Near-neutral Conditions Research Articles

Tetracycline adsorption by tilapia fish bone-based biochar: Mass transfer assessment and fixed-bed data prediction by hybrid statistical-phenomenological modeling

The intense use of antibiotics and their presence in water bodies has risen serious health and environmental concerns. Adsorption stands out as a promising method for the treatment of such persistent contaminants; however, a suitable adsorbent material and operational conditions must consider the specificities of one target pollutant. For an adequate process development, a comprehensive understanding of the involved mechanisms and phenomena are crucial. In this context, the objective of this work was to evaluate the potential of a biochar produced from tilapia fish bone-residue for tetracycline (TC) adsorption, in batch and fixed-bed systems. For this, the biochar was characterized in terms of its textural and surface chemistry properties. Also, a mathematical model was used to support the understanding of mass transfer and equilibrium mechanisms as well as to obtain relevant parameters to support the prediction and scale-up of the adsorption system in fixed bed columns. First, the biochar production was investigated, with the TC removal capacity as a response variable, then biochar (in the best carbonization condition – 550 °C) was submitted to the characterization. In the mathematical modeling, three different rate-limiting steps were applied to kinetic data, namely, external mass transfer resistance (EMTR), internal mass transfer resistance (IMTR) and monolayer-multilayer adsorption (MMA). Based on equilibrium and kinetic parameters obtained in the batch mode, a hybrid (statistical-phenomenological) model was developed to predict the behavior of the breakthrough curves in fixed bed column. IMTR (homogeneous intraparticle diffusion) and BET isotherm models adequately described the kinetic and equilibrium data in batch system, indicating that the adsorption kinetics is governed by the internal diffusion of the TC within the biochar porous structure and that the adsorption may undergo multilayer formation for high TC concentration levels. The biochar characterization showed presence of apatites and predominance of a mesoporous structure with a 124 m2 g−1 superficial area. Near-neutral pH conditions, namely, between the isoelectric point of the TC (5.30) and the zero point of surface charge of the biochar (7.81) favored the adsorption process due to electrostatic attraction. Based on the batch parameters the hybrid phenomenological model was able to adequately predict the fixed-bed column performance, which was validated by independent experimental data. Therefore, the predictive model can be useful for adsorption systems scale-up, while presenting potential to predict and optimize fixed bed operational conditions.

Racemic or enantioselective osmium-catalyzed dihydroxylation of olefins under near-neutral conditions

Racemic or enantioselective osmium-catalyzed dihydroxylation of olefins under near-neutral conditions

Electro-assisted sulfite activation by a silica supported cobalt catalyst for the degradation of organic pollutants in near-neutral pH condition

The desulfurization by-product (e.g. sulfite) treatment and water pollution are two widespread concerns, while the sulfite activation by transition metals can be adopted to solve both of them simultaneously. In this study, a silica-supported cobalt catalyst (CoSi) was used to activate sulfite for the degradation of organic pollutants in an electrochemical system (the EC/CoSi/sulfite system), which demonstrated remarkable water treatment efficiencies due to sulfate radical oxidation. The synergy mechanisms of the EC/CoSi/sulfite system were revealed. (i) The as-prepared CoSi played the dual roles as an electro-adsorbent and a catalyst for sulfite activation. (ii) The electrolytic oxygenation supported the conversion of cobalt species and the chain reactions of oxysulfur radicals. (iii) The anodic oxidation of sulfite also generated oxysulfur radicals. The influencing factors and operating parameters were investigated and optimized systematically. Moreover, the efficient degradation of highly concentrated X-3B and non-selective oxidation of various organic compounds confirmed the promising application of the EC/CoSi/sulfite system in practical water treatment. Overall, the EC/CoSi/sulfite system created new value of the industrial waste (e.g. sulfite) for further application in the environmental remediation.

