Abstract: There is provided a process for improving the quality of lignosulfonate at least partly derived form a spent sulfite cooking liquor in at least two steps, comprising: one step in which a lignosulfonate-containing fraction at least partly derived from the spent sulfite cooking liquor is subjected to filtration using a membrane having a cut-off of 40-150 kD (high cut-off) at the pressure, flow rate and temperature of the step and the permeate is recovered; and another step in which a lignosulfonate-containing fraction at least partly derived from the spent sulfite cooking liquor is subjected to filtration using a membrane having a cut-off of 1-20 kD (low cut-off) at the pressure, flow rate and temperature of the step and the retentate is recovered. Products, uses thereof as well as a system are also provided.