Properties of Different Molecular Weight Sodium Lignosulfonate Fractions as Dispersant of Coal‐Water Slurry

Four purified sodium lignosulfonate (SL) samples with different molecular weights were prepared by fractionation using ultrafiltration. The effect of the molecular weights of SL on the apparent viscosity of coal‐water slurry (CWS) was investigated by studying the adsorption amounts and the zeta potentials in the coal‐water interface. The results show that the adsorption behavior of the dispersants in the coal‐water interface is the key factor to affect the dispersing effect, that the higher adsorption amount and compact adsorption film help reduce the viscosity reduction of CWS, and that the zeta potential is also an important factor influenced by the sulfonic group and carboxy contents of the lignosulfonate molecule. Furthermore, SL with a molecular weight ranging from 10000 to 50000 has both a higher adsorbed amount and zeta potential on the coal surface and the best effect on reducing the viscosity of the coal‐water slurry.

Keywords:

• Sodium lignosulfonate (SL)
• molecular weight
• coal‐water slurry (CWS)
• dispersant

Acknowledgments

The authors express their sincere thanks to Professor Hongbin Ji for his very valuable suggestions. The authors would like to gratefully acknowledge the financial support of the National Natural Science Foundation of China (20276024) and National Natural Science Major Foundation of Guandong Province (05103536).