Clopyralid detection by using a molecularly imprinted electrochemical luminescence sensor based on the “gate-controlled” effect

A new strategy for trace analysis was proposed by preparing a molecularly imprinted polymer (MIP) sensor. The template molecules of clopyralid were determined based on “gate-controlled” electrochemiluminescence (ECL) measurement. A dense polymer film was electropolymerized on an electrode surface to fabricate the MIP–ECL sensor. The process of template elution and rebinding acted as a gate to control the flux of probes, which pass through the cavities and react on the electrode surface. ECL measurement was conducted in the luminol–H₂O₂ system. A linear relationship between ECL intensity and clopyralid concentrations in the range of 1?×?10^?9 mol/L to 8?×?10^?7 mol/L exists, and the detection limit was 3.7?×?10^?10 mol/L. The prepared sensor was used to detect clopyralid in vegetables. Recoveries of 97.9 % to 102.9 % were obtained. The sensor showed highly selective recognition, high sensitivity, good stability, and reproducibility for clopyralid detection.     

Efficient removal of tetracycline by H2O2 activated with iron-doped biochar: Performance,mechanism, and degradation pathways

In this study,novel iron-doped biochar（Fe-BC） was produced using a simple method,and it was used as an H₂ O₂ activator for tetracycline（TC） degradation.Generally,iron loading can improve the separation performance and reactivity of biochar（BC）.In the Fe-BC/H₂ O₂ system,92% of the TC was removed within 30 min with the apparent rate constant(k_obs) of 0.155 min^-1,which was 23.85 times that in the case of the BC/H₂ O_2<...     

Degradation of pyrazinamide in aqueous solution by electron beam irradiation: kinetics,influence factors and mechanism study

The degradation of pyrazinamide (PZA) by electron beam irradiation (EBI) was studied. It was found that the degradation of PZA was efficient with the removal rate of 99% for 0.2 mM PZA under 5 kGy, and the degradation kinetics followed pseudo-first-order kinetics. The presence of CO₃^2?, HCO₃^?, NO₃^?, and fulvic acid inhibited the degradation of PZA. The addition of H₂O₂ or K₂S₂O₈ effectively enhanced the degradation and mineralization of PZA. The scavenger experiments and quantum chemical calculations showed that ^·OH was the primary reactive species in the degradation. The identification of intermediates and quantum chemical calculations illustrated the mechanism of degradation.

     

Degradation of n-butylparaben and 4-tert-octylphenol in H2O2/UV system

The degradation of two endocrine disrupting compounds: n-butylparaben (BP) and 4-tert-octylphenol (OP) in the H₂O₂/UV system was studied. The effect of operating variables: initial hydrogen peroxide concentration, initial substrate concentration, pH of the reaction solution and photon fluency rate of radiation at 254 nm on reaction rate was investigated. The influence of hydroxyl radical scavengers, humic acid and nitrate anion on reaction course was also studied. A very weak scavenging effect during BP degradation was observed indicating reactions different from hydroxyl radical oxidation. The second-order rate constants of BP and OP with OH radicals were estimated to be 4.8×10⁹ and 4.2×10⁹ M^?1 s^?1, respectively. For BP the rate constant equal to 2.0×10¹⁰ M^?1 s^?1was also determined using water radiolysis as a source of hydroxyl radicals.     

Effect of simulated solar light on the autocatalytic degradation of nitrobenzene using Fe3+ and hydrogen peroxide

The effect of simulated solar light on nitrobenzene degradation in Fe³⁺/H₂O₂ solutions was investigated under different experimental conditions. Consumption profiles of NBE and H₂O₂ display an autocatalytic kinetic behavior for both dark and photo-assisted degradation experiments. The rates of the initial slow phase that precedes the catalytic phase are significantly enhanced by irradiation, although the effect of simulated solar light on the rates of the fast phase is negligible. The absolute rates of the slow phase increase with the concentrations of Fe³⁺ and H₂O₂, whereas the initial rate of the degree of conversion increase decreases with organic matter loading. The reaction progress was characterized by HPLC, GC–MS, IC, TOC (total organic carbon) and toxicity analyses. The main products detected were 4-nitrophenol, 3-nitrophenol, 2-nitrophenol, 1,3-dinitrobenzene, phenol, oxalic acid, formic acid, NO₂^? and NO₃^?. Product distribution profiles are discussed in connection with TOC and toxicity measurements. The results show that dark treatment is neither capable of lowering the organic content nor capable of reducing the effluent toxicity to acceptable levels. On the other hand, photo-assisted processes induced by simulated solar light can significantly enhance both mineralization and detoxification efficiencies.     

