LIGNIN PURIFICATION

Disclosed is a process for purifying lignin comprising metal cations. The process comprising the consecutive steps of: (a) providing lignin to be purified by acidifying black liquor， and subsequently separating the thereby formed raw lignin phase (LP3); (b) dissolving the raw lignin phase (LP3) in an acidic， aqueous solvent， at a temperature of at least 50°C， such as at least 60， 70°C， 80°C， or 90°C， to provide a liquid one-phase system (OPS) comprising dissolved lignin; (c) triggering phase separation by diluting the one-phase system by adding water， and/or by lowering the temperature of the one-phase system， to provide a two-phase system， in which two-phase system the first phase is a lignin rich phase (LP1)， and the second phase is a liquid， aqueous phase poor in lignin and comprising metal cations extracted from the lignin; and (d) separating the lignin rich phase (LP1) from the two-phase system to recover purified lignin.