Adsorption capacity of chitosan hydrogel beads fabricated from Penaeus monodon shrimp shell waste for safranin o dye

In this study, we extracted chitosan from Penaeus monodon shrimp shell waste and used it as a bio-sorbent to remove safranin O (SO) dye in aqueous solutions. The chitosan adsorbent was characterised by using SEM and FTIR techniques. Batch adsorption experiments were carried out to evaluate the influence of solution pH (3–10), chitosan dosage (0.1–3 g), contact time (1–720 min), and initial SO concentration (10–200 mg·L–1) on adsorption. The results show that the adsorption of SO with chitosan reached equilibrium after 120 min, and after that, an insignificant change in SO removal efficiency was observed. The maximum adsorption capacity of SO, calculated according to the Langmuir model, was 17.86 mg·g–1 under ambient temperature (25 ± 2 °C), pH 7, chitosan dose of 0.2 g, and SO concentration of 50 mg·L–1. The adsorption kinetics followed the pseudo-second-order model with a correlation coefficient R2 of 0.95. The Langmuir and Freundlich adsorption isotherm models described the SO’s adsorption well, with R2 higher than 0.95.