Increasing H2O2 Concentration Research Articles

Investigation of Alkaline Hydrogen Peroxide in Aqueous Organic Solvent to Enhance Enzymatic Hydrolysis of Rice Straw

Alkaline hydrogen peroxide (AHP) pretreatment is a promising process for enhancing enzymatic digestibility of lignocellulosic biomass in biorefineries. In the present work, the effects of organic bases (NH4OH and tri-ethylamine) and co-solvents (ethanol, isopropanol, tert-butyl alcohol, water) on AHP pretreatment efficiency of rice straw were studied and compared to the typical aqueous reaction with NaOH. It was found that the glucose recovery from enzymatic hydrolysis of the biomass pretreated by AHP at 35 °C for 24 h using NH4OH in aqueous/tert-butyl alcohol (73.6%) was higher than that achieved using ethanol and isopropanol (31.6–48.6%) and water (71.2%) under the same experimental conditions. Increasing H2O2 concentration from 1 to 10% v/v in the aqueous/tert-butyl alcohol with NH4OH led to enhancing sugar yield to from 349 to 623 mg/g pretreated rice straw, equivalent to the highest glucose recovery of 83.0%. Formation of highly porous structures in pretreated rice straw by removals of hemicelluloses and lignin was revealed by Fourier transform infrared spectroscopy and scanning electron microscopy while the increased crystallinity index was shown by X-ray diffraction. This modified low-temperature AHP pretreatment using organic solvent system is advantageous on recyclability potential of the reagents and potent for further implementation in lignocellulosic biorefineries.

Optimization of triple dye mixture removal by oxidation with Fenton

Azo dyes are widely used in textile industry due to their easy production, high stability during washing and variety of colors. It raises concern over the ecosystem because of its structural features. Some advanced oxidation process that is tertiary treatment is one of the conventional treatment methods. Pollutants that cannot be removed by primary and secondary treatment are treated by tertiary treatment methods. Primary and secondary treatment methods are not generally sufficient for removal of azo dyes. For this reason, it has an important place in its treatment with advanced oxidation processes. The aim of this study is to investigate the effect of different parameters on color and COD removal yields of triple dye mixtures by Fenton method and to optimize with the Taguchi method. Moreover, the aim is to examine the relationship between these parameters and ORP by regression analysis, and the change of organic groups by FTIR analysis in the effluent. As a result of the study, it was observed that the parameters considered had different effects on COD and color removal. There was an increase in both color and COD removal only with the increase in H2O2 concentration. The highest COD and color removal yields were 95.8% and 99.3%, respectively. As a conclusion, Fenton process is a method that can be preferred in the treatment of textile dyestuffs since the chemicals used are non-toxic, abundant and economical, and therefore, the operation cost of the system is quite favorable, providing advantages to compete with other advanced oxidation processes.

Humic Acid and Auxins Induced Metabolic Changes and Differential Gene Expression during Adventitious Root Development in Azalea Microshoots

Auxins and humic acid (HA) were investigated for their roles in adventitious root induction in azalea microshoots in our previous study. To reveal the regulatory mechanisms of auxins and HA in this process, measurements of the levels of reactive oxygen species (ROS), carbohydrates, and phenolic compounds and gene expression during in vitro root development were performed. During the adventitious root induction process, ROS levels in shoots treated with auxins and HA increased compared to untreated shoots, especially during the earliest period after transfer to the media. Media supplemented with NAA experienced increases in H2O2 contents by 480%and 250%, respectively, after 7 and 14 days of culture. The phenolic compound levels were also enhanced in the shoots treated with auxins and HA, reflecting the different rooting-promoting abilities of both auxins and HA. The highest levels of total phenolic [68.6 mg·g−1 fresh weight (FW)], polyphenolic acids (121.72 μg caffic acid/g FW), and total flavonols (162.42 μg quercetin/g FW) were recorded after 21 days for NAA media, but the maximum levels of anthocyanins (49.76 μg cyanindin/g FW) were recorded after 21 days for IBA medium. Soluble carbohydrate, starch, and soluble protein levels were increased in the shoots treated with all treatments; however, the influence of NAA treatments was stronger than that of other treatments for most investigated parameters. The NAA significantly enhanced soluble carbohydrates by 30%, 37%, and 25%, respectively, at 14, 21, and 28 days compared with untreated microshoots. Expression of the POD1 gene increased in the shoots submitted to HA treatment media. Expression levels of auxin response factors (ARFs) increased with IBA- and NAA-treated explants, suggesting that ARFs may have diverse regulatory roles in adventitious root induction in evergreen azalea. Moreover, the profiles of the IAA1, IAA9, IAA14, and IAA27 transcripts were analyzed to reveal their roles in the adventitious rooting of evergreen azalea microshoots. These results indicate that auxins and HA promote adventitious root induction in Rhododendron plants through their impact on ROS, carbohydrate contents, phenolic compound levels, and expression levels of different genes related to root development in evergreen azalea plants.

