Triphenylene-modified chitosan: novel high efficient sorbent for cationic and anionic dyes

The first example of triphenylene-modified chitosan 4 was prepared by reacting chitosan with triphenylene aldehyde derivative 3. Its structure and morphology was characterized by elemental analysis, ¹H NMR, FTIR, XRD, SEM and AFM image. The triphenylene units in Tp-chitosan 4 appended on the skeleton of chitosan and possessed orderly layered structure. Adsorption experiments of Tp-chitosan 4 indicated that it possessed excellent adsorption capacities for both cationic and anionic dyes [Orange G sodium salt, Brilliant ponceau 5R, Victoria blue B (VB), Crystal violet (CV), Neutral red (NR) and Methylene blue]. The highest adsorption capacities for CV, VB and NR were 5.612, 5.353 and 5.375 mmol/g, respectively. Adsorption kinetics and isotherms analysis showed that the adsorption processes obeyed pseudo second-order model and the Langmuir isotherm equation. The adsorption processes were exothermic and spontaneous. The best pH values for adsorption were pH = 6–8.