Teijin Fibers Develops Epochal Soil Cleaning Technology
As a result of the Soil Pollution Control Law, which came into effect last February, the liabilities associated with polluted land have substantially increased. Conventional processes for treating contaminated soil do not remove heavy metals. Teijin's method, however, is based on its unique new technology, selectively removing and recovering heavy metals pollutants on-site, then cleaning and replacing the cleaned soil on-site. Moreover, recovered heavy metals become recyclable with the new process, and the risk of secondary pollution is therefore eliminated.
The new process has been developed by Teijin Fibers Limited, the core company of the Textile Fibers Business Group of the Teijin Group, in cooperation with Ehime University (Assistant Professor Hiroshi Yamashita, Department of Applied Chemistry, Faculty of Engineering). It is a new application of Teijin's secondary waste processing technology, used in the highly advanced chemical recycling of polyester products in soil cleaning. This new application now extends that recycling technology to include inorganic compounds, in addition to organic compounds, through "Highly Advanced Chemical Recycling".
1. Background of Technological Development
- Teijin Fibers Limited has been steadily developing the capacity to recycle organic parts from polyester products, and launched its "Highly Advanced Chemical Recycling" system at the Tokuyama factory in April, 2002 with the goal of complete recycling of polyester products. Teijin Fibers started a full-scale "Fiber-to-Fiber" recycling process implementation from July of last year, and will launch the world's first commercial PET "Bottle-to-Bottle" chemical recycling operation this autumn.
- "Highly Advanced Chemical Recycling" is an original technology
developed by the Teijin Group that recovers high quality polyester raw
materials from used polyester products such as fiber products and PET
bottles, among others. This was achieved by separating and removing the
various dyestuff and additives contained in the catalyst metals used in
the manufacturing processes of polyester products and final products.
Teijin Fibers is developing technology that can separate, refine and
recover useful components from the removed materials. The aim is to reduce waste as much as possible and reuse these components through recycling. The company has succeeded in developing and applying the capability to recover heavy metals from the soil based on its metal compound recovery technology.
- The soil pollution problem is becoming increasingly apparent
nationwide, and the costs of soil cleaning have been estimated at 11
trillion yen by the Geo-Environmental Protection Center, a corporation in public interest. Immediate measures are required.
- The February 2003 Soil Pollution Control Law has now set standards for the content level of contaminants. As a consequence, technology that can effectively decrease the amount of contaminants in soil on-site without removing the polluted soil is in very strong demand.
- To meet this demand, Teijin Fibers extended in-house technology to develop an epochal on-site soil cleaning technology.
- This new soil cleaning technology extracts heavy metals contaminating the soil by chemical means using a unique technology called "precipitate flotation". This process causes heavy metals in the soil to precipitate with iron elements contained in the soil, then separates and recovers them.
- This extraction technology makes it possible to remove all regulated heavy metals from polluted soil and actively control the cleaning degree, from set Environmental Quality Standards for Soil Pollution levels to completely pollutant-free levels. This technology also makes it possible to select the heavy metals to be removed by setting and controlling the extraction standards.
- The technology allows for the separation of polluted soil into "clean soil" and "heavy metals." Clean soil can be buried back on-site, and the recovered heavy metals can be reused, creating a virtuous recycling of materials.
- Because the device is compact it is possible to treat the polluted
soil on site. This enables prevention of contaminated soil from dropping and abandonment to outside during transporting of polluted soil, and alleviates the risk of secondary pollution.
- The extraction technology allows for the removal of chlorinated
hydrocarbon compounds and other organic compounds, as well as heavy
- In addition to soil cleaning, the technology can be applied to the
detoxification of fly ash (extraction of heavy metals), as well as to the treatment of wastewater containing heavy metals.
- Ten patent applications related to this technology have been filed.
- The outline of the new soil cleaning process is attached.
Methods 1- 7 below represent the conventional processes for treating soil pollution. Compared to these technologies, the new technology has superior characteristics of reducing heavy metal content, treating the polluted soil on-site without transporting it to an outside venue, and working on more kinds of heavy metals.
- Digging method to remove contaminated soil
With this method the polluted soil is dug up and carried away and the site is then refilled with clean soil. This method merely removes the contaminated substances to another site and does not solve the underlying problem. In addition, because it is then necessary to contain the transported polluted soil in a controlled waste landfill site, responsibility remains with the producer of the waste materials. This also raises subsequent environmental issues due to the lack of landfill sites.
- Solidification method
This method solidifies polluted soil (example: crystallizing into glass, etc.) to control elution. Because the pollutants remain, the site treated in this fashion is listed on as an assignment area in government records, which requires continued monitoring for a certain period of time. This is a not a preferred solution because solidified soil is difficult to re-use.
- Insolubilization method
This is a method of preventing the elution of heavy metals, by mixing these metals with insolubilization agents. As with the solidification method, a site treated in this fashion is also listed as an assignment area in government records and requires continued monitoring for some period of time.
- Soil washing with classification method
This is a method for sorting and removing fine particles, thereby lowering the contamination level of the remaining soil. This method is based on the theory that the degree of contamination of fine particles is high. However this method has limited application, depending on the properties of the soil and the overall level of contamination. Furthermore the separated fine particles need to be transported off-site as waste, and then monitored.
- Heat-treating method
This method involves heating polluted soil in specialized equipment, evaporating pollution compounds and removing these from the soil. This has limited application, being useful only for heavy metals with comparatively low boiling points, such as mercury and lead, etc.
This is a method that makes use of microorganisms. This method is applicable for the treatment of organic contaminants such as trichloroethylene, but is not effective for heavy metals. Moreover, the entire cleaning process requires a long time.
- Oxidative decomposition method
This is a method to convert polluted soil into a harmless compound using an oxidant. As with the bioremediation method, this method is applicable only to organic pollutants such as trichloroethylene, and is not effective for heavy metals.
The Teijin Group will continue to study and develop its polluted soil cleaning business and this technology. Further, the Teijin Group is considering the possibility of alliances with other companies.
About Teijin Ltd.
Teijin Limited (TSE: 3401), established in 1918, was the first Japanese company to produce rayon yarn, and has remained an innovator and leader in the development and commercialization of fibers. Since then, the Company has capitalized on its expertise in fibers to diversify into other fields. Today, the Company's operations encompass five segments: Fibers and Textiles; Films and Plastics; Pharmaceuticals and Home Health Care; Machinery and Engineering; and New Products and Other Businesses. At present, Teijin is utilizing its proprietary technologies to expand into promising new areas, notably health-care products and services, advanced materials and IT-related products. During its 83-year history, Teijin has grown from a small domestic venture into a major multinational enterprise. The Company has production and sales subsidiaries and affiliates in more than 10 countries. The parent company also has six overseas offices, as well as four plants and three research institutes in Japan.