In vitro phytotoxicity of Mikania laevigata Schultz Bip. ex Baker extracts on Lactuca sativa L. and Bidens pilosa L.

Extratos vegetais possuem metabólitos secundários que podem atuar como bioherbicidas com a vantagem de promoverem menores riscos ao ambiente. Mikania laevigata pertence à família Asteraceae e possui a cumarina 1,2-benzopirona como marcador químico, capaz de inibir ou estimular a germinação e crescimento de plantas adjacentes. Diante do exposto, objetivou-se avaliar a fitotoxicidade dos extratos aquoso e etanólico de M. laevigata sobre Lactuca sativa (alface) e Bidens pilosa (picão preto). Foram testadas cinco concentrações (0,1; 1,0; 1,5; 2,0 e 3,0 mg.mL-1) dos extratos, aquoso e etanólico, em experimentos separados, e água destilada como controle. Para isso, foram avaliados a porcentagem de germinação, o índice de velocidade de germinação, o crescimento inicial e os teores de peróxido de hidrogênio (H2O2) e do malonaldeido (MDA). Na presença do extrato etanólico, as espécies (alface e picão preto) reduziram 85 e 90% da germinação, respectivamente. O comprimento da radícula, na menor concentração dos extratos, não foi afetado. Entretanto, na concentração de 2,0 mg.mL-1, as reduções foram de 85%, para alface, e 65%, para picão preto. O aumento do teor de H2O2 foi dose dependente, ou seja, conforme o aumento da concentração dos extratos maior a produção de peróxido, seguido do aumento do MDA para alface e picão preto. As plântulas cultivadas na concentração de 3 mg.mL-1 do extrato etanólico sofreram necrose, impossibilitando as análises subsequentes. Os extratos da M. laeviagata nas concentrações 2,0 e 3,0 mg.mL-1 demonstraram fitointoxicação com aumento do estresse oxidativo nas espécies alface e picão preto.

Metabolomic, proteomic and physiological insights into the potential mode of action of thymol, a phytotoxic natural monoterpenoid phenol

Thymol is a natural phenolic monoterpene widely produced by different species belonging to the Labiateae family. Although the thymol phytotoxicity is well known, the knowledge of its potential toxic mechanism is still limited. In this regard, the model species Arabidopsis thaliana was treated for 16 days by sub-irrigation with 300 μM of thymol. The results confirmed the high phytotoxic potential of this phenolic compound, which caused a reduction in plant growth and development. Thymol induced a water status alteration accompanied by an increase in ABA content and stomatal closure. Furthermore, leaves appeared necrotic in the margins and their temperature rinsed. The increase in H2O2 content suggested an oxidative stress experienced by treated plants. Both metabolomic and proteomic analysis confirmed this hypothesis showing a strong increase in osmoprotectants content, such as galactinol and proline, and a significant up-accumulation of proteins involved in ROS detoxification. Furthermore, the down-accumulation of proteins and pigments involved in the photosynthetic machinery, the increase in light sensitivity and the lower PSII efficiency well indicated a reduction in photosynthetic activity. Overall, we can postulate that thymol-induced phytotoxicity could be related to a combined osmotic and oxidative stress that resulted in reduced plant development.

