H2O2 Oxidation Processes Research Articles

Autocatalytic oxidation of thiophene derivatives and co-degradation of refractory contaminants in Fenton reaction

The sluggish reduction of Fe(III) to Fe(II) restricts the decontamination efficiency of Fenton reactions. New strategy development toward enhancing Fe(II) regeneration and decontamination efficiency relies primarily on the well-established inorganic Fenton chemistry, yet the involvement of organic contaminants and its potential role in the Fenton reactions have been insufficiently concerned. Here, using 2,5-thiophene carboxylic acid (TDA) as a representative sulfur-containing heterocyclic contaminant and atrazine as a coexisting contaminant, we uncovered the promoting effect of thiophene derivatives on Fenton oxidation. The degradation of TDA and coexisting refractory contaminants was highly efficient in the sluggish Fe(III)/H2O2 oxidation process with autocatalytic features. Spin trapping and chemical scavenging results underpinned the crucial contribution of hydroxyl radicals (HO•) to organic oxidation. Analysis of iron cycling combined with theoretical calculations revealed that the enhancement of TDA on Fenton oxidation originated from the rapid reduction of Fe(III) by the primary radicals generated from addition of HO• to the thiophene ring.

REMOVAL OF ORGANIC IMPURITIES BY PEROXIDE OXIDATION

Waste sulfuric acid is a big environmental problem in modern world. The amount of waste sulfuric acid produced is huge every year1. Many small and medium-sized businesses produce lots of waste acids, but they do not have an appropriate method to treat and recover them. Also due to norms set by pollution control boards across the countries, the waste Sulphuric acid cannot be dumped without proper treatment. This paper focuses on removal of organic impurities in waste Sulphuric acid by using H2O2oxidation process. This method is economical and feasible for most small and medium-sized industries / business.

Cyanide removal for ultrafine gold cyanide residues by chemical oxidation methods

Because of the highly toxic cyanide in the gold cyanide residues, cyanide must be removed for environmental protection. The process mineralogy of residues was studied firstly, and then cyanide removal was carried out by three chemical methods. The results showed that the residue mainly contained Si, S and Fe. Pyrite was the main metallic mineral, and the iron-complex cyanides make cyanide removal difficult. The minerals in residues were in ultrafine particle size with high monomer dissociation degrees. In H2O2 oxidation process, the self-decomposition and side reactions resulted in high consumption of H2O2. In Na2S2O5-air oxidation process, the time for complete process was long because of the reactions between Na2S2O5 and O2. Na2SO3 oxidation method was found to be a new method for cyanide removal without air inflation device. The cyanide content was reduced to the national standard level in 90 min at pH 9.0 with optimum Na2SO3 dose of 2.0 g/L.

Quantification of the Influence of Citrate/Fe(II) Molar Ratio on Hydroxyl Radical Production and Pollutant Degradation during Fe(II)-Catalyzed O2 and H2O2 Oxidation Processes.

Ligand-enhanced hydroxyl radical (•OH) production is an important strategy for Fe(II)-catalyzed O2 and H2O2 oxidation processes. However, the influence of the molar ratio of ligands to Fe(II) on •OH production remains elusive. This study employed citrate and inorganic dissolved Fe(II) (Fe(II)dis) as the representative ligand and Fe(II) species, respectively, to quantify this relationship. Results showed that •OH production was highly dependent on the citrate/Fe(II) molar ratio. For instance, for the oxygenation of Fe(II)dis, the •OH accumulations were 2.0–8.5, 3.4–28.5 and 8.1–42.3 μM at low (0.25–0.5), moderate (0.5–1), and high (1–2) citrate/Fe(II) molar ratios, respectively. At low citrate/Fe(II) molar ratio (<0.5), inorganic Fe(II)dis mainly contributed to •OH production, with the increase in the citrate/Fe(II) molar ratio to a high level (1–2), Fe(II)-citrate complex turned to the electron source for •OH production. The change in Fe(II) speciation with the increase of citrate/Fe(II) molar ratio elevated •OH production. For pollutant degradation, 1 mg/L phenol was degraded by 53.6% within 40 min during oxygenation of Fe(II)-citrate system (1:1) at pH 7. Our results suggest that a moderate molar ratio of ligand/Fe(II) (0.5–1) may be optimal for Fe(II)-catalyzed O2 and H2O2 oxidation processes.

