Graphite oxide/chitosan composite for reactive dye removal

Abstract

In the current work a novel composite material consisted of cross-linked chitosan (Ch) and graphite oxide (GO) (and not graphene oxide, as numerous studies deal with) was prepared for the removal of Reactive Black 5 dye. After synthesis, the full characterization with various techniques (SEM/EDAX, FTIR, XRD, DTA, DTG, TGA) was achieved revealing many possible interactions/forces of dye-composite system. Through the latter interactions, the possible adsorption mechanism was elucidated and explained. Also, the adsorption evaluation of the composite material presented high adsorption capacity (277mg/g at 25°C). Equilibrium experiments are also performed studying the effect of pH on adsorption (optimum 2) and desorption (optimum 12), initial dye concentration, contact time (pseudo-first, -second order equations and a generalized fractal kinetic model), temperature (isotherms at 25, 45 and 65°C fitted to Langmuir, Freundlich, Langmuir–Freundlich model) and ionic strength. A full thermodynamic evaluation was carried out, calculating the parameters of enthalpy, free energy and entropy (ΔH0, ΔG0, and ΔS0). The adsorption behavior of the composite material was also compared with the respective of its components (GO and Ch).