Fenton's Reagent Research Articles

Kinetic modelling of total organic carbon degradation in dairy wastewater

ABSTRACT Several treatment strategies have been proposed to minimize the environmental impact of dairy wastewaters. However, their complex and variable composition makes it difficult to predict the degradation kinetics of organic compounds. In this study, we used a mathematical approach to describe the kinetics of total organic carbon degradation in real dairy wastewater by photo-Fenton oxidation. The reactions were conducted under different ultraviolet light intensities, pH, temperature and Fenton reagent concentrations, obtaining a maximum TOC removal of 90.84%. The kinetic model was developed based on well-established photo-Fenton reactions. The present approach considers that account that small and large molecules of unknown contaminants are present in the effluent, and the smaller molecules are consumed first. The specific degradation rate (kd ) was considered as an exponential function of total organic carbon conversion, comprising this effect of molecular size distribution on the treatment process. Fitting of experimental data to model predictions provided mean R 2 values of 0.843–0.953.

Catalytic Oxidation of Polymers Remained in Oilfield by Transition Metal-Ethylenediamine Complex

This work is intended to seek for an efficient Fe-based Fenton reagent for clean oxidation of waste fracturing fluid containing hydroxypropyl guar gum (HGG) and other polymers in wide pH range. A series of complex was prepared with transition metal and ethylenediamine (L) by the coordination. The catalytic performance of the complexes were evaluated in the degradation of HGG, and the reaction conditions were optimized. The kinetics of HGG degradation was evaluated by means of the chemical oxygen demand (COD) and the viscosity. The results show that Fe(II)L exhibits high catalytic performance for the degradation of hydroxypropyl guar gum in a wide pH range of 7.0–11.0, the COD removal can reach to 86.4%. Under the optimum experimental conditions, the relative viscosity of hydroxypropyl guar gum solution can be reduced effectively to 7.99 from 247 with 10.0% H2O2in presence of 5.0% Fe(II)L. Besides, under the optimized condition, three typical polymers used in oilfield can be degradated effectively.

Screening of microplastics in water and sludge lines of a drinking water treatment plant in Catalonia, Spain

Microplastics (MPs) are emerging pollutants detected everywhere in the environment, with the potential to harm living organisms. The present study investigated the concentration, morphology, and composition of MPs, between 20 μm and 5 mm, in a drinking water treatment plant (DWTP) located close to Barcelona (Catalonia, NE Spain). The sampling included different units of the DWTP, from influent to effluent as well as sludge line. Sampling strategy, filtration, allows sampling of large volumes of water avoiding sample contamination, and during 8 h in order to increase the representativeness of MPs collected. The pre-treatment of the samples consisted of advanced oxidation with Fenton's reagent and hydrogen peroxide, followed by density separation of the particles with zinc chloride solution. Visual identification was performed with an optical and stereoscopic microscope with final Fourier-transform infrared spectroscopic (FTIR) confirmation. MPs were found in all DWTP samples, with concentrations from 4.23 ± 1.26 MPs/L to 0.075 ± 0.019 MPs/L in the influent and effluent of the plant, respectively. The overall removal efficiency of the plant was 98.3%. The most dominant morphology was fibers followed by fragments and films. Twenty-two different polymer types were identified and synthetic cellulose, polyester, polyamide, polypropylene, polyethylene, polyurethane, and polyacrylonitrile were the most common. Although MPs could be incorporated from the distribution network, MPs intake from drinking water from this DWTP was not an important route compared to fish and seafood ingestion.

