Activation Of Sodium Persulfate Research Articles

Synchronization of Ti3C2 MXene/Fe3+ with sodium persulfate for the degradation of reactive dyes

Rapid activation of sodium persulfate (SPS) for the degradation of C.I. Reactive Red 218 (RR218) was achieved using Ti3C2 MXene reduction of trace Fe3+. The degradation rate of RR218 reached 97.7% using a mixture containing 3 g L−1 of SPS, 3.35 mg L−1 of Fe3+ and 60 mg L−1 of MXene stirred at 25 °C for 30 min. The intense reduction of Ti3C2 MXene triggers the Fe3+/Fe2+ cycle thereby accelerating the activation of SPS. When reactive dyes were degraded by Fe3+/SPS/MXene process, ·OH played a major role. The dye degradation capacity of the Fe3+/SPS/MXene process decreased after 5 cycles of recycling. In addition, the wastewater treated under these conditions resulted in high dyeing efficiencies in reuse experiments. This study not only improves the understanding of the catalytic reaction of MXene but also provides a wastewater treatment and reuse process with low metal consumption and high efficiency.

Efficient degradation of phenol in water by ball-milling modulated nitrogen-doped structured biochar

Presently, most kinds of biochar rely on the addition of transition metals to improve their electron transport capacity, thereby boosting the activation of oxidants. However, challenges such as the precipitation of transition metals and the chemical inertness of biochar are commonly encountered. Biochar with nitrogen-containing functional groups has emerged as a promising solution as oxidant activators. The nitrogen doping of biochar through ball milling is a straightforward, cost-effective, and efficient preparation method. To optimize the activation properties, a multi-step process involving roasting, ball milling, and tempering was employed to produce biochar. Sesame dregs was chosen as the precursor for this biochar. By optimizing the roasting temperature to 900 °C and using urea as the nitrogen source, biochar derived from sesame residue was successfully prepared. This biochar featured pyridine nitrogen as the primary functional group, exhibiting improved crystallinity and aromaticity. The activation of sodium persulfate (3.0 mM) with biochar eliminated phenol from wastewater with an initial concentration of 50 mg/L in just 15 minutes, achieving a remarkable mineralization rate of 96.77%. Even after undergoing six cycles of repeated use, the system consistently removed 97.73% of phenol within the same timeframe, maintaining a high mineralization rate of 86.77%. Notably, it was found that N-CN, N-6, and N-q were instrumental in stimulating reactive oxygen species (ROS), while ·OH, SO4·-, and 1O2 served as the primary ROS responsible for degrading phenol. The research also revealed a linear relationship between active oxygen sites and oxidized substances, offering insights into the mechanism of phenol degradation.

Valorization of olive mill solid waste-derived biochar: An efficient approach for simultaneous adsorption and oxidation of micropollutant in surface water

This study explores the utilization of olive mill solid waste (OMSW) as a source of biochar (BC) for effective removal of micropollutants during surface water treatment. The conversion of OMSW into BC was accomplished via pyrolysis conducted at varying temperatures ranging from 400 to 600 °C. To improve its performance, BC was subjected to activation through either physical-thermal or chemical techniques. BC samples were characterized by SEM microscopy revealing a porous structure, surface area analysis showed an increase in surface area for biochar samples subjected to physical-thermal activation (BC-T) (20 m2/g) and chemical activation using potassium hydroxide (BC-KOH) (70 m2/g) or zinc/iron (BC-Zn/Fe) (456 m2/g). The zero point of charge range from <3 to 4.2 for the different BC samples whereas FTIR measurements showed that physical activation at 900 °C favors a graphitic structure in BC.The catalytic properties of the biochar samples were investigated in the activation of sodium persulfate (PSF) for the oxidation of micropollutants (MPS), including ciprofloxacin (CPX), sulfamethoxazole (SMZ), and paracetamol (PCM), in natural Lake Kinneret water. BC-KOH exhibited the highest removal efficiency, and the removal of MPS increased with higher dosages of BC and PSF. Under optimized conditions ([biochar]: 500 mg/L and [PSF]: 200 mg/L), significant removal efficiencies were achieved for PCM (88.2 % ± 0.7), CPX (80.8 % ± 1.9), and SMZ (64.1 % ± 3.2) after a 5-hour treatment. Finally, MPS adsorbed on BC experienced significant surface oxidation, resulting in removal efficiencies for PCM (97.9 %), CPX (92 %), and SMZ (77.9 %). This oxidation process is expected to enhance the treatment effectiveness prior to regeneration.

