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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.

Natural polymers have proven to be extremely interesting matrices for the immobilization of microbial biomasses, via various mechanisms, in order to bring them into a form easier to handle—the form of composites. This article aimed to study composites based on a residual microbial biomass immobilized in sodium alginate via an encapsulation technique as materials with adsorbent properties. Thus, this study focused on the residual biomass resulting from beer production (Saccharomyces pastorianus yeast, separated after the biosynthesis process by centrifugation and dried at 80 °C)—an important source of valuable compounds, used either as a raw material or for transformation into final products with added value. Thus, the biosorptive potential of this type of composite was tested—presenting in the form of spherical microcapsules 900 and 1500 μm in diameter—in a biosorption process applied to aqueous solutions containing the reactive dye Brilliant Red HE-3B (16.88–174.08 mg/L), studied in a batch system. The preparation and characterization of the obtained polymeric composites (pHPZC, SEM, EDS and FTIR spectra) and an analysis of different equilibrium isotherms (Langmuir, Freundlich and Dubinin-Radushkevich—D–R) were investigated in order to estimate the quantitative characteristic parameters of the biosorption process, its thermal effects, and its possible mechanisms of action. The modelling of the experimental data led to the conclusion that the studied biosorption process took place after reaching the Langmuir isotherm (LI), and that the main mechanism was possibly physical, being spontaneous and probably exothermic according to the values obtained for the free energy of biosorption (E = 8.45–13.608 kJ/mol, from the DR equation), as well as the negative values for the Gibbs free energy and the enthalpy of biosorption (ΔH0 = −87.795 kJ/mol). The results obtained lead to the conclusion that encapsulation of this residual microbial biomass in sodium alginate leads to an easier-to-handle form of biomass, thus being an efficient biosorbent for static or dynamic operating systems for effluents containing moderate concentrations of reactive organic dyes.

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In this paper, we describe an experimental study on the hot alkali extraction of hemicelluloses from wheat straw and corn stalks, two of the most common lignocellulosic biomass constituents in Romania. The chemical compositions of the raw materials were determined analytically, and the relevant chemical components were cellulose, hemicelluloses, lignin, and ash. Using the response surface methodology, the optimum values of the hot alkaline extraction parameters, i.e., time, temperature, and NaOH concentration, were identified and experimentally validated. The physicochemical characterization of the isolated hemicelluloses was performed using HPLC, FTIR, TG, DTG, and 1H-NMR spectroscopy. The main hemicellulose components identified experimentally were xylan, arabinan, and glucan. The study emphasizes that both corn stalks and wheat straw are suitable as raw materials for hemicellulose extraction, highlighting the advantages of alkaline pretreatments and showing that optimization methods can further improve the process efficiency.

The paper aims to present the environmental impact of pulp and paper manufacturing and the most important production and control practices to minimizing this impact. The environmental consequences of manufacturing pulp and paper from pulping and bleaching processes are discussed in qualitative and quantitative terms. In these processes, sulfur compounds and nitrogen oxides are emitted to the air, and chlorinated and organic compounds and nutrients are discharged to the wastewaters. Large quantities of solid wastes and sludges are also generated.

The valorization of indigenous flora waste by extraction of biologically active compounds has potential applications in the medical and cosmetic fields. The polyphenols and flavonoids extracted from this waste are valuable compounds for the manufacture of new cosmetic and/or dermato-cosmetic formulas to protect the skin from oxidative stress. This study obtained plant extracts from saffron waste—petals, tepals, and superior portions of stem—using different solid-liquid extraction techniques. The influence of some physical operating parameters was studied (extraction time, solid/liquid ratio, solvent extraction composition). The extraction method performance was assessed by the value of the extraction yields. The obtained extracts were characterized by the content of polyphenols and flavonoids, and the antioxidant activity determined with the DPPH and ABTS methods and the UV-VIS spectrometry. Some emulsions O/W were prepared and preliminarily characterized (pH, sensory analysis, stability after centrifugation and storage). The obtained results showed that the incorporation of this natural extract did not negatively affect the stability of the studied cosmetic formulations and advanced characterization (microbiological control of contamination, rheology studies and in vitro and in vivo studies) can be continued in order to implement a new product.

In this work, the active carbon adsorption and TiO2/UV decolorization of black liquor were studied through experimental analysis (planned using Design of Experiments), modelling and optimization (with Response Surface Method and Differential Evolution). The aim is to highlight the importance of optimization methods for increasing process efficiency. For active carbon adsorption, the considered process parameters were: quantity of active carbon, dilution, and contact time. For TiO2 promoted photochemical decolorization the process parameters were: TiO2 concentration, UV path length and irradiation time. The determined models had an R squared of 93.82% for active carbon adsorption and of 92.82% for TiO2/UV decolorization. The optimization of active carbon resulted in an improvement from 83.08% (corresponding to 50 g/L quantity of active carbon, 30 min contact time and 200 dilution) to 100% (corresponding to multiple combinations). The optimization of TiO2/UV decolorization indicated an increase of efficiency from 36.63% (corresponding to 1 g/L TiO2 concentration, 60 min irradiation time and 5 cm UV path length) to 46.83% (corresponding to 0.4 g/L TiO2 concentration, 59.99 min irradiation time and 2.85 cm UV path length). These results show that the experiments and the subsequent standard RSM optimization can be further improved, leading to better performance.