Insights into the mechanism of g-C3N4@a-Fe2O3 microsphere heterogeneous activation of hydrogen peroxide under visible light

A-Fe2O3 complex g-C3N4@a-Fe2O3 was successfully prepared by solvothermal method and used in optical Fenton photocatalytic process. Using experimental instruments such as XPS, XRD, DRS, TEM, FTIR, and photochemistry to characterize composite materials. According to the mechanism of the photocatalytic process, combining A-Fe2O3/H2O2 Fenton reagent with g-C3N4 photocatalyst under visible light conditions can effectively accelerate the mineralization of pollutants. The photocatalytic performance of g-C3N4@a-Fe2O3 were evaluated by the decomposition of bisphenol A. When the content of a-Fe2O3 is 15%, the photocatalytic efficiency of the composite is the highest. In addition, cyclic operation, iron leaching concentration, fresh and XRD pattern studies indicate that g-C3N4@a-Fe2O3 composites are very stable and reusable. The results show that the decomposition of BPA by persulfate is a non-free radical reaction, but the coupling a-Fe2O3 with g-C3N4 can effectively activate the formation of persulfate free radicals and reduce BPA under visible light radiation. Studies showed that free radicals generated by electron holes and persulfate formed on catalysts were the main causes of BPA decomposition. Therefore, combined with previous research results, this paper proposed the mechanism of g-C3N4@a-Fe2O3 composite photocatalytic reaction by photo-Fenton. More importantly, this work demonstrates a novel approach to activate persulfates that can efficiently degrade pops and gives some new ideas on the remediation of persulfates in contaminated Water.

Insights into the mechanism of g-C3N4@a-Fe2O3 microsphere heterogeneous activation of hydrogen peroxide under visible light

A-Fe2O3 complex g-C3N4@a-Fe2O3 was successfully prepared by solvothermal method and used in optical Fenton photocatalytic process. Using experimental instruments such as XPS, XRD, DRS, TEM, FTIR, and photochemistry to characterize composite materials. According to the mechanism of the photocatalytic process, combining A-Fe2O3/H2O2 Fenton reagent with g-C3N4 photocatalyst under visible light conditions can effectively accelerate the mineralization of pollutants. The photocatalytic performance of g-C3N4@a-Fe2O3 were evaluated by the decomposition of bisphenol A. When the content of a-Fe2O3 is 15%, the photocatalytic efficiency of the composite is the highest. In addition, cyclic operation, iron leaching concentration, fresh and XRD pattern studies indicate that g-C3N4@a-Fe2O3 composites are very stable and reusable. The results show that the decomposition of BPA by persulfate is a non-free radical reaction, but the coupling a-Fe2O3 with g-C3N4 can effectively activate the formation of persulfate free radicals and reduce BPA under visible light radiation. Studies showed that free radicals generated by electron holes and persulfate formed on catalysts were the main causes of BPA decomposition. Therefore, combined with previous research results, this paper proposed the mechanism of g-C3N4@a-Fe2O3 composite photocatalytic reaction by photo-Fenton. More importantly, this work demonstrates a novel approach to activate persulfates that can efficiently degrade pops and gives some new ideas on the remediation of persulfates in contaminated Water.

Defect-engineered WO3-x@MoS2 hollow tube exhibiting enhanced Fenton-like and photocatalytic activities via electric field rearrangement and band alignment

Here we report a defect-engineered WO3−x @MoS2 hollow tube that exhibits not only enhanced Fenton-like activity but also improved photoactivity in a wide range of pH as a versatile platform for water purification. Its successful performance was achieved by tuning oxygen defect and band position and investigated using tetracycline degradation and E. coli inactivation experiments as concept demonstration. The activity of WO3−x @MoS2 can reach one to two orders of magnitude higher than that of other materials used in this work and the ecotoxicity of intermediates was largely reduced. It exhibits an intrinsic radical character for H2O2 decomposition under dark condition and an efficient photon utilization under visible light irradiation, which is clearly different from the conventional photocatalysts and Fenton reagents. The present strategy of combing the dark Fenton-like and photocatalytic activities extends the applications of the conventional photocatalysts and should be an efficient way of energy utilization.