Heterogeneous Activation of Persulfate by Nickel Oxide/Strontium Carbonate Composite for Sulfamethoxazole Degradation in Water

The development of efficient heterogeneous persulfate activators is one of the main research topics in the wastewater treatment area. The present work deals with the heterogeneous activation of sodium persulfate (SPS) using nickel oxide/strontium carbonate (NiO/SrCO3) for the degradation of sulfamethoxazole (SMX), a representative compound from the group of antibiotics. Results showed that NiO/SrCO3 exhibited high performance towards the activation of SPS, leading to SMX elimination in brief time spans. The impact of SPS (25–100 mg/L), NiO/SrCO3 (50–250 mg/L), and SMX (0.25–3.00 mg/L) concentration, and initial pH on the decomposition of SMX was further examined. Experiments were also conducted in real matrices such as secondary effluent and bottled water, revealing the existence of retarding phenomena compared to ultrapure water. This behavior was further investigated with the addition of bicarbonates, chlorides, or humic acid in ultrapure water. It was found that organic matter significantly hampered SMX removal. The role of the main radicals (hydroxyl and sulfate radicals) was determined using appropriate radical traps (methanol and tert-butanol). These quenching experiments combined with the conducted electrochemical measurements revealed that both a radical and a non-radical mechanism contribute to the decomposition of SMX.

Degradation of Sulfamethoxazole Using a Hybrid CuOx–BiVO4/SPS/Solar System

In recent years, advanced oxidation processes (AOPs) demonstrated great efficiency in eliminating emerging contaminants in aqueous media. However, a majority of scientists believe that one of the main reasons hindering their industrial application is the low efficiencies recorded. This can be partially attributed to reactive oxygen species (ROS) scavenging from real water matrix constituents. A promising strategy to cost-effectively increase efficiency is the simultaneous use of different AOPs. Herein, photocatalysis and sodium persulfate activation (SPS) were used simultaneously to decompose the antibiotic sulfamethoxazole (SMX) in ultrapure water (UPW) and real water matrices, such as bottled water (BW) and wastewater (WW). Specifically, copper-promoted BiVO4 photocatalysts with variable CuOx (0.75–10% wt.) content were synthesized in powder form and characterized using ΒΕΤ, XRD, DRS, SEM, and HRTEM. Results showed that under simulated solar light irradiation alone, 0.75 Cu.BVO leads to 0.5 mg/L SMX destruction in UPW in a very short treatment time, whereas higher amounts of copper loading decreased SMX degradation. In contrast, the efficiency of all photocatalytic materials dropped significantly in BW and WW. This phenomenon was surpassed using persulfate in the proposed system resulting in synergistic effects, thus significantly improving the efficiency of the combined process. Specifically, when 0.75 Cu.BVO was added in BW, only 40% SMX degradation took place in 120 min under simulated solar irradiation alone, whereas in the solar/SPS/Cu.BVO system, complete elimination was achieved after 60 min. Moreover, ~37%, 45%, and 66% synergy degrees were recorded in WW using 0.75 Cu, 3.0 Cu, and 10.0 Cu.BVO, respectively. Interestingly, experimental results highlight that catalyst screening or process/system examination must be performed in a wide window of operating parameters to avoid erroneous conclusions regarding optimal materials or process combinations for a specific application.

Preparation of Hemicellulose Nanoparticle-Containing Ionic Hydrogels with High Strength, Self-Healing, and UV Resistance and Their Applications as Strain Sensors and Asymmetric Pressure Sensors.