Photocatalytic degradation kinetics of methyl orange in TiO2–SiO2–NiFe2O4 aqueous suspensions

Photocatalytic degradation of methyl orange by TiO₂–SiO₂–NiFe₂O₄ suspensions was investigated. Adsorption studies revealed photocatalytic degradation occurred mainly on the surface of the TiO₂–SiO₂–NiFe₂O₄. The disappearance of the compound followed the zero-order kinetics according to the Langmuir–Hinshelwood model and the rate constant was 0.0035 mg L^?1 min^?1. The rate constant depended on the amount of photocatalyst, initial pH, and the presence of additional scavengers. ^?OH radicals and h⁺ had important roles in the photocatalytic degradation of methyl orange by TiO₂–SiO₂–NiFe₂O₄.     

Effective norfloxacin elimination via photo-Fenton process over the MIL-101(Fe)-NH2 immobilized on α-Al2O3 sheet

MIL-101(Fe)-NH₂@Al₂O₃ (MA) catalysts were successfully synthesized by reactive seeding (RS) method on α-Al₂O₃ substrate, which demonstrated excellent photo-Fenton degradation performance toward fluoroquinolone antibiotics (i.e., norfloxacin, ciprofloxacin, and enrofloxacin). The structure and morphology of the obtained MA were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), atomic force microscope (AFM). The as-prepared MA could accomplish > 90% of norfloxacin degradation efficiency for 10 cycles’ photo-Fenton processes, owing to its excellent chemical and water stability. In addition, the effects of operational factors including H₂O₂ concentration, foreign ions, and pH on the photo-Fenton degradation of norfloxacin over MA were clarified. The ESR spectra further document that ^?O₂^?, ¹O₂ and ^?OH radicals are prominent in the decomposition process of antibiotic molecules. Finally, the plausible photo-Fenton norfloxacin degradation mechanisms were proposed and verified.     

Oxidative and reductive degradation of sulfamethoxazole in aqueous solutions: decomposition efficiency and toxicity assessment

Under radiolytic conditions at a concentration of 0.1 mmol dm^?3 the reactions of sulfamethoxazole, a worldwide used anti-infective sulfonamide antibiotic, were mainly induced by hydroxyl radicals. With a dose of 5 kGy complete degradation of aromatic system was observed. The sulfur of the molecule was entirely transformed to SO₄ ^2–, while NO₃ ^– and NH₄ ⁺ were formed from the nitrogen content. The chemical oxygen demand and total organic carbon values indicated complete mineralization during irradiation. In pursuance of toxicity tests, the observed increase in mortality of Vibrio fischeri bacteria was mainly due to H₂O₂ formed during the radiolytic procedure. The results showed that the degradation was effective; therefore, the irradiation technology can be recommended for treatment of wastewater containing sulfamethoxazole.     

Biohydrogen Production Based on the Evaluation of Kinetic Parameters of a Mixed Microbial Culture Using Glucose and Fruit–Vegetable Waste as Feedstocks

Hydrogen (H₂) production from the organic fraction of solid waste such as fruit and vegetable waste (FVW) is a novel and feasible energy technology. Continuous application of this process would allow for the simultaneous treatment of organic residues and energy production. In this study, batch experiments were conducted using glucose as substrate, and data of H₂ production obtained were successfully adjusted by a logistic model. The kinetic parameters (μ _max?=?0.101 h^?1, K _s?=?2.56 g/L) of an H₂-producing microbial culture determined by the Monod and Haldane–Andrews growth models were used to establish the continuous culture conditions. This strategy led to a productive steady state in continuous culture. Once the steady state was reached in the continuous reactor, a maximum H₂ production of 700 mL was attained. The feasibility of producing H₂ from the FVW obtained from a local market in Mexico City was also evaluated using batch conditions. The effect of the initial FVW concentration on the H₂ production and waste organic material degradation was determined. The highest H₂ production rate (1.7 mmol/day), the highest cumulative H₂ volume (310 mL), and 25 % chemical oxygen demand (COD) removal were obtained with an initial substrate (FVW) concentration of 37 g COD/L. The lowest H₂ production rates were obtained with relatively low initial substrate concentrations of 5 and 11 g COD/L. The H₂ production rates with FVW were also characterized by the logistic model. Similar cumulative H₂ production was obtained when glucose and FVW were used as substrates.     

