This work demonstrates new evidence of the efficient destruction and mineralization of an emergent organic pollutant using UV-A and titanium nanosized catalysts. The target compound considered in ...this work is the primary metabolite of a lipid regulator drug, clofibrate, identified in many studies as refractory during conventional wastewater treatment. The photocatalytic performance study was carried out in batch mode at laboratory scale, in aqueous suspension. Kinetic data showed that titanium dioxide P25 Aeroxide® exhibits the highest photocatalytic efficiency compared to the other investigated catalysts. Pollutant degradation and mineralization efficiencies strongly increased when decreasing the initial substrate concentration. Target molecules oxidized faster when the catalyst load increased, and the mineralization was enhanced under acidic conditions: 92% of mineralization was achieved at pH 4 after 190 min of reaction. Radical quenching assays confirmed that HO• and ( h vb + ) were the reactive oxygen species involved in the photocatalytic oxidation of the considered pollutant. In addition, further results revealed that the removal efficiency decreased in real water matrices. Finally, data collected through a series of phytotoxicity tests demonstrated that the photocatalytic process considerably reduces the toxicity of the treated solutions, confirming the process’s effectiveness in the removal of persistent and biorefractory emergent organic water pollutants.
Biosorbtive removal of the antibacterial drug, ethacridine lactate (EL), from aqueous solutions was investigated using as biosorbent Saccharomyces pastorianus residual biomass immobilized in calcium ...alginate. The aim of this work was to optimize the biosorption process and to evaluate the biosorption capacity in the batch system. Response surface methodology, based on a Box–Behnken design, was used to optimize the EL biosorption parameters. Two response functions (removal efficiency and biosorption capacity) were maximized dependent on three factors: initial concentration of EL solution, contact time, and agitation speed. The highest values for the studied functions (89.49%, 26.04 mg/g) were obtained in the following operational conditions: EL initial concentration: 59.73 mg/L; contact time: 94.26 min; agitation speed: 297.57 rpm. A number of nonlinear kinetic models, including pseudo-first-order, pseudo-second-order, Elovich, and Avrami, were utilized to validate the biosorption kinetic behavior of EL in the optimized conditions. The kinetic data fitted the pseudo-first-order and Avrami models. The experimental results demonstrated that the optimized parameters (especially the agitation speed) significantly affect biosorption and should be considered important in such studies.
TiO2 nanoparticles synthesized by the sol-gel method and doped with Ag were characterized by SEM, EDAX, FTIR, BET, XRD and TEM, then tested in the photocatalytic degradation of methylene blue (MB) ...under UV irradiation. The experimental results indicate that the average size of the raw particles was 10 nm, and their size was increased by calcination. The photocatalytic degradation of MB on nanostructured TiO2-Ag shows a high degradation efficiency upon the addition of a photosensitizer. A parametric study of the process was performed and has revealed the optimal value of the photocatalyst dose (0.3 g L−1) at a MB concentration of 4 ppm. Afterwards, the effect of acetone as a photosensitizer was studied. A MB degradation mechanism was proposed to explain the synergy between the TiO2 and the silver nanoparticles in the degradation performance. Under the optimal experimental conditions, at photosensitizer doses of 0.1 and 0.2%, yields of 92.38% and 97.25% MB degradation were achieved, respectively. Kinetic models showed that, at 0.1% acetone concentration, the data fit the pseudo-first-order model, while at 0.2% acetone, the photodegradation mechanism fits a second-order model. The values of the apparent rate constants indicate that the reaction rate increased between 24 and 40 times in the presence of acetone on TiO2 and TiO2-Ag. The addition of acetone modified the photodegradation mechanism and the Ag-doped samples became more active. The results of recycling tests using calcined TiO2-Ag material clearly show that the material was highly photocatalytically stable for the MB degradation. According to experimental results, the dye degradation decreased from 97.25% to 92.39% after four consecutive cycles. This simple approach could be applied for the advanced cleaning of wastewater contaminated with dyes, in the perspective of its reuse.
