Improvement of sonochemical degradation of Brilliant blue R in water using periodate ions: Implication of iodine radicals in the oxidation process

Photothermal-catalytic activation periodate over MnO2/g-C3N4 S-scheme heterojunction for rapidly tetracycline removal: intermediates, toxicity evaluation and mechanism

The MnO2/CN S-scheme heterojunctions were prepared using the hydrothermal method, which significantly promoted periodate (PI) activation for the TC removal. Notably, the MnO2/CN-0.1 achieved a TC removal rate of 79.7 % within 25 min in the PI/Vis system, which was 1.39 and 3.68 times that of MnO2 and g-C3N4, respectively. The improved TC degradation performance could be attributed to the synergetic effect of photothermal effect of MnO2 and the S-scheme heterojunction. On the basis of the infrared thermography images, the photothermal properties of MnO2 could increase temperatures of the reaction system, leading to the promotion of the PI activation. The formation of the MnO2/CN S-scheme not only effectively suppressed charge recombination, but also facilitated the Mn(IV)/Mn(III) redox cycle within the reaction. Under different pH and anion conditions, the MnO2/CN-0.1/PI system exhibited excellent capability in TC removal. Additionally, the toxicity of the degraded solution was evaluated based on the LC-MS test results and the growth experiment of Mung bean seeds. This work put forward an efficient approach on S-scheme photothermal catalysts to achieve efficient utilization of PI on TC degradation, which demonstrates a promising method for photothermal assistance PI activation to remediate the water environment efficiently.

Degradation of Atrazine in Water by Dielectric Barrier Discharge Combined with Periodate Oxidation: Enhanced Performance, Degradation Pathways, and Toxicity Assessment

The widespread occurrence of atrazine (ATZ) in water environments presents a considerable risk to human health and ecosystems. Herein, the performance of dielectric barrier discharge integrated with periodate (DBD/PI) for ATZ decomposition was evaluated. Results demonstrated that the DBD/PI system improved ATZ decomposition efficiency by 18.2-22.5% compared to the sole DBD system. After 10 min treatment, the decomposition efficiency attained 82.4% at a discharge power of 68 W, a PI dosage of 0.02 mM, and an initial ATZ concentration of 10 mg/L. As the PI dosage increased, the decomposition efficiency exhibited a trend of initially increasing, followed by a decrease. Acidic conditions were more favorable for ATZ removal compared to alkaline and neutral conditions. Electron paramagnetic resonance (EPR) was adopted for characterizing the active species produced in the DBD/PI system, and quenching experiments revealed their influence on ATZ decomposition following a sequence of 1O2 > O2-• > IO3• > OH•. The decomposition pathways were proposed based on the theoretical calculations and intermediate identification. Additionally, the toxic effects of ATZ and its intermediates were assessed. This study demonstrates that the DBD/PI treatment represents an effective strategy for the decomposition of ATZ in aquatic environments.

Pseudo-water-soluble Fe2O3 as Nanozyme catalyzed chemiluminescent reaction for detection of brilliant blue in gelatin and beverages

Converting solid iron oxide nanoparticles into a "pseudo-water-soluble" form before applying them to chemiluminescent reactions leads to enhance the chemiluminescence intensity. Using 8-hydroxyquinoline as a colloidal agent, a new, fast, and simple method of synthesizing pseudo-water-soluble Fe2O3 nanoparticles was developed. SEM, VSM, SAED, HRTEM, XRD, FTIR, and EDS techniques were used to characterize the synthesized Fe2O3 nanoparticles. Fe2O3 nanoparticles synthesized in this study have superior peroxidase-like activity (POD-like) and are stable under a wide range of pH and temperature. The chemiluminescence reaction of luminol-H2O2 is intensified and accelerated by a colloidal solution of Fe-nanoparticles/8-hydroxyquinoline. Reverse-flow injection analysis was employed to determine brilliant blue. A chemiluminescent sensing method based on iron oxide nanozymes was utilized for sensitive detection of the brilliant blue synthetic dye, achieving a limit of detection of 0.06 mg/L and a dynamic linear range of 0.1 to 50 mg/L. The recovery and relative standard deviations of real samples were found to be 97.83-99.93% and 0.09-3.07%, respectively. An analysis of a sample, from injection to obtaining the maximum peak, could be performed in less than one minute.

