Removal of toxic indigo blue with integrated biomaterials of sodium carboxymethyl cellulose and chitosan

• Natural biopolymers of NaCMC and CS were combined via amidation reaction.
• CMC-CS-A was used for the adsorption of toxic indigo blue (IB) for the first time.
• CMC-CS-A was a promising adsorbent owing to its interconnected porous structure.
• Adsorption of IB fitted well with Langmuir isotherm and pseudo-second-order model.
• It opened a new avenue for the treatment of wastewater with integrated biopolymers.

Sodium carboxymethyl cellulose (NaCMC) and chitosan (CS) are successfully combined via amidation, and the obtained product, CMC-CS-A, is used for the adsorption of toxic indigo blue (IB) for the first time. The results of control experiments indicate that the adsorption performance of CMC-CS-A is superior to that of NaCMC, CS, and the composites of NaCMC and CS integrated via electrostatic attractions (CMC-CS-E), which can be attributed to the unique interconnected porous network structure of the as-prepared CMC-CS-A. The mass fraction of CS in the CMC-CS-A is also investigated to achieve the best adsorption of IB, and it reveals that satisfactory removal of IB can be achieved at the CMC-CS-A (50 wt%). Important parameters such as contact time, temperature and initial concentration are discussed in detail in this work. Finally, adsorption isotherms and adsorption kinetics are investigated and compared by using classic models, and the results indicate that the adsorption fits well with the Langmuir isotherm model and the pseudo-second-order kinetic model. It opens a new avenue for the effective and convenient treatment of textile wastewater with integrated natural biopolymers.