Biofuels, as a renewable, eco-friendly, and cost-effective energy source, can reduce the dependence on fossil fuels. The researchers considered different approaches for obtaining high biodiesel ...yields from microalgae biomass. This work aims to present an overview of the feasibility of microalgae use in biodiesel production. Therefore, biodiesel production from microalgae oil via the transesterification process was explained in detail. The application of non-catalytic transesterification and catalytic transesterification was reviewed. The achievements in the application of homogenous catalysts, heterogeneous catalysts, and enzymatic catalysts for microalgae oil transesterification were discussed. The present technologies for biodiesel production from microalgae need more improvements to increase their efficiencies and reduce costs. Therefore, future research should focus on the development of effective catalysts for biodiesel production from microalgae biomass.
The aim of this work was to explore the possibility of using a Cu-exchanged zeolitic volcanic tuff (which is natural and easy to prepare and apply) for the preparation of a new low-cost carbon paste ...amperometric sensor for H2O2 detection. The properties of the zeolitic volcanic tuff were determined using chemical analysis, energy-dispersive X-ray spectroscopy, the specific surface area, electron microscopy, X-ray diffraction spectroscopy, and Fourier-transform infrared spectroscopy. The sensor was successfully built and operates at pH 7, at an applied potential of −150 mV Ag/AgCl/KClsat, presenting a sensitivity of 0.87 mA M−1, a detection limit of 10 µM and a linear domain up to 30 mM H2O2. These good electroanalytic parameters for H2O2 detection (a low detection limit and high sensitivity) support the possibility of using these sensors for the detection of many analytes in environmental, food and medical applications.
Iron-doped carbon xerogels were prepared using sol-gel synthesis, with potassium-2,4-dihydroxybenzoate and formaldehyde as starting materials, followed by an ion exchange step. The obtained samples ...were characterized (XRD, FTIR, SED-EDX, TEM) and investigated as catalysts in heterogeneous Fenton and catalytic wet air oxidation (CWAO) processes. Experiments were conducted in the same conditions (0.1 g catalysts, 25 mL of 100 mg/L dye solution, 25 °C, initial solution pH, 3 h) in thermostated batch reaction tubes (shaking water bath, 50 rpm) at atmospheric pressure. A series of three cationic dyes were considered: Brilliant green (BG), crystal violet (CV), and methyl green (MG). Dyes and TOC removal efficiencies up to 99% and 92%, respectively, were obtained, in strong correlation with the iron content of the catalyst. Iron content measured in solution at the end of the reaction, indicated that its amount was less than 2 ppm for all tested catalysts.
The study of natural clays, activated with sulfuric acid and pillared clays for treating aqueous solutions containing humic acids was the focus of this work. It appears that the equilibrium is ...reached after 20 min. A max elimination yield is obtained with pillared clay in a low pH medium (pH = 4) using clays of size Ø <2 μm. Pillared clay fixes more than 124% of humic acids compared to raw clay. The maximum adsorption capacities of clays are obtained with pillared clay, which is an indication that Al is probably the preferred adsorption site of humic acids.
The aim of this work was to prepare a composite material based on cocoa cortex and sodium alginate and test it to remove Cu(II) ions in aqueous solution in batch conditions. The composite was ...characterized using elemental analysis, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTG), and point of zero charge. The highest amount of adsorbed Cu(II) for the composite was 19.54 mg/g, i.e., 95.32% of an initial concentration of 100 mg/L. Under the same conditions, the cocoa cortex untreated exhibited extremely low adsorption, while when it was treated with hot soda, it adsorbed 13.67 mg/g. Adsorption by the composite reached the equilibrium after 220 min. Kinetic data analysis suggested that the process was governed by adsorption (pseudo-second-order model) and diffusion through macropores and/or mesopores (intra-particle model). The adsorption isotherm that best described the system was Langmuir’s. The maximum adsorption capacity of Cu(II) was 76.92 mg/g. The values of the thermodynamic parameters indicated that the process was spontaneous, with ΔG° values between (− 7.886 and − 9.458 kJ/mol) and endothermic, with ΔH° = 7.728 kJ/mol.