Current trends and patterns of PFAS in agroecosystems and environment: A review

Per- and polyfluoroalkyl substances (PFASs) are one of the more well-known highly persistent organic pollutants with potential risks to agroecological systems. These compounds are of global concern due to their persistence and mobility, and they often lead to serious impacts on environmental, agricultural, and human health. In the past 20 years, the number of science publications on PFAS has risen; despite this, certain fundamental questions about PFAS occurrence, sources, mechanism of transport, and impacts on agroecosystems and the societies dependent on them are still open and evolving. There is a lack of systematic and comprehensive analysis of these concerns in agroecosystems. Therefore, we reviewed the current literature on PFAS with a focus on agroecosystems; our review suggests that PFASs are nearly ubiquitous in agricultural systems. We found the current research has limitations in analyzing PFAS in complex matrices because of their small size, distribution, and persistence within various environmental systems. There is consistency in the properties and composition of PFAS in and around agroecosystems, suggesting evidence of shared sources and similar components within different tropic levels. The introduction of new and varied sources of PFAS appear to be growing, adding to their residual accumulation in environmental matrices and leading to possible new types of chemical compounds that are difficult to assess accurately. This review determines existing research trends, understands mechanisms and incidence of PFAS within agroecosystems and their impact on human health, and thereby recommends further studies to remedy research gaps.

Research Progress on the Degradation of Organic Pollutants in Wastewater via Ultrasound/Periodate Systems: A Review

In recent years, the efficient removal of organic pollutants from wastewater has emerged as a critical area of global research interest. Against this backdrop, an array of innovative technologies for wastewater treatment has been developed. Among numerous advanced oxidation processes (AOPs), periodate (PI), an emerging oxidizing agent in AOPs, has garnered significant attention from researchers. Particularly, the integration of ultrasound (US)-activated PI systems has been recognized as an exceptionally promising approach for the synergistic degradation of organic pollutants in wastewater. In this paper, we conducted a thorough analysis of the mechanisms underlying the degradation of organic pollutants using the US/PI system. Furthermore, we comprehensively delineated the effects of ultrasonic power, periodate concentration, temperature, pH, coexisting inorganic ions, and dissolved organic matter on the removal efficiency of organic pollutants and summarized application cases of the US/PI system for the degradation of different pollutants. Finally, we also offered prospective discussions on the future trajectories of US/PI technology development.

Sustainable bioelectric activation of periodate for highly efficient micropollutant abatement

The periodate (PI)-based advanced oxidation process is valued for environmental remediation, but current activation methods involve high costs, secondary contamination risks, and limited applicability due to external energy inputs (e.g., UV), catalyst incorporation (e.g., Fe2+), or environmental modifications (e.g., freezing). In this work, novel bioelectric activation of PI using the electrons generated by electroactive bacteria was developed and investigated for rapid removal of carbamazepine (CBZ), achieving 100 %, 100 %, and 76 % removal efficiency for 4.22 µM of CBZ in 20 min at pH 2, 120 min at pH 6.4, and HRT of 30 min at pH 8.5, respectively, with a 1 mM PI dose and without an input voltage. It was deduced that electrons derived from bacteria could directly activate PI using Ti mesh electrodes and generate •IO3 via single electron transfer under strongly acidic conditions (e.g., pH 2). Nevertheless, under weak alkaline conditions (e.g., pH 8.5), biogenic electrons indirectly activated PI by generating OH-via 4e-reduction at the Ti mesh cathode, resulting in the formation of •O2- and 1O2. In addition to the metal cathode, a carbon-based cathode finely modulates the 2e-reduction, yielding H2O2 and activating PI to mainly form •OH. Moreover, primarily non-toxic IO3- was produced during treatment, while no detectable reactive iodine species (HOI, I2, and I3-) were observed. Furthermore, the bioelectric activation of PI demonstrated its capability to remove various micropollutants present in secondary-treated municipal wastewater, showcasing its broad-spectrum degradation ability. This study introduces a novel, cost-effective, and environmentally friendly PI activation technique with promising applicability for micropollutant elimination in water treatment.

Thermo-activated periodate oxidation process for tetracycline degradation: Kinetics and byproducts transformation pathways

Periodate-based advanced oxidation processes have been diffusely practiced for pollutant decontamination. However, the thermo-activation of periodate process (heat/PI), an effective water pollution removal process, has been rarely discussed, and the degradation pathway of this heat/PI system requires investigation. In this work, tetracycline antibiotics were selected as the model micropollutant for the comprehensive evaluation of the heat/PI system. The heat/PI system exhibited good performance for tetracycline (TC) remediation with temperature increases. The principal reactive oxidative species in the heat/PI system was confirmed using quenching experiments and electron paramagnetic resonance experiments. Further, the potential reactive sites in the TC were identified based on the density functional theory calculation. Based on the detection results of intermediates, there was no significant difference in byproducts generated during TC degradation under various temperatures in the heat/PI system. The Toxicity Estimation Software Tool (T.E.S.T.) method was applied to calculate the individual toxicity of the byproducts. This study contributes to a comprehensive explanation of the process of the thermal activation of periodate, and in particular, it explains the source of oxidation power, the transformation of byproducts, and the toxicity of reaction systems.