Porous Au/AAO: A simple and feasible SERS substrate for dynamic monitoring and mechanism analysis of DNA oxidation

Herein, a simple strategy was proposed to acquire an orderly and controllable periodic structure. Firstly, the optimal parameters of porous anodic aluminum oxide (AAO) were screened out by FDTD solutions. Combined with magnetron sputtering of gold nano-film, the Au/AAO SERS substrate was thus fabricated. The enhancement factor (EF) was calculated to be 4.87 × 106, and SERS spectra with good reproducibility were also acquired. The oxidization process of plasmid DNA was thus monitored under the conditions of low detection power and short integration time. Fenton's reagent was used as oxidizing reagent, and Na2SO4 was applied for the internal standard in SERS analysis. The changes of I657/I998, I723/I998, I1587/I998, I1648/I998 were studied over time. DNA oxidation product 8-OHdG was also detected in this process. Then the relationship between the relative peak intensity ratios and the base structure change in DNA was established. The conclusions of SERS spectral analysis were verified by agarosegelelectrophoresis, DNA oxidative damage gel detection and colorimetric detection of 8-OHdG. The mechanism analysis of DNA oxidation process was thus studied. The simple and feasible detection strategy proposed could extend the application of SERS technology in the process monitoring of photosensitive or other unstable biological samples.

Adsorption of heavy metals from acid mine drainage using poly (hydroxamic acid) ligand

Acid mine drainage (AMD) causes severe environmental concerns worldwide due to its high acidity, toxic metals and sulphate contents. Conventional treatment methods may not be effective for AMD. There is a need for wastewater remediation; however, it requires cost-effective technologies for efficiently removing heavy metals. The current study reports the remediation of AMD using a modified pine cone powder. The surface of the biosorbent was improved by pre-treatment using Fenton reagent and then modified using chemical grafting of acrylic acid onto pine cone powder with free radical initiation. The modified adsorbent was used for adsorption of (Fe3+), (Cu2+), (Mn2+), (Zn2+), and (Pb2+) from single components solution and acid mine drainage sampled from an abandoned mine at Witbank. The adsorption behaviour of poly (hydroxamic acid) ligand has been studied to determine its application in treating Witbank acid mine drainage (AMD). The rate of adsorption and the uptake at equilibrium were investigated using batch conditions from single and multi-component solutions (AMD). The optimum pH for the poly (hydroxamic acid) ligand was 6 for all heavy metal ions investigated with the percentage removal of 79,83, 82,90 and 73% for Fe3+, Cu2+, Mn2+, Zn2+ and Pb2+ respectively. The ligand's binding capacity (qe) with metal ions such as iron, copper, manganese, zinc and lead were 13, 14, 11, 11 and 12 mg g−1, respectively. The adsorption of the heavy metal ions onto the ligand fitted well with the Langmuir isotherm model due to R2 > 0.99 compared to the Freundlich model. Additionally, RL values were in a range of 0,0020 to 0,0560, which indicates favourable adsorption. Furthermore, pseudo second-order kinetics was the best to describe adsorption kinetics for AMD metal ions using poly (hydroxamic acid) ligand. The AMD treatment using poly (hydroxamic acid) ligand showed great potential as a low-cost alternative material.

Electrodeposited Fe on Cu foam as advanced fenton reagent for catalytic mineralization of methyl orange.

In many countries, the textile industry remains the major contributor to environmental pollution. Untreated textile dyes discharged into water negatively impact the performance of aquatic organisms and may cause a variety of serious problems to their predators. Effective wastewater treatment is a key to reducing environmental and human health risks. In this work, the Fe/Cu catalysts were used in heterogeneous Fenton’s reaction for the degradation of high concentrations of methyl orange (model azo dye) in aqueous solutions. For the first time, the catalysts were prepared onto commercial copper foams by potentiostatic electrodeposition of iron using an environmentally friendly electrolyte. The influence of electrodeposition conditions, H2O2 concentration, dye concentration and temperature on the model dye degradation was investigated. It was revealed that both the surface area and the catalyst loading play the major role in the effective dye degradation. The experimental results involving spectrophotometric measurements coupled with total carbon and nitrogen quantification suggest that a solution containing up to 100 mg/L of methyl orange can be successfully decolorized within 90 s at 50°C using porous Fe/Cu catalyst in the presence of hydrogen peroxide that largely surpasses the current state-of-the-art performance. Already within the first 10°min, ∼ 30% of total methyl orange concentration is fully mineralized. The described process represents a cost-efficient and environmentally friendly way to treat azo dyes in aqueous solutions.