Oxidation absorption of hydrogen sulfide from gas stream using vacuum ultraviolet/H2O2/urea wet scrubbing system

Hydrogen sulfide has serious harm to human body and equipment. Advanced oxidation technology shows excellent development prospect for hydrogen sulfide (H2S) removal due to strong oxidation ability and green process. This article proposed a novel separation process for H2S from gas stream using vacuum ultraviolet (VUV)/H2O2/urea wet scrubbing system in a VUV-spraying scrubber, and studied the effectiveness of H2S removal and removal pathways using VUV/H2O2/urea wet scrubbing system. Results indicated that the highest H2S removal efficiency was up to 98.2 % under optimal experimental conditions. Increasing UV-light intensity and solution pH improved the H2S removal efficiency. Increasing flue gas flow rate and H2S concentration decreased the H2S removal efficiency. The increase of H2O2 concentration, reaction temperature, liquid-gas ratio or urea concentration first increased and then reduced the H2S removal efficiency. H2S was removed by five pathways such as ionization, urea absorption, H2O2 oxidation, photolysis and ·OH oxidation. Photolysis and ·OH oxidation were the two major pathways for the H2S removal.

Poplar Tree Response to Feeding by the Petiole Gall Aphid Pemphigus spyrothecae Pass.

Pemphigus spyrothecae Pass. which is a member of the subfamily Pemphiginae is one of the gall-inducing aphids that occurs on poplar trees. Phloem feeding of a founding mother on leaf petiole results in the formation of a new organ, i.e., the spiral gall. This study documents aphid development inside the galls during the growing season and the effect of their feeding on leaf architecture and physiology of the host plant. In particular, leaf length, width, and area were measured, as well as hydrogen peroxide (H2O2) content, electrolyte leakage (EL), malondialdehyde (MDA) concentration, and the activity of ascorbate (APX) and guaiacol peroxidase (GPX) were determined in galls and galled leaves. The presence of petiole galls significantly decreased the length, width, and leaf area. Aphid activity increased H2O2 concentration in galls and EL from galls and leaf tissues, which was accompanied by a strong decrease in MDA content and both peroxidase activities, especially in gall tissues. It can be suggested that P. spyrothecae can manipulate physiological machinery of the host plant for its own benefit.

The roles of Brønsted acidity in low-temperature catalytic oxidation of NO over acidic zeolites with H2O2

In this study, low-temperature catalytic NO oxidation with H2O2 over Na- and H-exchanged Y and ZSM-5 zeolites was investigated at 140 °C which is the average exhaust temperature of coal-fired power plant. Fast catalytic NO oxidation rates were observed over H-zeolites, and catalytic activity was proportional to the amount of Brønsted acid sites. HZSM-5 and HY zeolites show 65% and 95% NO removal efficiency, respectively, but the catalytic stability of HY was lower than HZM-5 due to partial dealumination during the reaction. In-situ DRIFTS analysis showed that NO+ species coordinated at framework sites played a direct role in the catalytic NO oxidation. Moreover, the possible reaction pathway was proposed to elucidate the mechanism of NO oxidation with H2O2 catalyzed over Brønsted acid sites. The effect of reaction temperature, H2O2 concentration, H2O2 flow and SO2 concentration on NO oxidation were investigated over H-zeolites. The experimental results indicated that the NO removal efficiency was increased with the increase of H2O2 concentration, but decreased with the increase of SO2 concentration. The NO removal efficiency first increased and then decreased with the increase of H2O2 flow and reaction temperature.

Response of brassinosteroids to nitrogen rates and their regulation on rice spikelet degeneration during meiosis

