(Japan PatentNo.3961558)

Createrra Inc., 6-39-18, matsubara, Setagaya-ku, Tokyo 156-0043,Japan
Tel:03-5300-2501, Fax:03-5300-8287, e-mail：kaihatsu@createrra.co.jp

Japanese | English

Introduction

　Arsenic (As) in drinking water or staple foods will cause arsenism, cancer and sometimes even death of the human.
　The arsenism has been spreading in South Asia, Southeastern Asia and Inner Mongolia owing to agricultural development through irrigation using water from deep wells or to the tin mining. In both cases, an As-mineral (arsenopyrite: FeAsS) in the depth is oxidized to release water-soluble As compounds (arsenious acid, arsenic acid) when the groundwater level is lowered by the active drawing up of water from the well or the detritus carried out from the mine is exposed to the air. In addition, the water in the tin-mining area is often enriched with Pb ion, another toxic

　As-Catch2 is a newly formed As-adsorbent for cleaning up the water polluted with As. Its ability to absorb As(III) as well as As(V) is about 10 times higher than that of the As-adsorbent that has been claimed to be as the most efficient As-adsorbent in the world.
　Clean up of water is urgently required in these As-polluted areas. However, existing methods are too costly or too troublesome or too large in scale for family use, especially in developing countries. In addition, these methods are ineffective for removing arsenious acid and cause the problem of disposing the residues containing As. As-catch can provide the methods to meet this urgent and complicated requirement.
　As-catch makes possible for the family to establish various simpler, cheaper and smaller in scale methods to completely detoxicate the water under varying conditions in the As-polluted areas. As-catch solves also the public problems of disposing the residues.
　The As-catch is a new inorganic material synthesized from a volcanic ash soil, ferrous sulfate and calcium hydroxide. It has high ability to adsorb the water-soluble arsenious and arsenic acids and Pb ion.

Some properties of As-Catch2

1. Adsorption isotherm of As
Because of exceptionally high ability of As-Catch2, water containing As at high level can be easily cleaned to 5ppb(As 5mg/L). Fig.1 shows adsorption isotherms of As(V) and As(III) on As-Catch2. Fig.2 shows the ability of As-Catch2 is more than 10 times higher than that of effective As-adsorbents so far known

Fig.1 Adsorption isotherm of As(V) and As(III) on As-Catch2 (pH 7.0, 20℃,with 20mgAs/L)

Fig.2. Adsorption isotherm of As(V) on As-Catch2 and other effective As-adsorbents (Data of As-Catch2 are plotted on a figure of “Arsenic Removal with Agglomerated Nanoparticle Media”, AWWA Research Foundation which shows commercially available nanopowder with the highest arsenic adsorption capacity from screening experiments.)

2. Adsorption rate of As

　As shown in Fig.3, adsorption rate of As on As-Catch2 is very high. This permits rapid flow (SV10) through an As-Catch column for cleaning up the water polluted with As. In other words, a small As-Catch column is sufficient for providing clean water to any family.

Fig.3 Adsorption rate of As(V) and As(III) on As-Catch (As: 20mg/L. As-Catch2: 10g/L, 20℃)

3. Effect of pH on adsorption of As

The high ability of As-Catch2 to adsorb As (V) and As(III) is kept in the pH range of 3～9. This implies that almost all the water polluted with As can be effectively cleansed with As-Catch2.

Fig.4 　Effect of pH on ability of As-Catch2 to adsorb As
(As: 20mg/L, As-Catch2: 10g/L. after shaking for 1 hr.)

4. Effects of coexisting ions on the ability of As-Catch2

All the coexisting ions examined do not affect the ability of As-Catch2 as shown in Table 1. This is desirable for cleaning up the water polluted with As, because the water usually contains these ions.

As(V): 20mg/L As(III): 20mg/L As-Catch2: 10g/L

Table 1 Effects of coexisting ions on the ability of As-Catch2

5. pH of the polluted water after treatment with As-Catch2

Prolonged treatment of polluted water by percolating through an As-Catch2 column does not change pH of the water (Fig.5).

Fig.5 Change in pH of the water treated with As-Catch2 for a long period.

6. Prolonged use of As-Catch2

As-Catch2 can be used for a long period. For example, 40L of water containing As (0.1mg/L) can be completely purified every day in a year by percolating through a column packed with 200g of As-Catch2. Fig.6 shows data of a prolonged percolation experiment for water containing As (As(V):0.31mg/L ,As(III): 0.65mg/L).

Fig.6 Change in As content of the water treated with As-Catch2 for a long period.

7. Chemical and physicochemical properties of As-Catch2

As-Catch2 is composed of pellets (mainly 0.1~0.3mm in diameter) which are actually aggregates of tiny particles (about 0.7μｍ in diameter) consisting chiefly of amorphous ferric hydroxide (Fig.7,Table 2) that is produced by a novel technology, and does not contain any toxic substances (Table 2).

Table 2 Effects of coexisting ions on the ability of As-Catch2

Fig.7 X-ray of As-Catch2 　　 Fig.8 Electron micrograph of As-Catch2

Advantages of As-Catch2 for cleaning As-polluted water
As-Catch2 has the following many advantages when used for cleaning up instruments:
	1)　The polluted water containing As at high level can be easily cleaned to 5ppb.
	2)　As(III) in the polluted water can be effectively removed without its pre-oxidation into As(V).
	3)　pH-adjustment of the polluted water is unnecessary before its treatment.
	4)　Co-existing ions in the polluted water do not affect removal of As.
	5)　The polluted water can be treated well by percolating though As-Catch2 at high flow rates (e.g. SV10) so that small size system is sufficient not only for family use but public use.
	6)　As-Catch2 can be used for a long period to make its renewal expense is small.
	7)　As-Catch2 saturated with As by prolong use can be safely disposed after easily removing the adsorbed As.

Createrra

HOME > English TOP > As-Catch 2