Reactivity of O2 − radical anions on hydrated ZrO2 surface

The concentration of O₂ ^? radical anions generated on the surface of hydrated ZrO₂ in an H₂O₂ solution was found to depend on H₂O₂ concentration. It was shown that this method can be used for detecting H₂O₂ in solutions at concentration as low as 0.01 wt%. The radical anions were found to react with organic molecules, even at room temperature. The decomposition kinetics of O₂ ^? radical anions was double-exponential with two reaction rate constants. The existence of two distinct rate constants suggests that two types of O₂ ^? radical anions with similar spectroscopic properties but different reactivity are present on the surface of hydrated ZrO₂. It is highly likely that different arrangements of hydroxyl groups near the radical anions account for the presence of the two types of O₂ ^? with different reactivity. The rate constants obtained in the presence of the organic compounds studied were found to conform with the expected order of reactivity: toluene > benzene ? hexane.     

Role of reactive oxygen species and effect of solution matrix in trichloroethylene degradation from aqueous solution by zeolite-supported nano iron as percarbonate activator

The role of reactive oxygen species (ROSs) and effect of solution matrix have been investigated for the degradation of trichloroethylene (TCE). Zeolite-supported nano iron (Z-nZVI) was synthesized as an activator to catalyze sodium percarbonate (SPC) with or without hydroxylamine, i.e. as reducing agent (RA). The probe tests confirmed the generation of OH^· and O ₂ ^?· in the Z-nZVI activated SPC system in absence of the RA, while the presence of RA significantly increased the generation of OH^· and O ₂ ^?· radicals. Scavenger tests demonstrated that OH^· was the main ROS responsible for TCE degradation, whereas O ₂ ^?· also participated in TCE degradation. From the solution matrix perspective, the experimental results confirmed significant scavenging effects of Cl^? (1.0, 10.0, and 100 mmol L^?1) and HCO₃ ^? (1.0 and 10.0 mmol L^?1), whereas the scavenging effects were fairly impeded at 100 mmol L^?1 concentration of HCO₃ ^?. On the other hand, a considerable decline in scavenging effect was observed in the presence of RA in tested Cl^? and HCO₃ ^? concentration ranges. In addition, negligible scavenging effects of NO₃ ^? and SO₄ ^2? anions were found in all tested concentrations. The effect of initial solution pH on catalytic activity indicated a significant increase in the TCE degradation in the presence of RA even at higher pH value of 9. The results indicated that the Z-nZVI activated SPC system in presence of RA can effectively degrade chlorinated organic solvents, but it is important to consider the intensive existence of anions in groundwater.     

A pathway of free radical generation via copper corrosion and its application to oxygen and ozone activation for the oxidative destruction of organic pollutants

This study investigated the commercially available zero-valent copper powder and copper foil to activate molecular oxygen (O₂) and ozone for the degradation of organic pollutants. Under aerobic atmospheric conditions, copper powder effectively removed 50 mg/L of acetaminophen (ACT) within 2 h, though the degradation rate using the foil was less than 20% of the powder. However, copper foil activated ozone to effectively degrade ACT. The total organic carbon (TOC) removal reached a high of 58.3% at a catalyst concentration of 40 g/L, but only 26.8% with ozone alone. The initial solution pH and dosage of copper foil were key operational parameters affecting the ozone activation process. H₂O₂ and Cu(I) were important intermediates in the process as hydroxyl radicals (^·OH) were identified via EPR (electron paramagnetic resonance) experiments and free radical scavengers. The generation of ^·OH was attributed to a Fenton-like reaction between Cu(I) and H₂O₂; this free-radical generation mechanism differs from typical transition metal oxide catalysts. This study outlines a promising approach to significantly increase the generation of ^·OH and effectively remove refractory organic compounds. Furthermore, these copper products are applied in structural components of practical water treatment. Thus, the study of corrosion resistance to oxygen and ozone in aqueous solution have both a practical and theoretical significance. It was determined that copper products were resistant to oxygen corrosion in aqueous solution, but not resistant to ozone corrosion.     

A Novel Dielectric-Barrier-Discharge Loop Reactor for Cyanide Water Treatment

A novel dielectric-barrier-discharge (DBD) loop reactor was designed for the efficient degradation of cyanide anion (CN^?) in water. The circulation of cyanide water as a falling film through plasma gas discharge zone enhanced gas–liquid mass and energy transfer and induced formation of H₂O₂ which was associated with the efficient destruction of CN^?. It was observed that among different discharge gases, the CN^? degradation rate decreased in the order of Ar > air > H₂/air mixture. Depending on discharge voltage, the treatment time for complete removal of 100 ppm CN^? in this DBD loop reactor is in the range 120–300 min. The dose of Cu²⁺ catalyst in combination with in situ production of H₂O₂ enhanced the destruction of CN^? apparently in this DBD loop reactor. The treatment time for complete degradation of 100 ppm CN^? decreased from 180 min with Ar DBD discharge alone to 40 min with 40 mg/L dose of Cu²⁺ ion in water, making it an efficient means to degrade cyanide water.     

