H2O2 Process Research Articles

Promotion of O2 activation by ZIF-8 derived N-rich aluminum-graphite (Al-Gr-NPC) composite for non-radical degradation of antibiotic at neutral pH

Recently, the activation of molecular oxygen (O2) by graphite (Gr) supported aluminum (Al) composite for the in-situ generation of H2O2/OH gains increasing attention. However, the limited O2 mass transfer and low catalytic activity of decomposition H2O2 at neutral pH restrict its further application in the wastewater treatment. In this work, a novel N-rich graphite supported aluminum (Al-Gr-NPC) composite was fabricated by introducing the nitrogen-rich porous carbon (NPC) obtained from ZIF-8 derivative as precursor, and by a ball-milling and sintering process. The results showed that the NPC introduction not only improved the physiochemical property of Al-Gr, such as specific surface area, pore structure and hydrophobicity, facilitating the mass transfer of O2, but also made Al-Gr contain plentiful N species, serving as active sites for the two-electron ORR process and catalytic decomposition of H2O2. These excellent performances of Al-Gr-NPC favored the production and utilization of H2O2 by the activation of O2 at neutral pH and air aeration. The carbonization temperature of ZIF-8 determined the type of N species, surface area and the hydrophobicity of NPC. 1O2 was the main oxidant for tetracycline hydrochloride (TC) degradation. 100 % TC degradation and 60.57 % of TOC removal were achieved within 60 min at neutral pH, Al-Gr-NPC dosage of 0.5 g/L and initial TC concentration of 20 mg/L. The toxicity of the final products of TC degradation were much lower than TC by ECOSAR software analysis. Al-Gr-NPC could be used for the removal of antibiotic contaminants from wastewater.

Sequential coagulation/flocculation and sonolytic oxidation using persulfate and hydrogen peroxide for real rubber processing industry wastewater treatment: Kinetic modelling and treatment cost analysis

Rubber processing industry consumes huge quantity of water, uses chemicals and produces enormous quantity of toxic wastewater with high level of chemical oxygen demand (COD), solids and turbidity. In this study, treatability of rubber processing industry effluent using a sequential coagulation-flocculation (CF) followed by sonolytic oxidation was studied with the real wastewater collected from a rubber processing industry located near to Agartala, Tripura, the second largest rubber producing state in India. Initially aluminium sulfate was used as coagulant in the CF process to reduce the COD of the wastewater followed by only ultrasonication (CF + US), sonolytic oxidation using persulfate (CF + US + PS), sonolytic oxidation using hydrogen peroxide (CF + US + H2O2) and sonolytic oxidation using both persulfate and hydrogen peroxide (CF + US + PS + H2O2) as oxidants. Real rubber processing wastewater was also treated with only sonication (US). Firstly, the only CF process (aluminium sulphate dose: 500 mg/L) could reduce the COD of wastewater from 18267 mg/L to 12800 mg/L (COD removal: 29.93 %). Thereafter, CF + US (sonication time: 30 min), CF + US + PS (PS dose: 500 mg/L), CF + US + H2O2 (H2O2 dose: 0.75 mmol/L), and CF + US + PS + H2O2 (PS dose: 500 mg/L and H2O2 dose: 0.75 mmol/L) resulted to effluent COD value to ∼ 6800 mg/L, 4200 mg/L, 3200 mg/L and ∼ 1600 mg/L, respectively. The CF + US + PS + H2O2 process was the best option among the considered combination of treatment techniques to treat the real rubber processing industry effluent in terms of COD removal (%). Kinetic analysis for the degradation of COD in various treatment processes were found to be consistent with pseudo second order kinetic model. The treatment cost analysis revealed that COD degradation by CF + US + H2O2 process cost ∼ 2.5 USD/kg of COD removal with 82.48 % of COD removal.

