Catalytic Oxidation Effect Research Articles

STUDY OF THE BEHAVIOR OF ARSENIC IN COPPER ELECTROLYTE

Abstract. In industrial wastewater, arsenic is most often present in the trivalent state. An analysis of existing purification methods shows that in all cases, with a few exceptions, the most complete removal of arsenic is observed from solutions in which it is in the pentavalent state. This is explained by the significantly lower solubility of arsenates of heavy and alkaline earth metals compared to the corresponding arsenites. The chemical oxidation of As(III) in the following systems was studied: As(III)-H2SO4-H2O, As(III)-MeSO4-H2O, As(III)–H2SO4–MeSO4–H2O (where Me is Cu, Ni, Co, Mn, Zn). The influence of temperature, the amount of transition metal ions, the duration of the experiment, and the concentration of sulfuric acid on the degree of transition of As(III) to As(V) was studied. The effect of catalytic oxidation of As(III) in sulfuric acid solutions was discovered. The maximum degree of oxidation of trivalent arsenic (55-60%) is observed when transition metal salts are introduced into an arsenic solution in the presence of a platinum plate. It has been established that the nature of the studied transition metal salts (Cu2+, Ni2+, Co2+, Mn2+, Zn2+), process duration and temperature do not have a significant effect on the degree of As(III) conversion. The results obtained largely explain the predominance of pentavalent forms of arsenic in production solutions of non-ferrous metallurgy. Key words: copper electrolyte, arsenic, transition metals, catalytic role, instant oxidation effect, activated oxygen.

Catalytic effects of transition metal oxides on HTPB-based fuel polymer matrices

Low regression rate due to difficult pyrolysis is a major challenge in the practical application of terminated hydroxyl‑terminated polybutadiene (HTPB)-based fuels in hybrid rocket propulsion. Accelerating the decomposition of the polymer matrix is an effective method to improve the regression rate of HTPB fuels. To determine the difference in combustion performance between different transition metal oxides loaded HTPB-based fuels, nickel oxide (NiO), ferric oxide (Fe2O3), copper oxide (CuO) and manganese dioxide (MnO2) were introduced into the HTPB matrix at 5% mass fraction. The experimental results showed that the metal oxides could significantly catalyze the pyrolysis of HTPB-based fuels and enhance the fuel regression rate, and the catalytic effect was mainly concentrated in the middle and late stages of the thermal decomposition process of polybutadiene components. Among the four transition metal oxides, CuO and MnO2 showed better catalytic effects on the combustion performance of HTPB-based fuels in the high oxygen mass flux region, while NiO showed better catalytic effects in the low oxygen mass flux region. The present study compares the regression rate of fuel grains modified with different transition metal oxides, which provides a basis for the selection of future catalysts, verifies the catalytic effect of the transition metal oxides on the combustion of HTPB-based fuels and further analyzes the combustion reaction mechanism of the fuels.

Alkali-fluoride-salt-accelerated oxidation behavior of graphite under air atmosphere

Air ingress accident scenarios may result in the oxidation of graphite matrix materials and cause serious safety problems in molten salt reactor. However, the oxidation behavior of the molten-salt-infiltrated graphite remains elusive. In this study, the effect of alkali fluoride salts (LiF, NaF, KF and ternary salt FLiNaK) on the oxidation behavior of graphite powder under air atmosphere was investigated. Thermogravimetric analysis and oxidation tests manifest that the initial oxidation temperature of the graphite is reduced from 720 °C to 510–610 °C, because of the presence of the alkali fluoride salts. The catalytic oxidation effect follows the order of KF > NaF > LiF. Careful characterizations reveal that the pristine graphite is mainly oxidized at the graphite edges, while salt-infiltrated graphite is mainly damaged at the graphitic basal planes. Density functional theory calculations suggest that the doping of alkali metal atoms does not change the physical adsorption feature of the oxygen molecule on the graphite plane surface, but increases its adsorption energy to facilitate the graphite oxidation reactions.