AbstractThe plant steroid hormones brassinosteroids (BRs) play pivotal roles in modulating flower and fruit production. Nitrogen (N) is a key factor affecting rice (Oryza sativa L.) production. We hypothesized that BRs would respond to N application rates at spikelet differentiation (SD) and regulate spikelet degeneration in rice. Three rice cultivars were field‐grown and treated with five N rates at SD. Plant N and BRs contents, antioxidant capacity, and energy status were observed during meiosis in young panicles, and their relationships with spikelet degeneration were evaluated. In all the N treatments, the BRs, adenosine triphosphate, and energy charge levels, activities of the enzymes involved in energy metabolism, including cytochrome C oxidase and succinate dehydrogenase, total antioxidant capacity, and grain yield, were the highest, whereas hydrogen peroxide (H2O2) content and vacuolar processing enzymes (VPE) genes expression levels, and spikelet degeneration rate were the lowest when plant N content was 2.6% during meiosis. The rice BRs‐deficient mutants showed substantial reduction in BRs levels, antioxidant capacity, and energy status, but great increase in H2O2 content, VPE genes expression levels, and spikelet degeneration rate than the wild type (WT); moreover, these parameters in WT panicles could be regulated, whereas in BRs‐deficient mutant panicles, they were not distinctly affected by N application. The results indicated that BRs mediate the effects of N rates on spikelet degeneration, and elevated BRs levels in rice panicles effectively inhibit spikelet degeneration when plant N content is 2.6% during meiosis by elevating antioxidant capacity and energy status.

Vanadium-dependent haloperoxidase activity and phlorotannin incorporation into the cell wall during early embryogenesis of Fucus vesiculosus (Phaeophyceae)

ABSTRACT Vanadium-dependent haloperoxidases (V-HPO) are specific enzymes involved in the metabolism of reactive oxygen species in marine algae. These enzymes contribute to early embryogenesis of algae in the order Fucales, catalyzing the reactions which result in phlorotannin incorporation into the newly forming zygote cell wall and adhesive material. In this study we showed that early embryogenesis in Fucus vesiculosus is accompanied by synchronous changes of V-HPO activity, hydrogen peroxide content and content of cell-wall-associated phlorotannins. Phlorotannin incorporation into the cell wall of Fucus zygotes had already begun 1 h after fertilization, and this process was accompanied by rapid increase of H2O2 content and V-HPO activity. We suggest that altogether this initiates polymerization of phenolics and their cross-linking with the major cell wall constituent, alginic acid. Presumably, de novo phlorotannin biosynthesis is involved in this process, as GC-MS analysis showed dramatic changes in content of intracellular phloroglucinol and low-molecular-weight phlorotannins during the first 9 days of F. vesiculosus embryogenesis.

Involvement of triadimefon induced early ABA-dependent H2O2 accumulation in soybean against water stress

The present study showed that pretreatment of triadimefon (TDM), a triazole compound, could improve tolerance of soybean seedlings to subsequent water stress. TDM pretreatment resulted in early and late rise in superoxide dismutase (SOD) and catalase (CAT) activities, and upregulation of ascorbate (AsA) content in non-stressed and water-stressed seedlings, leading to late increase in net photosynthetic rate (Pn), late decrease in hydrogen peroxide (H2O2) and electrolyte leakage in stressed ones. These TDM-induced changes were blocked by application of abscisic acid (ABA) biosynthesis inhibitor tungstate, which inhibited early rise of ABA and H2O2 contents in non-stressed and stressed seedlings. However, ABA pretreatment overcomed the effects of this inhibitor. Application of NADPH oxidase inhibitor diphenyleneiodonium (DPI), polyamine oxidase (PAO) inhibitor 2-hydroxyethylhydrazine (2-HEH) and H2O2 scavenger dimethylthiourea (DMTU) prevented early TDM-induced rise of H2O2 content. DPI, 2-HEH and DMTU also decreased SOD, CAT and AsA levels, but did not affect ABA content during early and late phases in both seedlings pretreated with TDM. In addition, these chemicals decreased Pn, and increased H2O2 content and electrolyte leakage during late phase in TDM-pretreated stressed seedlings. Overall, these results indicated that TDM pretreatment alleviated adverse effects of water stress on soybean seedlings, which was at least in part, due to increase of antioxidant capacity and decrease of oxidative damage induced by early ABA-dependent H2O2 generation.

Improving Photosynthetic Capacity, Alleviating Photosynthetic Inhibition and Oxidative Stress Under Low Temperature Stress With Exogenous Hydrogen Sulfide in Blueberry Seedlings.

