Press Release Back Number(2005)

Hitachi's Air Purifier Incorporating "Circulash" Recycled Coal Ash Material

August 4, 2005
Chubu Electric Power Co., Inc.

Hitachi Home & Life Solutions, Inc. (hereinafter referred to as "Hitachi H&L"; President and Director: Tadahiko Ishigaki; Address: 15-12 Nishi-Shinbashi 2-chome, Minato-ku, Tokyo) has adopted our "Circulash" artificial zeolite product as a deodorizing agent for use in its new air purifiers. Hitachi H&L will begin sales of this new model on August 20.


Hitachi H&L selected Circulash, made from a by-product of thermal power generation (coal ash), determining that use of this material fit perfectly with their corporate mission: the manufacture of reliable consumer home appliances. Once this selection was made, we worked with Hitachi H&L to process Circulash as a deodorizing agent for air purifiers.


Circulash was adopted as a deodorizing agent for Hitachi's new air purifiers following a number of rigorous performance tests, which resulted in the company's enthusiastic approval of the product's performance. Naturally this represents a significant step forward for our artificial zeolite sales business.


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1. Background to adoption of Circulash

One of the features of Circulash is its outstanding deodorizing abilities. In particular, it has the outstanding capacity to adsorb ammonia-a frequent cause of odors in daily life. To adapt Circulash as a deodorizing agent for air purifiers, we carried out joint R&D with Hitachi H&L, as described below.

(1) Enhancement of capacity to adsorb ammonia and other malodorous gases

  1. 1) Capacity to adsorb ammonia
  2. 2)
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    Circulash
  3. 3) Figure 1: Capacity to adsorb ammonia

(2) Development of a granular product similar to activated carbon

  1. 4)
    Circulash for use in air purifiers (left); and in powder form (right)
    Figure 2: Appearance of Circulash

2. Features of Circulash

Most air purifiers use activated carbon, which has a long track record of use in deodorant applications. The major difference between Circulash and activated carbon is found in Circulash's ion-exchange properties.

As shown in Figure 5, Circulash adsorbs ammonia molecules through ion exchange (ammonia molecules are replaced by the ions contained in Circulash).

We received technical guidance for Circulash from Professor Atsushi Yamazaki, Department of Resources and Environmental Engineering, School of Science and Engineering, Waseda University. His comments on this material were as follows:

"An artificial zeolite particle is a spherical cluster of NaP1 zeolite that is mainly composed of crystalline quartz and mullite. Although zeolite is a generic name for a skeleton structure of nanoporous aluminosilicates, NaP1 zeolite in particular features outstanding ammonia adsorption/ion exchange properties.

Zeolite is hydrophilic. Therefore, when used as an adsorbent, it is considered as complementary to carbon, which is usually hydrophobic (and lipophilic)."


  1. 1) Left: Circulash
  2. 2) Right: Activated carbon
  3. 3) Figure 3: Micrographs (equal magnification)
  4. 4) Figure 4: Micrograph of cross section of Circulash
  5. 5) Adsorption through ion exchange
  6. 6) Surface adsorption
  7. 7) Circulash
  8. 8) Figure 5: Conceptual diagram of adsorption