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

A Sustainable Solution for the Adsorption of C.I. Direct Black 80, an Azoic Textile Dye with Plant Stems: Zygophyllum gaetulum in an Aqueous Solution

The presence of pollutants in water sources, particularly dyes coming by way of the textile industry, represents a major challenge with far-reaching environmental consequences, including increased scarcity. This phenomenon endangers the health of living organisms and the natural system. Numerous biosorbents have been utilized for the removal of dyes from the textile industry. The aim of this study was to optimize discarded Zygophyllum gaetulum stems as constituting an untreated natural biosorbent for the efficient removal of C.I. Direct Black 80, an azo textile dye, from an aqueous solution, thus offering an ecological and low-cost alternative while recovering the waste for reuse. The biosorbent was subjected to a series of characterization analyses: scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), and infrared spectroscopy (IR) were employed to characterize the biosorbent. Additionally, the moisture and ash content of the plant stem were also examined. The absorption phenomenon was studied for several different parameters including the effect of the absorption time (0 to 360 min), the sorbent mass (3 to 40 g/L), the pH of the solution (3 to 11), the dye concentration (5 to 300 mg/L), and the pH of the zero-charge point (2-12). Thermodynamic studies and desorption studies were also carried out. The results showed that an increase in plant mass from 3 to 40 g/L resulted in a notable enhancement in dye adsorption rates, with an observed rise from 63.96% to 97.08%. The pH at the zero-charge point (pHpzc) was determined to be 7.12. The percentage of dye removal was found to be highest for pH values ≤ 7, with a subsequent decline in removal efficiency as the pH increased. Following an initial increase in the amount of adsorbed dye, equilibrium was reached within 2 h of contact. The kinetic parameters of adsorption were investigated using the pseudo-first-order, pseudo-second-order and Elovich models. The results indicated that the pseudo-first-order kinetic model was the most appropriate for the plant adsorbent. The isotherm parameters were determined using the Langmuir, Frendlich, Temkin, and Dubinin-Radushkevich models. The experimental data were more satisfactory and better fitted using the Langmuir model for the adsorption of dye on the plant. This study demonstrated that Zygophyllum gaetulum stems could be employed as an effective adsorbent for the removal of our organic dye from an aqueous solution.

4-Coumarate-CoA ligase (4-CL) enhances flavonoid accumulation, lignin synthesis, and fruiting body formation in Ganoderma lucidum

It is now understood that 4-Coumarate-CoA ligases (4-CL) are pivotal in bridging the phenylpropanoid metabolic pathway and the lignin biosynthesis pathway in plants. However, limited information on 4-CL genes and their functions in fungi is available. In this study, we cloned the 4-CL gene (Gl21040) from Ganoderma lucidum, which spans 2178 bp and consists of 10 exons and 9 introns. We also developed RNA interference and overexpression vectors for Gl21040 to investigate its roles in G. lucidum. Our findings indicated that in the Gl21040 interference transformants, 4-CL enzyme activities decreased by 31 %-57 %, flavonoids contents decreased by 10 %-22 %, lignin contents decreased by 20 %-36 % compared to the wild-type (WT) strain. Conversely, in the Gl21040 overexpression transformants, 4-CL enzyme activity increased by 108 %-143 %, flavonoids contents increased by 8 %-37 %, lignin contents improved by 15 %-17 % compared to the WT strain. Furthermore, primordia formation was delayed by approximately 10 days in the Gl21040-interferenced transformants but occurred 3 days earlier in the Gl21040-overexpressed transformants compared to the WT strain. These results underscored the involvement of the Gl21040 gene in flavonoid synthesis, lignin synthesis, and fruiting body formation in G. lucidum.

Statistical Analysis and Optimization of the Brilliant Red HE-3B Dye Biosorption onto a Biosorbent Based on Residual Biomass

Using various techniques, natural polymers can be successfully used as a matrix to immobilize a residual microbial biomass in a form that is easy to handle, namely biosorbents, and which is capable of retaining chemical species from polluted aqueous media. The biosorption process of reactive Brilliant Red HE-3B dye on a new type of biosorbent, based on a residual microbial biomass of Saccharomyces pastorianus immobilized in sodium alginate, was studied using mathematical modeling of experimental data obtained under certain conditions. Different methods, such as computer-assisted statistical analysis, were applied, considering all independent and dependent variables involved in the reactive dye biosorption process. The optimal values achieved were compared, and the experimental data supported the possibility of using the immobilized residual biomass as a biosorbent for the studied reference dye. The results were sufficient to perform dye removals higher than 70-85% in an aqueous solution containing around 45-50 mg/L of reactive dye, and working with more than 20-22 g/L of prepared immobilized microbial biosorbent for more than 9.5-10 h. Furthermore, the proposed models agreed with the experimental data and permitted the prediction of the dye biosorption behavior in the experimental variation field of each independent variable.