Hydroxyl-aluminum pillared bentonite enhanced Mn(II) removal by chlorine oxidation

Al-PILC was used to catalyze the chlorine oxidation of Mn(II) in aqueous solution. The effects of various catalysts, catalyst dosage, chlorine dosage, pH value, temperature and organic content on the oxidation process were investigated. Results show that 1.5 mg/L chlorine can quickly oxidize Mn(II) from 0.5 mg/L to less than 0.04 mg/L with 10 mg/L Al-PILC. Using catalysts with higher porosity and higher SA, increase in chlorine concentration, increase in catalyst dosage, higher pH, and higher temperature can significantly enhance the rate of Mn(II) catalytic oxidation. The Mn(II) oxidation process includes the homogeneous oxidation, catalytic oxidation on the surface of the catalysts and self-catalytic oxidation produced by the newly produced MnOx. Al-PILC surface provides active sites for chlorine oxidation Mn(II) in the water, and also provides binding sites for the newly produced MnOx, which has higher catalytic activity and thus has an self-catalytic oxidation effect. The higher the porosity and SA of Al-PILC, the more catalytic oxidation active sites and loading sites, and the better the catalytic oxidation effect. The study promotes the understanding of chlorine catalyzed oxidation Mn(II) in aqueous solution, but also provide important guide to study newly efficient catalysts to oxidize Mn(II) with chlorine in aqueous solution.

Catalytic fixation of hydrogen sulfide over CuO-CaCO3 co-impregnated tea stalk-derived biochar

Effective treatment of hydrogen sulfide (H2S) is crucial for minimizing nuisance odors from intensive livestock and poultry operations. The development of high-performance desulfurizers holds practical significance in this context. Herein, a novel CuO-CaCO3 co-impregnated biochar desulfurizer (CuxCay/BCT) was synthesized by impregnation-pyrolysis method, using waste tea stalks and metal salts as raw materials, and it is intended for the treatment of H2S at room temperature. The optimized Cu0.75Ca0.25/BC800 shows an excellent H2S removal capacity of 182.67 mg/g, which is 31 times and 5.6 times that of inactivated biochar (BC800) and copper-oxide-impregnated biochar (Cu0.75/BC800). The desulfurization mechanism of Cu0.75Ca0.25/BC800 involves synergistic effect of reactive adsorption and catalytic oxidation. CaCO3’s alkaline adsorption sites and copper-mediated activation of superoxide radicals (∙O2-) were critical in this reaction. Besides, Cu0.75Ca0.25/BC800 demonstrated excellent reusability, retaining approximately 85 % of its initial H2S removal capacity after seven cycles of desulfurization and regeneration. This study aims to develop a metal oxide- and carbonate-impregnated biochar-based desulfurizer, with the goal of advancing the technology for catalytic removal of H2S in a more environmentally friendly and effective manner.

High efficiency manganese cobalt spinel structure catalytic ozonation ceramic membrane for in situ BPA degradation and membrane fouling elimination

In recent years, micropollutants contamination in aquatic environments has received increasing attention. Bisphenol A (BPA), an endocrine-disrupting compound, has emerged as a substantial threat to water safety owing to its widespread presence in various aquatic environments. To address this issue, this study focused on the development of ceramic membranes incorporating manganese-cobalt oxides (MCOs) to catalyze the ozone-based degradation of BPA. The catalytic layer was prepared by hydrothermal in-situ growth method, which enhanced BPA degradation during water treatment and improved the ceramic membrane’s resistance to contamination. Moreover this study investigated the synergistic effect of catalytic ozone oxidation in mitigating ceramic membrane pollution and degrading micropollutants. The catalytic mechanism and the contamination modeling were examined systematically to determine the mechanism of micropollutant contamination on ceramic membranes. The experimental results showed that the modified ceramic membrane exhibited a higher BPA removal efficiency (90.6%) and flux recovery (99.5%) than the unmodified membrane (64.2% and 79%, respectively). Furthermore, the MCOs-modified ceramic membrane (CCM) effectively enhanced the generation of hydroxyl radicals during ozonolysis. This enhancement resulted in better degradation of organic pollutants in water, thus improving the quality of the treated water. The combination of ceramic membrane catalytic separation with ozone oxidation technology offers a potential solution for the degradation of emerging pollutants and the mitigation of ceramic membrane pollution.