Nowadays, water pollution by pharmaceuticals is a major issue that needs an urgent solution, as these compounds, even when found at trace or ultra-trace levels, could have harmful effects on ...organisms. Carbamazepine (CBZ) is a pharmaceutical product that is detected as a micropollutant in many water resources. Different treatment methods were lately employed for the removal of CBZ, which are often cheap but inefficient or efficient but expensive. Yet, there are limited available studies on the elimination of this molecule by algae despite their well-known highly adaptive abilities. In this study, the biological treatment of CBZ was carried out using the green microalgae, Ankistrodesmus braunii (A. braunii), which has been reported to be particularly resistant to CBZ toxicity in the literature. The respective effects of the culture medium, the initial inoculum, and CBZ concentrations were studied on CBZ removal. Lastly, the mechanism of CBZ elimination by A. braunii was investigated. The presented data clearly demonstrates that the presence of this molecule did not completely repress A. braunii growth or the ability of these algae to remove CBZ; after 60 days of incubation, the highest percentage of CBZ elimination achieved was 87.6%. Elimination was more successful in Bold’s basal medium than in proteose peptone medium. Finally, the removal mechanism was also investigated to provide a better understanding of the transformation mechanism of this molecule. It was shown that the main removal mechanism was the bioaccumulation of CBZ by A. braunii cells, but the biotransformation of the initial CBZ into metabolites was also observed.
The treatment of contaminated water is currently a major concern worldwide. This work was directed towards the preparation of a composite hydrogel by entrapping cherry stones powder on chitosan, ...which is known as one of the most abundant natural polymers. The synthesized material was characterized by scanning electron microscopy, by Fourier transform infrared spectroscopy, and by the point of zero charge determination. Its ability to remove two azo dyes models (Acid Red 66 and Reactive Black 5) existing in single form and in binary mixture was evaluated. Response Surface Methodology-Central Composite Design was used to optimize three parameters affecting the process while targeting the lowest final contaminant concentrations. The best results were obtained at pH 2, an adsorbent dose of 100 g/L, and a temperature of 30 °C, when more than 90% of the pollutants from the single component systems and more than 70% of those of the binary mixtures were removed from their aqueous solutions. The adsorption process was in accordance with Elovich and pseudo-second-order kinetic models, and closely followed the Freundlich and Temkin equilibrium isotherms. The obtained results led to the conclusion that the prepared hydrogel composite possesses the ability to successfully retain the target molecules and that it can be considered as a viable adsorbent material.
N-nitrosamines are a new class of emerging nitrogenous drinking water disinfection by-products. These compounds are probably carcinogenic which could seriously affect the safety of drinking water ...consumers. The aim of this study is to develop a simple, fast, and specific analytical method for the routine determination of low part per trillion levels of N-nitrosamines in waters. An ultra high pressure liquid chromatography coupled with tandem mass spectrometry (UHPLC/MS/MS) method was developed for the qualitative and quantitative analysis of N-nitrosamines in waters. N-nitrosamines were extracted, purified and concentrated from water samples in one step using a solid-phase extraction (SPE). The compounds were detected in multiple reaction monitoring via electrospray ionisation source with positive ionisation mode. To achieve symmetrical peak shapes and a short chromatographic analysis time, the mobile phase consisting of acetonitrile, water and formic acid (60:40:0.1, v/v/v) was used in the experiment. Chromatographic separation of N-nitrosamines was done in less than two minutes. All calibration curves had good linearity (r
2
≥ 0.9989). The intra- and inter-day precision of the assay ranged from 0.59% to 3.11% and accuracy ranged from 99.66% to 104.1%. The mean recoveries of N-nitrosamines in spiked water were 98%-101%. The reproducability was acceptable with relative standard deviations of less than 3.53%. The proposed method yielded detection limits very low which ranges from 0.04 to 0.16 ng L
−1
. Finally, the developed analytical method was successfully applied to the analysis of N-nitrosamines in natural water sample
