Biosorption of lac dye by the red marine alga Gracilaria tenuistipitata: biosorption kinetics, isotherms, and thermodynamic parameters

Abstract

The hypothesis that the dried, ground biomass of the red marine alga Gracilaria tenuistipitata could be used for the efficient removal of lac dye from aqueous solution was assessed in this work. The effects of parameters such as initial pH, biosorbent dosage, contact time, initial dye concentration, and temperature on the biosorption capacity of the dye were investigated. Equilibrium data were analysed using Langmuir, Freundlich, and Temkin isotherm models, and the Freundlich model provided the highest coefficient of determination values. Biosorption kinetic data were successfully described with a pseudo-second-order model at initial dye concentrations of 50, 80, 100, and 120 mg l −1 . The thermodynamic parameters of biosorptionenthalpy change (∆H° = −30.64 kJ mol −1 ), free energy change (∆G° = 4.32 kJ mol −1 at 303 K to 7.78 kJ mol −1 at 333 K), and entropy change (∆S° = −115.38 J mol −1 K −1 ) -were determined. The negative value of the enthalpy change and positive values of the free energy change indicate that the biosorption process is exothermic and non-spontaneous. The negative value of the entropy change is consistent with decreased randomness at the solid-liquid interface with dye biosorption. Attenuated total reflectance-Fourier transform infrared spectroscopic analysis confirmed the presence of lac dye on the G. tenuistipitata material. The efficiency of lac dye removal by this biomass material at 20 g l −1 and with an initial dye concentration of 50 mg l −1 in acidic solution was 71%, which indicated its potential usefulness as a new dye biosorbent. Running title: Removal of lac dye by Gracilaria tenuistipitata AbstractThe hypothesis that the dried, ground biomass of the red marine alga Gracilaria tenuistipitata could be used for the efficient removal of lac dye from aqueous solution was assessed in this work. The effects of parameters such as initial pH, biosorbent dosage, contact time, initial dye concentration, and temperature on the biosorption capacity of the dye were investigated. Equilibrium data were analysed using Langmuir, Freundlich, and Temkin isotherm models and the Freundlich model provided the highest coefficient of determination values. Biosorption kinetic data were successfully described with a pseudo-second-order model at initial dye concentrations of 50, 80, 100, and 120 mg l

Factors Affecting Efficiency of Biosorption of Fe (III) and Zn (II) by Ulva lactuca and Corallina officinalis and Their Activated Carbons

“…Temperature affects the biosorption efficiency of algae species for each metal ion [85,97,98]. Although the constants for metal-ligand complex formation are predominantly temperature-dependent, some studies have suggested that an increase in algal culture temperatures is responsible for an increase in metal-ion biosorption, without considering the changes in the formation constants [99,100]. The percentage of Zn +2 and Fe +3 ions that were removed from DAP and AAC of U. lactuca and C. officinalis increased as the temperature increased, indicating an endothermic adsorption process, which is a positive effect when considering the use of these algae in the environment, as well as their potential conservation and sustainability.…”