Rapid and efficient removal of organic matter from sewage sludge for extraction of microplastics

Microplastic pollution is recognized as an emerging global issue; however, no standardized method for the extraction of these pollutants from the environment currently exists and existing methods are ineffective for specific environmental matrices. An appropriate organic matter removal method is essential for the extraction of microplastics from organic-rich sludge to minimize interference during their identification and enhance compatibility of the identification steps. The present study aimed to establish an effective technique for the digestion of organic matter-rich sludge using hydrogen peroxide and Fenton's reagent at varying temperatures, times, and concentrations of an iron catalyst. The organic matter removal efficiency of the five protocols utilized varied from 81.5 % to 87.1 %. Polymers such as polyvinyl chloride (PVC), high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS) retained most of their physical and chemical properties after the treatments, with minor changes in the surface area, weight, and FTIR spectra properties. Polyethylene terephthalate (PET), PET fiber, polyamide (PA) fiber, and polymethyl methacrylate (PMMA) fiber were significantly degraded via treating with H2O2 at 50 °C for 24 h. Protocol 4, treating with Fenton's reagent (H2O2 (30 %) + (0.05 M) FeSO4.7H2O) at 50 °C for 1 h is proposed as a rapid and effective method for the removal of organic matter from sludge. In addition to its rapidity, this method minimally impacts most polymers, and its high organic matter removal efficiency is associated with a significant reduction of suspended solids in sludge. The present study provides a validated approach that facilitates as an effective organic removal step during the extraction of MPs in sludge.

Investigation on intensified degradation of Rhodamine B and heat generation using a novel thermally assisted hydrodynamic cavitation device

In this study, a thermally assisted hydrodynamic cavitation (HC) system was established by adding a water pre-heater in front of the cavitation device (orifice plate), which realizes the local heating of the flowing liquid, intensifies the HC effect and enhances Rhodamine B (RhB) degradation ratio and heat generation efficiency. The effects of preheating temperature, RhB initial concentration, orifice hole number, inlet pressure and solution volume on RhB HC degradation and heat generation were investigated. Free radical trapping experiments were performed to explore the active substances produced by the HC effect. Based on LC-MS and TOC data, the possible RhB degradation pathway and mechanism were proposed. When the preheating temperature rose from 10 °C to 50 °C, the RhB degradation ratio increased from 23.42% to 34.49% within 90 min cycle time, and the treatment cost decreased from 130.699 USD/m3 to 91.701 USD/m3. At 30 min cycle time, the solution temperature rose from 45.6 °C to 56.4 °C, the heat production increased from 149.46 KJ/L to 194.81 KJ/L and the corresponding thermal efficiency increased from 47.45% to 61.84%. Further, at 60 min cycle time, under the conditions of 30 °C preheating temperature, 30 mg/L RhB initial concentration, 3-hole orifice plate, 3 bar inlet pressure and 5.0 L RhB solution volume, the RhB degradation ratio was the highest (40.38%). After Fenton reagent was used, the RhB degradation ratio and heat production both were further enhanced. At 60 min cycle time, the RhB degradation ratio was 65.52%, solution temperature rose to 72.8 °C, the heat production reached 131.83 KJ/L and the treatment cost was only 45.447 USD/m3 at 30 °C preheating temperature. TOC test results show that the RhB mineralization ratio can reach 61.53% after 90 min cycle. All in all, this work proves that thermally assisted HC is an effective method to degrade organic dyes and generate heat, which can be used for large-scale treatment of organic dye wastewater.

