Lignin-based nano adsorbent and preparation method thereof

The invention discloses a lignin-based nano adsorbent and a preparation method thereof. Dilute acid such as sulfuric acid is used to adjust the pH value of papermaking black liquor step by step to enable lignin to be subjected to fractional precipitation, and lignin with different phenolic hydroxyl group contents is obtained. Lignin separated out when the pH value is 2 is selected as a raw material, the lignin is compounded with graphene oxide through a simple self-assembly method to obtain a lignin-based nano adsorption material, namely lignin- graphene oxide nanospheres. The nanospheres areused for adsorbing hexavalent chromium ions in wastewater, a good adsorption effect is shown, the maximum adsorption capacity can reach 368.51 mg/g, the recycling performance is excellent, and a goodadsorption effect can still be achieved after the nanospheres are repeatedly used for five times. Besides, the adsorbent is prepared by using a green and environment-friendly organic solvent, water isused as a dialyzing agent,