Degradation of Azo Dyes with Different Functional Groups in Simulated Wastewater by Electrocoagulation

Increasing attention has been paid to the widespread contamination of azo dyes in water bodies globally. These chemicals can present high toxicity, possibly causing severe irritation of the respiratory tract and even carcinogenic effects. The present study focuses on the periodically reverse electrocoagulation (PREC) treatment of two typical azo dyes with different functional groups, involving methyl orange (MO) and alizarin yellow (AY), using Fe-Fe electrodes. Based upon the comparative analysis of three main parameters, including current intensity, pH, and electrolyte, the optimal color removal rates for MO and AY could be achieved at a rate of up to 98.7% and 98.6%, respectively, when the current intensity is set to 0.6 A, the pH is set at 6.0, and the electrolyte is selected as NaCl. An accurate predicted method of response surface methodology (RSM) was established to optimize the PREC process involving the three parameters above. The reaction time was the main influence for both azo dyes, while the condition of PREC treatment for AY simulated wastewater was time-saving and energy conserving. According to the further UV–Vis spectrophotometry analysis throughout the procedure of the PREC process, the removal efficiency for AY was better than that of MO, potentially because hydroxyl groups might donate electrons to iron flocs or electrolyze out hydroxyl free radicals. The present study revealed that the functional groups might pose a vital influence on the removal efficiencies of the PREC treatment for those two azo dyes.

Establishment of electrochemical treatment method to dye wastewater and its application to real samples

It is of great significance to study the treatment of organic dye pollution. In this work, a method of electrochemical treatment for reactive blue 19 dye (RB19) wastewater system was established, and it was applied to the actual dye wastewater treatment. The effects of applied voltage, electrolyte concentration, electrode spacing, and initial concentration on the removal effect of RB19 have been studied in detail. The results show that the removal rate of RB19 can reach 82.6% and the chemical oxygen demand (CODcr) removal rate is 54.3% under optimal conditions. The removal of RB19 in the system is mainly the oxidation of hydroxyl free radicals. The possible degradation pathway is inferred by ion chromatography: hydroxyl free radicals attack the chromophoric group of RB19 to make it fall off, and then decompose it into ring-opening. The product is finally oxidized to CO2 and water. The kinetic fitting is in accordance with the zero-order reaction kinetics. At the same time, using the established electrochemical system to treat the actual dye wastewater has also achieved good results. After 3 hours of treatment, the CODcr removal rate of the raw water is 44.8%, and the CODcr removal of the effluent can reach 89.5%. The degradation process conforms to the zero-order reaction kinetics. The result is consistent with the electrochemical treatment of RB19.

Initiation and Prevention of Biological Damage by Radiation-Generated Protein Radicals

Ionizing radiations cause chemical damage to proteins. In aerobic aqueous solutions, the damage is commonly mediated by the hydroxyl free radicals generated from water, resulting in formation of protein radicals. Protein damage is especially significant in biological systems, because proteins are the most abundant targets of the radiation-generated radicals, the hydroxyl radical-protein reaction is fast, and the damage usually results in loss of their biological function. Under physiological conditions, proteins are initially oxidized to carbon-centered radicals, which can propagate the damage to other molecules. The most effective endogenous antioxidants, ascorbate, GSH, and urate, are unable to prevent all of the damage under the common condition of oxidative stress. In a promising development, recent work demonstrates the potential of polyphenols, their metabolites, and other aromatic compounds to repair protein radicals by the fast formation of less damaging radical adducts, thus potentially preventing the formation of a cascade of new reactive species.

Characterization and Biological Activity of a Novel Exopolysaccharide Produced by Pediococcus pentosaceus SSC–12 from Silage

In this study, 22 strains of exopolysaccharides-producing lactic acid bacteria were isolated from silage, and the strain SSC–12 with the highest exopolysaccharide (EPS) production was used as the test strain. The SSC–12 was identified as Pediococcus pentosaceus, based upon 16S rDNA gene sequencing and Neighbor Joining (NJ) phylogenetic analysis. The analysis of the kinetic results of EPS generation of SSC–12 showed that the EPS generation reached the maximum value at 20 h of culture. The characterization study showed the EPS produced by SSC–12 was a homogeneous heteropolysaccharide comprising glucose (42.6%), mannose (28.9%), galactose (16.2%), arabinose (9.4%), and rhamnose (2.9%). The EPS had good antioxidant activity, especially the activity of scavenging hydroxyl free radicals. At the same time, the EPS also had strong antibacterial ability and could completely inhibit the growth of Staphylococcus aureus. The EPS produced by the Pediococcus pentosaceus SSC–12 can be used as a biologically active product with potential application prospects in the feed, food, and pharmaceutical industries.