Evaluation of anticancer activity of ferrocene based benzothiazole and β-ketooxothioacetal

Ferrocene-based compounds have recently gained widespread importance in cancer treatment becuase of their lower toxicity and cost-effective synthesis. However, ferrocene-based compounds do not exist in nature. Moreover, the synthesis of thianes containing ferrocene is quite rare. In the recent past, our group has reported iodine catalyzed synthesis of ferrocenated benzothiazole and β-ketooxothioacetal by the thermal reaction of ferrocenated β-chlorocinnamaldehyde with 2-aminothiophenol and 2-mercaptoethanol respectively.The molecular structure of both the compounds is quite interesting due to the presence of ferrocene which makes them highly important from an anticancer point of view. In this script, the synergistic effect of ferrocene and thiol has been observed in ferrocene functionalized thiols (Fenton reagents) for tumour growth suppression. The anticancer properties of both the compounds separately as well as in combination show a significant anticancer effect on cancer cell lines HCT116 (Colon), A549 (lung cancer), and MCF7 (Breast cancer). Both compounds and their combinations reflect cell death by generating ROS and depolarization of mitochondrial membrane potential. Gene expression profiling and protein expression studies of apoptosis-related genes (cleaved caspase 9, cleaved caspase 3, cleaved PARP and Bcl-2) were also evaluated. Results indicated that ferrocenated benzothiozole and β-ketooxothioacetal induced apoptosis through oxidative stress-mediated activation of intrinsic apoptosis pathway by generating intracellular ROS, loss of MMP, and alteration of expression of genes related to apoptosis. In addition, the anti-metastatic activity of benzothiozole and β-ketooxothioacetal was seen by wound healing assay showing anti-migratory properties. The properties like anti metastatic activity, cytotoxicity and showing synergistic effect when used in combination make benzothiozole and β-ketooxothioacetal potent platforms for the development of new anticancer agents. Benzothiazole and β-ketooxothioacetal can replace existing organometallic compounds with rare metals like platinum, due to their higher stability, lower cost, and lower toxicity.

Utilization of sludge-based alginate beads for the application of rare earth elements (REEs) recovery from wastewater: A waste to resource approach

The main purposes of this research work were to realize the potential of sludge valorization by converting the sludge into adsorbents and to investigate the performance of sludge-based adsorbents for rare earth elements (REEs) recovery from dilute aqueous solutions. Hydrochloric acid and Fenton reagents were employed as pretreatment procedures to enhance the surface area and adsorption yield. Following this, sludge-based alginate beads were prepared by using HCl treated (HT) and Fenton treated (FT) sludge materials. The chemical composition and surface chemistry of sludge-based adsorbent beads were thoroughly analyzed by state-of-the-art analytical techniques, such as Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) analysis. The prepared beads were then investigated for the recovery of REEs. The batch adsorption studies revealed that the FT sludge beads performed better in comparison to the HT sludge beads. Among REEs, the HT- and FT-sludge beads demonstrated higher affinity towards Sm 3+ ions, displaying the maximum adsorption capacities of 2.83 mg/g and 4.16 mg/g, respectively, in a multi-component system (C o = 25 ppm of each REE; pH = 5, t = 24 h and dosage = 5 g/L). In conclusion, the results from this work showed that the prepared sludge-based alginate beads can be used for REEs recovery from diluted waste streams and the tested sludge treatment options were also found effective in converting the waste to resource i.e., sludge to adsorbent for REEs recovery. • Hydrochloric acid and Fenton reagents were used in the pre-treatment of sludge. • Treated sludge was transformed into beads to recover REEs from wastewater. • Sorption capacity of beads were investigated at pH (2–5) and pH 5 became optimal point. • Max. adsorption capacities of Sm 3+ , 2.83 mg/g (HCl treated) and 4.16 mg/g (Fenton treated).

Treatment of Laboratory Wastewater by Using Fenton Reagent and Combination of Coagulation-Adsorption as Pretreatment

Treatment of Laboratory Wastewater by Using Fenton Reagent and Combination of Coagulation-Adsorption as Pretreatment

Comment on "Liquid-Gas Interface of Iron Aqueous Solutions and Fenton Reagents".