Degradation of Orange G in water by nano-Cu0/H2O2 process with nano-Cu0 synthesized in a rotating packed bed with blade packings

In this investigation, Orange G in water was degraded by the nano-Cu0/H2O2 process with nano-sized copper particles (RPB-nano-Cu0) that were synthesized by chemical reduction in a rotating packed bed (RPB) with blade packings. The effects of H2O2 dosage and RPB-nano-Cu0 dose on the degradation of Orange G by the RPB-nano-Cu0/H2O2 process were investigated. An optimal H2O2 dosage in the degradation of Orange G by the RPB-nano-Cu0/H2O2 process was 5 mmol/L for a RPB-nano-Cu0 dose of 0.25 g/L. An optimal RPB-nano-Cu0 dose in the degradation of Orange G by the RPB-nano-Cu0/H2O2 process was 0.25 g/L for an H2O2 dosage of 5 mmol/L. The RPB-nano-Cu0/H2O2 process with 25 °C, pH 3, an H2O2 dosage of 5 mmol/L, and a RPB-nano-Cu0 dose of 0.25 g/L exhibited an efficiency of degradation of Orange G (10 mg/L) of 93% at 30 min. The efficiency of degradation of Orange G (10 mg/L) using commercial nano-Cu0 from Sigma-Aldrich (0.25 g/L) in the presence of H2O2 (5 mmol/L) at pH 3 was 73% after 30 min. The RPB-nano-Cu0/H2O2 process exhibited the great potential in the efficient degradation of Orange G in water.

Greywater treatment by anodic oxidation, photoelectro-Fenton and solar photoelectro-Fenton processes: Influence of relevant parameters and toxicity evolution

In this study, the applicability of factorial design to the treatment of greywater (GW) containing dodecyl-benzene sulfonic acid (LAS) by electrochemical advanced oxidation processes (EAOPs) is demonstrated. At bench scale, anodic oxidation with electrogenerated H2O2 (AO-H2O2) and photoelectro Fenton (PEF) processes were studied following a 23 factorial design with central point insertion, using a first-order mathematical polynomial. In the former process, the combination of a boron-doped diamond (BDD) anode with a carbon-PTFE air-diffusion cathode, both of 3 cm2, yielded a 76% degradation of LAS at 40 mg L−1 along with 52% TOC removal under optimized conditions. The PEF process with 5 mg L−1 Fe2+ at current density of 77.5 mA cm−2 allowed attaining a 63% of LAS degradation and 78% of TOC abatement. The best conditions found for PEF according to the factorial design, in terms of Fe2+ concentration and current density, were applied for the treatment of 10 L of raw GW by solar PEF (SPEF) using a compound parabolic collector (CPC) as solar reactor and a filter-press electrochemical cell. A 70% of LAS removal and a 55% of GW mineralization were attained after 240 min of treatment. Artemia salina toxicity tests were performed with effluents resulting from the different methods under optimum conditions, and the SPEF process was proven to be the most effective and promising EAOP for the reduction of GW toxicity.

Synergizing Fenton oxidation and in-situ coagulation over a wide pH range for the simultaneous removal of multiple pollutants

Efficient removal of multiple pollutants from discharged antibiotic wastewater effluents by a single processing unit is highly desirable, yet challenging. In this study, intrinsically synergizing Fenton oxidation and in-situ coagulation were achieved in the tannic acid (TA)/Fe(III)/H2O2 process, demonstrating the simultaneous removal of multiple pollutants over a wide pH range. Under the optimal conditions (TA/Fe(III)/H2O2 = 25 mg/L/0.1 mM/0.5 mM), 95.43 % of SMR and 98.41 % of turbidity were simultaneously removed at pH = 7. Moreover, the applicability of this process was validated by treating a spiked actual secondary effluent. Compared with polymer ferric sulphate coagulation and conventional Fe(II)/H2O2 Fenton, TA/Fe(III)/H2O2 process exhibited significantly enhanced removal performance in terms of SMR, COD, UV254 and turbidity without any pH adjustment. The mechanism analysis revealed that the introduction of TA can not only promote the iron redox cycle for the production of ∙OH, but also neutralize the charge for the generation of the porous flocs. Due to the bridging of TA, the synergy of Fenton oxidation and in-situ coagulation was achieved in a single processing unit. Finally, the synergy mechanism proposed that a four-step process sequentially proceeded during the treatment. This study may provide new insights into the simultaneous removal of multiple pollutants in the advanced treatment of refractory industrial wastewater.

An assessment of the UV/nFe0 /H2 O2 system for the removal of refractory organics in the effluent produced by the biological treatment of landfill leachate.

