**4. Conclusions**

In conclusion, cationic lignocellulose nanofibers (CLCNF) with nanoscale diameters and quaternary ammonium group contents in the range of 0.97–1.76 mmol/g were successfully prepared by cationic modification of bagasse in deep eutectic solvents (DES) followed by mechanical defibrillation. Such lignocellulosic nanomaterials showed excellent adsorption performance in removing dissolved and colloidal substances (DCS) model contaminant polygalacturonic acid (PGA). The cationic modification in DES changed the surface charge of bagasse from negative to positive and obtained a large number of active adsorption sites, so CLCNF can easily adsorb the negatively charged PGA in water. Electrostatic interactions were considered as the main mechanism for capturing PGA by CLCNF in water. The kinetic process of PGA adsorption by CLCNF can be predicted by a pseudo-second-order model and the Langmuir model fitted the data well, indicating monolayer adsorption. The CLCNF adsorbent in current research has the advantages of low cost, high efficiency and large adsorption capacity, which can meet the new demand of DCS adsorbents. It is expected to be used for the adsorption of other anionic contaminants in water.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/polym14050910/s1, Figure S1: Optical microscope images of bagasse (A), the precursors of LCNF, CLCNF-1, CLCNF-2, and CLCNF-3 (B–E); Figure S2: Separation factor of PGA adsorption by CLCNF-3.

**Author Contributions:** Methodology, L.Y.; formal analysis, L.Y., X.L. and Y.J.; investigation, X.Z., L.Y., Y.J., H.Z. and G.C.; data creation, X.Z. and S.Z.; writing original draft preparation, L.Y.; writing review and editing, X.L. and Y.J.; supervision, X.L.; project administration, S.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research was supported by the China Postdoctoral Science Foundation (2020M683209), the Natural Science Foundation of Guangxi (2020GXNSFBA159009, 2021GXNSFBA075043, 2018GXNS-FAA138126), the Opening Project of Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control (2019ZR04, 2019KF28), the Scientific Research Foundation of Guangxi University for Nationalities (2019KJQD10), Guangxi Ba-Gui Scholars Program, the Guangxi Major Projects of Science and Technology (GXMPSTAB21196064) and the Specific Research Project of Guangxi for Research Bases and Talents (AD18126002).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare that they have no conflict of interest.