Mechanistic insights into a novel nitrilotriacetic acid-Fe0 and CaO2 process for efficient anaerobic digestion sludge dewatering at near-neutral pH

Traditional Fenton or Fenton-like oxidation has been widely studied for waste activated sludge dewaterability. However, the narrow pH range (2.0–4.0) and the instabilities of Fe2+ and H2O2 have hindered its commercial application. Owing to the high alkalinity of anaerobic digestion (AD) sludge, traditional Fenton or Fenton-like oxidation is economically unfeasible for its dewatering. In this study, we successfully demonstrated a novel and feasible method that used nitrilotriacetic acid (NTA)-Fe0 combined with CaO2 (NTA-Fe0/CaO2) at near-neutral pH (∼6.0) (a slight pH adjustment) in which capillary suction time ratio (CST0/CST) and centrifuged weight reduction (CWR) improved by 6 folds and 42.98 ± 0.37%, respectively, under the optimal conditions. The presence of NTA accelerated the Fe0 corrosion, Fe2+ stability and turnover between Fe2+ and Fe3+. As such, Fe0 could effectively catalyze CaO2 to produce hydroxyl radicals (•OH) under near-neutral conditions. Accordingly, various molecular weight hydrophilic compounds in different extracellular polymeric substances fractions were significantly reduced after treatment. The hydrophilic functional groups especially protein molecules were largely reduced. Consequently, the viscosity of sludge and particle size effectively decreased, while the release of bound water, surface charge, flocculation, and flowability of sludge were improved. The cost-benefit analysis further demonstrated the NTA-Fe0/CaO2 treatment has high reusability and stability and is also more economical over the FeCl3/CaO and Fenton’s reagent/CaO treatments. In summary, the NTA-Fe0/CaO2 process is a cost-effective and practically feasible technology for improving AD sludge dewaterability.

Persistence analysis of velocity and temperature fluctuations in convective surface layer turbulence

Persistence is defined as the probability that the local value of a fluctuating field remains at a particular state for a certain amount of time, before being switched to another state. The concept of persistence has been found to have many diverse practical applications, ranging from non-equilibrium statistical mechanics to financial dynamics to distribution of time scales in turbulent flows and many more. In this study, we carry out a detailed analysis of the statistical characteristics of the persistence probability density functions (PDFs) of velocity and temperature fluctuations in the surface layer of a convective boundary layer using a field-experimental dataset. Our results demonstrate that for the time scales smaller than the integral scales, the persistence PDFs of turbulent velocity and temperature fluctuations display a clear power-law behavior, associated with a self-similar eddy cascading mechanism. Moreover, we also show that the effects of non-Gaussian temperature fluctuations act only at those scales that are larger than the integral scales, where the persistence PDFs deviate from the power-law and drop exponentially. Furthermore, the mean time scales of the negative temperature fluctuation events persisting longer than the integral scales are found to be approximately equal to twice the integral scale in highly convective conditions. However, with stability, this mean time scale gradually decreases to almost being equal to the integral scale in the near-neutral conditions. Contrarily, for the long positive temperature fluctuation events, the mean time scales remain roughly equal to the integral scales, irrespective of stability.

Hydrogenated hematite nanoplates for enhanced photocatalytic and photo-Fenton oxidation of organic compounds

