The present invention relates to a process for purifying, such as salt/ion depletion, and/or ash reduction, and/or sulphur removal, and/or free sugar depletion, and/or VOC depletion or fractionating, preferably by using dewatering, of a slurry comprising a lignin or lignin derivative or a combination thereof. A lignin or lignin derivative obtainable from said process and uses thereof are also disclosed.