Electrochemical sensor for simultaneous determination of antiviral favipiravir drug, paracetamol and vitamin C based on host–guest inclusion complex of β-CD/CNTs nanocomposite

Favipiravir (FVI) is extensively used as an effective medication against several diverse infectious RNA viruses. It is widely administered as an anti-influenza drug. Combination therapy formed from FVI, paracetamol (PAR) and vitamin C (VC) is needed for treating patients diseased by RNA viruses. Thus, an efficient electrochemical sensor is developed for detecting FVI in human serum samples. The sensor is fabricated by casting a thin layer of carbon nanotubes (CNTs) over a glassy carbon (GC) electrode surface followed by electrodeposition of another layer of β-cyclodextrin (β-CD). Under optimized conditions, the sensor shows excellent catalytic effect for FVI, PAR and VC oxidation in the concentration ranges (0.08 µM → 80 µM), (0.08 µM → 50 µM) and (0.8 µM → 80 µM) with low detection limits of 0.011 μM, 0.042 μM and 0.21 μM, respectively. The combined effect of host–guest interaction ability of β-CD for the drugs, and a large conductive surface area of CNTs improves the sensing performance of the electrode. The sensor exhibits stable response over 4 weeks, good reproducibility, and insignificant interference from common species present in serum samples. The reliability of using the sensor in serum samples shows good recovery of FVI, PAR and VC.

Synthesis of magnetic biochar-supported Fe-Cu bimetallic catalyst from pulp and paper mill wastes for the Fenton-like removal of rhodamine B dye

Treating the wastes generated from pulp and paper mills, such as black liquor and Fenton sludge is challenging. In this study, the biochar-supported Fe-Cu bimetallic catalysts were synthesized by a one-step pyrolysis method using Fenton sludge as iron source, acid-precipitated black liquor (APBL) as carbon source and copper nitrate as copper source. The catalysts were used to remove rhodamine B (RhB) dye from aqueous solution by Fenton-like reaction. The optimal catalyst (FeCu@BC600-2) was pyrolyzed at 600 °C with an Fe/Cu mixing ratio of 2 and consisted of mesoporous biochar supported nanoscale Fe3O4 and Cu0. It had a specific surface area of 104.6 m2·g−1 and a saturation magnetization of 33.3 emu·g−1. In the FeCu@BC600-2/H2O2 system, RhB dye (10 mg·L-1) was completely removed within 60 min at acidic pH (initial pH 3, 0.2 g·L-1 catalyst, 1 mM H2O2) or 6 h at neutral pH (initial pH 7, 0.25 g·L-1 catalyst, 25 mM H2O2) at 30 °C. Moreover, the FeCu@BC600-2 exhibited good magnetic separation ability, low metal leaching, excellent reusability and broad applicability to other synthetic dyes. The dye removal mechanism involved the synergistic effect of adsorption and catalytic oxidation (especially heterogeneous catalytic oxidation). At acidic pH, RhB degradation was due to •OH radical, which was generated from the activation of H2O2 by ≡Cu(I) or Cu(I) oxidized from Cu0 and ≡Fe(II) in Fe3O4. At neutral pH, RhB degradation was mainly due to •OH and 1O2 with the former being produced by ≡Cu(I) and ≡Fe(II). Furthermore, Cu(I) oxidized from Cu0 and the active functional groups (such as sp2 C = C) in the biochar facilitated the reduction of Fe(III) to Fe(II), resulting in a high catalytic oxidation efficiency.