Smart functional fillers can significantly enhance the comprehensive properties of ionic hydrogels, such as their mechanical properties, which are key features of hydrogels in wearable sensor applications. As a plant-derived natural polymer, hemicellulose can serve as smart functional fillers. In this study, tannic acid-modified hemicellulose nanoparticles (TA@HC) and Fe3+ were used in the preparation of PAA/TA@HC/Fe3+ hydrogels. The addition of TA@HC and Fe3+ in the sodium persulfate (SPS) and acrylic acid (AA) polymerization system resulted in a fast gelation process that was completed within a short time (as short as 30 s) at room temperature. The catechol-rich TA and Fe3+ system allows for quick activation of SPS to produce free radicals, generating abundant hydroxyl groups in a short period of time, which was responsible for the fast gelation. Furthermore, due to the TA@HC effect and the dynamic catechol (TA)-Fe3+ redox system, the PAA/TA@HC/Fe3+ hydrogel exhibited excellent mechanical properties with an exceptionally high strain (as high as 5600%), adhesiveness, rapid and efficient self-healing ability, and reproducible self-adhesion onto various substrates. More importantly, asymmetric adhesive PAA/TA@HC/Fe3+ hydrogels were prepared by selective Fe3+ coating of the upper hydrogel surface to render the top surface nonadhesive so that the same hydrogel with different adhesiveness between the upper and bottom surfaces was obtained. The asymmetric adhesive hydrogel design permits the adhesive side to fit comfortably to the skin and the nonadhesive side showing anti-interference against various different pollutant materials, accurately serving as a pressure sensor.

LED Light Integrated Reactors: Study of the Methylene Blue Chemical Oxidation Process

The contamination of water by organic dyes, such as methylene blue, is a risk factor for the environment, since all aquatic fauna and flora are immensely affected due to the reduction of the amount of dissolved oxygen and the passage of light, affecting the photosynthesis. The main source of contamination comes from the textile industry, so it is necessary to study efficient techniques for treating effluent without the cogeneration impact. In the present work, a study was developed to evaluate the best combination of factors of a batch treatment to be applied in a continuous treatment system. The removal of methylene blue by chemical oxidation was evaluated using sodium persulfate as an oxidizing agent. A complete experimental design 2 3 was devised to evaluate the effects of the activation of the oxidizing agent by iron sulfate (II) and visible light (LED), these being the factors. After this batch step, the tests that were efficient in degrading the contaminant were carried out in the continuous reactor. The degradation results showed that, in batch, the oxidation with activation of sodium persulfate by iron sulfate (II) is more efficient, removing 91.2% of the dye in 20 minutes. In the continuous reactor, activation with a visible light source showed greater conversion due to its greater contact surface with water contaminated with dye, removing 59.2% over 15 meters from the reactor and residence time of 109 seconds.

Activation of sodium persulfate by TiO2@MIL-101(Fe): Boosting the Fenton-like process by interfacial charge transfer

Advanced oxidation processes based on sulfate radicals are considered as a promising approach for environmental remediation. In this study, TiO2@MIL-101(Fe) is successfully fabricated by a facile impregnation method and is used for sodium persulfate (SPS) activation. TiO2@MIL-101@SPS combines the advantages of photocatalysis and SPS activation, which shows high removal efficiency for nitrobenzene and methyl orange. In addition, the effect of multiple factors, including light source, SPS amount and catalyst amount, on nitrobenzene degradation have been investigated. Results show that the nitrobenzene degradation efficiency is up to 66.53 % while that of TOC removal is 32.21 % under 4-h visible light irradiation with 30 mg catalyst and 1.6 mM SPS. Moreover, LC-MS have been carried out to study the route of nitrobenzene degradation. Besides, ESR analysis reveals that both ●SO4− and ●OH radicals are generated sustainably under visible light irradiation, and more ●OH radicals can be detected owing to the synergic effect of photocatalysis and SPS activation. Interfacial charge transfer effect provides photoinduced electrons for the Fe3+/Fe2+ cycle in MIL-101(Fe), which boosts the SPS activation process, resulting in high photocatalytic activity.

