.2013, p. 117-125

[2] TYMCZYNA, L. et. al.: Efficacy of a novel biofilter in Hatchery sanitation: II. Removal of odorgenous pollutants.-

Ann. Agric. Environ. Med. 14 (2007), 151-157

[3] OPALINSKI, S. et. al.: Application of selected alumosilicates for ammonia adsorption.- Przemysl chemiczny 88/5 (2009), Univ. Wroclawin, 2-5



I-Minerals Helmer-Bovill project

I-Minerals’ Helmer-Bovil project is located in western Idaho, and the company’s 2013 prefeasibility study highlighted the potential of the property as having an after tax NPV of $150m, 28% IRR, 3 year payback and $67m initial CAPEX.

The prefeasibility study also outlined potential CAPEX of $84m including life of mine sustaining capital over the 26-year mine life.

Work so far has defined an inferred resource of 38.4m tonnes primary clay comprised of an estimated share of 6.6% hallyosite, 16.7% kaolin, 29.7% quartz and 13% K-spar.

In March the US exploration company completed the evaluation of drill core from its 2013 drilling programme. The company expects that the most recent

drilling in the Kelly’s Hump area will increase its halloysite reserves to about 20 years when the prefeasibility study is

updated, up from previous estimates of 10 years made in January 2013.

Relevant data has now been submitted to mining consultant SRK, which designed the programme in collaboration with I-Minerals, for resource modelling, mining planning and reserve calculations.

Resource modelling will take places using drill hole lithologic data, hole coordinates, material balances information, and Scanning Electron Microscopy (SEM) photographs.

This information will then be used to put together a mine plan and calculation of quartz, potassium feldspar (K-spar), kaolinite and halloysite.