Doina Bilba

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 ΔG, ΔH and ΔS 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.

Removal of Mercury (II) Ions from Aqueous Solutions by the Polyacrylamidoxime Chelating Fiber

Abstract A fibrous sorbent containing chelating amidoxime groups –C(NH2)˭NOH prepared from the Romanian commercial polyacrylonitrile ‐based fiber Melana was used for the removal of Hg2+ from aqueous solutions. The optimum conditions for the Hg2+ uptake were developed with respect to initial pH of solution, nature of anions, equilibration time, concentration of Hg2+, and temperature. The sorption was described quantitatively by fitting the equilibrium data to the Langmuir isotherm. The Langmuir parameters and thermodynamic quantities (ΔG, ΔH, ΔS) were calculated. The chelation mechanism of Hg2+ uptake on polyacrylamidoxime fiber was confirmed by IR spectroscopy. The experimental results point out the possibility of polyacrylamidoxime fiber to reversibly bind Hg2+ from wastewaters.

Sorption of Brilliant Red HE-3B Reactive Dye from Aqueous Solution onto Seashells Waste: Equilibrium and Kinetic Studies

The potential of waste seashells powder, as a new adsorbent for Brilliant Red HE-3B reactive dye removal from aqueous solutions, was examined by the batch technique. The Freundlich, Langmuir, and Dubinin-Radushkevich adsorption models were applied to describe the equilibrium sorption data and to determine the corresponding isotherm constants. The values of the thermodynamic parameters, ΔG, ΔH, and ΔS, indicate that the sorption of reactive dye is a spontaneous and endothermic process. The kinetic data evaluated by pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models suggested that the sorption of reactive dye onto seashell is a complex process and both surface sorption and intraparticle diffusion contributes to the rate limiting step.