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Adsorption of indigo carmine on functional chitosan and β-cyclodextrin/chitosan beads: Equilibrium, kinetics and mechanism studies

Kekes, Tryfon, Tzia, Constantina
Journal of environmental management 2020 v.262 pp. 110372
Fourier transform infrared spectroscopy, adsorbents, adsorption, beta-cyclodextrin, chitosan, crosslinking, dyes, heat production, indigo carmine, pH, scanning electron microscopy, sorption isotherms, temperature
The present study was designed to produce novel cross-linked Chitosan and Chitosan/β-Cyclodextrin beads and study the adsorption of Indigo Carmine. Both adsorbents were characterized by SEM and FTIR techniques. Batch experiments were conducted in order to evaluate the effect of initial adsorbent's concentration, dye's initial concentration, initial pH and temperature. In all cases Chitosan/β-Cyclodextrin crosslinked beads exhibited higher removal efficiency of Indigo Carmine. Higher removal rates of Indigo Carmine were observed at low values of dye's initial concentration, pH and temperature, and high concentrations of adsorbent. The equilibrium adsorption data were a good fit for both Langmuir and Freundlich models and maximum adsorption capacity was 500.0 and 1000.0 mgIC/gₐdₛₒᵣbₑₙₜ for Chitosan and Chitosan/β-Cyclodextrin crosslinked beads, respectively. Adsorption of Indigo Carmine was found to follow the pseudo-second order. The negative values of ΔGᵒ, ΔHᵒ and ΔSᵒ indicate that the adsorption process is exothermic, spontaneous and favorable at low temperatures.