Removal of reactive dye brilliant red HE-3B from aqueous solutions by hydrolyzed polyacrylonitrile fibres: equilibrium and kinetics modelling

A cheap and efficient fibrous hydrolyzed polyacrylonitrile (HPAN) sorbent was obtained by alkaline hydrolysis of Romanian polyacrylonitrile fibres. Scanning electronic microscopy and infrared spectroscopy were used to characterize the hydrolyzed product and to confirm its functionalization. The adsorptive potential of the proposed sorbent for reactive dye Brilliant Red HE-3B removal from aqueous solutions of pH=2 was examined by the batch technique as a function of dye concentration, temperature solution and contact time. The Freundlich, Langmuir and Dubinin-Radushkevich adsorption models were applied to describe equilibrium sorption data and to determine the corresponding isotherm constants. The thermodynamic parameters Delta G, Delta H and Delta S were also determined; the values obtained show that sorption of reactive dye on HPAN fibres is a spontaneous, endothermic and entropy-driven process. The kinetics of sorption of the reactive dye were analyzed using pseudo-first order and pseudo-second order kinetic models. The kinetic data fitted well to pseudo-second order kinetics, indicating the chemisorption of reactive dye onto the fibrous sorbent. The sorption mechanism of the dye onto hydrolyzed fibres was confirmed by FTIR spectroscopy. The dye-loaded HPAN sorbent can be regenerated by treatment with 0.1M NaOH and the regenerated sorbent may be reused in several adsorption-desorption cycles. The results of this study provided evidence that the HPAN fibres are effective for removing reactive dye Brilliant Red HE-3B from aqueous effluents.