Performance of treatment schemes comprising chromium-hydrogen peroxide-based advanced oxidation process for textile wastewater

The present study investigated the performance of a chromium-based advanced oxidation process using chromium (as Cr3+ or Cr6+) and H2O2 for the treatment of synthetic and simulated textile wastewaters. With the Cr3+/H2O2 system, the maximum total organic carbon (TOC) and color removals from the synthetic dye wastewater (Remazol Brilliant Violet 5R dye concentration = 100mg/L) were 75% and 99%, respectively, within 30min duration ([Cr3+]:[H2O2] = 1:30, stoichiometric H2O2 dose = 2.01ml/L and pH = 7). Whereas the same catalyst and oxidant combination resulted in chemical oxygen demand (COD) and color removals of ~ 46%, and 84%, respectively, after 3h of reaction at the optimized reaction conditions (i.e., [Cr3+]:[H2O2] = 1:50, stoichiometric H2O2 dose = 11.6ml/L and pH = 7) from the simulated textile wastewater (initial pH = 10.2, and COD = 1820mg/L). Further, the addition of stoichiometric H2O2 dose to the pretreated wastewater and pH adjustment increased the overall COD removal to 77%. Both oxidation and precipitation reactions were found responsible for organics removal from the wastewater. The other alternative involving activated carbon adsorption as second step, was not found as effective as the above scheme. The data on COD removal from simulated textile wastewater could be fit adequately in the retarded first-order kinetic model. Based on the COD and color removal results and preliminary cost analysis, this can be suggested that the Cr3+/H2O2 oxidation process followed by pH adjustment and further H2O2treatment was the best option for the removal of COD and color from thesimulated combined textile wastewater.

Metal-organic frameworks decorated pomelo peel cellulose nanofibers membranes for high performance dye rejection

In this work, the cellulose nanofibers based membranes with both high dye solution flux and rejection rates were obtained. The cellulose nanofibers (PPCNFs) were prepared from pomelo peels by simple H2O2 oxidation process, decorated with ZIF-8 crystals, and vacuum filtrated to form composite membranes (PPCNFs@ZIFx). Ascribing to the highly porous structures of ZIF-8, as well as their uniform and stable deposition on the surfaces of PPCNFs, the resultant membranes were mechanically strong (tensile strength up to ~72.25 MPa), surface area rich (~ 199.46 m2/g), and with a maximal dye solution flux of ~32.3 L m−2 h−1 bar−1 and dye rejection rates larger than 85 % (89.95 % for methyl blue, 98.83 % for methyl violet, 95.91 % for malachite green, 95.36 % for rhodamine 6 G, and a high rejection rate of ~98.6 % toward methyl violet after 30-day cycles). Thus, this work paved a simple and green way to fabricate cellulose nanofibers based membranes with high performance in the remediation of dye contaminated water.

Exploration of the H2O2 Oxidation Process and Characteristic Evaluation of Humic Acids from Two Typical Lignites.

To study the effect of H2O2 on the content and properties of humic acids (HAs) in lignites, the experimental conditions including oxidation time, H2O2 concentration, and the solid–liquid ratio were investigated. Under the optimum oxidation conditions, the contents of HAs of YL and HB lignite were 45.4 and 40.9%, respectively. The HAs extracted from oxidized and raw lignites were characterized and compared. The results showed that the HAs extracted from oxidized lignites contain more total acidic groups, carboxyl groups, and aliphatic carbon than that in HAs extracted from raw lignites, and their hydrophilic–hydrophobic index value is higher and thermooxidative stability is better than those in HAs extracted from raw lignites. In addition, the composition of polycyclic aromatic hydrocarbons and fluorophore types in HAs extracted from oxidized lignites are similar to the HAs extracted from raw lignites. The results indicated that the oxidation operation can increase the content of HAs in lignites, and simultaneously increase the content of oxygen-containing functional groups and biological activity of HAs, which provided a reference for the subsequent application of HAs.