Graphical abstract
In the present study the biosorption characteristics of Cd (II) and Zn (II) ions from monocomponent aqueous solutions by Agaricus bisporus macrofungus were investigated. The initial metal ion ...concentrations, contact time, initial pH and temperature were parameters that influence the biosorption. Maximum removal efficiencies up to 76.10% and 70.09% (318K) for Cd (II) and Zn (II), respectively and adsorption capacities up to 3.49 and 2.39mg/g for Cd (II) and Zn (II), respectively at the highest concentration, were calculated. The experimental data were analyzed using pseudo-first- and pseudo-second-order kinetic models, various isotherm models in linear and nonlinear (CMA-ES optimization algorithm) regression and thermodynamic parameters were calculated. The results showed that the biosorption process of both studied metal ions, followed pseudo second-order kinetics, while equilibrium is best described by Sips isotherm. The changes in morphological structure after heavy metal-biomass interactions were evaluated by SEM analysis. Our results confirmed that macrofungus A. bisporus could be used as a cost effective, efficient biosorbent for the removal of Cd (II) and Zn (II) from aqueous synthetic solutions.
Various lignoceNulosic waste materials were assessed for their potential usage as biosorbents for Cd(II) removal from wastewaters. Sunflower seed shells, carrot peel, bean pods, eggplant peel, and ...orange peel in dry form and different grain sizes were evaluated. Contact time, initial Cd(II) concentration, and biosorbent amount were also tested. Eggplant peel was the most efficient biosorbent with an experimental biosorption capacity of 9.33 mg/g, a monolayer capacity (Langmuir) of 18.05 mg/g, and maximum % yield removal of 97.33%. Experimental data best fitted the Langmuir isotherm model (exception, orange peel) and the pseudo-second-order kinetic model (all materials). Keywords: cadmium(II), biosorption, waste valorisation, circular economy, sunflower seed shell, carrot peel, bean pod, eggplant peel, orange peel
The aim of this study was to investigate the ability of Lemna minor for Toluidine Blue (TB) removal. Influence of the initial concentration over the removal process was considered. Experimental data ...have been analyzed using Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Elovich isotherm models. In addition, several kinetic models, pseudo-first-, pseudo-second-order, intraparticle and film diffusion models were considered. Langmuir and Freundlich isotherm suggested a favorable adsorption of TB by Lemna minor plants. From the D-R the mean free energy was calculated to be 11.18 kJ/mol, which indicates that TB adsorption was characterized by a chemisorption process. Kinetic studies showed that liquid film diffusion plays an important role during the process. Adsorption capacities of up to 26.69 mg/g and a high capacity of adaptation indicated that phytoremediation using Lemna minor could be a valuable alternative for dyes removal from wastewaters.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Natural bearing (raw and calcined at 500 °C) and iron-enriched (impregnation and pillaring) montmorillonitic clay samples were prepared. The obtained samples were characterized (X-ray diffraction, ...Fourier Transformed Infrared Spectroscopy, Scanning Electron Microscopy, and Energy Dispersive X-ray Spectroscopy) and evaluated as catalysts in catalytic wet oxidation of Brilliant Green and Crystal Violet. Experiments were conducted in the same conditions (0.5 g catalysts, 300 mL air/min or 0.5 mL H2O2, 25 mL of dye solution, 25 °C, initial solution pH = 6.0, for 3 h) in thermostated batch reaction tubes. Process evolution was followed using UV-Vis spectrometry (200–1100 cm−1) and total organic carbon. Dye removal efficiencies (decolorization) between 98 and 99% were determined, while total organic carbon removal efficiencies were calculated to be in the 53–98% range. Iron leakage investigation showed that iron is lost in higher amounts for the catalysts prepared using the impregnation method by comparison with the pillared sample.
The aim of this study was to examine the capacity of anionic resins to remove zinc as zinc chloride complexes in fixed bed. The applicability of the kinetics models and the characteristics of the bed ...(sorption capacity, breakthrough curve, depth of the adsorption zone) were taken into account. The influence of the process parameters, such as resin quantity (bed height) and zinc initial concentration, on the removal process was also considered. The obtained results (Amberlite IRA410) were analyzed using sorption kinetic models such as Thomas, Adam-Bohart, and Clark, by linear regression analysis. Similarly, the concept of the mass transfer zone was applied in order to properly design the fixed bed adsorption process. By comparing various resins, the following series was depicted based on sorption capacities: Amberlite IRA410>Purolite A103S>Purolite NRW700>Purolite A400MBOH. The experimental data were in good agreement with the Clark model, while for the other models, lower correlation coefficients were obtained under the same experimental conditions. The MTZ height and rate of movement increased with increasing initial concentration.
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