Biorefining is a key technology for the sustainable production of chemicals, fuels and energy from abundant lignocellulosic resources. Within the concept, production of micro- and nanoscaled lignin particles recently gained increasing interest due to their excellent properties and potential application in high-value products. Fabricated via direct precipitation of Organosolv extracts, Nanolignin suspensions need to be increased in concentration and cleaned from impurities. Additionally, solvent background needs to be exchanged from hydroalcoholic solution to pure water for most applications. This work focuses on the application of ultrafiltration in diafiltration mode for this separation task. Experimental operation on lab-scale apparatuses demonstrate the reduction of Ethanol and impurities like sugars, dissolved lignin and sugar degradation products accessed by TOC analysis. Most important, the size of Nanolignin particles is not changed during 9 h of operation. Nevertheless, significant performance degradation due to compaction of polymeric membrane material as well as fouling resulting from deposited lignin particles has been monitored. Consequently, a rigorous optimisation of operating pressure and the development of an adequate membrane regeneration procedure is mandatory.