Ozone- and Hydroxyl Radical-Induced Degradation of Micropollutants in a Novel UVA-LED-Activated Periodate Advanced Oxidation Process

In this study, novel light emitting diode (LED)-activated periodate (PI) advanced oxidation process (AOP) at an irradiation wavelength in the ultraviolet A range (UVA, UVA-LED/PI AOP) was developed and investigated using naproxen (NPX) as a model micropollutant. The UVA-LED/PI AOP remarkably enhanced the degradation of NPX and seven other selected micropollutants with the observed pseudo-first-order rate constants ranging from 0.069 ± 0.001 to 4.50 ± 0.145 min-1 at pH 7.0, demonstrating a broad-spectrum micropollutant degradation ability. Lines of evidence from experimental analysis and kinetic modeling confirmed that hydroxyl radical (•OH) and ozone (O3) were the dominant species generated in UVA-LED/PI AOP, and they contributed evenly to NPX degradation. Increasing the pH and irradiation wavelength negatively affected NPX degradation, and this could be well explained by the decreased quantum yield (ΦPI) of PI. The degradation kinetics of NPX by the UVA-LED/PI AOP in the presence of water matrices (i.e., chloride, bicarbonate, and humic acid) and in real waters were examined, and the underlying mechanisms were illustrated. A total of nine transformation products were identified from NPX oxidation by the UVA-LED/PI AOP, mainly via hydroxylation, dealkylation, and oxidation pathways. The UVA-LED/PI AOP proposed might be a promising technology for the treatment of micropollutants in aqueous solutions. The pivotal role of ΦPI during light photolysis of PI may guide the future design of light-assisted PI AOPs.

Periodate-based advanced oxidation processes: A review focusing on the overlooked role of high-valent iron and manganese species

Periodate-based advanced oxidation processes (AOPs) have received mounting attention in scientific research in the past two decades due to their fair oxidizing capability for satisfactory decontamination performance. Unlike iodyl (IO₃^•) and hydroxyl (^•OH) radicals are widely recognized as the predominant species generated from periodate activation, the role of high-valent metal as a dominant reactive oxidant has been proposed recently. Although several excellent reviews concerning periodate-based AOPs have been reported, there are still prevalent knowledge roadblocks to high-valent metals' formation and reaction mechanisms. Therefore, this work aims to provide a comprehensive overview of high-valent metals, especially concerning the identification methods (e.g., direct and indirect strategies), formation mechanisms (e.g., formation pathways and interpretation based on density functional theory calculation), reaction mechanisms (e.g., nucleophilic attack, electron transfer, oxygen-atom transfer, electrophilic addition, and hydride and hydrogen-atom transfer), and reactivity performance (e.g., chemical properties, influencing factors, and practical applications). Furthermore, points for critical thinking and further prospects for high-valent metal-mediated oxidation processes are suggested, emphasizing the need for parallel efforts to enhance the stability and reproducibility of high-valent metal-mediated oxidation processes in real world applications.

Comparison of effects of multiple oxidants with an ultrasonic system under unified system conditions for bisphenol A degradation

Bisphenol A (BPA) as a trace contaminant has been reported, due to widespread use in the plastics industry. This study applied the 35 kHz ultrasound (US) to activate four different common oxidants (H₂O₂, HSO₅^-, S₂O₈^2-, and IO₄^-) for BPA degradation. With increasing initial concentration of oxidants, the degradation rate of BPA increased. The synergy index confirmed that a synergistic relationship between US and oxidants. This study also examined the impact of pH and temperature. The results showed that the kinetic constants of US, US-H₂O₂, US-HSO₅^- and US-IO₄^-decreased when the pH increased from 6 to 11. The optimal pH for US-S₂O₈^2- was 8. Notably, increasing temperature decreased the performance of US, US-H₂O₂, and US-IO₄^- systems, while it could increase the degradation of BPA in US-S₂O₈^2- and US-HSO₅^-. The activation energy for BPA decomposition using the US-IO₄^- system was the lowest, at 0.453nullkJnullmol^-1, and the synergy index was the highest at 2.22. Additionally, the ΔG# value was found to be 2.11 + 0.29T when the temperature ranged from 25 °C to 45 °C. The main oxidation contribution is achieved by hydroxyl radicals in scavenger test. The mechanism of activation of US-oxidant is heat and electron transfer. In the case of the US-IO₄^- system, the economic analysis yielded 271 kwh m^-3, which was approximately 2.4 times lower than that of the US process.

Activation of periodate by N-doped iron-based porous carbon for degradation of sulfisoxazole: Significance of catalyst-mediated electron transfer mechanism

Periodate (PI) has recently been studied as an excellent oxidant in advanced oxidation processes, and its reported mechanism is mainly the formation of reactive oxygen species (ROS). This work presents an efficient approach using N-doped iron-based porous carbon (Fe@N-C) to activate periodate for the degradation of sulfisoxazole (SIZ). Characterization results indicated the catalyst has high catalytic activity, stable structure, and high electron transfer activity. In terms of degradation mechanism, it is pointed out that the non-radical pathway is the dominant mechanism. In order to prove this mechanism, we have carried out scavenging experiments, electron paramagnetic resonance (EPR) analysis, salt bridge experiments and electrochemical experiments, which demonstrate the occurrence of mediated electron transfer mechanism. Fe@N-C could mediate the electron transfer from organic contaminant molecules to PI, thus improving the efficiency of PI utilization, rather than simply inducing the activation of PI through Fe@N-C. The overall results of this study provided a new understanding into the application of Fe@N-C activated PI in wastewater treatment.