A recent Letter in this Journal (Gladich et al. J. Phys. Chem. Lett. 13, 2994-3001) reported that photoelectron spectroscopy could not detect any products on the surface of aqueous Fe2+ jets dosed with gaseous hydrogen peroxide. The Letter however concluded that Fe(aq)2+ ions react with H2O2(g) at the water-vapor interface to produce the same Fe3+ + HO• products as their reaction with H2O2(aq) in bulk water. We argue that this conclusion is untenable because nothing can be asserted about undetected species.

Reply to "Comment on 'Liquid-Gas Interface of Iron Aqueous Solutions and Fenton Reagents'".

A Viewpoint regarding our recently published Letter in this Journal (Gladich et al. J. Phys. Chem. Lett. 13, 2994-3001) criticizes some of our conclusions. While a sentence in the abstract and one in the conclusion of the Letter might seem too conclusive, in the body text we objectively discussed experimental results obtained by means of three different surface-/interface-sensitive spectroscopies. Such results were supported by theoretical calculations. The aim of our work was not to criticize past results. On the contrary, we critically discussed our data taking into account those obtained in the past.

Promoted degradation of ofloxacin by ozone integrated with Fenton-like process using iron-containing waste mineral enriched by magnetic composite as heterogeneous catalyst

In this study, a heterogeneous catalyst derived from iron-containing waste mineral was enriched by magnetic composite (Fe3+/Fe2+) at modification ratio of 5 % for the highest mineralization of ofloxacin (OFL) by ozone/Fenton system. A comparative study between O3, perozone (H2O2) and O3/Fenton systems in mineralization of ofloxacin (OFL) under various solution pH, H2O2 dosages, initial OFL concentrations and catalyst (MFS-5) dosages was performed. Adding Fenton reagent (H2O2/MFS-5) into ozonation system gave the highest OFL removal efficiency of 70 % at optimal operational conditions of pH 9, catalyst dosage of 1.5 g/L, H2O2 dosage of 100 mg/L with initial OFL concentration of 100 mg/L due to synergistic effect of O3 and Fenton reagent. The catalyst's properties were evaluated through BET, SEM image, EDS and mapping data, FTIR and XRD. The main mineralization mechanism of OFL was through hydroxyl radicals (⁎OH) which were formed during ozonation process because FeO, Fe3O4 and SiO2 in the MFS-5's constituent accelerated decomposition of O3 and promoted reaction rate with H2O2. The catalyst exhibited a good reusability and stability after five consecutive runs with negligible change in mineralization efficiency of OFL and a very low leached iron amount into solution. Besides, there was an efficient improvement of biodegradability of real pharmaceutical wastewater after treatment by O3/Fenton with 71 % and 62 % removal of COD and TOC, respectively. These findings indicated utilizing magnetic-modified waste iron mineral as heterogeneous catalyst in combination with H2O2 and O3 achieved high efficiency and feasibility in removal of OFL antibiotic from real pharmaceutical wastewater.

MnO2 nanosheet-mediated generalist probe: Cancer-targeted dual-microRNAs detection and enhanced CDT/PDT synergistic therapy