A series of yeast strains was tested in order to evaluate their catalytic potential in biocatalysis of one-pot indolizine’s synthesis. Yeast cultivation was performed in a submerged system at 28 °C ...for 72 h at 180 rpm. An assessment of the reagents’ toxicity on yeast viability and metabolic functionality concluded that the growth potential of three Yarrowia lipolytica strains were least affected by the reactants compared to the other yeast strains. Further, crude fermentation products (biomass and cell-free supernatant)—obtained by submerged cultivation of these yeasts—were used in multistep cascade reactions for the production of fluorescent indolizine compounds with important biologic activities. A whole–cell catalyzed multicomponent reaction of activated alkynes, α-bromo-carbonyl reagents and 4,4′-bipyridine, at room temperature in buffer solution led to the efficient synthesis of bis-indolizines 4a, 4b and 4c, in good-to-excellent yields (47%–77%). The metabolites of the selected Y. lipolytica strains can be considered effective biocatalysts in cycloaddition reactions and the high purity and bioconversion yields of the synthesized indolizines indicates a great potential of this type of “green” catalysts. Seeds of Triticum estivum L. were used to investigate the impact of the final products on the germination and seedling growth. The most sensitive physiological parameters suggest that indolizines, at the concentrations tested, have non-toxic effect on germination and seedling growth of wheat, fact also confirmed by confocal laser scanning microscopy images.
The aim of this study is to characterize and assess the sorption potential of brown peat, in relation to colored pollutants from the textile industry wastewater. The objectives of this paper were: ...the physicochemical, morphological, and mineralogical characterization of brown peat, testing the adsorption capacity of natural and chemically treated peat samples for Astrazone Blue, evaluation of adsorption process from equilibrium isotherm and kinetic point of view. The characteristics of the peat samples were investigated using elemental analysis, scanning electron microscopy and X-ray diffractometry. Experimental data indicated that the brown peat tested confirm a high level of adsorption (removal efficiency >93.00%, adsorption capacity reaching up to 24.27 mg/g) of Astrazone Blue from aqueous solution. The Langmuir and Freundlich adsorption isotherm models were used to find the best equation able to describe the adsorption process. Experimental adsorption data were successfully described by the Langmuir equilibrium isotherm model. This fact is supported by the agreement between the q values obtained using the Langmuir equation (26.32 mg/g), and the ones obtained experimentally (24.27 mg/g). The kinetic studies showed that the pseudo-second-order model described Astrazone Blue sorption kinetics, as confirmed by the high values of R
2
, which are over 0.99 for the whole investigated concentration range (200 to 800 mg/L). The use of brown peat adsorbent is more advantageous compared with other materials since it does not require a preliminary treatment, is low-cost and is an eco-friendly adsorbent. Hence, this peat appears to be a viable material for the decontamination of effluents containing dyes.
Diclofenac (DCF) is a non-steroidal anti-inflammatory drug and, as pollutant, it represents a persistent residue hazard to health and to the environment. Trametes versicolor was previously selected ...for its ability in diclofenac biodegradation (up to 20%) during cultivation in submerged system under aerobic conditions at an initial DCF concentration of 10 mg L^sup -1^. The influence of some factors such as nitrogen sources glucose, MnSO^sub 4^·H^sub 2^O, CuSO^sub 4^·5H^sub 2^O, inoculum level, initial DCF concentration and incubation time, upon the biodegradation potential was examined by Plackett-Burman analysis. The parameters significantly influencing the DCF biotransformation were found to be yeast extract, glucose, CuSO^sub 4^·5H^sub 2^O and inoculum level. In these optimum conditions, the DCF biotransformation yield was 80%. This result was 60% superior in comparison with the medium without optimization. Analysis of variance exhibited a high coefficient of determination (R^sup 2^) value of 0.9987 and ensured that the polynomial model with the experimental data was a satisfactory one. Optimal conditions obtained in this work led to a solid foundation for further use of Trametes versicolor in biotreatment of high strength DCF pollutant effluents in water wastes.
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