Lanthanum Nickel Oxide: An Effective Heterogeneous Activator of Sodium Persulfate for Antibiotics Elimination

In recent years, the presence of pharmaceutically active compounds (PhACs) in surface waters and wastewaters has b the effectiveness of conventional water treatment methods. Towards this direction, advanced oxidation processes (AOPs) for the complete elimination of micro pollutants in waters have become an emerging area of research. The present study reports the heterogeneous activation of sodium persulfate (SPS) by LaNiO3 (LNO) perovskite oxide for the degradation of sulfamethoxazole (SMX), an antibiotic agent. LNO was prepared according to a combustion method, and its physicochemical characteristics were identified by means of XRD, BET, TEM, and SEM/EDS. SMX degradation results showed the great efficiency of LNO for SPS activation. Increasing LNO and SPS dosage up to 250 mg/L enhanced the SMX degradation. In contrast, increasing SMX concentration resulted in longer time periods for its degradation. Considering the pH effect, SMX removal was obstructed under basic conditions, while the efficiency was enhanced at near-neutral conditions. The present system’s activity was also tested for piroxicam (PIR) and methylparaben (MeP) degradation, showing promising results. Unfortunately, experiments conducted in real water matrices such as bottled water (BW) and wastewater (WW), showed that SMX removal was limited to less than 25% in both cases. The hindering effects were mainly attributed to bicarbonate ions and organic matter present in aqueous media. The results obtained using suitable radical scavengers revealed the contribution of both hydroxyl and sulfate radicals in degradation reactions. Finally, LNO exhibited good stability under consecutive experimental runs.

Persulfate activation by modified red mud for the oxidation of antibiotic sulfamethoxazole in water

Different pre-conditioning treatments were evaluated in order to stabilize red mud, a waste product from bauxite processing, for obtaining heterogeneous catalysts (named as B1–B3) that can be employed as suitable activators of sodium persulfate (SPS) for the degradation of sulfamethoxazole (SMX), a model antibiotic, in water. The presence of Fe3O4 in the composition of the catalysts was found to be a key factor for a suitable activation of SPS, according to the XPS measurements. The oxidation of SMX was successfully fitted to a pseudo-first-order kinetic model (r2 > 0.96), obtaining a 68% removal after 180 min when 0.8 mg/L of SMX was oxidized with 2 g/L of SPS and 2 g/L of catalyst B3. The presence of organic and/or inorganic constituents in the water matrix significantly hindered the degradation rate of SMX, the apparent kinetic constants being from 2 to 3 times lower than that determined in ultrapure water test. The use of ultrasound irradiation coupled to the addition of B3 catalyst improved importantly the SMX oxidation in real aqueous matrices, thus attaining values of removal which almost triplicated the ones obtained in absence of ultrasounds.

Potassium Hydrogen Phthalate Abatement by Activated Persulfate in ZVI-PS Systems

The advanced oxidation process based on sulfate radicals (SO4.−) is one of the most promising wastewater treatment technologies. In this study, we utilized potassium hydrogen phthalate (KHP) as an organic pollutant to configure simulated wastewater that was then treated by activation of sodium persulfate (PS) by zero-valent iron (ZVI) to produce SO4.−. Our results showed that the ZVI-PS system had a greater degradation rate in acidic, neutral, and weakly alkaline solutions compared with the Fenton method. After 180 min of reaction time under the experimental conditions (pH = 3.0, temperature = 20 °C, ZVI = 3.57 mM, and PS = 2.52 mM), chemical oxygen demand (COD) was 53.72%, indicating that these reaction conditions were optimal for COD degradation. This reaction was described by the kinetic rate Eqs. Y = K1X + b (0–10 min) and Y = C + B X + K2X2 (30–180 min) within the above experimental conditions. The results of this study showed that the ZVI-PS system may be an interesting alternative for the treatment of organic pollutants.