Synergetic effect of photocatalytic oxidation plus catalytic oxidation on the performance of coconut shell fiber biochar decorated α-MnO2 under visible light towards BPA degradation

Photocatalytic technology is regarded as a promising approach for fast degradation of refractory organic pollutant in water. However, the performance of the photocatalyst can be restricted by the variation of water matrix conditions. Herein, coconut shell fiber was pyrolyzed to biochar (CSB800) and incorporated with α-MnO2 to degrade bisphenol A (BPA) in water under visible light irradiation. The prepared α-MnO2/CSB800 composites demonstrated high efficacy in degrading BPA. Specifically, 0.01 mM of BPA could be completely degraded by 0.1 g/L of MnO2/CSB800 within 45 min. It was found that the incident light could effectively trigger the separation of electron and hole in α-MnO2. The electron and hole were afterwards converted to hydroxyl radical (●OH), superoxide radical (●O2−) and non-radical singlet oxygen (1O2), which subsequently initiated the photocatalytic degradation of BPA. Additionally, α-MnO2/CSB800 could simultaneously participate the oxidative degradation pathway of BPA with its high oxidation-reduction potential. The introduction of CSB800 led to higher BPA degradation efficiency since CSB800 could accelerate the charge carrier transferring rate during BPA degradation process via either pathway. The co-existence of both photocatalytic and oxidative degradation synergy enables α-MnO2/CSB800/visible light system with high catalytic performance stability towards various water matrices. This study proposes an effective strategy to prepare easy-available photocatalysts with high and stable performance towards for addressing organic pollution issues in water.

Oxidative pyrolysis of ion exchange resin in the presence of manganese dioxide: Product analysis, conversion and simplification mechanism

The development of nuclear energy has brought a great challenge of the efficient treatment of spent radioactive ion exchange resin, and oxidative pyrolysis is a potential method of solving this issue. This study aims to investigate the oxidative degradation and conversion mechanism of tar and off-gas, byproducts produced in the pyrolysis process, in the presence of a catalyst, manganese dioxide. The results show that it presents three processes including liquefaction, gasification and direct gasification in pyrolysis, in which manganese dioxide could reduce the dominant temperature of gasification by 200 ℃. Tar and off-gas undergo secondary pyrolysis, and the yield of tar decreased by approximately 50%. Simultaneously, manganese dioxide could promote the conversion of tar into off-gas, making both of them simplified, for which long-chain hydrocarbons are transformed into short-chain hydrocarbons, CO2, H2O, H2, etc. The catalytic oxidation effect of manganese dioxide is attributed to the adsorption and catalysis of oxygen vacancy, which significantly simplifies the composition of tar and off-gas.

Glazes induced degradation of tea catechins

In present work, the degradation behavior of tea catechins on various commercial glazes was elucidated for the first time. Four kinds of Japanese typical commercial glaze powders (Oribe /Namako/Irabo /Toumei) based on Fe/Mg /Cu /Ti oxides were utilized and deposited on ceramic tiles. Tea solution extracted from green tea leaves at 80 °C and then utilized for the examination of degradation behavior with glazes to meet a nearly identical condition in human daily tea drinking with ceramicwares. It was found that the degradation of tea catechins significantly dependent on the chemical structure of glazes, that is: Fe/Cu/Mg oxides contained glazes can promote the degradation of epigallocatechin, epicatechin, epigallocatechin gallate and epicatechin gallate, while Ti oxide contained glaze stimulated the degradation of epigallocatechin gallate selectively. Coloring pigments were produced in degraded tea solutions, whose color shows glaze dependent property. We presume that these color pigments can be assigned as oxytheotannin, especially theaflavin and its oxides as well as thearubigins, that produced through the polymerization of intermediate free radical catechin and/or the ortho-quinone generated by catalytic effect of glaze oxides worked as Lewis’s acids. The specific function of glazes on degradation of catechins discovered here not only provides principal information for design and development of functional materials but also bring new impacts on daily tea drinking and long-term human health-related issues.