The removal efficiency and mechanism of the ultraviolet/nanoscale Fe0 /H2 O2 (UV/nFe0 /H2 O2 ) system for refractory organics in membrane bioreactor effluent were investigated. The most effective removal of organics was achieved at initial pH = 3.0, H2 O2 dosage = 50 mM, nFe0 dosage = 1.0 g/L, and UV power = 15 W, with a reaction time of 60 min. Under these conditions, the absorbance at 254 nm, chromaticity, and total organic carbon removal efficiencies were 65.13%, 79.67%, and 61.51%, respectively, and the aromaticity, humification, molecular weight, and polymerization of organics were all significantly reduced. The surface morphology and elemental valence analysis of nano zero-valent iron (nFe0 ) before and after the reaction revealed the formation of iron-based (hydrated) oxides, such as Fe2 O3 , Fe3 O4 , FeOOH, and Fe (OH)3 , on the surface of the nFe0 . Refractory organics were removed by Fenton-like reactions in the homogeneous and heterogeneous adsorption-precipitation of iron-based colloids. At the same time, UV radiation accelerated the formation of Fe2+ on the nFe0 surface and promoted the Fe3+ /Fe2+ redox cycle to a certain extent, enhancing the removal of refractory organics. The results provide a theoretical basis for the application of the UV/nFe0 /H2 O2 system to remove refractory organics in the effluent produced by the biological treatment of landfill leachate. PRACTITIONER POINTS: The UV/nFe0 /H2 O2 process is effective in refractory organics removal in leachate treatment. Humus in leachate was largely destroyed and mineralized by the UV/nFe0 /H2 O2 process. Active nFe0 material participated in the Fenton-like process and was promoted by UV. The effects of nFe0 material and UV introduction were investigated.

Release of free-state ions from fulvic acid-heavy metal complexes via VUV/H2O2 photolysis: Photodegradation of fulvic acids and recovery of Cd2+ and Pb2+ stripping voltammetry currents

Fulvic acid (FA), a ubiquitous organic matter in the environment, can enhance the mobility and bioavailability of Cd2+ and Pb2+ through competitive complexation to form FA-heavy metal ions (FA-HMIs) complexes with excellent solubility. Because FA-HMIs are electrochemically inactive, square wave anodic stripping voltammetry (SWASV) cannot accurately detect the content of bioavailable Cd2+ and Pb2+ in soils and sediments. This study ostensibly aimed to efficiently recover SWASV signals of Cd2+ and Pb2+ in FA-HMIs by disrupting FA-HMIs complexes using the combined vacuum ultraviolet and H2O2 (VUV/H2O2) process. Essentially, this study explored the photodegradation behavior and photolysis by-products of FA and their effects on the conversion of FA-HMIs complexes to free-state Cd2+ and Pb2+ using multiple characterization techniques, as well as revealed the complexation mechanism of FA with Cd2+ and Pb2+. Results showed that reactive groups such as carboxyl and hydroxyl endowed FA with the ability to complex Cd2+ and Pb2+. After FA-HMIs underwent VUV/H2O2 photolysis for 9 min at 125 mg/L of H2O2, FA was decomposed into small molecular organics while removing its functional groups, which released the free-state Cd2+ and Pb2+ and recovered their SWSAV signals. However, prolonged photolytic mineralization of FA to inorganic anions formed precipitates with Cd2+ and Pb2+, thereby decreasing their SWSAV signals. Moreover, the VUV/H2O2 photolysis significantly improved the SWASV detection accuracy toward the Cd2+ and Pb2+ in real soil and sediment samples, verifying its practicality.

Zeolite imidazole framework-8-derived nitrogen-doped nanocarbon boosted Fenton-like oxidation: Another sustainable path for Fe(III)/Fe(II) circulation

Zeolite imidazole framework-8 (ZIF-8) is a promising template to obtain porous nanocarbons. In this study, microporous nitrogen-doped nanocarbons from the carbonization of ZIF-8 (ZCN) was prepared as an efficient metal-free catalyst to improve several micropollutants degradation in Fe(III)/H2O2 process. The sulfamethoxazole (SMX) ratio was increased from 20% to 100% with the addition of ZCN (50 ​mg/L) in Fe(III)/H2O2 within 20 ​min, and the working pH was endowed. The direct reduction for Fe(III) resulting from carbonyl on ZCN's surface was revealed. Hydroxyl radical (•OH) was determined to be the main reactive species, and the evolution of different Fe species during the reaction was discussed by monitoring the mass balance of Fe species. We found that part of the iron was bound to the surface of ZCN during the reaction. Additionally, the dissociative Fe was captured by ZCN to form Fe-Nx bonds. Surface-bound Fe with a lower energy barrier was more likely to react with H2O2 to generate Fe(II). Our work revealed that in addition to the direct reduction by ZCN, another catalytic reduction pathway for the sustainable conversion of Fe(III) to Fe(II) in the ZCN/Fe(III)/H2O2 process was operative.

