Peroxydisulfate Research Articles

Enhancing carbamazepine degradation in electrochemical systems: The interplay of sulfur vacancies and absorbed peroxydisulfate in molybdenite electrodes

Achieving high reaction efficiency with low energy input is crucial for electrochemical water remediation processes, yet remains a significant challenge. This study reported a practicable method, utilizing natural molybdenite as particle electrodes in an electro-activated peroxydisulfate (PDS) process (3D system) to develop a cost-efficient electrocatalytic oxidation system. Molybdenite’s unique ability to generate sulfur vacancies during electrocatalysis significantly enhances system efficiency. The 3D system enhanced the rate constant of carbamazepine (CBZ) abatement sixfold compared to the system without molybdenite. Additionally, a substantial decrease in electrical energy per order (EE/O) from 7.13 kWh/m3 to 0.326 kWh/m3 indicates a near 22-fold increase in energy efficiency. Characterizations involving electron microscopies, electrochemical experiments and density functional theory calculations confirm that hydroxyl radicals (•OH) and adsorbed PDS(PDS*) are the main active species. Molybdenite’s surface with plenty of edge-S, released S vacancy during electrocatalytic oxidation, providing adsorption and activation sites for PDS and H2O. This led to more active sites and facilitating the generation of PDS*, lowering the energy barrier for •OH formation and boosting the oxidation performance of the 3D system. The results underscore the constructed 3D system is a robust and energy-efficient method for practical water treatment.

VUV/UV/Peroxydisulfate oxidation for the elimination of acetaldehyde in reverse osmosis permeates of secondary effluents

Aldehydes have attracted increasing attention owing to their odor and potential carcinogenicity. Because aldehydes are formed during oxidation processes (e.g., ozonation and chlorination) and easily penetrate reverse osmosis (RO) membranes, they are the main organic substances in RO permeates designated for potable reuse. In this study, peroxydisulfate (PDS) was combined with VUV/UV (185/254 nm) irradiation (VUV/UV/PDS) to generate multiple reactive species, including ⋅OH and SO4⋅−, for the elimination of acetaldehyde (CH3CHO) and mineralization of organic matters. With VUV/UV/PDS at 0.05 and 0.5 mmol/L PDS, 99% of CH3CHO was eliminated within 6 and 1.5 min, respectively, which were approximately 2-fold and 7-fold more efficient with VUV/UV. Additionally, with VUV/UV/PDS at 0.05 and 0.5 mmol/L PDS, the proportions of total organic carbon mineralized were 90.7% and 93.7%, respectively. In contrast to VUV/UV, VUV/UV/PDS rapidly mineralized CH3CHO without the obvious accumulation of acetate or oxalate. The computational toxicity assessment indicated that the organic substances generated during VUV/UV/PDS posed lower potential risks to various organisms than those generated during VUV/UV. Moreover, the energy efficiency of VUV/UV/PDS was greater than that of VUV/UV. This study demonstrated that VUV/UV/PDS is a promising alternative treatment for the elimination of aldehydes in RO permeates designated for potable reuse.

Intraplanar heterostructure-mediated activation of peroxydisulfate for singular-electron-transfer degradation of organic pollutants

Activating peroxydisulfate (PDS) through electron transfer pathways (ETP) is promising for degrading organic pollutants in aquatic environments. However, enhancing the activation selectivity remains a challenge. Herein, this study developed an intraplanar heterojunction with C-ring grafted g-C3N4 (CCN) as the catalyst, enabling PDS activation through a singular ETP. The CCN/PDS system achieved complete degradation and efficient mineralization (87.15 %) of bisphenol F (BPF), significantly reducing its ecological toxicity. Both experimental and theoretical investigations revealed that the intraplanar heterojunction could modulate the orbital occupation in g-C3N4/PDS, enhancing PDS adsorption and activation selectivity. Driven by the differences in the frontier orbital energy, the CCN/PDS system achieved a singular ETP without active species formation. The CCN/PDS system efficiently degraded BPF in complex water environments, showing performance stability across a wide pH range and against various coexisting ions. In a continuous-flow automatic catalytic device, the CCN/PDS system maintained a constant 100 % BPF degradation for 600 min. This study advances the understanding of PDS activation via singular ETP and introduces a new approach to water purification.

