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.
Highlights
Water pollution is considered one of the most important environmental problems due to its essential role in life since the presence of pollutants is a severe threat to ecosystems and public health [1].Microbial cells can be used for the removal of pollutants from aqueous effluents through biosorption, a passive process that implies inactive biomass able to adsorb toxic substances on its surface [1,2]
The aim of this paper is to investigate the biosorptive behavior of a new type of biosorbent based on residual microbial biomass of Saccharomyces pastorianus immobilized in sodium alginate
The influence of contact time of dye and biosorbent on the biosorbent itself, based on the residual biomass of Saccharomyces pastorianus immobilized in sodium alginate, was studied in batch experiments, mixing 0.271 g of biosorbent and 100 mL
Summary
Water pollution is considered one of the most important environmental problems due to its essential role in life (metabolism, irrigation, industrial) since the presence of pollutants is a severe threat to ecosystems and public health [1].Microbial cells can be used for the removal of pollutants from aqueous effluents through biosorption, a passive process that implies inactive biomass able to adsorb toxic substances on its surface [1,2]. Fungi, or algae are potential biosorbents, as they are relatively abundant and inexpensive (results as by-product in industrial fermentation) [3,4,5]. Advantages of using inactive biomass include having no nutrients or energy requirements, better sorption capacity, rapid processes, and no toxic effects of the contaminants on the cells. Even in inactive form (nonliving), microorganisms have the capacity to bind different molecules, but their use in free form is limited due to difficult separation (small size, less operational stability, difficult recovery and reusability) [3]. By immobilization through different techniques using natural polysaccharides, including alginate, chitosan, starch, and cellulose, better-suited biosorbents (easier to handle, reusable, more stable and robust) can be obtained [4,6]
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