Chelating agents (also called sequestering agents) are compounds that form complexes with metal ions, rendering them more soluble and less likely to precipitate as solid salts. These agents are used in a wide variety of applications, including water treatment, detergents, personal care products, and industrial processes.
Here is a list of common chelating agents, categorized based on their chemical structures and applications:
1. Phosphonates
These chelating agents are widely used for water treatment, scale control, and detergents.
HEDP (1-Hydroxyethylidene-1,1-diphosphonic acid)
ATMP (Aminotris(methylenephosphonic acid))
DTPMP (Diethylenetriaminepenta(methylenephosphonic acid))
EDTMP (Ethylene Diamine Tetra Methylene Phosphonic Acid)
DTPMPA (Diethylenetriaminepenta(methylenephosphonic acid) sodium salt)
IDS-Na₄ (Tetrasodium Iminodisuccinate)
2. Amino Acids and Their Derivatives
These are naturally occurring chelators or synthetic derivatives, often used in agriculture, personal care, and food processing.
EDTA (Ethylenediaminetetraacetic acid)
DTPA (Diethylenetriaminepentaacetic acid)
NTA (Nitrilotriacetic acid)
IDA (Imidodiacetic acid)
MGDA (Methylglycinediacetic acid)
GLDA (Glutamic acid diacetic acid)
TSP (Tetra sodium pyrophosphate)
3. Hydroxycarboxylic Acids
These agents often form stable complexes with metal ions and are used in both industrial and household applications.
Citric Acid
Lactic Acid
Malic Acid
Tartaric Acid
Fumaric Acid
4. Polycarboxylates and Polyphosphates
These agents are used in detergents, cleaning products, and water treatment to prevent scale and improve cleaning efficiency.
Polyacrylic Acid (PAA)
Sodium Gluconate
Sodium Tripolyphosphate (STPP)
Polyaspartic Acid
5. Organic Acids and Their Salts
These chelators are often used in food, pharmaceuticals, and environmental applications.
Oxalic Acid
Tartaric Acid
Acetic Acid (and its salts)
Succinic Acid
6. Amino Alcohols
These agents are used in water treatment and as dispersants in various industries.
Ethylenediamine
Diethylenetriamine
Triethanolamine
7. Nitrogen-Containing Chelators
These chelating agents contain nitrogen atoms and are often used in heavy metal ion removal, water treatment, and pharmaceuticals.
EDDS (Ethylenediamine-N,N’-disuccinic acid)
TTHA (Tetra(hydroxypropyl)ethylenediamine)
L-ascorbic acid (Vitamin C)
8. Organic Phosphorus Compounds
These are often used for water treatment and as scale inhibitors in industrial processes.
Phosphonates (like HEDP, ATMP, and DTPMP)
Polyphosphates (e.g., Sodium Hexametaphosphate)
9. Other Complexing Agents
These chelators are used in specialized applications like cleaning, metal extraction, or pharmaceuticals.
Crown Ethers (e.g., 18-Crown-6)
Lignosulfonates
Chitosan
Sodium Alginate
Applications of Chelating Agents
Water Treatment: Chelating agents like EDTA, HEDP, and DTPMP are used to control scale formation in industrial systems, such as boilers, cooling towers, and pipelines.
Detergents and Cleaning Products: Agents like Citric Acid, EDTA, and MGDA are added to laundry detergents, dishwashing liquids, and surface cleaners to prevent mineral buildup and improve cleaning efficiency.
Agriculture: Chelators like EDTA and DTPA are used in fertilizers to enhance the solubility of metal micronutrients (e.g., iron, zinc) and improve their uptake by plants.
Personal Care: EDTA and Citric Acid are commonly found in shampoos, conditioners, and skin care products to protect against hard water effects, such as dryness and mineral residue buildup.
Food and Beverage: EDTA and Citric Acid are commonly used to preserve color and flavor, prevent spoilage, and improve the stability of food products by binding metal ions.
Pharmaceuticals: Chelating agents are used in medicine for heavy metal detoxification, such as the treatment of lead poisoning (using EDTA).
Conclusion:
Chelating agents play a crucial role in many industries by improving the efficiency of water treatment, detergents, agricultural fertilizers, cleaning products, and even pharmaceuticals. The most commonly used chelating agents include EDTA, DTPA, HEDP, Citric Acid, and IDS-Na₄, with each suited for specific applications based on the metal ions they are designed to sequester and the conditions they are used under.