Hematite (α-Fe2O3) has been widely used as a photocatalyst for photo-Fenton oxidation due to its low cost, environmental friendliness, and high efficiency. The Photo-Fenton oxidation performance can be improved for practical applications via bandgap engineering of the photocatalyst. Herein, hematite nanoplate (HNP) is synthesized via a solvothermal method and a hydrogenation treatment, resulting in hydrogenated HNP (H-HNP). Materials characterizations demonstrate the even distribution of oxygen vacancies, formation of Fe (II) species on H-HNP, the enhanced light absorption, and separation of photogenerated e−/h+ pairs. Under simulated solar light, in comparison with pristine HNP, the H-HNP delivered significantly higher photo-Fenton oxidation activities under near-neutral pH conditions for the degradation of 50 mg L−1 Rhodamine B, Congo red, and Methylene blue after 20 min, i.e., 92.7%, 98.2%, and 77.2%, respectively. Mechanistic explorations, including XPS and radical trapping analysis, suggest that positively charged holes (h+) and catalytically formed hydroxyl radicals (OH) were the main factors contributing to the higher photo-Fenton oxidation performance of H-HNP. Overall, hydrogenation treatment is an easy and effective means for bandgap engineering to improve the photocatalytic performance of photocatalysts as demonstrated by the as-prepared H-HNP as a high-performance photocatalyst for the photo-Fenton oxidation reaction.

Experimental evidence of a phase transition in the multifractal spectra of turbulent temperature fluctuations at a forest canopy top

Ramp–cliff patterns visible in scalar turbulent time series have long been suspected to enhance the fine-scale intermittency of scalar fluctuations compared to longitudinal velocity fluctuations. Here, we use the wavelet transform modulus maxima method to perform a multifractal analysis of air temperature time series collected at a pine forest canopy top for different atmospheric stability regimes. We show that the multifractal spectra exhibit a phase transition as the signature of the presence of strong singularities corresponding to sharp temperature drops (respectively jumps) bordering the so-called ramp (respectively inverted ramp) cliff patterns commonly observed in unstable (respectively stable) atmospheric conditions and previously suspected to contaminate and possibly enhance the internal intermittency of (scalar) temperature fluctuations. Under unstable (respectively stable) atmospheric conditions, these ‘cliff’ singularities are indeed found to be hierarchically distributed on a ‘Cantor-like’ set surrounded by singularities of weaker strength typical of intermittent temperature fluctuations observed in homogeneous and isotropic turbulence. Under near-neutral conditions, no such a phase transition is observed in the temperature multifractal spectra, which is a strong indication that the statistical contribution of the ‘cliffs’ is not important enough to account for the stronger intermittency of temperature fluctuations when compared to corresponding longitudinal velocity fluctuations.

An Integrated Approach to Remove PAHs from Highly Contaminated Soil: Electro-Fenton Process and Bioslurry Treatment

A combined process comprised of electro-Fenton and bioslurry (EF–bioslurry) was developed at lab scale for remediating a real coking plant soil with an initial polycyclic aromatic hydrocarbons (PAHs) content of 3605 mg/kg. Sodium citrate was used as a complexant to keep the iron in solution at near-neutral pH conditions for increasing the reaction rate. The appropriate order of application was to perform EF process followed by bioslurry, which was evaluated through analysis of degradation characteristics of individual processes. The optimum EF duration was assessed through an analysis of the induced changes in PAHs degradation and bacterial counts. The optimum application time of EF process was determined to be 24 h. The removal of PAHs was 95.2% for EF–bioslurry after 40 days, and the efficiency was increased by almost 150%, compared with the individual bioslurry treatment. The EF reaction caused significant cell death and high inhibition to polyphenol oxidase (PPO) activity of soil. The bacterial activity and counts in the slurry recovered rapidly after EF oxidation through the addition of raw soil (2%, w/w). Therefore, the combined process of EF–bioslurry process may be an efficient and promising approach for the remediation of highly organic-contaminated soil.

Geochemical behavior of rare earth elements in acid drainages: Modeling achievements and limitations