Heterogeneous activation of persulfate by lanthanum strontium cobaltite for sulfamethoxazole degradation

This study reports the heterogeneous activation of sodium persulfate (SPS) by La0.8Sr0.2CoO3-δ (LSC) perovskite oxide for the degradation of sulfamethoxazole (SMX), a representative antibiotic agent. LSC was synthesized by a combustion method and characterized with respect to its physicochemical characteristics by means of nitrogen isotherm absorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM/EDS) and transmission electron microscopy (TEM/HRTEM). LSC showed high activity towards SPS activation, resulting in complete SMX degradation in short time periods. The effect of SPS (100−500 mg/L), catalyst (100−500 mg/L) and SMX (0.125-0.5 mg/L) concentrations, as well as initial solution pH on SMX removal was studied. Apart from ultrapure water (UPW), additional experiments were conducted in bottled water (BW) and secondary treated wastewater (WW), showing the existence of retarding phenomena in SMX degradation. In order to further investigate these phenomena, experiments in UPW spiked with bicarbonate or chloride ions and humic acid were also carried out. The role of reactive oxygen species (sulfate and hydroxyl radicals) was determined with the use of suitable scavengers (methanol, t-butanol). Catalyst stability was assessed for five consecutive runs showing LSC superior recyclability. Coupling activators (LSC with simulated solar irradiation) resulted in faster SMX degradation in a synergistic rather than cumulative way.

Degradation of pesticide thiamethoxam by heat – activated and ultrasound – activated persulfate: Effect of key operating parameters and the water matrix

This work studied the degradation of pesticide thiamethoxam (TMX) by heat-activated and ultrasound-activated persulfate systems. The effect of different parameters on degradation in ultrapure water, such as initial pH (3–10), sodium persulfate (SPS) concentration (50−1000mg/L), TMX concentration (1−10mg/L), temperature (20−70°C) and ultrasound power density (20−42W/L) were examined. For the heat-activated system, TMX degradation increased with increasing temperature and SPS concentration and was favored at pH 6; the activation energy was computed at 108.7kJ/mol based on the Arrhenius law. Ultrasound alone was capable of partially degrading TMX, but the process was favored in the presence of SPS. For the ultrasound-activated system, degradation increased with increasing SPS concentration and power density at pH 6. The effect of temperature was controversial since the beneficial effect of high temperatures on SPS activation is offset by the reduced sonochemical activity due to the “cushioning” effect. Regardless of the activation system, the presence of chloride, bicarbonate and humic acid impeded TMX removal. Besides, TMX degradation was reduced in actual matrices, i.e. wastewater and bottled water, showing the competition between TMX and other matrix constituents for free radicals. For either system, mineralization was slower than TMX degradation, implying the formation of persistent by-products.

Utilization of raw red mud as a source of iron activating the persulfate oxidation of paraben

Abstract The degradation of emerging micro-contaminant propylparaben (PP) by persulfate oxidation was studied in this work. The activation of sodium persulfate (SPS) was done utilizing raw red mud (RM), a by-product of bauxite processing. RM with a specific surface area of ∼10 m2/g is rich in metal oxides, including Fe, Al, Ti, Si, Na and Cu, as this has been evidenced by X-ray diffraction (XRD) patterns, and scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). Experiments were conducted at RM concentrations between 0.5 and 4 g/L, SPS concentrations of 1 and 2 g/L and PP concentrations between 0.4 and 6.4 mg/L at pH = 3 in ultrapure water. PP degradation, approached by a pseudo-first order rate expression, increased with increasing SPS and RM concentrations (for the latter up to 2 g/L) and decreasing PP concentration. Acidic conditions favor iron dissolution, whose extent depends on the operating conditions; leached iron contributes significantly to PP degradation. The reaction is retarded in environmental matrices, i.e. bottled water and secondary treated wastewater highlighting possible interactions amongst RM, PP, inherent water constituents and reactive species; the latter include sulfate and hydroxyl radicals as this has been evidenced by electron paramagnetic resonance (EPR) measurements. SPS activation by RM was also coupled with other activators, i.e. simulated solar irradiation, 20 kHz ultrasound or heating to 40 °C and 50 °C in an attempt to evaluate the level of synergy. Depending on the integrated processes and the operating conditions in each case, the effect was negative (i.e. −177% for solar light), near zero or positive (i.e. 48% for ultrasound at 8 W/L).