Hydrodynamic cavitation coupled with zero-valent iron produces radical sulfate radicals by sulfite activation to degrade direct red 83

In the present research, hydrodynamic cavitation (HC) and zero-valent iron (ZVI) were used to generate sulfate radicals through sulfite activation as a new source of sulfate for the efficient degradation of Direct Red 83 (DR83). A systematic analysis was carried out to examine the effects of operational parameters, including the pH of the solution, the doses of ZVI and sulfite salts, and the composition of the mixed media. Based on the results, the degradation efficiency of HC/ZVI/sulfite is highly dependent upon the pH of the solution and the dosage of both ZVI and sulfite. Degradation efficiency decreased significantly with increasing solution pH due to a lower corrosion rate for ZVI at high pH. The corrosion rate of ZVI can be accelerated by releasing Fe2+ ions in an acid medium, reducing the concentration of radicals generated even though ZVI is solid/originally non-soluble in water. The degradation efficiency of the HC/ZVI/sulfite process (95.54 % + 2.87%) was found to be significantly higher under optimal conditions than either of the individual processes (<6% for ZVI and sulfite and 68.21±3.41% for HC). Based on the first-order kinetic model, the HC/ZVI/sulfite process has the highest degradation constant of 0.035±0.002 min-1. The contribution of radicals to the degradation of DR83 by the HC/ZVI/sulfite process was 78.92%, while the contribution of SO4•- and •OH radicals was 51.57% and 48.43%, respectively. In the presence of HCO3- and CO32- ions, DR83 degradation is retarded, whereas SO42- and Cl- ions promote degradation. To summarise, the HC/ZVI/sulfite treatment can be viewed as an innovative and promising method of treating recalcitrant textile wastewater.

Activation of periodate using ultrasonic waves and UV radiation for landfill leachate treatment

In the present work, saline leachate of the Bushehr coastal city (Iran) was purified using the ultraviolet/ultrasonication wave/periodate process. The initial TDS and TOC values of the leachate studied were 7390 mg/L and 975 mg/L, respectively. During the effect of various parameters on leachate purification, the experiments were optimized at pH 3, oxidizer concentration of 4 mM, and treatment time of 120 min. The initial BOD₅/COD ratio of 0.66 was reduced to 0.42 at the end of the purification time (120 min). After leachate treatment under optimal conditions, the amount of BOD₅, COD, and UV₂₅₄ were 451.5 mg/L, 1072 mg/L, and 12.69 cm^-1, respectively. Concentrations of heavy metals in crude leachate by ICP-OES were checked. Also, the concentration of organic compounds before and after purification was determined using GC-Mass. The leachate purification kinetics followed the first-order model using the designed method. Based on the COD factor, the system energy consumption for leachate treatment was calculated to be 11.4 kWh/m³. The results showed that the system explored (UV/US/IO₄^-) can effectively purify high salinity waste leachate.

Emerging periodate-based oxidation technologies for water decontamination: A state-of-the-art mechanistic review and future perspectives

With the ever-increasing severity of the ongoing water crisis, it is of great significance to develop efficient, eco-friendly water treatment technologies. As an emerging oxidant in the advanced oxidation processes (AOPs), periodate (PI) has received worldwide attention owing to the advantages of superior stability, susceptible activation capability, and high efficiency for decontamination. This is the first review that conducts a comprehensive analysis of the mechanism, pollutant transformation pathway, toxicity evolution, barriers, and future directions of PI-based AOPs based on the scientific information and experimental data reported in recent years. The pollutant elimination in PI-based AOPs was mainly attributed to the in situ generate reactive oxygen species (e.g., ^•OH, O(³P), ¹O₂, and O₂^•-), reactive iodine species (e.g., IO₃^• and IO₄^•), and high-valent metal-oxo species with exceptionally high reactivity. These reactive species were derived from the PI activated by the external energy, metal activators, alkaline, freezing, hydroxylamine, H₂O_2, etc. It is noteworthy that direct electron transport could also dominate the decontamination in carbon-based catalyst/PI systems. Furthermore, PI was transformed to iodate (IO₃^-) stoichiometrically via an oxygen-atom transfer process in most PI-based AOPs systems. However, the production of I₂, I^-, and HOI was sometimes inevitable. Furthermore, the transformation pathway of typical micropollutants was clarified, and the in silico QSAR-based prediction results indicated that most transformation products retained biodegradation recalcitrance and multi-endpoint toxicity. The barriers faced by the PI-based AOPs were also clarified with potential solutions. Finally, future perspectives and research directions are highlighted based on the current state of PI-based AOPs. This review enhances our in-depth understanding of PI-based AOPs for pollutant elimination and identifies future research needs to focus on the reduction of toxic byproducts.