Rare earth elements (REE) concentrations in acid mine drainage (AMD) are several orders of magnitude higher than those in other surface waters and could be a future supplementary source of highly valuable REE. Therefore, knowing the mobility constraints of REE in natural waters, particularly in AMD, is of interest.Precipitation of schwertmannite and basaluminite occurs due to mixing of REE-enriched AMD and neutral streams. The REE fractionation between AMD and solid phases has been investigated in several localities in the Odiel-Tinto (SW Spain) and Arroyo del Val (N Spain) basins. The mobility of REE is related to the precipitation of Fe and Al phases that occurs at different pH values. The behavior of REE during the mixing is conservative under low pH conditions (pH <4 approximately), at which schwertmannite precipitates, whereas REE are scavenged under near-neutral pH conditions, at which basaluminite precipitates and what suggest that this phase could be responsible for REE retention. Indeed, when Fe and Al phases can be sampled separately, schwertmannite does not contain REE, which are entirely retained in basaluminite, confirming the REE removal by this later phase.The strengths and limitations of a recently proposed thermodynamic model of REE sorption on basaluminite have been assessed by comparing the model predictions with observations of samples recovered in the field. The model is able to predict the REE distribution pattern and confirms the preferential sorption of heavy REEs (HREEs) and Y over light REEs (LREEs) in all the samples. However, the lack of synchronicity between basaluminite precipitation and REE sorption during mixing in an open flow setting precludes an accurate prediction of the REE concentration in the solid phase.

In situ encapsulation of horseradish peroxidase in zeolitic imidazolate framework-8 enables catalyzing luminol reaction undernear-neutral conditions for sensitive chemiluminescence determination of cholesterol.

HRP@ZIF-8 nanocomposite was prepared by in situ encapsulation of horseradish peroxidase (HRP) in the frame of zeolitic imidazolate framework-8 (ZIF-8) with a simple one-pot method. The HRP@ZIF-8 nanocomposite displays outstanding thermal stability and efficiently catalyzes the chemiluminescence (CL) reaction of luminol with hydrogen peroxide (H2O2) under near-neutral pH condition (pH 7-8). This CL system has a good response to H2O2 with a linear range of 0.1-100.0μmolL-1. The limit of detection (LOD) is 0.06μmolL-1 H2O2. By marriage with cholesterol oxidase, cholesterol is determined with a linear range from 0.1 to 100.0μmolL-1 and a LOD of 0.04μmolL-1. The relative standard deviations (RSD) are 1.7% and 2.5%, respectively, in 11 repeated measurements of 50.0μmolL-1 solutions of H2O2 and cholesterol, indicating excellent precision of the method. The method shows good selectivityand has been applied to the determination of total cholesterol in real serum samples. No significant difference has been observed between the results obtained by this method and thecholesterol oxidase-peroxidase coupling method. Graphical abstract Schematic presentation of in situ one-pot synthesis of horseradish peroxidase@zeolitic imidazolate framework-8 (HRP@ZIF-8) nanocomposite and chemiluminescence determination of cholesterol with HRP@ZIF-8 catalyzing luminol-H2O2 system.

Unconventional electro-Fenton process operating at a wide pH range with Ni foam cathode and tripolyphosphate electrolyte

We propose an unconventional electro-Fenton (EF) system with a nickel-foam (Ni-F) cathode and tripolyphosphate (3-PP) electrolyte at near-neutral pH (EF/Ni-F-3-PP) to overcome pH restrictions in EF while preventing Ni-F corrosion. Response surface modelling was used to optimize the main operating parameters with a model prediction analysis (R2 = 0.99): pH = 5.8, Fe2+ = 3.0 mM and applied current = 349.6 mA. Among the three variables, the pH exerted the highest influence on the process. Under optimal conditions, 100 % of phenol removal was achieved in 25 min with a pseudo-first-order apparent rate constant (kapp) of 0.2 min−1, 3.2-fold higher than the kapp of EF/Ni-F with SO42− electrolyte at pH 3. A mineralization yield of 81.5 % was attained after 2 h; furthermore, it was found that 3-PP enhanced H2O2 accumulation by preventing bulk H2O2 decomposition. Finally, toxicity evaluation revealed the formation of toxic by-products at the early stages of treatment, which were totally depleted after 2 h, demonstrating the detoxifying capacity of the system. In conclusion, this study shows for the first time the potential of Ni-F as a cathode for EF under near-neutral conditions, rendered possible by the 3PP electrolyte. Under these conditions, the Ni-F corrosion issue could be alleviated.

