Preparation and characterization of cellulose-based adsorbent and its application in heavy metal ions removal

•A facile route to prepare a CMF bio-adsorbent for the removal of heavy metal ions in water.•The CMF adsorbent has the advantages in biodegradability and solid-liquid separation.•The inner charges of CMF have a more significant contribution to the adsorption capacity.•It will provide a new strategy for the further modification and improvement of cellulose-based adsorbent. In this work, we develop a facile route to prepare a cellulose-based adsorbent, namely carboxymethylated cellulose fiber (CMF), for the water purification. The as-prepared CMF bio-adsorbent was synthesized via a controllable carboxymethylation modification in the case of maintaining inherent fibrous framework. The CMF bio-adsorbent was applied to adsorb the heavy metal ions, such as Cu(II) and Ni(II), from aqueous solution. Results showed that the CMF adsorbent exhibited excellent adsorption capacity toward these ions and a higher selectivity for the Cu(II) removal based on surface complexation and electrostatic interaction mechanisms. Besides, the adsorption isotherm of Cu(II) fitted better with the Langmuir isotherm model. Moreover, the relationship between the charges and adsorption capacity of CMF to Cu(II) revealed that the enhanced adsorption capacity of CMF adsorbent can mainly attributed to its increased inner charges rather than surface charges, which can provide a new strategy for the further modification of cellulose-based adsorbent.