In this study, we investigated the mechanism of photosynthesis and physiological function of blueberry leaves under low temperature stress (4–6°C) by exogenous hydrogen sulfide (H2S) by spraying leaves with 0.5 mmol·L–1 NaHS (H2S donor) and 200 μmol·L–1 hypotaurine (Hypotaurine, H2S scavenger). The results showed that chlorophyll and carotenoid content in blueberry leaves decreased under low temperature stress, and the photochemical activities of photosystem II (PSII) and photosystem I (PSI) were also inhibited. Low temperature stress can reduce photosynthetic carbon assimilation capacity by inhibiting stomatal conductance (Gs) of blueberry leaves, and non-stomatal factors also play a limiting role at the 5th day of low temperature stress. Low temperature stress leads to the accumulation of Pro and H2O2 in blueberry leaves and increases membrane peroxidation. Spraying leaves with NaHS, a donor of exogenous H2S, could alleviate the degradation of chlorophyll and carotenoids in blueberry leaves caused by low temperature and reduce the photoinhibition of PSII and PSI. The main reason for the enhancement of photochemical activity of PSII was that exogenous H2S promoted the electron transfer from QA to QB on PSII acceptor side under low temperature stress. In addition, it promoted the accumulation of osmotic regulator proline under low temperature stress and significantly alleviated membrane peroxidation. H2S scavengers (Hypotaurine) aggravated photoinhibition and the degree of oxidative damage under low temperature stress. Improving photosynthetic capacity as well as alleviating photosynthetic inhibition and oxidative stress with exogenous H2S is possible in blueberry seedlings under low temperature stress.

The Impacts of Gallic Acid on Redox State of Antioxidants Related to Ascorbate–Glutathione Cycle in Wheat (Triticum aestivum) Grown Under Cadmium Toxicity

This work was conducted to define the efficacy of gallic acid (GLA) on growth, water management, ROS content, the antioxidant capacity including ascorbate–glutathione cycle and their redox state and lipid peroxidation (TBARS) in wheat grown under cadmium (Cd) toxicity. Germinated wheat was hydroponically grown for 21 days (d) and was treated with the combination form and alone of GLA (25 and 75 μM) and Cd stress (100 and 200 μM) for 7 d. The findings revealed that the decrement on growth, water content and proline content was observed under stress. The decreases were reversed by GLA applications. Despite the increased superoxide dismutase (SOD) activity, stress caused an inactivation of catalase (CAT), peroxidase (POX), glutathione reductase (GR) and NADPH oxidase (NOX) but, only ascorbate peroxidase (APX) activity was induced. APX activity was not enough for scavenging of Cd-induced hydrogen peroxide (H2O2) content. Therefore, in stress-treated wheat, the enhancement in TBARS content was detected. After GLA applications to plants exposed to stress, the increased H2O2 content by the activation of SOD and NOX was eliminated by the activities of APX, GR, monodehydroascorbate reductase and dehydroascorbate reductase and glutathione (GSH) rather than CAT and POX enzymes. From this study, we conclude that 25 μM GLA was more effective in protection against the damages triggered by both Cd treatments by maintaining the pool of ascorbate and glutathione, decreasing TBARS levels and improving the scavenging activity of hydroxyl radical. The redox state of enzymes/non-enzymes antioxidants including ascorbate–glutathione cycle was also induced by 75 μM GLA under low Cd concentration.

Silencing of OsCV (chloroplast vesiculation) maintained photorespiration and N assimilation in rice plants grown under elevated CO2

High CO2 concentrations stimulate net photosynthesis by increasing CO2 substrate availability for Rubisco, simultaneously suppressing photorespiration. Previously, we reported that silencing the chloroplast vesiculation (cv) gene in rice increased source fitness, through the maintenance of chloroplast stability and the expression of photorespiration-associated genes. Because high atmospheric CO2 conditions diminished photorespiration, we tested whether CV silencing might be a viable strategy to improve the effects of high CO2 on grain yield and N assimilation in rice. Under elevated CO2 , OsCV expression was induced, and OsCV was targeted to peroxisomes where it facilitated the removal of OsPEX11-1 from the peroxisome and delivered it to the vacuole for degradation. This process correlated well with the reduction in the number of peroxisomes, the decreased catalase activity and the increased H2 O2 content in wild-type plants under elevated CO2 . At elevated CO2 , CV-silenced rice plants maintained peroxisome proliferation and photorespiration and displayed higher N assimilation than wild-type plants. This was supported by higher activity of enzymes involved in NO3 - and NH4 + assimilation and higher total and seed protein contents. Co-immunoprecipitation of OsCV-interacting proteins suggested that, similar to its role in chloroplast protein turnover, OsCV acted as a scaffold, binding peroxisomal proteins.