Degradation of phenanthrene in sulfate radical based oxidative environment by nZVI-PDA functionalized rGO catalyst

The ability of SO4− based advanced oxidation processes activated by nano zero-valent iron (nZVI) on reduced graphene oxide (rGO) functionalized by polydopamine (PDA) (nZVI-PDA@rGO) in degradation of phenanthrene (PHE) was investigated under various environmental conditions. The results showed that, compared with nZVI, the catalytic degradation of PHE was enhanced after anchoring nZVI on the PDA@rGO nanosheet in the activation of sodium persulfate (SPS) and peroxymonosulfate (PMS). The maximum PHE removal efficiency reached 95.9% and 98.7% in the nZVI-PDA@rGO/SPS (50 mg L−1/0.3 mM) and nZVI-PDA@rGO/PMS (50 mg L−1/0.0375 mM) systems, respectively. The effects of pH, anions and humic acid (HA) on the PHE degradation were tested in the nZVI-PDA@rGO coupling with PMS or SPS system. The higher PHE removal could be maintained in the nZVI-PDA@rGO/SPS system at pH up to 7.74 and in the nZVI-PDA@rGO/PMS system at pH up to 7.86, respectively. Cl− had a positive effect on PHE removal in both SPS and PMS systems, while a negative effect was observed in the presence of SO42−, NO3− and HCO3− (HCO3− > SO42− > NO3−). In addition, the PHE removal was inhibited significantly after addition of 50 mg L−1 HA. The radical scavenger tests were carried out to identify the dominant reactive oxygen species (ROSs), which demonstrated that SO4− and HO were the two primary ROSs responsible for the PHE removal. The intermediate products were identified by LC-MS and the degradation pathway of PHE was proposed.

Degradation of antibiotic sulfamethoxazole by biochar-activated persulfate: Factors affecting the activation and degradation processes

Spent malt rootlets were valorized to synthesize biochars for water treatment. In particular, the ability of biochar (BC) to activate sodium persulfate (SPS) for the oxidation of sulfamethoxazole (SMX), a representative antibiotic belonging to the family of emerging micro-contaminants, was tested. The biochar was fully characterized by nitrogen adsorption, FTIR spectroscopy, SEM, XRD, TGA and potentiometric mass titration (PMT); the biochar has a specific surface area of 100 m2/g, a point of zero charge value of 8.4 and its surface contains, amongst others, a considerable amount of hydroxyl groups probably in phenolic structure.The effect of various parameters such as SPS concentration (100–600 mg/L), SMX concentration (125–500 μg/L) and the water matrix (pure water, bottled water, treated domestic wastewater, alcohols as radical scavengers and humic acid) on degradation was investigated. The actual matrix effect on degradation was minor and so was the effect of radical scavengers. Based on the PMT curves, persulfate activation seems to occur on the biochar surface through interactions with the surface functional groups, generating radicals that are not released in the solution; this mechanism is promoted by the presence of humic acid.The biochar-induced SPS activation was also coupled with either 20 kHz ultrasound irradiation or simulated solar light. In either case, the combined activation was more efficient than the individual ones, leading to process synergy; the degree of synergy, based on pseudo-first order rate constants, was 23–35%.