Activation of Kraft Lignin by an Enzymatic Treatment with a Versatile Peroxidase from Bjerkandera sp. R1

Enzymatic lignin activation may be an environmentally friendly alternative to the use of chemicals in the production of wood fibers composites. Most studies on enzymatic activation of lignin for improving the adhesion of lignocellulosic products have been carried out using laccases. In this work, the use of a versatile peroxidase (VP) from the white-rot fungus Bjerkandera sp. (anamorph R1) for activating Kraft lignin was studied. The effect of enzyme dosage, incubation time, and H₂O₂ addition profile on lignin activation was evaluated by quantifying the phenoxy radicals formed using electron paramagnetic resonance (EPR) spectroscopy. Two alternative enzymatic systems based on the use of VP (a two-stage and an enzymatic cascade system) were also assayed. At optimal conditions (dose of 15 U?g^?1 and continuous addition of H₂O₂ (5.24 μmol?h^?1) during 1 h) the content of phenoxy radicals was doubled as compared with an untreated control. Moreover, using the two-stage VP system, a lignin activation similar to that found at optimal conditions could be reached in a shorter time.     

Treatment of pharmaceutical wastewater containing clofibric acid by electron beam irradiation

In this study, clofibric acid (CA) degraded by the electron beam (EB) irradiation was investigated at CA initial concentration of 10 mg L^?1. Results showed that more than 90% CA degradation is achieved at 0.5 kGy. The acid conditions (pH 3.00) and the addition of N₂ remarkably improved the CA degradation efficiency. The addition of CO₃^2?, HCO₃^? anions and H₂O₂ reduced the CA degradation efficiency. It showed that ·H had a primary role to play in the EB degradation of CA. The determination of byproducts showed hydrosilylation reaction of CA molecules. The byproducts were clofibric acid, chlorophenol, phenol, hydroquinone, benzoquinone and dihydroxybenzene. These results suggested that electron beam irradiation (EBI) can be used to eliminate CA.

     

Removal of multiple pollutants from water using noble Ag/Au/magnetite/graphene/H2O2 system under light and ultrasound irradiation

Ag/Au/Fe₃O₄/graphene composites prepared by a hydrothermal method demonstrated excellent activation of H₂O₂ and were used to degrade methylene blue (MB) in solution in the presence of organic acids and inorganic ions under light and ultrasound irradiation. The physicochemical properties of the obtained composites were characterized using various methods. The results showed that the composites exhibited excellent magnetic properties, crystallinity, and stability. The results of catalysis experiments revealed that the removal efficiency of MB increased when Ag and Au were both incorporated into the Fe₃O₄/graphene/H₂O₂ system compared with the removal efficiency achieved with separate Ag-Fe₃O₄/graphene/H₂O₂ and Au-Fe₃O₄/graphene/H₂O₂ systems, indicating a substantial synergistic interaction between the two metallic nanoparticles and the Fe₃O₄/graphene/H₂O₂ systems. The presence of an organic acid accelerated degradation of the MB/H₂O₂ system, whereas almost all of the investigated anions inhibited the degradation of MB; their inhibition effects followed the order CO₃^2? > NO₃^? > Cl^? > F^? > H₂PO₄^? > SO₄^2? > I^?. Cations of Na⁺, K⁺, Ca²⁺, and Mg²⁺ also suppressed MB degradation, likely because of the influence of Cl^? coexisting in the solutions.     

Removal of water-soluble lignin model pollutants with graphene oxide loaded ironic sulfide as an efficient adsorbent and heterogeneous Fenton catalyst

Advanced oxidation processes (AOPs) have gained extensive attentions in organic decontamination in past decades. Iron-contained compound is an interesting material due to its adsorptive and catalytic performance, which has been applied widely in AOPs. Thus, graphene oxide (GO)-Fe₃S₄ composite was synthesized by a solvothermal process and assessed as an effective adsorptive and catalytic dual functional material in this work. The composite displayed prominent adsorptive and heterogeneous Fenton-like catalytic performance, which was affected by preparation condition and the reactive parameters in catalytic system. Under optimized reactive conditions, the GO-Fe₃S₄ composite yielded rapid degradation of vanillic acid, which the corresponding apparent rate constant was 1.81 × 10^?1 min^?1. Catalytic mechanism analysis revealed that the main oxygen species was hydroxyl radicals bounded on the surface of the composite. And the generation of ?O₂^– was contributed to the conversion of H₂O₂ to ?OH. The analysis of degradation intermediates of vanillic acid and p-hydroxybenzoic showed that these compounds could be mineralized to small molecules. The prominent enhanced heterogeneous Fenton-like catalytic performance of GO-Fe₃S₄ was due to a larger specific surface area, plenty of reductive active sites in the composite and a high mass transfer efficiency of oxidizing radicals in the reactive system.     

