Lignosulfonate Glossary: Key Terms Explained

This glossary defines the terms used in lignosulfonate chemistry, specifications and applications, in plain language. Terms are grouped by topic. Each entry is a short definition; follow the links for the full explanation.

Origin and Types

Lignin: The aromatic polymer that binds cellulose fibres in plant cell walls, built from coniferyl, sinapyl and p-coumaryl alcohol units.
Lignosulfonate (lignosulphonate): Water-soluble sulfonated lignin recovered from sulfite pulping, sold as calcium, sodium, magnesium, ammonium or potassium salts.
Sulfite pulping: Wood pulping with sulfite or bisulfite salts; it sulfonates lignin and dissolves it.
Spent sulfite liquor (SSL): The liquor left after sulfite pulping; it contains lignosulfonate, sugars and salts.
Kraft lignin: Lignin recovered from kraft (sulfate) pulping black liquor; not sulfonated and insoluble at neutral pH.
Sulfonated kraft lignin: Kraft lignin that has been sulfonated afterwards, for example by sulfomethylation, to make it water-soluble.
Counter-ion (cation): The metal or ammonium ion balancing the sulfonate charge: Ca, Na, Mg, NH₄ or K.

Composition and Specification

Lignosulphonate content: The share of the dry product that is lignosulfonate polymer, as opposed to sugars, ash and other matter.
Dry matter / solids: What remains after drying; for liquids usually 40–55%.
Reducing sugars: Residual wood sugars that reduce copper reagents; they retard cement and are limited in food and feed grades.
Desugared: Informal term for a lignosulfonate with sugars reduced by fermentation or ultrafiltration.
Ultrafiltration: Membrane separation that keeps large lignosulfonate molecules and removes sugars and salts.
Degree of sulfonation: Sulfonate groups per lignin unit, measured as organic sulfur to methoxyl; JECFA range 0.3–0.7 for food-grade calcium lignosulfonate.

Chemistry and Structure

Weight-average molecular weight (Mw): An average that gives more weight to larger molecules; reported in g/mol.
Polydispersity: Width of the molecular weight distribution; lignosulfonates are highly polydisperse.
Methoxyl group: An –OCH₃ group on the aromatic ring; used to count lignin units.
Guaiacyl / syringyl units: Lignin units with one or two methoxyl groups; softwood is mainly guaiacyl, hardwood has both.
Sulfonate group: An –SO₃^– group; strongly acidic, gives solubility and negative charge.
Carboxyl group: A –COOH group; contributes charge and metal binding, more pH-sensitive than sulfonate.
Phenolic hydroxyl: An –OH on the aromatic ring; involved in antioxidant activity and crosslinking.
Anionic polyelectrolyte: A polymer carrying many negative charges in water; describes lignosulfonate.
Dispersant: An additive that keeps particles separated in a liquid by charge or steric repulsion.

Function in Use

Electrostatic repulsion: Repulsion between particles that carry the same charge after lignosulfonate adsorbs on them.
Binder: An additive that holds particles together after drying, as in pellets, briquettes or ceramics.
Water reducer (plasticizer): A concrete admixture that lowers water demand at equal workability; lignosulfonates are normal-range water reducers.
Set retarder: An admixture that delays cement setting; sugars and some lignosulfonate fractions act this way.
Deflocculant: An additive that thins clay or mineral slurries by dispersing particles.
Chelating / complexing agent: A substance that binds metal ions; lignosulfonate forms weaker complexes than chelates such as EDTA.
Ferrochrome lignosulfonate (FCLS): Lignosulfonate complexed with iron and chromium, used as a drilling-mud thinner.
Chrome-free lignosulfonate: Drilling-mud thinner made without chromium.
Ash: Inorganic residue after burning; includes the cation and salts.

Data Sheets and Identity

Water-insoluble matter: Undissolved residue, often fibre or salts; low values mean a cleaner product.
Sulphate (SO₄): Inorganic sulfate in the product, from pulping chemicals.
pH (10% solution): pH of a defined solution; differs by cation and processing.
Hygroscopic: Absorbs moisture from air; lignosulfonate powders cake if stored open.
TDS: Technical data sheet: typical values and use guidance.
COA: Certificate of analysis: measured values for a specific batch.
SDS / MSDS: Safety data sheet: hazards, handling and transport information.
CAS number: Chemical Abstracts Service identifier, e.g. 8061-52-7 (calcium lignosulfonate), 8061-51-6 (sodium lignosulfonate), 8061-54-9 (magnesium lignosulfonate).
1g565: EU identification number of lignosulphonate as a feed binder (Regulation (EU) 2024/749).

Frequently Asked Questions

What is the difference between lignin and lignosulfonate?

Lignin is the natural polymer in wood. Lignosulfonate is lignin that has been sulfonated and dissolved during sulfite pulping, which makes it water-soluble and negatively charged.

What is the difference between a TDS and a COA?

A TDS gives typical values for a grade; a COA gives the measured values of one specific batch.

Is lignosulphonate the same as lignosulfonate?

Yes. “Lignosulphonate” is the British spelling and “lignosulfonate” the American spelling of the same material.

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