Treatment of real deplating wastewater through an environmental friendly precipitation-electrodeposition-oxidation process: Recovery of silver and copper and reuse of wastewater

In order to avoid the discharge of deplating wastewater with high concentration of NO3−, an environmental friendly process, consisting of precipitation, electrodeposition and oxidation, is developed in this research for the treatment of real high acidic deplating wastewater containing Ag+, Cu2+, NO3− and chemical oxygen demand (COD). The wastewater is treated by precipitation to remove Ag+, electrodeposition to remove Cu2+, oxidation to reduce COD successively and then reused for deplating plastic plated parts. In precipitation process, 99.9% Ag+ in wastewater is precipitated by HCl and silver metal is then recovered through the replacement of AgCl by iron powder. Because of the high conductivity, Cu2+ in wastewater is then separated and recovered as copper metal on cathode through electrodeposition. The effect of electrodeposition parameters including cathode material, current density, electrode distance, reaction temperature and Cu2+ initial concentration is investigated. Up to 89.3% Cu2+ can be recovered in 80 min at the optimal condition. Finally, the COD is removed from 1360 mg L−1 to 378 mg L−1 in subsequent H2O2 oxidation process to ensure the reuse of water. Because the valuable Ag and Cu metals are recovered and the COD is removed, the wastewater can be reused as deplating solution. The estimated profit of this precipitation-electrodeposition-oxidation process reveals its practical feasibility. Furthermore, the process realizes the cleaner production of the deplating technology because it avoids the discharge of unmanageable wastewater with high NO3− concentration. More importantly, the process can also be improved to treat similar wastewater.

Advanced Oxidation Process Efficiently Removes Ampicillin from Aqueous Solutions

Background: Antibiotics are considered important and integral parts of modern life, and are widely used for treating human and animal illnesses, in medicine and veterinary medicine. However, they can cause environmental pollution and may lead to increased bacterial resistance even at low concentrations. Methods: In this study, Ampicillin degradation from β-lactam antibiotic family was studied, using a surface methodology consisting of ultraviolet radiation (254 nm) and H2O2 oxidation process in an 8-watt Pyrex reactor. The variables used included the reaction time (30-60 min), Ampicillin concentration (5-25 mg/l), H2O2 concentration (5-25 mg/l), and pH range of 3-9 at three alpha levels of -1, 0 and +1. Results: The data were analyzed by the analysis of variance test (ANOVA), while the validity was evaluated using regression coefficients. The optimum condition for Ampicillin degradation followed a linear model, at a 60-min. reaction time and pH 3, the Ampicillin (5mg/l) and hydrogen peroxide (25mg/l) provided the maximum antibiotic removal efficiency (82%). Conclusions: The results suggest a positive and significant effect for the antibiotic concentration and a negative effect for the pH. The Ampicillin concentration with a coefficient of 8.91 had the highest impact on the efficiency of the removal process. Therefore, antibiotic pollution in the environment can be reduced through the UV-H2O2 process, so as to protect human health from the associated hazards.

Influence of Different Sulfur Forms on Gas-Phase Mercury Removal by SO2-Impregnated Porous Carbons

Due to widespread global mercury pollution via anthropogenic activities such as coal combustion and its severe toxicity even at low concentrations, it is necessary to remove mercury from power plant flue gas to protect both human and ecosystem. Currently, significant efforts are being made to maximize Hg0 adsorption rates while minimizing the impact on the cost of electricity. The purpose of this study is to explore the influence of different sulfur forms on vapor Hg0 removal by SO2 impregnated porous carbons. After SO2 impregnation, reductive heat-treatment in N2 and H2O2 oxidation process were used to diverge the sulfur form composition in porous carbons. The ultimate and XPS analysis were used to verify the sulfur species. The pore structures of sorbents were determined by nitrogen adsorption/desorption measurements. Then their mercury removal performance was investigated in a fixed-bed reactor, and the influence of different sulfur forms on equilibrium mercury adsorption capacity and mercury desorptio...