Development of CuCo2O4 integrated ceramic membrane for peroxymonosulfate activation: An efficient oxidation process for bisphenol A degradation

In this study, a new functionalized flat-sheet ceramic membrane (CuCo2O4-CM) was prepared by an impregnation-calcination strategy and used in the removal of Bisphenol A (BPA). Various characterization results indicated that a CuCo2O4 layer was uniformly anchored on the membrane surface and the internal porous channels. The CuCo2O4-CM possessed a smaller mean pore size (80 nm) and better hydrophilicity than the pristine α-Al2O3 substrate after modification. The catalytic degradation in CuCo2O4-CM /PMS system revealed that 92.1% of BPA and 70.0% of TOC could be removed under optimal conditions (pH = 7.0, CBPA = 30 mg/L and CPMS = 2 mM). Meanwhile, the membrane showed good reusability and improved antifouling properties. During the reaction, four reactive oxygen species (·OH, SO4·-, O2·- and 1O2) were generated and they all responded for the degradation of BPA. In addition, the mechanism of PMS activation and BPA degradation were proposed. This study presented an efficient oxidation process for BPA degradation and outlines the synergistic effect of separation and catalytic oxidation.

Boosting the hydrogen storage performance of MgH2 by Vanadium based complex oxides

MgH2, a solid-state hydrogen storage material with high storage capacity, is facing the obstacles of high thermodynamic stability and slow reaction kinetics. Herein, different Vanadium (V) based catalysts (V2O5, Fe–V and V–Ni oxides) were synthesized by a hydrothermal method and ball milled with MgH2 to modify its hydrogen storage property. It is observed that the dehydrogenation performance (initial dehydrogenation temperature and desorption rate) of Fe–V oxide doped MgH2 was the best, followed by V2O5 and V–Ni oxide modified systems. The MgH2+7 wt% Fe–V composite exhibited an onset dehydrogenation temperature of 200 °C, 128 °C lower compared with the original MgH2. The absorption performance of MgH2 was also greatly enhanced by Fe–V oxide. The 7 wt% Fe–V modified MgH2 after dehydrogenation began to charge hydrogen from 25 °C to 5.1 wt% hydrogen was absorbed at 150 °C. The activation energy for hydrogen uptake of MgH2 was reduced from 76.5 ± 3.4 kJ/mol to 41.2 ± 4.7 kJ/mol. Additionally, the MgH2+7 wt% Fe–V composite maintained 97.2% hydrogen capacity after10 cycles. Our work here proves that elements substitution is a feasible way to tune the catalytic effect of oxides and may shed light on designing catalysts with higher activation in the future.

Preparation of Co3O4@carbon nanotubes modified ceramic membrane for simultaneous catalytic oxidation and filtration of secondary effluent

To improve the efficiency of wastewater reclamation, a novel Co3O4@carbon nanotubes modified ceramic membrane (Co3O4@CNT-CM) was prepared in this work for simultaneous catalytic peroxymonosulfate (PMS) oxidation and filtration of secondary effluent. The synthesized Co3O4@CNT catalyst showed better dispersibility with more active sites exposed, and Co3O4@CNT-CM exhibited relatively smooth surface, higher permeate flux and excellent catalytic PMS ability. The antifouling and water purification performance of Co3O4@CNT-CM were systematically investigated in secondary effluent purification. With the dual effect of catalytic oxidation and filtration, the organic pollutants were observably reduced. Fluorescent components were also significantly removed, and more macromolecular substances were degraded into small molecular substances. The flux of Co3O4@CNT-CM was significantly improved, with the reversible and irreversible resistances decreased by 82.5% and 78.6%, individually. With respect to the fouling mechanism, the volume entering the stage of cake filtration dramatically increased. The prepared Co3O4@CNT-CM accelerated the generation of various active species for oxidative degradation of pollutants, thus improving the antifouling performance of membrane. These results demonstrated the application potential of Co3O4@CNT-CM for wastewater treatment and reclamation.

The catalytic aerial oxidation of As(III) in alkaline solution by Mn-loaded diatomite.