Novel insights into the mechanism of periodate activation by heterogeneous ultrasonic-enhanced sludge biochar: Relevance for efficient degradation of levofloxacin

In this study, a novel heterogeneous ultrasonic (US)-enhanced sludge biochar (SBC) activated periodate (PI) system was established and explored for the rapid removal of levofloxacin in the aqueous environment. This study focused on the mechanisms of US-enhanced SBC co-activation of PI for levofloxacin degradation. The results indicated that US and SBC exhibited a remarkable synergistic reinforcing activation effect on PI compared to single PI activation systems. The SBC/US/PI system achieved approximately 95% of levofloxacin removal, 51.5% of TOC removal, and 22% of dechlorination rate within 60 min with virtually no heavy metals released into the water matrix. In addition, the acute ecotoxicity of the solutions treated with the SBC/US/PI system was substantially reduced. The presence of IO₃^•, ^•OH, ¹O₂ and O₂^•- were identified in the SBC/US/PI system using quenching experiments and EPR technology while ^•OH and ¹O₂ were the predominant reactive species. Mechanistic studies have suggested that the cavitation effect of ultrasonic improved the dispersion and mass transfer efficiency of SBC and accelerated the desorption process of SBC. Possible pathways of levofloxacin degradation were proposed. This study provides a novel and promising strategy for the efficient removal of emerging contaminants such as antibiotics from the water matrix.

Kinetics and mechanisms of the carbamazepine degradation in aqueous media using novel iodate-assisted photochemical and photocatalytic systems

The present study investigates the kinetics and mechanisms of carbamazepine (CBZ) degradation using a novel UV/iodate (IO₃^-) system for the first time and explores the influence of process conditions on its degradation. UV/IO₃^- showed high degradation efficiencies in a wide range of pHs, especially under neutral and acidic conditions, indicating that the system can be considered as a promising method to deal with effluents under various pH conditions. Radical scavenging experiments show that both iodine radicals (IO, IO₂ and IO₃) and hydroxyl radicals play an important role in CBZ degradation. Furthermore, the combination of UV/IO₃^- with TiO₂ was studied to explore the potential of the addition of IO₃^- to improve the efficiency of the conventional TiO₂ photocatalytic system. Scavenging experiments indicated that iodine radicals (IO, IO₂ and IO₃) were mainly involved in the degradation of CBZ in the UV/IO₃^-/TiO₂ system, and the reaction mechanism equations were proposed for the first time for the studied UV/IO₃^-/TiO₂ system. Several degradation products and four possible pathways of CBZ degradation were also elucidated using ultra-high-performance liquid chromatography in combination with a quadrupole time-of-flight mass spectrometer (Q-TOF MS). Respirometric tests indicated that the treatment has a positive impact on biomass behavior during subsequent biological purification, highlighting that the developed IO₃^--assisted AOPs are eco-friendly.

Surface-mediated periodate activation by nano zero-valent iron for the enhanced abatement of organic contaminants

Periodate (PI)-based advanced oxidation processes have recently received increasing attentions. Herein, PI was readily activated by nano zero-valent iron (nZVI) and subsequently led to the enhanced oxidation of organic contaminants, with the removal performance of sulfadiazine (SDZ) in the nZVI/PI process even higher than that in the nZVI/peroxydisulfate process under identical conditions. Kinetic experiments indicated that the decay of SDZ was susceptible to the dosage of nZVI and PI, but was barely affected by pH values (4.0-7.0) under buffered conditions, suggesting the promising performance of the nZVI/PI process in a relatively wide pH range. Selective degradation of contaminants and ¹⁸O-isotope labeling assays collectively demonstrated that iodate radical (^•IO₃), high-valent iron-oxo species (Fe(IV)) and hydroxyl radical (^•OH) were responsible for the abatement of organic contaminants. More importantly, due to the relatively weak steric hindrance effect of PI, PI easily adsorbed on the surface of nZVI and no iron leaching was detected throughout the reaction, implying that PI activation induced by nZVI was a surface-mediated process. Besides, PI was not transformed into harmful reactive iodine species. This study proposed an environmental-friendly approach for PI activation and shed new lights on the PI-based processes.