H2O2 assisted photoelectrocatalytic degradation of diclofenac sodium at g-C3N4/BiVO4 photoanode under visible light irradiation

In this paper, g-C3N4/BiVO4 composite was electrospinned onto FTO substrate and used as photoanode for photoelectrocatalytic degradation of diclofenac sodium. The photoelectrocatalytic degradation efficiency of DCF by the g-C3N4/BiVO4 photoanode is much higher than that by the individual g-C3N4 and BiVO4 photoanodes. The first order kinetic constants are estimated to be 3.2×10−3min−1 for g-C3N4/BiVO4 photoanode, while the kinetic constants are 1×10−4min−1 and 1.1×10−3min−1 for g-C3N4 and BiVO4 photoanode. To further increase the degradation of DCF in PEC process, H2O2 was added into the system, and the results indicated that DCF degradation was largely increased. The kinetic rate constant was 5.6×10−3min−1 for H2O2 assisted PEC process and it was estimated to be 3.2×10−3min−1 and 1×10−5min−1 for the individual PEC process and H2O2 oxidation process, respectively. Effect of initial pH, H2O2 dosage and applied bias on DCF degradation was investigated in detail. The highest DCF degradation efficiency was achieved at initial pH of 3.17 and applied bias potential of 1.0V (vs. SCE) with 10mM H2O2 addition. Involved reactive active species were studied using electron spin resonance; a proposed reaction pathway was proposed.

Hybrid zero valent iron (ZVI)/H2O2 oxidation process for landfill leachate treatment with novel nanosize metallic calcium/iron composite

ABSTRACTA novel nanosize metallic calcium/iron dispersed reagent was synthesized and tested as coagulant/catalyst in a hybrid zero valent iron (ZVI)/H2O2 oxidation process to treat leachate. Two different types of leachates, one from municipal solid waste (MSW) tipping hall (MSWIL) and second from an MSW landfill site (MSWLL), were collected and characterized. The morphology, elemental composition, and mineral phases of the nano-Ca/CaO and nano-Fe/Ca/CaO were characterized by scanning electron microscopy–electron dispersive spectroscopy (SEM-EDS) and x-ray powder diffraction (XRD) analysis. The coagulation process with 2.5 g L−1 nano-Ca/CaO attained 64.0, 56.0, and 20.7% removal of color, chemical oxygen demand (COD), and total suspended solids (TSS) in MSWLL. With only 1.0 g L−1 of nano-Fe/Ca/CaO, relatively high color, COD and TSS removal was achieved in MSWLL at 67.5, 60.2, and 37.7%, respectively. The heavy metal removal efficiency reached 91–99% after treatment with nano-Fe/Ca/CaO in both leachate samples. The coupling process, using 1.0 g L−1 of nano-Fe/Ca/CaO and 20 mM H2O2 doses, achieved enhancement removal of color, COD, and TSS, up to 95%, 96%, and 66%, respectively, without initial pH control. After this treatment, the color, COD, TSS, and heavy metals were significantly decreased, fitting the Korean discharge regulation limit. A hybrid coupled zero valent iron (ZVI)/H2O2 oxidation process with novel nanosized metallic calcium/iron dispersed reagent proved to be a suitable treatment for dealing with leachate samples.Implications: Conventional treatments (biological or physicochemical) are not sufficient anymore to reach the level of purification needed to fully reduce the negative impact of landfill leachates on the environment. This implies that new treatment alternatives species must be proposed. A coupled zero valent iron (ZVI)/H2O2 oxidation process proved to be a suitable treatment for dealing with leachate samples. Coagulation with nFe/Ca/CaO allows 91–99% of heavy metals removal. The coupled coagulation–oxidation process by nFe/Ca/CaO reveals excellent ability to treat leachate. After coupled treatment the color, COD, and TSS were also much lower than the discharge regulation limit.