The oxidization of As(III) to As(V) is necessary for both the detoxification of arsenic and the removal of arsenic by solidification. In order to achieve high efficiency and low cost As(III) oxidation, a novel process of catalytic aerial oxidation of As(III) is proposed, using air as oxidant and Mn-loaded diatomite as a catalyst. Through systematic characterization of the reaction products, the catalytic oxidation reaction law of Mn-loaded diatomite for As(III) was found out, and its reaction mechanism was revealed. Results show that Mn-loaded diatomite achieved a good catalytic effect for aerial oxidation of As(III) and maintained high performance over multiple cycles of reuse, which was directly related to the structure of diatomite and the behavior of manganese. Under the conditions of a catalyst concentration of 20g/L, an air flow rate of 0.3m3/h, a reaction temperature of 50°C and an initial pH of 12.6, 96.04% As(III) oxidation was achieved after 3h. Furthermore, the efficiency of As(III) oxidation did not change significantly after ten cycles of reuse. XPS analysis of the reaction products confirmed that the surface of the catalyst was rich in Mn(III), Mn(IV) and adsorbed oxygen(O-H), which was the fundamental reason for the excellent performance of Mn-loaded diatomite in the catalytic oxidation of As(III).

Mechanistic and thermodynamic insights into the SO2 oxidation on MnO2 catalysts: A combined theoretical and experimental study

Manganese oxide (especially manganese dioxide [MnO2]) is an excellent catalytic material for SO2 removal in flue gas desulfurization. In this study, the effect of crystalline structure of MnO2 (α-MnO2, β-MnO2, γ-MnO2 and δ-MnO2) on their activity for SO2 oxidation was studied based on density functional theory with Hubbard U corrections (DFT + U). The calculated results showed that α-MnO2 has mild energy barriers of 0.69 eV and 0.46 eV, and β-MnO2 has poor redox performance on SO2 molecules, which has the highest energy barrier of 2.17 eV and the largest oxygen formation energy of 1.74 eV, making it difficult for the oxygen atom to remove from the surface lattice to form reactive sites. Thermodynamic calculations showed that α-MnO2 is suitable for SO2 oxidation for its low energy barriers, reaction energy close to zero in the first half, and relatively high spontaneity in the whole reaction. Experimental tests showed that α-MnO2 had the best catalytic oxidation effect, with the highest sulfur capacity (304.11 mg/g), but β-MnO2 had poor catalytic oxidation performance, with a sulfur capacity of 41.59 mg/g. This work studies the catalytic performance and mechanism of SO2 removal and proposes a strategy to improve the catalytic activity by phase structure.

Catalytic oxidation of toluene by metal phthalocyanine loaded on cordierite honeycomb

AbstractBACKGROUNDAs one of the common VOCs, toluene is not only hazardous to human health, leading to respiratory disease, cancers, but also harmful to the environment, causing destruction of the ozone layer, photochemical smog and global warming. Catalytic oxidation is one of the most advanced technologies for eliminating VOCs and can convert VOCs to benign components such as carbon dioxide (CO2) and water. As catalysts are important in the catalytic process, finding highly active, low cost catalysts is critical. Metal phthalocyanine(MPc) has potential practical value and wide application prospects as catalysts for its uniquely high catalytic activity and selectivity. Thus, four monolithic catalysts were prepared by impregnating MPc onto cordierite honeycomb.RESULTSCharacterization by scanning electron microscopy, X‐ray diffraction, Fourier transform infrared and energy‐dispersive X‐ray spectroscopy showed that the metal phthalocyanines were successfully loaded on the cordierite honeycomb. A fixed‐bed reactor was used to examine the catalytic oxidation effects of metal phthalocyanine species, catalyst amount, feed concentration, feed flow and temperature on toluene. The result showed that the catalytic activity of phthalocyanine iron (FePc) to toluene was better than other three MPcs. The optimal reaction conditions were 120 mg catalyst, 6.3 × 10−3 mol m−3feed concentration and 250 mL min−1 feed flow. The conversion of toluene increased with increasing temperature.CONCLUSIONFePc/C also had a good catalytic oxidation effect on different aromatic hydrocarbon compounds (benzene and 1,4‐dimethyl‐benzene). The oxidation products of the catalytic system were CO2 and H2O, which met the requirements of green chemistry. FePc/C is a promising catalytic material because it has high catalytic activity and can be operated in simple conditions, such as low temperatures. © 2022 Society of Chemical Industry (SCI).