Photochemical mineralization of amoxicillin medicinal product by means of UV, hydrogen peroxide, titanium dioxide and iron

ABSTRACT In the present study, the photochemical degradation of amoxicillin and total organic carbon (TOC) removal in pharmaceutical aqueous solutions was studied using UV irradiation, titanium dioxide, hydrogen peroxide and iron in a batch photoreactor operated for 120–150 min. The effect of the initial concentrations of the target compound, hydrogen peroxide and ferric ions and of their combination was examined. It was found that under direct UV photolysis, considerable TOC removals were obtained only when the initial concentration of amoxicillin (AM) was below 100 mg/L. For initial concentration of AM 250 mg/L, the TOC removals achieved were of no practical use (below 5%). The TOC removals achieved in the presence of TiO2 were lower than 20% in all cases. In the presence of hydrogen peroxide in the range of 12.2–146.9 mmol/L and initial AM concentration 250 mg/L, for increasing H2O2 concentrations higher TOC removals were achieved up to the concentration of 73.4 mmol/L H2O2. The presence of even very small amounts of Fe(III) in the solution resulted in significantly increased TOC removals; 2.2 times higher than without Fe(III) after 120 min. Fe(III) presence accelerated dramatically the process during the first 60 min. The origin of Fe(III) ions was not important since practically the same results were obtained whether FeCl3 or Fe(NO3)3 was used as source of ferric ions. Adjusting the initial concentrations of AM, Fe(III) and H2O2, TOC removals above 90% were achieved.

Autonomous Motion of Bubble-Powered Carbonaceous Nanoflask Motors.

We report a carbonaceous nanomotor with a characteristic flask-like hollow structure that can autonomously move under the propulsion of oxygen bubbles. The carbonaceous nanoflask (CNF) motor was fabricated by encapsulating platinum nanoparticles (Pt NPs) into the hollow cavity of the CNF. The internally encapsulated Pt NPs act as catalysts to decompose hydrogen peroxide (H2O2) fuel into oxygen bubbles. The generated oxygen bubbles recoil the motion of the CNF motors. Besides, the velocity of CNF motors can be controlled by adjusting the concentration of the H2O2 solution. The motion velocity increases with the increase of H2O2 concentration, up to 109.25 μm s-1 at 10% H2O2. This study provides important implications for understanding the motion behaviors of nanomotors with an internal cavity, and the self-propelled CNF motors as smart carrier systems have potential applications in the future.

Developing a Silk Fibroin Composite Film to Scavenge and Probe H2O2 Associated with UV-Excitable Blue Fluorescence.

A silk fibroin composite film that can simultaneously scavenge and probe H2O2 in situ was developed for possibly examining local concentrations of H2O2 for biomedical applications. A multi-functional composite film (GDES) that consists of graphene oxide (G), a photothermally responsive element that was blended with polydopamine (PDA, D)/horseradish peroxidase (HRP, E) (or DE complex), and then GDE microaggregates were coated with silk fibroin (SF, S), a tyrosine-containing protein. At 37 °C, the H2O2-scavenging ability of a GDES film in solution at approximately 7.5 × 10−3 μmol H2O2/mg film was the highest compared with those of S and GS films. The intensities of UV-excitable blue fluorescence of a GDES film linearly increased with increasing H2O2 concentrations from 4.0 μM to 80 μM at 37 °C. Interestingly, after a GDES film scavenged H2O2, the UV-excitable blue fluorescent film could be qualitatively monitored by eye, making the film an eye-probe H2O2 sensor. A GDES film enabled to heat H2O2-containing samples to 37 °C or higher by the absorption of near-IR irradiation at 808 nm. The good biocompatibility of a GDES film was examined according to the requirements of ISO-10993-5. Accordingly, a GDES film was developed herein to scavenge and eye-probe H2O2 in situ and so it has potential for biomedical applications.