Origin of the different behavior of some platinum decorated nanocarbons towards the electrochemical oxidation of hydrogen peroxide

The electrochemical behavior of different platinum-decorated nanocarbons (Pt@C) towards the oxidation of hydrogen peroxide (H2O2) was investigated. Three different types of nanocarbons were considered: i) carbon black, ii) dahlia-like carbon nanohorns and iii) carbon nanotubes, which included both commercial (single-wall and multi-wall) and laboratory prepared (multi-wall) samples. Shape and size distribution of the platinum nanoparticles and morphology of the nanocarbons were analyzed by transmission electron microscopy. Their nanostructure was investigated by micro-Raman spectroscopy, while elemental composition of the samples and chemical bonding states were studied by X-ray photoelectron spectroscopy. Electrochemical behavior towards H2O2 oxidation was evaluated by means of cyclic voltammetry modifying the working screen-printed carbon electrode surface with the prepared Pt@C nanocomposites. Data obtained suggest that the size and dispersion of the Pt nanoparticles play a key role in increasing the sensitivity towards H2O2 detection. Thanks to the presence of smaller and more dispersed platinum particles and of a greater amount of platinum hydroxide, acting as intermediary in the H2O2 oxidation process, Pt@dahlia-like carbon nanohorns result to be the most promising platform for the development of H2O2 electrochemical sensors.

Effect of persulfate and persulfate/H2O2 on biodegradability of an anaerobic stabilized landfill leachate

The current study investigated the effects of S2O82− and S2O82−/H2O2 oxidation processes on the biodegradable characteristics of an anaerobic stabilized leachate. Total COD removal efficiency was found to be 46% after S2O82− oxidation (using 4.2g S2O82−/1g COD0, at pH 7, for 60min reaction time and at 350rpm shaking speed), and improved to 81% following S2O82−/H2O2 oxidation process (using 5.88g S2O82− dosage, 8.63g H2O2 dosage, at pH 11 and for 120min reaction time at 350rpm). Biodegradability in terms of BOD5/COD ratio of the leachate enhanced from 0.09 to 0.1 and to 0.17 following S2O82− and S2O82−/H2O2 oxidation processes, respectively. The fractions of COD were determined before and after each oxidation processes (S2O82− and S2O82−/H2O2). The fraction of biodegradable COD(bi) increased from 36% in raw leachate to 57% and 68% after applying S2O82− and S2O82−/H2O2 oxidation, respectively. As for soluble COD(s), its removal efficiency was 39% and 78% following S2O82− and S2O82−/H2O2 oxidation, respectively. The maximum removal for particulate COD was 94% and was obtained after 120min of S2O82−/H2O2 oxidation. As a conclusion, S2O82−/H2O2 oxidation could be an efficient method for improving the biodegradability of anaerobic stabilized leachate.

Removal of phenolic endocrine disrupting compounds from waste activated sludge using UV, H2O2, and UV/H2O2 oxidation processes: Effects of reaction conditions and sludge matrix

Removal of six phenolic endocrine disrupting compounds (EDCs) (estrone, 17β-estradiol, 17α-ethinylestradiol, estriol, bisphenol A, and 4-nonylphenols) from waste activated sludge (WAS) was investigated using ultraviolet light (UV), hydrogen peroxide (H2O2), and the combined UV/H2O2 processes. Effects of initial EDC concentration, H2O2 dosage, and pH value were investigated. Particularly, the effects of 11 metal ions and humic acid (HA) contained in a sludge matrix on EDC degradation were evaluated. A pseudo-first-order kinetic model was used to describe the EDC degradation during UV, H2O2, and UV/H2O2 treatments of WAS. The results showed that the degradation of the 6 EDCs during all the three oxidation processes fitted well with pseudo-first-order kinetics. Compared with the sole UV irradiation or H2O2 oxidation process, UV/H2O2 treatment was much more effective for both EDC degradation and WAS solubilization. Under their optimal conditions, the EDC degradation rate constants during UV/H2O2 oxidation were 45–197 times greater than those during UV irradiation and 11–53 times greater than those during H2O2 oxidation. High dosage of H2O2 and low pH were favorable for the degradation of EDCs. Under the conditions of pH=3, UV wavelength=253.7nm, UV fluence rate=0.069mWcm−2, and H2O2 dosage=0.5molL−1, the removal efficiencies of E1, E2, EE2, E3, BPA, and NP in 2min were 97%, 92%, 95%, 94%, 89%, and 67%, respectively. The hydroxyl radical (OH) was proved to take the most important role for the removal of EDCs. Metal ions in sludge could facilitate the removal of EDCs during UV/H2O2 oxidation. Fe, Ag, and Cu ions had more obvious effects compared with other metal ions. The overall role of HA was dependent on the balance between its competition as organics and its catalysis/photosensitization effects. These indicate that the sludge matrix plays an important role in the degradation of EDCs.