Ultrasound/chlorine sono-hybrid-advanced oxidation process: Impact of dissolved organic matter and mineral constituents

In this work, after exploring the first report on the synergism of combining ultrasound (US: 600 kHz) and chlorine toward the degradation of Allura Red AC (ARAC) textile dye, as a contaminant model, the impact of various mineral water constituents (Cl-, SO42-, NO3-, HCO3- and NO2-) and natural organic matter, i.e., humic acid (HA), on the performance of the US/chlorine sono-hybrid process was assessed for the first time. Additionally, the process effectiveness was evaluated in a real natural mineral water (NMW) of a known composition. Firstly, it was found that the combination of ultrasound and chlorine (0.25 mM) at pH 5.5 in cylindrical standing wave ultrasonic reactor (f = 600 kHz and Pe = 120 W, equivalent to PA ∼ 2.3 atm) enhanced in a drastic manner the degradation rate of ARAC; the removal rate being 320% much higher than the arithmetic sum of the two separated processes. The source of the synergistic effect was attributed to the effective implication of reactive chlorine species (RCS: Cl, ClO and Cl2-) in the degradation process. Radical probe technique using nitrobenzene (NB) as a specific quencher of the acoustically generated hydroxyl radical confirmed the dominant implication of RCS in the overall degradation rate of ARAC by US/chlorine system. Overall, the presence of humic acid and mineral anions decreased the efficiency of the sono-hybrid process; however, the inhibition degrees depend on the type and the concentration of the selected additives. The reaction of these additives with the generated RCS is presumably the reason for the finding results. The inhibiting effect of Cl-, SO42-, NO3- and NO2- was more pronounced in US/chlorine process as compared to US alone, whereas the inverse scenario was remarked for the effect of HA. These outcomes were associated to the difference in the reactivity of HA and mineral anions toward RCS and OH oxidizing species, in addition to the more selective character of RCS than hydroxyl radical. The displacement of the reaction zone with increasing the additive concentration may also be another influencing factor that favors competition reactions, which subsequently reduce the available reactive species in the reacting medium. The NMW exerted reductions of 43% and 10% in the process efficiency at pH 5.5 and 8, respectively, thereby confirming the RCS-quenching mechanism by the water matrix constituents. Hence, this work provided a precise understanding of the overall mechanism of chlorine activation by ultrasound to promote organic compounds degradation in water.

Efficient degradation of diclofenac sodium by periodate activation using Fe/Cu bimetallic modified sewage sludge biochar/UV system

Iron/copper bimetallic nanoparticles based sludge biochar (Fe/Cu-SBC) was prepared by using a modified co-precipitation route. The Fe/Cu-SBC system prepared was subsequently applied to activate periodate (IO₄^-) to degrade diclofenac sodium (DCF) by using UV light at room temperature (25 °C). The physicochemical properties of both SBC and Fe/Cu-SBC such as morphology, physical properties, crystal structures and functional groups were examined. The type and number of surface functional groups were found to be increased and the catalytic performance was improved by the modification of Fe/Cu bimetallic nanoparticles. The influence of various parameters to evaluate the catalytic efficiency such as periodate (PI) concentration, dosage of catalysts, UV power, initial pH and coexisting anions were investigated. Under the optimized conditions (pH 6.9, UV-power 60 W, PI concentration of 5 mM and 0.1 g Fe/Cu-SBC), it was observed that 99.7% of DCF was degraded with a pseudo-first-order kinetics reaction constant 9.39 × 10^-2 min^-1. The radical scavenging experiments showed that IO₃ radicals were the predominantly reactive oxidants in the Fe/Cu-SBC/UV system. Therefore, this investigation provides a feasible alternative for the degradation of PPCPs in wastewater.

A Review on Additives-assisted Ultrasound for Organic Pollutants Degradation

In the past 2 decades, considerable attentions have been paid to the sonochemical advanced oxidation processes (SAOPs) in the fields of pollutants removal. SAOPs are powerful methods for refractory pollutants degradation due to the free radicals (e.g., •OH and •H) generated by water pyrolysis and extremely high temperature and pressure in and around cavitation bubbles. Reports on various additives for the improvement of sonochemical pollutants degradation including oxidants, inorganic anions, etc. have been made. This paper presents a comprehensive review on the ultrasound (US) alone and sono-hybrid systems for various pollutants degradation. In this paper, the degradation efficiency of various pollutants in sono-hybrid systems are elucidated in detail, and particular emphasis is placed on the reaction mechanism of additives in US for the enhancement of pollutants degradation. The problems on the applications of the current sono-hybrid systems are identified and discussed, and the outlooks for further in-depth studies on the challenges and some research needs for the applications of SAOPs for the removal of organic pollutants from aquatic systems are made at the end.

Sonochemical degradation of poly- and perfluoroalkyl substances - A review

Poly- and perfluoroalkyl substances (PFAS) have received considerable attention from environmental scientists and engineers because of their stability and widespread. Sonochemical process has been widely used in the environmental field to remove pollutants due to its advantages in terms of operational simplicity, no secondary pollutant formation and safety. Currently, many studies have reported sonochemical degradation of various PFAS in laboratory settings and showed excellent removal potential. This article reviewed the effects of different power densities, ultrasonic frequencies, temperatures, atmosphere conditions, additives, and initial concentration and chemical properties of PFAS on the sonochemical degradation of PFAS. Sonochemical methods combined with conventional techniques for PFAS removal were elaborated as well. Additionally, this article discussed the challenges and prospects of using sonochemical approaches for PFAS remediation.