Investigation of H2O2/UV advanced oxidation process on the removal rate of coliforms from the industrial effluent: A pilot-scale study

Wastewater recycling and reuse is very important, specially in countries with water shortage problem. Disinfection is very crucial step of wastewater treatment, particulary from the reuse and environmental protection point of view. In this research, the efficiency of the advanced oxidation process using UV and H2O2 combination was investigated on fecal coliform (FC) inactivation from a real industrial effluent; furthermore, the optimal condition for disinfection of the effluent using various parameters such as pH, H2O2 concentration, and contact time was determined. Based on the acquired outcomes, by pH decline from 11 to 7 and 3 inactivation rate increased (6.7% and 20.9%, sequentially), indicating the efficacy of acidic condition on the process. Increasing H2O2 concentration from 5 mg/L to 15 mg/L, 25 mg/L, and 35 mg/L, was led to increase FC inactivation by 16.6%, 29.75%, and 36.33%, respectively. Considering contcat time impact on the process performance, our findings revealed that the best efficiency obtained after 40 (s) contact time. It can be concluded that the combined UV/H2O2 is more potent than single UV and H2O2 process, making it possible to reach irrigation standards.

Characteristics and Sonophotocatalytic Activity of Natural Sphalerite under Ultrasonic (1.7 MHz) and UVA LED (365 nm) Irradiation.

Naturally occurring sono- and photoactive minerals, which are abundant on Earth, represent an attractive alternative to the synthesized sonophotocatalysts as cost-effective materials for water and wastewater treatment. This study focuses on characterizing and evaluating the sonophotocatalytic activity of natural sphalerite (NatS) from Dovatka deposit (Siberia) under high-frequency ultrasonic (US, 1.7 MHz) and ultraviolet light-emitting diodes (UVA LED, 365 nm) irradiation towards degradation of 4-chlorophenol as a model organic pollutant. Since raw natural sphalerite did not exhibit a measurable photocatalytic activity, it was calcined at 500, 900 and 1200 °C. The natural sphalerite after calcination at 900 °C (NatS*) was found to be the most effective for sonophotocatalytic degradation of 4-chlorophenol, attaining the highest efficiency (55%, 1 h exposure) in the following row: UV < US ≈ UV/US ≈ US/NatS* < UV/NatS* < UV/US/NatS*. Addition of 1 mM H2O2 increased the removal to 74% by UV/US/NatS*/H2O2 process. An additive effect between UV/NatS* and US/NatS* processes was observed in the sonophotocatalytic system as well as in the H2O2-assisted system. We assume that the sonophotocatalytic hybrid process, which is based on the simultaneous use of high-frequency ultrasound, UVA light, calcined natural sphalerite and H2O2, could provide a basis of an environmentally safe and cost-effective method of elimination of organic pollutants from aqueous media.

Investigation of flame structure and precessing vortex core instability of a gas turbine model combustor with different swirler configurations

Numerical simulation of a dual-swirl gas turbine model combustor is performed under cold and reacting flow conditions using a three-dimensional unsteady Reynolds-averaged Navier–Stokes approach. A multi-species chemical mechanism is used in this study for the analysis of the numerous radicals participating in the ignition process and the flame structure. The other objective of this study is to investigate the flow field under different injector configurations, including both co-rotating and counter-rotating swirler arrangements, different swirl intensities, and vane areas. A comparison of the results with experimental data shows that the predicted velocity and temperature profiles follow the experimental data reasonably. In these studies, a precessing vortex core is found in the shear layer of the inner recirculation zone for all injector arrangements considered, and a co-rotating vortex exists in the outer shear layer for some of these arrangements. OH mass fraction field shows that the reactions take place mostly near the vortex core. Furthermore, it is shown that the build-up process of H2O2 and CH2O inside the cold jet has an important effect on combustion initiation. In addition, the formation and consumption of the H atoms in the recirculation zones and the balance between OH and H2O2 are shown to have important roles in the flame formation process. Finally, the precession frequency of the PVC is found to scale almost linearly with the spatial gradient of swirl velocity in the inner swirler and almost independent from the inclusion of the combustion reactions.

