▎ 摘　　要

NOVELTY - Preparing lignin-based nanoadsorbent comprises e.g. filtering the black liquor sample to remove the solid impurity, and adding distilled water to dilute to obtain diluent, adding diluted acid into the diluted solution under the condition of stirring, adjusting the pH and separating out the precipitate, separating to obtain the first-level precipitate and the first-level supernatant, continuously adding diluted acid into the primary supernatant under the condition of stirring, adjusting the pH and separating out the precipitate and separating to obtain secondary precipitate and secondary supernatant, continuously adding diluted acid into the secondary supernatant under the condition of stirring, adjusting pH value of the liquid and separating out precipitate, separating to obtain third-level precipitate and third-level supernatant, washing three-level precipitate by water, drying to obtain raw material lignin, and dissolving the raw material lignin in the organic solvent. USE - The method is useful for preparing lignin-based nanoadsorbent. ADVANTAGE - The method: uses nanospheres to adsorb hexavalent chromium ions in wastewater, can shows good adsorption and the maximum adsorption capacity can reaches to 368.51 mg/g; ensures excellent recycling performance, has a good adsorption effect after repeated use for five times; uses a green and environmentally-friendly organic solvent to prepare the adsorbent, and uses water as the dialysis agent, can be recycle the reagents; and has no pollution, no solvent residues, which provides a high-value utilization of lignin. DETAILED DESCRIPTION - Preparing lignin-based nanoadsorbent comprises (i) filtering the black liquor sample to remove the solid impurity, and adding distilled water to dilute to obtain diluent; (ii) adding diluted acid into the diluted solution under the condition of stirring, adjusting the pH to 6 and separating out the precipitate, separating to obtain the first-level precipitate and the first-level supernatant, continuously adding diluted acid into the primary supernatant under the condition of stirring, adjusting the pH to 4 and separating out the precipitate and separating to obtain secondary precipitate and secondary supernatant, continuously adding diluted acid into the secondary supernatant under the condition of stirring, adjusting pH of the liquid to 2 and separating out precipitate, separating to obtain third-level precipitate and third-level supernatant; (iii) washing three-level precipitate by water, drying to obtain raw material lignin, dissolving the raw material lignin in the organic solvent to obtain the lignin solution; (iv) dispersing graphene oxide in the water to obtain the graphene oxide dispersion liquid; and (v) under the condition of stirring, adding graphene oxide dispersion into the lignin solution to obtain the mixed solution, pouring the mixed solution into the dialysis bag, then placing the dialysis bag in distilled water to remove the organic solvent, freezing and drying. An INDEPENDENT CLAIM is also included for lignin-based nano adsorbent, is prepared by the preparation method.