While integrated nanoplatform for diagnosis and therapy has received much recent interest, its widespread application has been hampered by the complicated preparation process, high-cost and low-efficacy. Herein, we designed a MnO2 nanosheet-mediated generalist probe (MNSGP), for intracellular dual-microRNAs (miRNAs) imaging and enhanced synergistic therapy of chemodynamic therapy (CDT) and photodynamic therapy (PDT). Because MNSGP can specifically target nucleolin receptor overexpressed on the cancer cell surface, it can be internalized via a receptor-mediated endocytosis pathway. After entering the cells, MnO2 NS was degraded to Mn2+ by the excessive glutathione (GSH), releasing the DNA probes for cyclic amplification detection of miR-155 and miR-21 based on toehold-mediated strand displacement amplification (TSDA). Meanwhile, the produced O2 by MnO2 NS catalysis can promote the photosensitizer TMPyP4 to produce singlet oxygen (1O2) for PDT. The degraded Mn2+, as Fenton reagent, can convert endogenous H2O2 to cytotoxic hydroxyl radical (·OH) for CDT. In addition, the depletion of GSH impairs the antioxidant defense system (ADS), enhancing the CDT/PDT synergistic effect. The prepared generalist probe was fully characterized. Accuracy of dual-miRNAs detection and the high curative effect of enhanced CDT/PDT synergistic therapy were attested via in vitro and in vivo experiments. Unarguably, MNSGP broadens new horizons in the design of nucleic acid nanoplatform, cancer-targeted detection and theranostic application.

Efficient remediation of heavily As(III)-contaminated soil using a pre-oxidation and stabilization/solidification technique

The high mobility of As(III) makes it difficult to remediate heavily As(III)-contaminated soil. A novel remediation technique that combines pre-oxidation and stabilization/solidification (PO + S/S) is proposed in this study to remediate heavily As(III)-contaminated soil. After oxidizing As(III) in the contaminated soil using Fenton's reagent, FeCl3·6H2O was used as a chemical stabilizing agent to reduce the toxicity and mobility of As. Finally, Portland cement (PC) was used for solidification. The effects and mechanisms of the proposed technique were studied using unconfined compressive strength tests, leaching tests, sequential extraction procedure (SEP), and a series of spectroscopic/microscopic investigations. The experimental results showed that the addition of FeCl3·6H2O increased the strength of the curing body because the hydration degree of PC and pore structure were improved. Portland cement can increase the pH of the curing body. At a 1:1 Fe to As molar ratio and a 15 wt% PC dosage, the leached As concentration decreased to 3.25 mg L−1, and the remediation efficiency reached 99.54%. The SEP results showed that the PO + S/S treatment converted As into more stable phases and effectively reduced the potential mobile phase risk. The majority of As was bound to hydrated iron oxides; however, the increased pH affected the Fe–As interactions and prompted the release of As from the surface of the hydrated iron oxides. Spectroscopic/microscopic investigations indicated that the PO + S/S treatment converted As(III) to less toxic and less mobile As(V) and then immobilized by the encapsulation of calcium silicate hydrate and ion exchange of ettringite. This study provides a scientific basis and theoretical support for the effective remediation of heavily As(III)-contaminated soil.

Degradation of Diazepam with Gamma Radiation, High Frequency Ultrasound and UV Radiation Intensified with H2O2 and Fenton Reagent

A degradation study of diazepam (DZP) in aqueous media by gamma radiation, high frequency ultrasound, and UV radiation (artificial-solar), as well with each process intensified with oxidizing agents (H2O2 and Fenton reagent) was performed. The parameters that influence the degradation of diazepam such as potency and frequency, irradiation dose, pH and concentration of the oxidizing agents used were studied. Gamma radiation was performed in a 60Co source irradiator; an 11 W lamp was used for artificial UV radiation, and sonification was performed at frequency values of 580 and 862 kHz with varying power values. In the radiolysis a 100% degradation was obtained at 2500 Gy. For the sonolysis, 28.3% degradation was achieved after 180 min at 862 kHz frequency and 30 W power. In artificial photolysis, a 38.2% degradation was obtained after 300 min of UV exposure. The intensification of each process with H2O2 increased the degradation of the drug. However, the best results were obtained by combining the processes with the Fenton reagent for optimum H2O2 and Fe2+ concentrations, respectively, of 2.95 mmol L−1 and of 0.06 mmol L−1, achieving a 100% degradation in a shorter treatment time, with a dose value of 750 Gy in the case of gamma radiation thanks to increasing in the amount of free radicals in water. The optimized processes were evaluated in a real wastewater, with a total degradation at 10 min of reaction.