Exploring the parameters of central redox hub for screening salinity tolerant rice landraces of coastal Bangladesh

Regulation of oxidative stress towards origin of favorable internal redox cue plays a decisive role in salinity stress acclimation and least studied in rice and hence is the subject of present investigation. Redox landscaping of seedlings of ten experimental land races of rice of coastal Bangladesh grown under post imbibitional salinity stress (PISS) has been done through characterization of ROS-antioxidant interaction dynamics at metabolic interface, transcriptional reprogramming of redox-regulatory genes along with the assessment of biomarkers of oxidative threat for standardizing redox strategies and quality parameters for screening. The results exhibited a strong correlation between salinity induced redox status (pro-oxidant/antioxidant ratio, efficacy of H2O2 turnover through integrated RboH-Ascorbate–Glutathione/Catalase pathway and estimation of sensitive redox biomarkers of oxidative deterioration) and germination phenotypes of all landraces of rice. Transcript abundance of the marker genes of the enzymes associated with central antioxidant hub for H2O2 processing (CatA, OsAPx2, SodCc2, GRase and RboH) of all experimental landraces of the rice advocate the central role of H2O2 turnover dynamics in regulating redox status and salinity tolerance. Landraces suffering greater loss of abilities of decisive regulation of H2O2 turnover dynamics exhibited threat on the oxidative windows of the germinating seeds under salinity.

Deriving an ɑ-Fe2O3/g-C3N4 nanocomposite from a naturally hematite-rich soil, for dual photocatalytic and photo-Fenton degradation of Acetaminophen under visible light

In this study, a facile synthesis route was reported for the fabrication of an ɑ-Fe2O3@g-C3N4 (FeCN) photocatalyst, derived from a hematite-rich soil. Among the various as-made catalysts prepared using different weights of hematite, FeCN-0.5 showed the best catalytic performance in Acetaminophen (ACT) degradation under visible light irradiation with high mineralization efficiency. The superb activity of this photocatalyst results from a Z-scheme structure formation between ɑ-Fe2O3 and g-C3N4 that increased the light adsorption capacity, facilitated the generation of charge-carries, and increased the generated electrons that participated in Fe3+/Fe2+ cycles, thus enhancing the photo-Fenton reaction. UV–Vis diffuse reflection spectroscopy (DRS) and photoluminescence analysis (PL) confirmed the excellent separation of charge carriers in the as-made photocatalyst. The reaction rate of the FeCN-0.5/Vis/H2O2 process was around 3, and 7 times of that in the FeCN-0.5/Vis and FeCN-0.5/H2O2 processes respectively, which indicated the synergy effect of the involved processes in ACT degradation. Based on the radical trapping experiments, hydroxyl radical (HO∙) was the dominant reactive species in ACT degradation. The catalyst showed high stability in consecutive reuse cycles. Overall, this study provides new insights into the fabrication of novel materials derived from natural sources, suitable for their use in advanced oxidation processes.

Al/Cu-PILC as a Photo-Fenton Catalyst: Paracetamol Mineralization.

Pillared clays have shown to effectively catalyze the photo-Fenton process without the necessity of acidic conditions, which is a very attractive feature from the perspective of environmentally friendly processes, especially when high natural abundance of chemical elements are incorporated. In this work, the catalytic activity of Al/Cu interlayered pillared clays for the degradation and mineralization of paracetamol through a photo-Fenton-like process was investigated. Al/Cu-pillared clays were prepared by adding ane Al/Cu pillaring solution to a bentonite suspension. X-ray diffraction (XRD) confirmed the enlargement of the interlayer space of the clay provoked by the pillaring process and Al and Cu species in the prepared samples were verified by atomic absorption spectroscopy (AAS). The specific surface area of pure bentonite was 2-fold increased after the Al/Cu pillaring process. A synthetic paracetamol solution with an initial concentration of 100 ppm was prepared for the assessment of the activity of the prepared materials. Different catalyst concentrations were tested (0.2, 0.5, 0.75, and 1 g L–1) and the complete removal of paracetamol was achieved in all cases, but the highest mineralization rate (69.8 mg total organic carbon (TOC) gcat–1 h–1) corresponds to the catalyst loading of 0.5 g L–1. An ultraviolet-C (UVC) light source was employed, and no adjustment of the pH to acidic conditions was needed to achieve these results. Liquid chromatography coupled to mass spectroscopy (LC-MS) was employed to identify the reaction intermediates of paracetamol degradation. A proposed pathway for the oxidation of paracetamol molecule is presented. The effect of Cu content in the pillared clay and the stability and reusability of the catalyst were also assessed. The kinetic constants of paracetamol removal were 0.2318 and 0.0698 min–1, under photo-Fenton and UV + H2O2 processes, respectively.