Impact of the Paper Degradation State and Constituents on Its Behavior During and After X-ray Exposure

Paper is a complex biopolymer material which contains papermaking additives and often bears inks and other graphic media. Cultural heritage paper-based artefacts are most often deteriorated to some extent. This research explores how intrinsic factors such as constituents and degradation state can impact the modifications incurred in aged papers during and after X-ray examination. To this end laboratory model papers, artificially aged, and 18th and 19th century archival documents, with and without additives (gelatin, calcium carbonate) and iron gallate ink, were exposed to Synchrotron X-ray radiation at doses that were previously shown to incur damage in unaged cotton papers (0.7 to 4 kGy). Glycosidic scissions, hydroxyl free radicals, UV luminescence and yellowing were measured immediately after the irradiation, and were monitored over a period of three years. The depolymerization of cellulose was lower in the aged papers, as well as in the papers containing calcium carbonate and gelatin, than in the unaged fully cellulosic papers. Compared to the papers with no additives, there were more hydroxyl free radicals in the papers with calcium carbonate and slightly less in the gelatin sized papers. UV luminescence and yellowing both appeared post-irradiation, with a delay of several weeks to months, while the intensity of the responses was impacted by the various paper constituents. The papers with iron gallate ink showed limited degradation in the low doses range, most probably due to recombination of the free radicals produced. Doses below 4 kGy did not cause yellowing or UV luminescence of the archival papers within the whole monitoring period. At higher doses (26 to 36 kGy), a slight UV luminescence appeared after 21 months, as well as a slight yellowing after three years, in some of them. No clear correlation between the degradation induced by the irradiation and the constituents in the paper nor its conservation state could be made. The archival papers in good conservation state depolymerized to the same extent as the model papers, while the most degraded archival papers were less impacted than the latter.

Effects of Autotoxicity on Alfalfa (Medicago sativa): Seed Germination, Oxidative Damage and Lipid Peroxidation of Seedlings

Alfalfa (Medicago sativa) is a highly valuable perennial forage legume that suffers from autotoxicity, which decreases plant resistance, reduces soil fertility, causes serious soil-borne diseases, and promotes ecological imbalance. We evaluated the effects of autotoxicity on the seed germination of 22 alfalfa varieties, and then elucidated the oxidative damage and lipid peroxidation in two alfalfa varieties with contrasting autotoxicity tolerances. The technique for order of preference by similarity to ideal solution (TOPSIS) method was used to rank the germination of the 22 alfalfa varieties when exposed to six autotoxic concentrations (0, 0.025, 0.075, 0.125, 0.175, and 0.225 g∙mL−1). We found WL656HQ and 3105C to be autotoxicity-tolerant and autotoxicity-sensitive varieties, respectively. The germination index mainly affects the comprehensive allelopathic index of WL656HQ and 3105C, which were the simple vigor index and radicle length according to the random forest model, respectively. 3105C eliminates reactive oxygen species (ROS) via antioxidant enzymes and antioxidants under T1 (0.025 g∙mL−1), but the oxidative stress system and the oxidative scavenging system cannot maintain the balance under T2 (0.125 g∙mL−1), causing oxidative bursts. In comparison, WL656HQ used its oxidative scavenging system (peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR)) to maintain its redox dynamic balance by removing excess ROS at all concentrations. In conclusion, the positive and negative indicators of autotoxicity for the two varieties were ascorbate (ASA) and hydroxyl free radicals (OH•), and proline (Pro) and dehydroascrobate (DHA), respectively. The most sensitive autotoxic concentrations of 3105C and WL656HQ were T2 (0.125 g∙mL−1) and T1 (0.025 g∙mL−1), respectively.

