Abstract: Three lignosulfonate fractions(LG-1, LG-2 and LG-3) were obtained by ultrafiltration with two cut-off molecular weight membrane of 6 000 and 20 000 u. The yield, purity, molecular weight and hydrophilic group content of lignosulfonate fractions were characterized and the performances of lignosulfonate fractions as dust suppressant were also compared. The results showed that ultrafiltration could effectively fractionate the lignosulfonate and the yields of LG-1, LG-2 and LG-3 were 58.32%, 24.50% and 17.18%, respectively. The weight average molecular weights of the three fractions were 4 841, 15 239 and 37 768 and the polydispersities were 2.78, 2.40 and 2.06, respectively. With the increase of lignosulfonate molecular weight, the ash and sulfonic acid group content decreased while the total sugar content increased. The ultrafiltration fractionation had significant effects on the performance of lignosulfonate as dust suppressant. With the increase of molecular weight cut-off, the water absorption capacity, compression strength and anti-wind erosion ability of lignosulfonate increased by 96.43%, 55.11% and 63.07%, respectively, which suggested that lignosulfonate fraction LG-3 with higher molecular weight performed better as dust suppressant. SEM analysis suggested that after spraying of lignosulfonate solution, a bonding layer was formed between sand grains and played the role of cohesiveness and incrustation for the sand grains. Moreover, the phenomenon was more obvious with the increase of lignosulfonate molecular weight.

Key words: lignosulfonate, molecular weight, fractionation, performance of dust suppressant