Highly efficient removal of p-arsanilic acid with Fe(II)/peroxydisulfate under near-neutral conditions

As a common animal feed additive, p-arsanilic acid (p-AsA) is thought to be excreted with little uptake and unchanged chemical structure, threatening the environment by potentially releasing more toxic inorganic arsenic. We herein investigated the removal of arsenic by in situ formed ferric (oxyhydr)oxides with the promotion of p-AsA degradation in Fe(II)/peroxydisulfate (PDS) system. Results showed that under acid conditions, p-AsA degraded very quickly and over 99% of p-AsA (5 μM) was degraded within 10 min at the optimal dosage of Fe(II) (100 μM) and PDS (150 μM) at pH 3, while less than 66.4% of arsenic was removed at pH 3–5. Higher pH (3–7) would inhibit the degradation of p-AsA but promote the arsenic removal. At pH 6–7, over 98.5% of total arsenic was removed, while the degradation efficiency of p-AsA was lower than 52.4%. HPLC-ICP-MS results indicated that the arsenic group was cleaved from p-AsA in the form of As(III) and then rapidly oxidized to As(V). FTIR and XPS analysis indicated that both As(V) products and residual p-AsA were bonded to ferric (oxyhydr)oxides via hydroxyl groups. Common cations (e.g., Na+, Ca2+, Mg2+) and anions such as Cl−, SO42−, CO32− had no significant influence on arsenic removal, while SiO32−, PO43− and HA inhibited the removal of total arsenic, mainly by affecting the zeta potential of iron particles. In summary, the Fe(II)/PDS process, as an efficient method for partial oxidation and simultaneous adsorption of p-AsA under near-neutral conditions, is expected to control the potential environmental risks of p-AsA.

Mechanistic Investigation of Biomass Oxidation Using Nickel Oxide Nanoparticles in a CO2-Saturated Electrolyte for Paired Electrolysis.

A highly efficient CO2 electrolysis system could be created by introducing biomass oxidation as an alternative anodic reaction to the sluggish oxygen evolution reaction in a CO2-saturated and near-neutral electrolyte. Here, we successfully demonstrate anodic biomass oxidation by synthesizing 5 nm nickel oxide nanoparticles (NiO NPs). NiO NPs show a unique electrocatalytic activity for 5-hydroxymethylfurfural (HMF) oxidation under near-neutral conditions, exhibiting an anodic current onset (1 mA cm-2) at 1.524 V versus the reversible hydrogen electrode and a total Faradaic efficiency of ≤70%. Electrokinetic and in situ ultraviolet-visible spectroscopic analyses suggest that a redox active nickel hydroxide species is formed on the surface of NiO electrocatalysts during HMF oxidation, and this oxidation of Ni(II) hydroxide to Ni(III) oxyhydroxide could be the rate-determining step. This mechanistic study of biomass oxidation in a CO2-saturated electrolyte provides insight into constructing a highly efficient system for the paired electrolysis of CO2 reduction and biomass oxidation.

Ultrasensitive determination of mercury ions using a glassy carbon electrode modified with nanocomposites consisting of conductive polymer and amino-functionalized graphene quantum dots.

