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Presidential Green Chemistry Challenge: 2001 Greener Synthetic Pathways Award

Bayer Corporation

Bayer AG (technology acquired by LANXESS)


BaypureTM CX (Sodium Iminodisuccinate): An Environmentally Friendly and Readily Biodegradable Chelating Agent


Innovation and Benefits: Chelating agents are ingredients in a variety of products, such as detergents, fertilizers, and household and industrial cleaners. Most traditional chelating agents do not break down readily in the environment. Bayer Corporation and Bayer AG developed a waste-free, environmentally friendly manufacturing process for a new, biodegradable, nontoxic chelating agent. This new process eliminates the use of formaldehyde and hydrogen cyanide.

Summary of Technology: Chelating agents are used in a variety of applications, including detergents, agricultural nutrients, and household and industrial cleaners. Most traditional chelating agents, however, are poorly biodegradable. Some are actually quite persistent and do not adsorb at the surface of soils in the environment or at activated sludge in wastewater treatment plants. Because of this poor biodegradability combined with high water solubility, traditional chelators are readily released into the environment and have been detected in the surface waters of rivers and lakes and in make-up water processed for drinking water.

As part of its commitment to Responsible Care®, Bayer Corporation manufactures a readily biodegradable and environmentally friendly chelating agent, D,L-aspartic-N-(1,2-dicarboxyethyl) tetrasodium salt, also known as sodium iminodisuccinate. This agent is characterized by excellent chelation capabilities, especially for iron(III), copper(II), and calcium, and is both readily biodegradable and benign from a toxicological and ecotoxicological standpoint. Sodium iminodisuccinate is also an innovation in the design of chemicals that favorably impact the environment. This accomplishment was realized not by "simple" modification of molecular structures of currently used chelating agents, but instead by the development of a wholly new molecule. Sodium iminodisuccinate is produced by a 100 percent waste-free and environmentally friendly manufacturing process. Bayer AG was the first to establish an environmentally friendly, patented manufacturing process to provide this innovative chelant commercially.

Sodium iminodisuccinate belongs to the aminocarboxylate class of chelating agents. Nearly all aminocarboxylates in use today are acetic acid derivatives produced from amines, formaldehyde, sodium hydroxide, and hydrogen cyanide. The industrial use of thousands of tons of hydrogen cyanide is an extreme toxicity hazard. In contrast, Bayer's sodium iminodisuccinate is produced from maleic anhydride (a raw material also produced by Bayer), water, sodium hydroxide, and ammonia. The only solvent used in the production process is water, and the only side product formed, ammonia dissolved in water, is recycled back into sodium iminodisuccinate production or used in other Bayer processes.

Because sodium iminodisuccinate is a readily biodegradable, nontoxic, and nonpolluting alternative to other chelating agents, it can be used in a variety of applications that employ chelating agents. For example, it can be used as a builder and bleach stabilizer in laundry and dishwashing detergents to extend and improve the cleaning properties of the eight billion pounds of these products that are used annually. Specifically, sodium iminodisuccinate chelates calcium to soften water and improve the cleaning function of the surfactant. In photographic film processing, sodium iminodisuccinate complexes metal ions and helps to eliminate precipitation onto the film surface. In agriculture, chelated metal ions help to prevent, correct, and minimize crop mineral deficiencies. Using sodium iminodisuccinate as the chelating agent in agricultural applications eliminates the problem of environmental persistence common with other synthetic chelating agents. In summary, Bayer's sodium iminodisuccinate chelating agent offers the dual benefits of producing a biodegradable, environmentally friendly chelating agent that is also manufactured in a waste-free process.

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