Activation of sodium persulfate by magnetic carbon xerogels (CX/CoFe) for the oxidation of bisphenol A: Process variables effects, matrix effects and reaction pathways

An advanced oxidation process comprising sodium persulfate (SPS) and a novel magnetic carbon xerogel was tested for the degradation of bisphenol A (BPA), a model endocrine-disrupting compound. The catalyst, consisting of interconnected carbon microspheres with embedded iron and cobalt microparticles, was capable of activating persulfate to form sulfate and hydroxyl radicals at ambient conditions.The pseudo-first order degradation rate of BPA in ultrapure water (UPW) was found to increase with (i) increasing catalyst (25–75 mg/L) and SPS (31–250 mg/L) concentrations, (ii) decreasing BPA concentration (285–14,200 μg/L), and (iii) changing pH from alkaline to acidic values (9–3).Besides UPW, tests were conducted in drinking water, treated wastewater, groundwater and surface water; interestingly, the rate in UPW was always lower than in any other matrix containing several organic and inorganic constituents. The effect of natural organic matter (in the form of humic acids) and alcohols was detrimental to BPA degradation owing to the scavenging of radicals. Conversely, chlorides at concentrations greater than 50 mg/L had a positive effect due to the formation and subsequent participation of chlorine-containing radicals.Liquid chromatography time-of-flight mass spectrometry was employed to identify major transformation by-products (TBPs) of BPA degradation in the absence and presence of chlorides; in the latter case, several chlorinated TBPs were detected confirming the role of Cl-related radicals. Based on TBPs, main reaction pathways are proposed.

Sono-activated persulfate oxidation of bisphenol A: Kinetics, pathways and the controversial role of temperature

The sonochemical degradation of bisphenol A (BPA) in the presence of sodium persulfate (SPS) was investigated at 20kHz. Experiments were performed at 110–450μg/L BPA and 1–100mg/L SPS concentration and an ultrasound power density between 4 and 60W/L. The liquid bulk temperature was either kept constant at 30°C or left uncontrolled and gradually increased up to 80°C. BPA degradation occurs due to the combined action of hydroxyl radicals generated by the ultrasound and sulfate radicals generated by SPS sonolysis and this was confirmed with experiments with methanol and t-butanol as radical scavengers. Considerable thermal SPS activation can also occur at increased temperatures (60–80°C) although the enhanced formation of sulfate radicals is compensated by a decrease in sonochemical activity. Kinetics can be approached by a pseudo-first order expression with the apparent rate constant decreasing with increasing BPA concentration; this implies that the actual order is below first. The rate increases with increasing power density and SPS concentration and decreases at alkaline conditions (i.e. pH=9) and in the presence of inorganic and organic constituents (e.g. bicarbonate, humic acid etc) typically found in environmental matrices.Liquid chromatography time of flight mass spectrometry (LC–TOF–MS) analysis revealed the formation of twelve transformation by-products that accompany BPA sonodegradation in the presence of SPS. Based on their evolution profiles, a reaction mechanism is proposed consisting of two major pathways: (i) hydroxylation that can occur mainly in the aromatic ring through HO, SO4− radical attack and to a lesser extent in methyl groups, through hydrogen abstraction by HO radicals, with subsequent O2 addition, and (ii) scission of the bond between the isopropylidene carbon and the phenyl group.

Removal of trichloroethylene in groundwater with two oxidants: siderite catalyzed hydrogen peroxide and sodium persulfate

Trichloroethylene (TCE), a widely used solvent, is often determined in groundwater and is one of biologically refractory organic contaminants. The aim of the study is to use a new chemical oxidation method to degrade TCE source pollution in groundwater. Fenton-like reactions (hydrogen peroxide catalyzed by iron minerals generates hydroxyl radicals) and sodium persulfate activation (sodium persulfate activated by heat/iron minerals to produce sulfate radicals) have strong oxidative capacity to degrade a wide range of organic contaminants. In this work, hydrogen peroxide and/or sodium persulfate catalyzed by siderite (designated as STO, SO, PO systems, respectively) degrading TCE in groundwater were investigated. Removal rates of TCE in STO, SO, and PO systems were 100%, 57%, 20%, respectively. The order of TCE removal rates is in agreement with that of hydroxyl radicals generated in the systems, indicating that hydroxyl radicals play a critical role in removing TCE. No by-product except CO2, Cl− and H2O generated as final products in the STO system suggests that TCE was near completely mineralized. The results show that the STO is an effective method to treat TCE contaminated source in groundwater.