Degradation of carbamazepine in piezo-activation of persulfate systems: Comparison of PDS and PMS

The choice of persulfate (PS) is crucial to the degradation and energy efficiencies for piezo-activation of PS (PE-PS) systems. Herein, a comparison between piezoelectrically activated peroxydisulfate (PDS) and peroxomonosulfate (PMS) using BaTiO3 are comparatively investigated for carbamazepine (CBZ) degradation. By contrast, the PE-PMS system achieves better degradation and mineralization of CBZ, as well as higher reaction stoichiometric efficiencies (%RSE). Nevertheless, the energy consumption of the PE-PDS system is only 9.69% of the PE-PMS system. The quenching test, chemical probe determination, and electron spin resonance (EPR) analysis suggest that the concentration of •OH, SO4∙-, and 1O2 except ∙O2- of the PE-PMS system, is higher than that of the PE-PDS system. The piezoelectric current density and carrier separation efficiency of the PE-PMS system are higher than that of the PE-PDS system, demonstrating that the piezoelectrically activated PMS has higher reactivity than piezoelectrically activated PDS. The ∙O2- and •OH are the primary ROS in the PE-PDS system, while 1O2 and •OH are the major ROS in the PE-PMS system. Additionally, CBZ is effectively degraded by both PE-PMS and PE-PDS systems from actual water sources. This work compares the performance, energy cost, and mechanism of PE-PMS and PE-PDS systems systematically. Hopefully, all of that is designed to tender a helpful reference for the choice of PS in piezocatalytic research and application.

Highly dispersed single-atom Fe and Fe3O4 clusters anchored hierarchical-pore carbon as efficient persulfate activation catalyst

The selective removal of Fe particles from carbonized Fe-MOFs presents an intriguing strategy for developing efficient peroxydisulfate (PDS) activators. It is commonly accepted that their outstanding performance is largely attributed to the high specific surface area/pore volume. However, our investigation into the structure–function relationship of these materials has revealed new insights. In this study, a highly dispersed single-atom Fe and Fe3O4 clusters anchored hierarchical-pore carbon (CM88-H) was obtained via post-acid treatment of carbonized MIL-88B (CM88). Various characterizations were comparatively conducted to highlight the beneficial effects of iron dissolution. The CM88-H/PDS system achieved a notable BPA degradation efficiency, with a reaction rate of 0.323 min−1, which is 3.94 times higher than that of the CM88/PDS system. DFT calculations indicate that the Fe3O4 clusters optimize the charge distribution around single-atom Fe, promoting favorable PDS adsorption and facilitating a higher oxidation state of CM88-H. As a result, BPA can be completely degraded within 10 min with 0.1 g/L CM88-H and 0.05 g/L PDS via both radical and non-radical pathways. The CM88-H/PDS/BPA system performs effectively under various conditions, with a general reduction in toxicity. Furthermore, the CM88-H/PDS system shows broad oxidation activity towards BPA substitutes and pollutants with high ionization potential (IP). Notably, the CM88-H sponge-based fixed-bed catalytic reactor demonstrated satisfactory BPA degradation, highlighting the promising application of CM88-H in water purification. This study provides a sustainable solution for water treatment and accelerates the practical application of powdered nanocatalysts to improve water quality.

Nanoconfined Cu clusters-activated peroxodisulfate for efficient wastewater decontamination via polymerization

In water treatment, the transition from mineralization to polymerization of organic pollutants is an essential step towards carbon and energy recovery. However, achieving efficient polymerization through the construction of heterogeneous catalysts remains a great challenge. In this work, we prepared Cu clusters nanoconfined in ZIF-derived carbon hollow structure to activate peroxodisulfate (PDS), achieving efficient wastewater decontamination via polymerization. The reaction rate is increased by a factor of 62. It shows excellent performance under different conditions (pH, anions, aqueous) as well as stability. Experiments and DFT calculations show that the removal of Bisphenol A was mainly by the direct oxidative transfer process, Cu–N and Cu clusters were involved in the catalytic oxidation. The removal of COD and TOC could reach 80% and 63.50%, respectively. This work provides technical support for the accelerated mechanism of oxidative polymerization during the treatment of toxic organic wastewater.