A one-pot method based on cyclic voltammetric scan was used to fabricate a glassy carbon electrode modified with nanocomposites consisting of poly(thionine) and amino-functionalized graphene quantum dots (afGQDs). Under near-neutral conditions, the dye polymer was effectively oxidized by hydroxyl radicals (·OH) that were derived from the copper-catalyzed Fenton-like reaction, and the cathodic peak current on the modified electrode greatly increased. The reaction of Cu2+ with thiourea (TU) and the generation of a complex, CuTU2+, led to the decrease of Cu2+/Cu+ species, which inhibited the Fenton-like reaction and reduced the electrochemical response change. Due to a displacement reaction, the addition of Hg2+ into the H2O2-Cu2+-TU system resulted in the release of cuprous ions that benefited the Fenton-like reaction. Under the following optimal conditions: 6mgmL-1 afGQDs and the 25-cycle potential cycling for the fabrication of the modified electrode, pH 6.5, and the [Formula: see text] ratio of 1.0, the increasing extent of the cathodic peak current exhibited a good linear response to the logarithm of the Hg2+ concentration in the range of 1pM-1μM with a detection limit of 0.6pM. Mercury ions in a water sample were determined with good recovery, ranging from 97 to 103%. The investigation on the uptake of Hg2+ into human vascular endothelial cells, HUVEC, shows that the cells incubated in the high-concentration glucose medium absorbed more mercury ions than HUVEC incubated in the normal medium. As a result, Hg2+ could lead to the greater damage to the former. Graphical abstract.

Degradation of methylparaben by sonocatalysis using a Co-Fe magnetic carbon xerogel.

The degradation of methylparaben (MP) through 20kHz ultrasound coupled with a bimetallic Co-Fe carbon xerogel (CX/CoFe) was investigated in this work. Experiments were performed at actual power densities of 25 and 52W/L, catalyst loadings of 12.5 and 25mg/L, MP concentrations between 1 and 4.2mg/L and initial pH values between 3 and 10 in ultrapure water (UPW). Matrix effects were studied in bottled water (BW) and secondary treated wastewater (WW), as well as in UPW spiked with bicarbonate, chloride or humic acid. The pseudo-first order kinetics of MP degradation increase with power and catalyst loading and decrease with MP concentration and matrix complexity; moreover, the reaction is also favored at near-neutral conditions and in the presence of dissolved oxygen. The contribution of the catalyst is synergistic to the sonochemical degradation of MP and the extent of synergy is quantified to be >45%. This effect was ascribed to the ability of CX/CoFe to catalyze the dissociation of hydrogen peroxide, formed through water sonolysis, to hydroxyl radicals. Experiments in UPW spiked with an excess of tert-butanol (radical scavenger), sodium dodecyl sulfate or sodium acetate (surfactants) led to substantially decreased rates (i.e. by about 8 times), thus implying that the liquid bulk and the gas-liquid interface are major reaction sites. The stability of CX/CoFe was shown by performing reusability cycles employing magnetic separation of the catalyst after the treatment stage. It was found that the CX/CoFe catalyst can be reused in up to four successive cycles without noteworthy variation of the overall performance of the sonocatalytic process.

High-sulfidation veins in the Jiama porphyry system, South Tibet

The giant Jiama polymetallic ore deposit is a porphyry–skarn system in the eastern Gangdese porphyry belt of the Tibetan Plateau. Steeply dipping high-grade massive sulfide veins are classified as lode-type high-sulfidation (HS) mineralization comprising mainly Cu-sulfosalts in Au-poor and Au-rich veins. Au-poor veins contain an As-rich pyrite–enargite–tennantite assemblage, whereas Au-rich veins contain an Sb-rich enargite–luzonite–tetrahedrite–chalcostibite–watanabeite assemblage. The coexistence of pyrite, dendritic muscovite, and euhedral quartz in the Cu-sulfosalts indicates slightly acidic or near-neutral formation conditions. Most Au- and Ag-bearing minerals are inclusions of tellurides (hessite, sylvanite, and petzite) in tennantite–tetrahedrite, and watanabeite. Au and Ag concentrations in tennantite–tetrahedrite, watanabeite, and chalcostibite are much higher than in enargite and luzonite, confirming that they were controlled by intermediate-sulfidation state Cu–As–Sb–S solid solutions, with Au tending to be enriched in Sb-rich minerals compared with As-rich solid solutions. The HS veins overlying the known porphyry intrusion and cutting skarn orebodies in the Jiama deposit constitute a porphyry–skarn–high sulfidation system. The occurrence of HS veins suggests that channels in paleo-fumaroles and the mineralization that resulted may be ascribed to expansion of magmatic vapor. HS veins close to the porphyry intrusion exposed at the surface indicate that shallow epithermal disseminated mineralization was likely removed by rapid regional uplift and erosion of the Gangdese porphyry belt.

