Polysaccharides Used in Biosorbents Preparation for Organic Dyes Retaining from Aqueous Media

Abstract

Natural polymers can themselves be efficient as materials with biosorptive properties but can also be used to transform microbial biomass into an easy-to-handle form, respectively, into biosorbents, through immobilization. The article aims to study biosorbents based on residual microbial biomass (Saccharomyces pastorianus yeast, separated after the brewing process by centrifugation and dried at 80 °C) immobilized in sodium alginate. The biosorptive properties of this type of biosorbent (spherical particles 2 and 4 mm in diameter) were studied for removal of reactive dye Brilliant Red HE-3B (with concentration in range of 16.88-174.08 mg/L) from aqueous media. The paper aims at three aspects: (i) the physico-chemical characterization of the biosorbent (Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared (FTIR) spectra); (ii) the modeling of biosorption data in order to calculate the quantitative characteristic parameters using three equilibrium isotherms (Langmuir, Freundlich, and Dubinin-Radushkevich-DR); and (iii) the evaluation of thermal effect and the possible mechanism of action. The results of the study showed that biosorption capacity evaluated by Langmuir (I) model is 222.22 mg/g (ϕ = 2 mm) and 151.51 mg/g (ϕ = 4 mm) at 30 °C, and the free energy of biosorption (E) is in the range of 8.45-13.608 KJ/mol (from the DR equation). The values of thermodynamic parameters suggested an exothermic process due the negative value of free Gibbs energy (ΔG⁰ = -9.031 kJ/mol till -3.776 kJ/mol) and enthalpy (about ΔH⁰ = -87.795 KJ/mol). The obtained results underline our finding that the immobilization in sodium alginate of the residual microbial biomass of Saccharomyces pastorianus led to an efficient biosorbent useful in static operating system in the case of effluents with moderate concentrations of organic dyes.

Keywords: Saccharomyces pastorianus immobilized; biosorption; organic dye; polysaccharides as biosorbent; sodium alginate.

Figure 1

(a) Schematic representation of the immobilized and biosorption processes; (b) immobilized biomass granules before and after dye biosorption.

Figure 2

Chemical structure of reactive dye, Brilliant Red HE-3B—C.I. 25810.

Figure 3

Scanning electron microscopy (SEM) and mapping of C, O, N, F, Ca, and Cl elements of the biosorbent after (a) and before (b) Brilliant Red HE-3B dye biosorption.

Figure 4

Energy-dispersive X ray (EDAX) spectra of the biosorbent after (a) and before (b) Brilliant Red HE-3B dye biosorption.

Figure 5

FT-IR spectra of the biosorbent before (1) and after (2) biosorption and of Brilliant Red HE-3B dye (3).

Figure 6

Biosorption isotherms of Brilliant Red HE-3B reactive dye on biosorbent based on residual Saccharomyces pastorianus biomass immobilized in sodium alginate, in the form of two-dimensional granule: ϕ 1 = 2 mm (a) and ϕ 2 = 4 mm (b). Conditions: pH = 3, contact time = 24 h, amount of biosorbent = 2.8 g/L (in the case of ϕ 1) and 2.4 g/L (in the case of ϕ 2) (5% d.w.).

Figure 7

The biosorption isotherms (Langmuir I and Freundlich) of reactive Brilliant Red HE-3B dye onto immobilized residual microbial biomass-based biosorbent. Conditions: ϕ1 = 2 mm (a) and ϕ 2 = 4 mm (b), pH = 3, contact time = 24 h, amount of biosorbent = 2.8 g/L (in case of ϕ 1) and 2.4 g/L (in the case of ϕ 2) (with 5% d.w.).

Figure 8

Influence of contact time (q = f(t) and F = f(t)) on reactive dye Brilliant Red HE-3B biosorption onto residual bacterial biomass of Saccharomyces pastorianus immobilized in sodium alginate expressed through the amount of dye adsorbed (q) and fractional attainment of equilibrium (F) (biosorbent dose of 2.71 g/L (5% d.w.); pH = 3; temperature of 25 °C).

Figure 9

Applicability of pseudo-first order and pseudo-second order diffusion kinetic models (a), Elovich model (b), intra-particle diffusion model (c), and film diffusion model (d) to reactive Brilliant Red HE-3B dye biosorption onto residual bacterial biomass of Saccharomyces pastorianus immobilized in sodium alginate (biosorbent dose of 2.71 g/L (5% d.w.); pH = 3; temperature of 25 °C).