Tetrasodium Iminodisuccinate: A Biodegradable Hydrogen Peroxide Stabilizer for Pulp Mills

The Peroxide Stability Challenge in Pulp Bleaching

Anyone who works in pulp bleaching knows the problem. Hydrogen peroxide is the standard bleaching agent for mechanical pulps and recycled fibres. It is effective, chlorine-free, and relatively economical . But it has a well-known weakness.

Trace metal ions—particularly iron, manganese, and copper—catalyse the decomposition of hydrogen peroxide . Instead of bleaching the pulp, the peroxide breaks down into oxygen and water before it can do its job. Mills end up using more peroxide, chasing brightness targets, and dealing with higher chemical costs.

Traditional chelating agents like EDTA and DTPA solve the problem. They sequester those metal ions and keep the bleach stable. The trouble is, EDTA and DTPA are non-biodegradable or only poorly biodegradable . They persist in the environment, and with tightening regulations across Europe, pulp mills are under pressure to find alternatives that actually work .

Tetrasodium iminodisuccinate (IDS-Na4) offers a way forward. It stabilises peroxide, chelates transition metals, and biodegrades completely . No trade-offs. Just chemistry that fits the new reality.

What Is Tetrasodium Iminodisuccinate?

IDS-Na4 is a biodegradable chelating agent based on iminodisuccinic acid. It belongs to the same family as MGDA and GLDA—chelates designed to replace persistent alternatives .

Basic specifications:

The key difference from EDTA is structural. IDS has a different molecular backbone that allows microorganisms to break it down quickly. But it still chelates calcium, magnesium, iron, copper, and manganese effectively .

How IDS Works in Pulp Bleaching

In peroxide bleaching, the problem is catalytic decomposition. Metal ions like Fe³⁺ and Mn²⁺ accelerate peroxide breakdown . IDS prevents this by forming stable complexes with those metal ions, rendering them inactive .

The pulp industry calls this the "Q stage"—a chelation step before the peroxide stage . Pulp is mixed with the chelating agent at 60–80°C for about an hour. Then the peroxide is added . The difference is measurable.

What IDS delivers in practice:

• Improved bleaching efficiency. By controlling metal ions, IDS improves peroxide utilisation .

• Higher brightness. Studies show IDS achieves equivalent or better brightness than EDTA, with reported whiteness improvements of 2–4% .

• Better fibre strength. Research found tensile index improvements of 5–6% and burst index improvements of 20–23% when IDS replaced EDTA .

• Less yellowing over time. IDS prevents iron from reacting with phenolic groups in the pulp, which would otherwise form dark-coloured compounds .

IDS vs EDTA: Performance Comparison

A comparative study on bagasse pulp put IDS side by side with EDTA :

The performance is essentially identical. The environmental profile is not .

Beyond Bleaching: Scale Control

Metal ions do not just affect bleaching. They also form deposits—calcium oxalate, calcium carbonate—on equipment surfaces. These deposits reduce heat transfer, restrict flow, and increase maintenance downtime .

IDS prevents this by chelating the hardness ions before they can precipitate . It is described as a "medium strong chelating agent with a well-balanced calcium- and heavy metal binding capacity" and is effective as both a water softener and a bleaching agent stabiliser .

Regulatory Alignment

European pulp mills are under pressure from multiple directions. The EU Industrial Emissions Directive, water framework directives, and retailer sustainability standards all point in the same direction: reduce persistent chemical use.

IDS is compliant with EU Ecolabel criteria and meets REACH requirements for biodegradability . EDTA and DTPA are not readily biodegradable . For mills supplying paper products to eco-conscious brands or markets with strict environmental procurement policies, that difference is decisive.

Practical Application

Typical use levels in bleaching baths: 0.8–1.2% of dry pulp mass in the chelation stage .

Form: Available as a liquid (34–40% solution) or solid granules . The liquid form is easier to dose in continuous bleaching lines.

Process conditions: Chelation temperature 60–80°C, reaction time 50–70 minutes .

Compatibility: IDS works with hydrogen peroxide and other bleaching chemicals. It is compatible with enzymes and shows good stability across pH and temperature ranges .

The Bottom Line

Tetrasodium iminodisuccinate does what EDTA does—just without the environmental persistence . It stabilises peroxide, controls metal ions, prevents deposits, and delivers comparable brightness and fibre strength. And it biodegrades.

For European pulp mills facing regulatory pressure and sustainability targets, IDS is a practical, proven alternative. It is available at scale, works in existing processes, and removes a compliance headache that is only going to get worse.