Impact of seawater salinity on the sonochemical removal of emerging organic pollutants

The results presented in this study illustrate the multiple roles of seawater salinity toward the sonochemical degradation, at variable frequencies (300-1700 kHz), of several hazardous substances, i.e. propylparaben (PPR) endocrine disruptor and several synthetic dyes: naphthol blue black (NBB), malachite green (MG), basic red 29 (BR29), acid orange 7 (AO7), Rhodamine B (RhB) and basic fuchsin (BF). Sonochemical treatment degraded all pollutants in seawater at faster rates than in deionized water. The seawater-salts through increasing the ionic strength of the solution act as a potential pusher of hydrophilic pollutants toward the reactive interfacial area of cavitation bubbles. Additionally, the salts reduce the bubble coalescence, which yields higher number of active bubbles in the irradiating media. Analysing the degradation rate of PPR and NBB with two heterogeneous models based on Langmuir kinetics mechanism indicated that the bubble interfacial area was the preferred reaction zone for the ultrasonic degradation of PPR and NBB in seawater.

Degradation of Acid Red 73 by Activated Persulfate in a Heat/Fe3O4@AC System with Ultrasound Intensification

This work aimed to investigate the degradation efficiency of waste water with an azo dye, Acid Red 73 (AR73), by persulfate/heat/Fe₃O₄@AC/ultrasound (US). The introduction of ultrasound into the persulfate/heat/Fe₃O₄@AC system greatly enhanced the reaction rate because of the physical and chemical effects induced by cavitation. Various parameters such as temperature, initial pH, sodium persulfate dosage, catalyst dosage, initial concentration of AR73, ultrasonic frequency and power, and free-radical quenching agents were investigated. The optimal conditions were determined to be AR73 50 mg/L, PS 7.5 mmol/L, catalyst dosage 2 g/L, ultrasound frequency 80 kHz, acoustic density 5.4 W/L, temperature 50 °C, and pH not adjusted. Nearly, 100% decolorization was achieved within 10 min under optimal conditions. Different from some other similar research studies, the reaction did not follow a radical-dominating way but rather had ¹O₂ as the main reactive species. The recycling and reusability test confirmed the superiority of the prepared Fe₃O₄@AC catalyst. The research achieved a rapid decolorization method not only using waste heat of textile water as a persulfate activator but also applicable to a complex environment where common radical scavengers such as ethanol exist.

Periodate activation with manganese oxides for sulfanilamide degradation

This study presents a novel periodate oxidation system mediated by manganese oxides for the rapid removal of aqueous contaminants. The catalytic activation of periodate on manganese oxides was demonstrated as an efficient advanced oxidation system for degradation of sulfanilamide. The reactivity of manganese oxides with different Mn valence followed the order of MnO₂>Mn₃O₄>Mn₂O₃, all of which showed extraordinary reusability during repeated activation of periodate. Sulfanilamide was rapidly degraded along with stoichiometric transformation of IO₄^- to IO₃^-, and both processes exhibited good linear correlations with the dosage of manganese oxides. While the degradation of sulfanilamide in the MnO₂/IO₄^- system was accelerated at lower solution pH, it was only slightly affected by ionic strength, water anions and humic acid. In contrast to the homogeneous system of Mn²⁺/IO₄^-, sulfanilamide degradation was not influenced in oxic and anoxic environment. It was evidenced by quenching studies and EPR tests that both singlet oxygen (¹O₂) and iodate radicals (IO₃^•) were generated when the metastable Mn(IV)-O-IO₃ interacted with sulfanilamide. The XPS spectra of Mn 2p and O 1s before and after reactions indicated that the catalytic activation of periodate on MnO₂ was not in company with the redox cycling of Mn(IV) species.

Sonolytic degradation of bisphenol S: Effect of dissolved oxygen and peroxydisulfate, oxidation products and acute toxicity

In this paper, the kinetics of bisphenol S (BPS) degradation in the presence of peroxydisulfate (PDS) or dissolved oxygen (DO) in ultrasound (US) system were investigated. For PDS (US/PDS), increased PDS concentration result in faster BPS degradation, but the enhancement was not remarkable with multiplying PDS dosages. Therefore, heterogeneous PDS activation model based on a Langmuir-type adsorption mechanism was proposed to explain the trait of BPS abatement. The equilibrium constant of PDS (K_PDS) was calculated to be 2.91 × 10^-4/μM, which was much lower than that of BPS, suggesting that PDS was hard to adsorb on the gas-liquid interface of the cavitation bubble following by activation. Besides, the formation of •OH and SO₄^•- in US/PDS system was reinvestigated. The result showed that SO₄^•- rather than •OH was the predominant radical, which was quite different from previous study. Dissolved oxygen largely improve the degradation of BPS in US system and •OH rather than O₂^•- was proved to be the main reactive oxygen species (ROS). The improvement of •OH generation possibly caused by the reaction of DO with •H so that it cannot recombine with •OH. The transformation of the BPS in US system mainly included BPS radical polymerization, hydroxylation and hydrolysis. Frustratingly, the acute toxicity assay of Vibrio fischeri suggests that the degradation products of BPS are more toxic. These results will improve the understanding on the activation mechanisms of PDS and the role of dissolved oxygen play in US. Further investigations may need to explore other treatment ways of BPS and evaluate the acute toxicity of degradation products.