Self-catalysis synthesis of Co3O4@SiO2-Ag nanocapsules under near-neutral condition as excellent performance catalyst

A degradation of organic dyes catalyst with stable structure and efficient performance, SiO2 coated Co3O4 and Ag nanocapsules have been successfully prepared by the simple in-situ method and template method, which shown excellent catalytic performance for degrade methyl orange dye in solution. The degradation rate constant (k) of Co3O4@SiO2-Ag was 0.150 min−1. The combination of two metals and the hollow mesoporous structure significantly improved the catalytic performance of the material.

Promotion effect of PANI on Fe-PANI/Zeolite as an active and recyclable Fenton-like catalyst under near-neutral condition

A Fenton-like catalyst, Fe doped PANI loaded on zeolite (Fe-PANI/Zeolite) was synthesized by polymerizing aniline (PANI) and loading iron via a one-pot in-situ hydrothermal process. The XPS and UV–Vis spectra indicated that the Fe2+ and Fe3+ were doped into PANI and formed a complex via Fe-N interaction, and the TEM image showed that no Fe oxides particles were formed. The Fe-PANI/Zeolite showed significant Fenton-like catalytic activity in a wide pH range (3.0–8.0), and its catalytic activity was studied in detail at pH 6. With the optimized FeCl3-to-aniline molar ratio of 3:1, the Fe-PANI/Zeolite synthesized at 130 °C for 12 h showed the highest efficiency for Fenton-like catalytic degradation of Acid Red G (ARG). The active species of the Fe-PANI/Zeolite were Fe and PANI, and especially under near-neutral condition the PANI played the key role by promoting the reduction of Fe3+ to Fe2+, resulting in enhancing the Fenton-like reaction activity. Fe-PANI/Zeolite catalyst shows high potential in organic pollutants removal in wastewater treatment without any additional assistant measure to enhance its activity.

Production of Hydrogen Peroxide for Drinking Water Treatment in a Proton Exchange Membrane Electrolyzer at Near-Neutral pH

We provide a detailed report on the electrosynthesis of H2O2 for drinking water treatment under near-neutral conditions using a proton exchange membrane (PEM) electrolyzer. Two novel cathode catalysts for O2 electroreduction to H2O2 were investigated in the PEM electrolyzer: an inorganic cobalt-carbon (Co–C) composite and an organic redox catalyst anthraquinone-riboflavinyl mixed with carbon (AQ–C), respectively. The impact of operational variables such as temperature, cathode carrier water flow rate, and anode configurations (aimed at mitigating carbon corrosion at the anode) were examined in single-pass and full recycle operation. Using a superficial current density of 245 mA cm−2 and an operating temperature of 40 °C, H2O2 molar fluxes of 360 μmol hr−1 cm−2 and 580 μmol hr−1 cm−2 were generated at near-neutral pH with the Co–C and RF-AQ catalysts, respectively. Seventy-two hour experiments with closed loop recirculation, produced H2O2 concentrations of 1300 and 3000 ppm for the Co–C and AQ–C catalysts, respectively. These concentrations are adequate for advanced oxidation (UV/H2O2) treatment of drinking water, rendering the PEM electrolysis approach particularly suitable for on-site and on-demand production of H2O2.

New ternary deep eutectic solvents for effective wheat straw deconstruction into its high-value utilization under near-neutral conditions

The new synthesized DES is used to reduce, which significantly reduces the maintenance cost of biomass refining equipment and provides a feasible way for biomass resource utilization under near-neutral conditions.