Which works better, HEDP (hydroxyethylidene diphosphonic acid) or EDTA (ethylenediaminetetraacetic acid)?

HEDP (Hydroxyethylidene Diphosphonic Acid) and EDTA (Ethylenediaminetetraacetic Acid) are both commonly used chelating agents, each with unique characteristics and application advantages, so it is not possible to make a simple judgement as to which is more effective. The following is a detailed comparison of the two:

I. Characteristics and application of HEDP

1. Strong scale inhibition: HEDP can effectively prevent scale accumulation in hard water and high temperature conditions, quickly reduce the carbonate, sulfate and rust in the water and other substances in the pipeline and equipment deposition, to prevent narrow pipelines and equipment clogging.
2. Excellent corrosion inhibition: HEDP can effectively inhibit corrosion of steel, copper, aluminium and other metal materials, reduce the corrosion phenomenon in the water system, and extend the service life of the equipment.
3. Wide-spectrum adaptability: HEDP is suitable for acidic, neutral and alkaline water quality, adaptable and widely used.
4. Environmental protection and economy: HEDP’s high saturation content and low usage can reduce the cost of water treatment and will not pollute the water ecosystem.

HEDP is mainly used in industrial and civil water treatment fields, such as petrochemical, textile, electronics, construction, metallurgy and other industries of water treatment, as well as boiler water treatment, cooling water treatment, oil field water treatment.

Characteristics and application of EDTA

1. Multi-functional chelating agent: EDTA can form stable complexes with most metal ions, preventing discolouration, deterioration, turbidity and other phenomena triggered by metal ions.
2. Heavy metal removal: EDTA is mainly used to remove heavy metal ions in water, such as iron, copper, nickel, manganese, etc., through the formation of stable complexes to make heavy metal ions inactive.
3. Wide range of applications: EDTA is not only used in water treatment, but also in chelation analysis, medical applications (e.g. drug stabilisers), detergents and cleaners, food and beverage industry (e.g. food preservatives and antioxidants, anti-scaling agents in soft drinks), and additives to micronutrient fertilisers.

However, EDTA also has potential side effects. If used in excess, it may cause essential trace elements such as calcium and magnesium to be chelated out of the body, leading to a deficiency of the above elements.

Suggestions for selection

When choosing HEDP and EDTA, it is necessary to choose according to specific application scenarios and needs. If the main concern is scale and corrosion inhibition performance, and environmental protection and economic requirements, HEDP is a better choice. If the main concern is the removal of heavy metal ions and multifunctionality, EDTA is more suitable.