Chitosan Modified Sawdust-Derived Cellulose Nanocrystals as Green Coagulant for Erichrome Black T

Cellulose nanocrystals (CNC) obtained from sawdust were modified with chitosan (CHT), as green coagulant (CNC/CHT) for the removal of Erichrome black-T (EBT) dye from aqueous solution. The pristine CNC, CNC/CHT and CNC/CHT-EBT floccules formed after the coagulation process were characterized by different techniques. The diffraction pattern of CNC/CHT showed peaks for both CNC and CHT, therefore, confirmed the co-regeneration of cellulose–chitosan mixing. In addition, the band at 1586 cm⁻¹ found in the infra-red spectrum of this composite, which was attributed to the NH bending of primary amine, and a major functional group of the chitosan, was an indication of the incorporation of chitosan with the CNC. Three different ratios of the CNC:CHT were explored in order to determine the best modification regime for EBT coagulation. Different parameters, including solution pH, coagulant dosage, settling time, initial dye concentration and effect of material ratios were studied. The maximum coagulation of 99.9% was achieved at the optimum pH value of 2.10 using 100 mg/L of EBT concentration. Overall, the performance achieved using the green synthesized CNC/CHT, within the maximum settling time of 30 min, confirmed the efficiency and cost effectiveness of this coagulant for the removal of EBT from water.