Supersensitive CeOx-based nanocomposite sensor for the electrochemical detection of hydroxyl free radicals

An electrochemical sensor comprised of cerium oxide nanoclusters grafted to a highly conductive carbon provided a limit of detection of 0.6 μM ˙OH and successfully detected in vitro the presence of ˙OH in preosteoblast cells from mouse bone tissue.

Investigation of the antioxidant capacity of the components of Astragalus after membrane separation

Astragalus is commonly used in health supplements, and its flavonoids and saponins are the important material basis for immune system enhancement. The study on the effective component contents and antioxidant capacities of astragalus extract after membrane separation lays the foundation of the application of membrane separation technology in health supplement development. The astragalus extract was filtered by suction and passed through membranes of 10000 Da, 2500 Da, and 600 Da to obtain retentate 1 (M1), retentate 2 (M2), retentate 3 (M3) and permeate MT. UV/vis spectrophotometer was used to compare the contents of total flavonoids and total saponins before and after each step of membrane separation. High performance liquid chromatography (HPLC) was used to analyze the contents of Verbasil Glucoside and Astragaloside IV of all membrane separation samples, and the antioxidant activities were determined. The contents of flavonoids in membrane separation samples were significantly different. In the freeze-dried powders obtained from the membrane separation, the contents of total flavonoids and Verbasil Glucoside were the lowest in MT, M1 was the highest, and M3 was the second highest. The order of contents of total saponins and Astragaloside IV of the freeze-dried powders from membrane separation was as follows: M3 > M1 > M2 > MT. Among them, the content of total saponins in the freeze-dried powder of M3 was the highest, which reached 2.67 times of that of the astragalus extract. The order of the scavenging activities of membrane separation samples for DPPH free radical was: MT > M3 > M2 > M1 > astragalus extract. The strongest scavenging activity of hydroxyl free radicals was found in M3, and the scavenging rates of hydroxyl free radicals in all samples were higher than those of VC. The total antioxidant capacity of FRAP showed a certain dose-effect relationship. At the same concentration, the FRAP values of M1 and MT were higher than other samples. Membrane separation technology can be used to separate and purify the effective components from astragalus extract. M3 has the highest contents of the total flavonoids and total saponins, and its antioxidant capacity is better than that of astragalus extract and other samples obtained by membrane separation.

The Influence of Lactic Acid Bacteria from Xinjiang Traditional Fermented Yogurt on Antioxidation of Geniposide in vitro

To investigate the influence of lactic acid bacteria on the antioxidant effect of geniposide in vitro, seven strains of lactic acid bacteria were isolated from natural fermented yoghurt from Xinjiang, China. Lactic acid bacteria, geniposide and their mixtures were used separately to evaluate the antioxidant effect through detecting the scavenging activity of 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH), Hydroxyl free radicals and 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS). The results showed that, compared with the group that geniposide separately used, the strains numbered x70-1, x70-2, x70-3, x70-4 and x70-5, combined with geniposide had more remarkable antioxidant effect, while the other two strains (numbered x43-2 and x43-3)combined with geniposide showed low oxidation resistance. These results may provide a potential method to promote antioxidant effect of geniposide.

Use of photo-fenton for macrolide antibiotic azithromycin removal

Azithromycin (AZT) is one of the most used antibiotics worldwide. This has led to its introduction into different environmental compartments, which implies that conventional technologies used in wastewater treatment are not enough to remove this kind of pollutants. Photo-Fenton is an advanced oxidation process in which ferrous ions (Fe2+), under light radiation, catalyzes H2O2 decomposition generating hydroxyl free radicals (HO?) which have the potential to oxidize different organic molecules. In this way, this study presents the main results regarding the evaluation of photo-Fenton using simulated sunlight in the removal of AZT from aqueous solutions. The effects of operational parameters such as ferrous ions and hydrogen peroxide initial concentrations were assessed. In addition, some tests were carried out in order to evaluate the extent of pollutant mineralization considering the dissolved organic carbon and the nitrate ions presence on treated samples. In general, results indicated that Fe2+ and H2O2 initial concentrations have a significant effect on pollutant removal.