Study on the density of trap states between CdZnTe and passivation layer based on MIS structure

CdZnTe room temperature nuclear radiation detectors are widely used in the fields of homeland security, medical imaging and astrophysics. In the Cd1-xZnxTe radiation detector, the purpose of passivation is to reduce dark current and improve stability. In this study, CdZnTe etched by bromine-methanol (BM) was treated with standard H2O2 and NH4F passivation process. With the help of TEM and EDS measurement results, the thickness of the passivation layer ranges from 126 nm to 183 nm, and X-ray photoelectron spectroscopy (XPS) measurement results show that the TeO2 fraction can be increased on the passivated surface. The dispersion phenomenon on the capacitance-voltage and conductance-voltage curves indicates the existence of carrier trap states in the area near the interface. In order to determine the size of the trap state under this passivation method, an equivalent circuit model was constructed using the calculation method of electrical conductivity. Based on this model, when the voltage increases from 0 V to 1.4 V, the value of the trap state density obtained changes in between 1.07 × 1010 eV−1cm−2 and 5.85 × 1010 eV−1cm−2.

Treatment of Distillery Industrial Wastewater Using Ozone Assisted Fenton’s Process: Color and Chemical Oxygen Demand Removal with Electrical Energy per Order Evaluation

Ozonation is one of the most effective and efficient advanced oxidation processes (AOPs) and has shown great potential in the treatment of industrial effluent and wastewater. In the present work, the ozone-Fenton process for % COD and color removal together with electrical energy per order (EE/O) determination for distillery industrial wastewater (DIW) was established. The process was developed by combining the ozone (O3) with the Fenton (Fe2+/H2O2) process. The ozone-Fenton (O3/Fe2+/H2O2) was compared with other treatment processes such as O3, Fe2+, H2O2, O3/Fe2+, O3/H2O2, and Fe2+/H2O2 for EE/O together with % COD and color removal efficiency for DIW. The removal of color at 100% and chemical oxygen demand (COD) of 96.875% were achieved with a minimum of EE/O of 0.5315 kWh/m3 using the O3/Fe2+/H2O2 process by operating at optimum conditions. The % COD and color values obtained using O3/Fe2+/H2O2 were significantly higher than those obtained using O3, Fe2+, H2O2, O3/Fe2+, O3/H2O2, and Fe2+/H2O2 processes. The % color, % COD removal, and its associated EE/O were evaluated by varying Fe2+, H2O2, O3 inlet and COD concentration, and initial wastewater pH using the O3/Fe2+/H2O2 process. The synergy effect of the O3 and Fe2+/H2O2 processes was evaluated and reported. Our experimental findings suggest that combining O3 with the Fe2+/H2O2 process could effectively treat industrial effluent and wastewater.

Molecular insights into the transformation of refractory organic matter in landfill leachate nanofiltration concentrates during a flocculation and O3/H2O2 treatment

During leachate treatment, molecular information regarding the completely removed, partially removed, less-reactive, increased, and produced parts of dissolved organic matter (DOM) remains unknown. This study applied ESI FT-ICR MS to investigate the transformation characteristics of leachate nanofiltration concentrate (NFC) DOM during a combined flocculation–O3/H2O2 process. The NFC contained 5069 compounds in four main classes (CHO, CHON, CHOS, and CHONS compounds). The DOM number decreased to 4489 during flocculation and to 2903 after the O3/H2O2 process. During flocculation, the completely and partially removed DOM was mainly low-oxygen unsaturated and phenolic compounds. Saturated DOM was produced and remained in the flocculated effluent. During the O3/H2O2 process, the completely and partially removed DOM were mainly low-oxygen unsaturated and phenolic compounds that were mainly in a reduced state. Flocculation can remove many (condensed) aromatic compounds, and methylation and hydrogenation reactions occurred during flocculation. In the O3/H2O2 process, dearomatization, demethylation, carboxylation, and carbonylation reactions further achieved the degradation of DOM that was resistant to flocculation. Overall, the combined flocculation-O3/H2O2 process collectively eliminated a broader range of DOM than the single processes could achieve. The results of this study provide an in-depth understanding of DOM transformation in an NFC treatment.