Syngas production from two-step CO2 gasification of low rank coal in an entrained flow reactor

Using CO2 as feedstock for syngas production is one hot topic in the field of clean energy due to the concern of global warming. Hence, two-step gasification (pyrolysis first and then subsequent char gasification) behaviour using CO2 as reactant was investigated under entrained flow conditions for one Inner Mongolia lignite and two Victorian brown coals (Maddingely and Morwell). The effects of CO2 concentration (5–30% CO2) and residence time(0–23 s) were assessed in the low temperature ranges of 700–1000 °C. High temperature improved H2 and CO yield in entrained flow pyrolysis. The higher CO2 concentration and longer residence time enhanced gasification syngas yield and carbon conversion. Three coal chars required around 23 s of residence time for 100% conversion under 20% CO2 and 1000 °C. It indicated that entrained flow gasification of the three chars was preferably performed above 1000 °C for industrial applications. Fe-rich Victorian brown coal achieved better pyrolysis performance than Inner Mongolia lignite because of the inherent catalytic effect of Fe oxides in coal. Morwell coal char achieved the best char-CO2 gasification performance due to higher gasification reactivity and better pore structure. This study provides essential information for the optimization of entrained flow gasifiers toward syngas production using CO2 as feedstock.

Simultaneous degradation of trace antibiotics in water by adsorption and catalytic oxidation induced by N-doped reduced graphene oxide (N-rGO): synergistic mechanism

Aimed at current difficulties in the treatment of trace antibiotics in water, an adsorption-catalytic oxidation system was established by combining persulfate and graphene, which have the dual functions of adsorption and catalysis, for simultaneous enrichment and degradation of trace antibiotics in water. The experimental results showed that over 90% sulfamethoxazole could be degraded by the proposed system. The activation energy of the proposed system was 7.9 kJ mol−1, which was significantly lower than those of typical Co catalysts and some carbon-based catalysts. Synergistic effect analysis revealed that catalytic oxidation was the key degradation kinetic of the proposed system, while adsorption showed a significant enhancement effect. Specifically, a compound with large adsorption capacity tended to be degraded preferably and rapidly. Characterization results indicated that N atoms were doped into the graphene framework, resulting in significant impacts on the activation process of potassium bisulfate by activating the sp2 C system. Quenching and free radical trapping experiments revealed that degradation catalyzed by the proposed system was a non-free radical oxidation reaction dominated by singlet oxygen. In summary, the proposed design was rational, N-rGO surface provided good adsorption and catalysis sites, the synergistic effect of adsorption and catalytic oxidation led to rapid and effective enrichment and in situ degradation of trace antibiotics in water.

Catalytic oxidation effect of MnSO4 on As(III) by air in alkaline solution

The catalytic oxidation effect of MnSO4 on As(III) by air in an alkaline solution was investigated. According to the X-ray diffraction (XRD), scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) analysis results of the product, it was shown that the introduction of MnSO4 in the form of solution would generate Na0.55Mn2O4·1.5H2O with strong catalytic oxidation ability in the aerobic alkaline solution, whereas the catalytic effect of the other product MnOOH is not satisfactory. Under the optimal reaction conditions of temperature 90°C, As/Mn molar ratio 12.74:1, air flow rate 1.0 L/min, and stirring speed 300 r/min, As(III) can be completely oxidized after 2 hr reaction. The excellent catalytic oxidation ability of MnSO4 on As(III) was mainly attributed to the indirect oxidation of As(III) by the product Na0.55Mn2O4·1.5H2O. This study shows a convenient and efficient process for the oxidation of As(III) in alkali solutions, which has potential application value for the pre-oxidation of arsenic-containing solution or the detoxification of As(III).