Abstract: The sulfonate composition of the industrial grade sodium lignosulfonate was analyzed and determined using Thermal Gravimetric Analysis,Multifunction Membrane,Atomic Absorption methods and advanced polymer chromatography.Analysis results showed that sodium lignosulfonate mainly contained sodium and potassium cations.Molar contents of the three ions including sodium,potassium and SO₃^2- in each gram of sodium Lignosulfonate were 2.138 mmol,0.197 mmol,2.348 mmol,respectively.Thus there were 222.352 mg of sodium sulfonate and 23.64 mg of potassium sulfonate within 1gram of lignosulfonate,about 24.7wt % in total sodium lignosulfonate.Membrane separation experiment showed that products were well separated into four fractions.Two fractions of molecular weight of 3500 to 15000 and more than 15000 presented major characteristic peaks of lignin related to depolymerized lignosulfonate;while that of fractions with low molecular weight of 3500 to 600800 and less than 600-800 mainly presented characteristic peaks of residual sugars from the hydrolysis of semi-cellulose.

Key words: sodium lignosulfonate, atomic absorption spectrophotometer, advanced polymer chromatography, membrane separation