Biosorbents Based on Biopolymers from Natural Sources and Food Waste to Retain the Methylene Blue Dye from the Aqueous Medium

The use of a biosorbent based on residual biomass from brewing industry (Saccharomyces pastorianus) immobilized in a natural biopolymer (sodium alginate) was investigated for Methylene Blue removal from aqueous medium. Saccharomyces pastorianus, immobilized by a simple entrapment technique and by microencapsulation in alginate was characterized using SEM, EDAX, pHPZC and the biosorption behavior toward organic pollutant, such as cationic dye. The biosorption experiments were studied by assessing, in a first stage, the influence of the most important operational physical parameters on the efficiency of the biosorbent: the initial concentration of the dye, the contact time between phases, the temperature, the dye solution pH, the biosorbent granule size, and the amount of biosorbent. The highest sorption capacity was obtained for the biosorbent obtained by microencapsulation, at pH 9, at biosorbent dose of 5.28 g/L and a contact time of about 100 min. The biosorption equilibrium was then studied by modeling the data on the Langmuir, Freundlich and Dubinin- Radushkevich isotherms. The Langmuir model is best suited for experimental data on both particle sizes leading to a maximum biosorption capacity of 188.679 mg/g at room temperature. The values of the adsorption energy, E, obtained with the help of the Dubinin-Radushkevich model-suggest that the type of mechanism (physical or chemical) involved in the biosorption process depends on the particle size of the biosorbent. The results confirm that the residual microbial biomass of Saccharomyces pastorianus immobilized in a polymeric matrix such as sodium alginate, can be considered an efficient biosorbent in retaining cationic organic dyes present in aqueous solutions in moderate concentrations.

Empirical Modeling and Optimization by Active Central Composite Rotatable Design: Brilliant Red HE-3B Dye Biosorption onto Residual Yeast Biomass-Based Biosorbents

(1) Introduction: Natural polymers can be successfully used as a matrix to immobilize residual yeast-based biomass in a form that is easy to handle and can be used as biosorbent capable of removing persistent polluting species from different aqueous systems such as reactive azo dyes. (2) Experimental: Two types of new biosorbents were prepared based on residual Saccharomyces pastorianus yeast biomass immobilized in sodium alginate (using two different practice techniques) and studied in the biosorption process of reactive Brilliant Red HE-3B dye using certain experimental planning matrices according to the active central composite rotatable design of 23 order. The experimental data obtained under certain selected working conditions were processed considering the influence of three independent variables (biosorbent concentration—X1, initial dye concentration—X2 and biosorption time—X3) onto the dependent variable (Y = f(X1,X2,X3)) expressing the performance of reactive dye biosorption onto the new prepared biosorbents (i.e., dye removal degree, %). (3) Results: Two mathematical models were proposed for each prepared biosorbent. The maximum dye removal was 52.878% (Y1) when 18 g/L biosorbent 1 (micro-encapsulated form) was applied in 70 mg/L dye-containing solution for at least 8 h, and 75.338% (Y2) for 22.109 g/L biosorbent 2 (immobilized form) in 48.49 mg/L dye-containing solution for at least 8.799 h. (4) Discussion: The optimal values achieved for the two tested biosorbents were compared, and we investigated the possibility of using this residual biomass as a biosorbent for the reactive dye removal, supported by the experimental results with the recommended variation domains of each influencing variable. The results are sufficient to permit performing dye removal higher than 50% (biosorbent 1) or 70% (biosorbent 2), working with more than 18–22 g/L biosorbent after at least 8 h (as an exchange at work). (5) Conclusions: The proposed models are in good agreement with the experimental data and permit the prediction of dye biosorption behavior onto the experimental variation domain of each independent variable.

Modified Polymeric Biosorbents from Rumex acetosella for the Removal of Heavy Metals in Wastewater

The contamination of water resources by effluents from various industries often contains heavy metals, which cause irreversible damage to the environment and health. The objective was to evaluate different biosorbents from the weed Rumex acetosella to remove metal cations in wastewater. Drying, grinding and sieving of the stems was carried out to obtain the biomass, retaining the fractions of 250 to 500 µm and 500 to 750 µm, which served to obtain the biosorbents in natura (unmodified), acidic, alkaline, and mixed. Proximal analysis, PZC, TOC, removal capacity, influence of pH, functional groups, thermal analysis, structural characteristics, adsorption isotherms, and kinetic study were evaluated. The 250 µm mixed treatment was the one that presented the highest removal percentages, mainly due to the OH, NH, -C-H, COOH, and C-O functional groups achieving the removal of up to 96.14% of lead, 36.30% of zinc, 34.10% of cadmium and 32.50% of arsenic. For contact times of 120 min and an optimum pH of 5.0, a loss of cellulose mass of 59% at 328 °C and a change in the surface of the material were also observed, which allowed for obtaining a topography with greater chelating capacity, and the Langmuir and pseudo-second order models were better fitted to the adsorption data. The new biosorbents could be used in wastewater treatment economically and efficiently.