Degradation of sodium isopropyl xanthate from aqueous solution using sonocatalytic process in the presence of chalcocite nanoparticles: Insights into the degradation mechanism and phyto-toxicity impacts

In the present work, the sonocatalytic degradation of sodium isopropyl xanthate (SIPX) was investigated in the presence of Cu₂S nanoparticles. Cu₂S nanoparticles were produced by means of a high-energy planetary mechanical ball milling method within the processing times of 0.5, 1.5, 3 and 4.5 h. The physical and chemical characteristics of Cu₂S particles were studied before and after ball milling process using various analytical techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) coupled Energy-dispersive X-ray spectroscopy (EDX), atomic absorption spectroscopy (AAS) and nanoparticles size distribution (NSD). The XRD pattern of the samples confirmed the presence of tetragonal and cubic crystalline phases of Cu₂S. In addition, the results of SEM and NSD analysis showed that the increase in the ball milling time from 0.5 to 4.5 h notably decreased the size of nanoparticles to the range of 20-40 nm. Furthermore, AAS result showed that the concentration of Cu⁺ ions was much lower than that of the accepted value in the aqueous media (0.009 mg/L) after 60 min of the sonocatalysis. The study on the effects of the main key parameters showed that 93.99% of SIPX (10 mg/L) was removed during 60 min of the sonocatalytic process under the optimum conditions: pH of 7.3, Cu₂S concentration of 1.5 g/L, and ultrasonic power of 150 W. The sonocatalytic degradation mechanism was thoroughly examined in the presence of different organic and inorganic scavenger compounds, including ethanol, EDTA, NaCl and Na₂SO₄. The obtained results confirmed OH and holes (h⁺) as the dominant oxidizing species in Cu₂S catalyzed sonolysis. In order to get the benefits of the integrated sonocatalytic process, different rate enhancing compounds were introduced into the system. For the first time, the S₂O₈^2- and Cu₂S catalyzed sonolysis (US/Cu₂S/S₂O₈^2-) system was introduced as an efficient and novel sonocatalytic system for fast degradation of SIPX. Moreover, the phyto-toxicological assessments proved the reduction in the toxicity of the sonocatalytic-treated SIPX solution by increase in the reaction time, from 20 to 60 min.

Efficient degradation method of emerging organic pollutants in marine environment using UV/periodate process: Case of chlorazol black

Sea has historically been subject to high anthropogenic pressures of direct and indirect loads of emerging organic pollutants (EOPs) from intensive industrial and agricultural activities. Photoactivated periodate (UV/IO₄^-) is an innovative oxidation technique that was never tested in seawater as pollutants matrix. In this work, we attempted to investigate the treatment of seawater contaminated with chlorazol black (CB) dye, as a model of EOPs, using photoactivated periodate process. It was found that periodate (0.5mM) assisted-UV treatment of CB (20mgL^-1) in seawater resulted in 13.16-fold increase in the initial degradation rate, compared to UV alone, and 82% of CB was removed after 40min face to 38% under UV alone. The beneficial effect of UV/IO₄^- treatment is strongly dependent on operational parameters. More interestingly, SDS surfactant, as an organic matter, did not affect the degradation process, making UV/IO₄^- a promising technique for treating seawater contaminated with EOPs.

A novel supramolecular organogel based on acylhydrazone functionalized pillar[5]arene acts as an I- responsive smart material

A novel organic gelator (PZ) has been synthesized by rationally connecting a pillar[5]arene moiety and a bis(hexadecyloxy)phenyl functionalized acylhydrazone moiety. PZ could self-assemble into a supramolecular polymer and form a stable organogel (OPZ) in cyclohexanol by multi-self-assembly driving forces such as C-Hπ, ππ, vdW and hydrogen bonding interactions. The organogel (OPZ) shows blue aggregation-induced emission (AIE). Interestingly, the organogel OPZ could sense iodide ions (I^-) in the gel-gel state with high selectivity and sensitivity. The detection limit of OPZ for I^- is 9.4 × 10^-8 M, indicating high sensitivity to I^-. Furthermore, a thin film based on OPZ was prepared, which could be used as a smart material for the detection of I^- as well as a fluorescent security display material.