Application of Box-Behnken design with response surface methodology for modeling and optimizing ultrasonic oxidation of arsenite with H2O2

Abstract A combined ultrasound (US)/H2O2 process was used to oxidize arsenite to arsenate, yielding a synergistic effect value of 1.26. This showed that the combined process could be an effective method of oxidizing arsenite, instead of using either ultrasonic or H2O2 oxidation processes. This combined process was successfully modeled and optimized using a Box-Behnken design with response surface methodology (RSM). The effects of the US power density, the initial concentration of arsenite, and the H2O2 concentration on the sonochemical oxidation efficiency of arsenite were investigated. Analysis of variance indicated that the proposed quadratic model successfully interpreted the experimental data with coefficients of determination of R 2 = 0.95 and adjusted R 2 = 0.91. Through this model, we can predict and control the oxidation efficiency under different conditions. Furthermore, the optimal conditions for the oxidation of arsenite were found to be a US power density of 233.26 W L−1, an initial arsenite concentration of 0.5 mg L−1, and an H2O2 concentration of 74.29 mg L−1. The predicted oxidation efficiency obtained from the RSM under the optimal conditions was 88.95%. A confirmation test of the optimal conditions verified the validity of the model, yielding an oxidation efficiency of 90.1%.

One-pot synthesis of magnetically separable ordered mesoporous carbon

Ordered mesoporous carbon materials with magnetic frameworks have been synthesized via a “one-pot” block-copolymer self-assembly strategy associated with a direct carbonization process from resol, ferric citrate and triblock copolymer F127. The effects of iron loading on framework, pore features and magnetic properties of the resultant mesostructured maghemite/carbon composites were investigated by SAXS, WXRD, TEM, N2 sorption, TG and magnetometer measurements. The results show that the mesoporous nanocomposites with a low γ-Fe2O3 content (such as 9.0 wt%) possess an ordered 2-D hexagonal (p6mm) structure, uniform mesopores (∼4.0 nm), high surface areas (up to 590 m2/g) and pore volumes (up to 0.48 cm3/g). Maghemite nanocrystals with a small particle size (∼9.3 nm) are confined in the matrix of amorphous carbon frameworks. With the increase in γ-Fe2O3 content, the surface area and pore volume of the nanocomposites decrease. The particle size of the γ-Fe2O3nanocrystals increases up to 13.1 nm. The iron oxide particles can extend from the carbon walls into mesopore channels, and hence bring a rough pore surface and gradually break down the mesoscopic regularity. The maghemite/carbon nanocomposites exhibit excellent superparamagnetic behaviors. The saturation magnetization strength can be easily adjusted from 2.5 to 12.1 emu/g by increasing the content of γ-Fe2O3. Further H2O2oxidation treatment of the magnetic nanocomposites endows plenty of oxygen-containing functional groups on the carbon surface, which improves their hydrophilic properties efficiently. The γ-Fe2O3 particles, embedding into the carbon matrix, show high stability during the H2O2oxidation process. Such modified nanocomposites with hydrophilic and magnetic framework show evidently improved adsorption properties of water and fuchsin base dye molecules in water and an easy separation procedure.