Polyoxidovanadate complexes: synthesis,structures and catalytic oxidative bromination of phenol red

By selecting appropriate ligands, two polyoxidovanadate complexes, [Ni(en)₂]₃[V₁₈O₄₂Cl]·7H₂O·2H₃O⁺ (1) and [H₂N(CH₃)₂]₃[PV₁₄O₄₂]·2TMP·6H₃O⁺ (2), have been synthesized at different pH values using V₂(SO₄)₃, Ni(CH₃COO)₂, and H₆TTHA (for 1), VO(acac)₂ and TPP (for 2) (en = C₂H₈N₂, TPP = thiamine pyrophosphate, TMP = thiamine monophosphate, H₆TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid). The complexes have been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TG), and single crystal X-ray diffraction. The complexes catalyze the oxidation of the organic substrate phenol red in the presence of H₂O₂ and bromide, and the reaction system is considered as a model for hydrogen peroxide determination. The reaction rate constants (k) for 1 and 2 are calculated as 3.729 × 10³ and 4.083 × 10³ (mol L)^?2 s^?1. The maximum conversion rate of phenol red for 1 is 83.32%, while for 2 is 81.12%.     

Synthesis,characterization and photocatalytic application of TiO2/magnetic graphene for efficient photodegradation of crystal violet

A magnetized nano‐photocatalyst based on TiO₂/magnetic graphene was developed for efficient photodegradation of crystal violet (CV). Scanning electron microscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy and elemental mapping were used to characterize the prepared magnetic nano‐photocatalyst. The photocatalytic activity of the synthesized magnetic nano‐photocatalyst was evaluated using the decomposition of CV as a model organic pollutant under UV light irradiation. The obtained results showed that TiO₂/magnetic graphene exhibited much higher photocatalytic performance than bare TiO₂. Incorporation of graphene enhanced the activity of the prepared magnetic nano‐photocatalyst. TiO₂/magnetic graphene can be easily separated from an aqueous solution by applying an external magnetic field. Effects of pH, magnetized nano‐photocatalyst dosage, UV light irradiation time, H₂O₂ amount and initial concentration of dye on the photodegradation efficiency were evaluated and optimized. Efficient photodegradation (>98%) of the selected dye under optimized conditions using the synthesized nano‐photocatalyst under UV light irradiation was achieved in 25 min. The prepared magnetic nano‐photocatalyst can be used in a wide pH range (4–10) for degradation of CV. The effects of scavengers, namely methanol (OH^? scavenger), p‐benzoquinone (O₂^?? scavenger) and disodium ethylenediaminetetraacetate (hole scavenger), on CV photodegradation were investigated.     

An H2O2 Biosensor Based on Immobilization of Horseradish Peroxidase Labeled Nano‐Au in Silica Sol‐Gel/Alginate Composite Film

Abstract

A novel approach to assemble an H₂O₂ amperometric biosensor was introduced. The biosensor was constructed by entrapping horseradish peroxidase (HRP) labeled nano‐scaled particulate gold (nano‐Au) (HRP‐nano‐Au electrostatic composite) in a new silica sol‐gel/alginate hybrid film using glassy carbon electrode as based electrode. This suggested strategy fully merged the merits of sol‐gel derived inorganic‐organic composite film and the nano‐Au intermediator. The silica sol‐gel/alginate hybrid material can improve the properties of conventional sol‐gel material and effectively prevent cracking of film. The entrapment of HRP in the form of HRP‐nano‐Au can not only factually prevent the leaking of enzyme out of the film but also provide a favorable microenvironment for HRP. With hydroquinone as an electron mediator, the proposed HRP electrode exhibited good catalytic activity for the reduction of H₂O₂. The parameters affecting both the qualities of sol‐gel/alginate hybrid film and the biosensor response were optimized. The biosensor exhibited high sensitivity of 0.40 Al mol^?1 cm^?2 for H₂O₂ over a wide linear range of concentration from 1.22×10^?5 to 1.46×10^?3 mol L^?1, rapid response of <5 s and a detection limit of 0.61×10^?6 mol L^?1. The enzyme electrode has remarkable stability and retained 86% of its initial activity after 45 days of storage in 0.1 mol L^?1 Tris‐HCl buffer solutions at pH 7.