Chemical Mechanical Planarization of Carbon-Doped Amorphous Ge2Sb2Te5 Film with Hydrogen Peroxide as Oxidizer in Alkaline Slurry

In this study, we investigate the chemical mechanical planarization (CMP), static dissolution and electrochemical performace of amorphous carbon-doped Ge2Sb2Te5 (GSTC) film in alkaline slurry with H2O2 employed as an oxidizer. It was found that the material removal rate (MRR) of GSTC first increase and then slowly decrease with the increase in concentration of H2O2. The surface quality of the GSTC post-CMP shows the same trend. To understand the mechanism of GSTC CMP with H2O2, the Energy Dispersive Spectrometer on the surface of the GSTC post-CMP, Inductively Coupled Plasma of the solution after static dissolution, potentiodynamic polarization curve and X-ray photoelectron spectroscope are measured and it is found that the change in carbon state is an important factor for the CMP of GSTC. Finally, a possible removal mechanism of GSTC in different concentrations of H2O2 in the alkaline slurry is proposed.

Weakened carbon and nitrogen metabolisms under post-silking heat stress reduce the yield and dry matter accumulation in waxy maize

Post-silking high temperature is one of the abiotic factors that affects waxy maize (Zea mays L. sinensis Kulesh) growth in southern China. We conducted a pot trial in 2016–2017 to study the effects of post-silking daytime heat stress (35°C) on the activities of enzymes involved in leaf carbon and nitrogen metabolisms and leaf reactive oxygen species (ROS) and water contents. This study could improve our understanding on dry matter accumulation and translocation and grain yield production. Results indicated that decreased grain number and weight under heat stress led to yield loss, which decreased by 20.8 and 20.0% in 2016 and 2017, respectively. High temperature reduced post-silking dry matter accumulation (16.1 and 29.5% in 2016 and 2017, respectively) and promoted translocation of pre-silking photoassimilates stored in vegetative organs, especially in leaf. The lower leaf water content and chlorophyll SPAD value, and higher ROS (H2O2 and O2−·) content under heat stress conditions indicated accelerated senescent rate. The weak activities of phosphoenolpyruvate carboxylase (PEPCase), Ribulose-1,5-bisphosphate carboxylase (RuBPCase), nitrate reductase (NR), and glutamine synthase (GS) indicated that leaf carbon and nitrogen metabolisms were suppressed when the plants suffered from a high temperature during grain filling. Correlation analysis results indicated that the reduced grain yield was mainly caused by the decreased leaf water content, weakened NR activity, and increased H2O2 content. The increased accumulation of grain weight and post-silking dry matter and the reduced translocation amount in leaf was mainly due to the increased chlorophyll SPAD value and NR activity. Reduced PEPCase and RuBPCase activities did not affect dry matter accumulation and translocation and grain yield. In conclusion, post-silking heat stress down-regulated the leaf NR and GS activities, increased the leaf water loss rate, increased ROS generation, and induced pre-silking carbohydrate translocation. However, it reduced the post-silking direct photoassimilate deposition, ultimately, leading to grain yield loss.

Colour and COD removal from aqueous solutions of direct yellow 86 textile dyestuff by electro-Fenton method

In this study, COD and colour removal were investigated by the electro-Fenton method from aqueous solutions of direct yellow 86 commercial textile dyes. The effects of electrolyte concentration (250-3,000 mg/L), H2O2 concentration (250-3,000 mg/L), the initial dye concentration (50-500 mg/L), the distance of anode-cathode (0.5-1.5 cm) on COD and colour removals were investigated. Under optimal experimental conditions (NaCl: 1,500 mg/L, H2O2: 1,500 mg/L, the initial dye concentration: 50 mg/L, the distance of anode-cathode: 1.5 cm), the maximum COD and colour removal efficiencies were 95.3% and 99.5%, respectively. It was determined that H2O2 concentration and dye concentration had the highest effect on the removal efficiencies. It was determined that pollutant removal efficiencies increased with increasing H2O2 concentration, and decreased with increasing initial dye concentration. The results showed that the electro-Fenton method can be effectively applied in COD and colour removal from aqueous solutions of direct yellow 86 commercial textile dyestuff.