Hydroxyl Radical Production via a Reaction of Electrochemically Generated Hydrogen Peroxide and Atomic Hydrogen: An Effective Process for Contaminant Oxidation?

An electrochemical advanced oxidation process (EAOP) is demonstrated with a catalytic cathode capable of simultaneously catalyzing the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR) with resultant in situ generation of atomic hydrogen (H*) and hydrogen peroxide (H2O2). A palladium-coated carbon-PTFE gas diffusion electrode (Pd/C GDE) was used as a catalytic cathode with hydroxyl radical (•OH) formed as a result of the reaction of electrogenerated H* with H2O2. As both the HER and ORR can be induced to occur at the same cathode, the H*/GDE process results in more effective degradation of organic contaminants than can be achieved by a conventional H*/H2O2 process involving direct addition of H2O2. At circumneutral pH, 82.7% of added formate was degraded after 2 h treatment at an applied potential of -1.0 V vs Ag/AgCl with relatively low concentrations of generated H2O2 remaining in the solution. We also show that H* and H2O2 (and thus •OH) can be electrogenerated effectively over a wide range of pH (3.2-7.0). These results suggest that by in situ generation of H* and H2O2, the H*/GDE process is able to produce significant amounts of •OH without external chemical addition and thus offers an alternative method for abatement of aqueous organic contaminants.

Antioxidant and Antiulcer property of different solvent extracts of Cassia tora Linn.

Aim: The fundamental objective and goal of the current research is to determine the effectiveness of Cassia tora in the treatment of gastric ulcers in order to produce an anti-ulcer medication of natural origin. Method: The plant material was successively extracted by the Soxhlet extraction technique with chloroform, methanol, butanol and water. The antioxidant activity of the plant extracts and the standard drugs were based on consideration of the radical scavenging influence of the stable "1,1-diphenyl-2-picrylhydrazyl" (DPPH) free radical action and hydrogen peroxide process. Two models, and non-steroidal anti-inflammatory induced ulcer and pyloric ligation, were analysed for methanolic extract of Cassia tora for its antiulcer activity. Results: Among all the extract, the percent of DPPH inhibition at 200 μg mL-1 for MECT extracts (Cassia tora methanolic extract) was 58.67±1.95. The overall scavenging potential for the H2O2 process was 68.23±0.19 at 200 μg mL-1 by MECT extract. Hence MECT extract was undertaken for the antiulcer property. Compared with control, there was a significant (p&lt;0.05) decrease in free acidity, gastric volume, and total acidity in the extract-treated classes and ranitidine (standard). The Cassia tora methanolic extract demonstrated significant (p&lt;0.05) inhibition activity, i.e. 59.42 and 69.59 percent at 500 mg mL-1 with the PL (Pylorus ligation) and NSAID (Non-steroidal anti-inflammatory drugs) process respectively. Conclusion: The findings of present study provide the scientific evidence to Cassia tora as a strong antiulcer and antioxidant agent.

Benzoic Acid Degradation by Highly Active Heterogeneous Fenton-like Process using Fe&lt;sup&gt;3+&lt;/sup&gt;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3 &lt;/sub&gt;Catalyst

This work examines oxidative degradation of benzoic acid in an aqueous solution using an eco-friendly advanced oxidation (heterogeneous Fenton) process. The degradation of benzoic acid (1,000 mgL−1) with H2O2 was performed using Fe3+ immobilized within an Al2O3 matrix as a heterogeneous Fenton catalyst and the efficiency of the system was compared to that of the homogeneous Fe3+/H2O2 system. The influence of various operational conditions like catalyst dosage, H2O2 concentration, Fe3+ concentration, pH of the solution and initial substrate concentration on % degradation for both the processes has been studied to find out the best operating conditions for these processes. The experimental results show that the optimum conditions for homogeneous Fe3+/H2O2 process are [Fe3+] = 1,250 mgL−1, [H2O2] = 2,000 mgL−1, initial pH = 3 and 87.5 % degradation was obtained within 35 min. In the case of heterogeneous catalyst, degradation improved to 91.7% using 12.5 gL−1 catalyst for the same duration keeping other operating conditions the same. The use of iron immobilized in alumina matrix as heterogeneous Fenton catalyst is an alternative approach for degrading organic contaminants.