New insights into the PFAS defluorination performance and mechanism of ultrasound-enhanced electrochemistry with peroxydisulfate electrolyte

Ultrasound (US)-assisted electrochemical oxidation (EO) has previously demonstrated its ability to degrade perfluorooctanoic acid (PFOA). However, the mechanisms of direct electron transfer and indirect oxidation by reactive oxygen species (ROS), as well as the involvement of these ROS, are unclear, particularly with the peroxydisulfate (PDS) electrolyte and the added effect of US. In this study, an US/EO/PDS system was first investigated, achieving nearly 100 % and 80.01 % defluorination for PFOA and perfluorooctane sulfonate, respectively (within 3 h). This US/EO/PDS system exhibited remarkable stability, pH tolerance, and practicality. Further experimental and theoretical studies revealed that the predominant mechanism of PFOA defluorination was indirect oxidation via ROS, rather than direct oxidation at the anode. Although none of these ROS could initiate the degradation of PFOA without additional energy, both ROS (SO4∙- ＞ •OH ＞ 1O2 ＞ O2∙-) and US/EO contributed to the initial step of PFOA defluorination. Furthermore, US enhanced the generation of ROS and the direct oxidation (electron transfer) ability of EO. The electrons were transferred from PFOA to PDS via the electrode assembly. This study clarified, for the first time, the synergistic effect of US/EO/PDS and the involvement of direct and indirect ROS oxidation in defluorination of PFOA, which shows potential for developing US and EO technology for complete degradation of polyfluoroalkyl substances.

Assessing the discrepant role of anions in the transformation of reactive oxygen species in H2O2 and PDS system: A comparative kinetic analysis

Clarifying reactive oxygen species (ROS) variation in the presence of co-existing anions is significant for understanding the catalytic effect of magnetite (Fe3O4)-induced advanced oxidation processes (AOPs) in natural environment, yet this remains controversial. Herein, we compare the specific impacts of NO3-, SO42-, and Cl- on ROS (•OH, SO4•-, O2•-, and 1O2) exposure concentration in H2O2 and peroxydisulfate (PDS) systems, as well as how these variations affect the catalytic efficiency by developing kinetic model. In both two systems, NO3- demonstrates no discernible effect on ROS, whereas SO42- inhibits the exposure of all ROS and thus micropollutants degradation. Through theoretical calculation, it is proposed that SO42- primarily exerts its influence through affecting the electronic structure over catalyst surface. Regarding Cl-, it affects ROS exposure mainly by reacting with ROS. It shows inhibitory effect on 1O2 in both systems, but its suppressive impact on •OH is markedly more pronounced in H2O2 system compared to PDS system, which may be related to its rapid reactivity with SO4•-. Besides, the chlorine radicals (mainly ClO•) generated through the reaction of Cl- may exert a selective influence on micropollutants degradation. This study can help to re-understand the influence behavior of co-existing anions during AOPs.

Natural Vanadium–Titanium Magnetite Activated Peroxydisulfate and Peroxymonosulfate for Acid Orange II Degradation: Different Activation Mechanisms and Influencing Factors

Persulfate-based advanced oxidation processes have emerged as a promising approach for the degradation of organic pollutants in aqueous environments due to their ability to generate sulfate radicals (SO4−·) within catalytic systems. In this study, peroxydisulfate (PDS) and peroxymonosulfate (PMS) were investigated with the natural vanadium–titanium magnetite (VTM) as the activator for the degradation of acid orange II. The degradation efficiency increased with higher dosages of VTM or persulfate (both PDS and PMS) at lower concentrations (below 10 mM). However, excessive PMS (higher than 10 mM) in the PMS/VTM system led to the self-consumption of free radicals, significantly inhibiting the degradation of acid orange II. The VTM-activated PDS or PMS maintained an effective degradation of acid orange II in a wide pH range (3~11), suggesting remarkable pH stability. The SO4−· was the main active species in the PDS/VTM system, while hydroxyl radical (·OH) also contributed significantly to the PMS/VTM system. In addition, PMS exhibited better thermal stability during VTM activation. Coexisting ions in an aqueous environment such as bicarbonate (HCO3–), carbonate (CO32–), and hydrogen phosphate (HPO42–) had obvious effects on persulfate activation. Our study systematically investigated the different activation processes and influencing factors associated with PDS and PMS when the natural VTM was used as a catalyst, thereby providing new insights into the persulfate-mediated degradation of organic pollutants in aqueous environments.

Unique role of doped Mo into Fe-based catalyst to intensify peroxydisulfate activation for micropollutants degradation: Promote the conversion of SO4•- to FeIV = O

Herein, Fe/Mo-based composite catalyst (FeMo@CN) was synthesized to catalyze peroxydisulfate (PDS) for efficient bisphenol A (BPA) degradation. Within 1 h, the FeMo@CN/PDS system could degrade BPA fully (kobs = 0.12 min−1, which was 129 times higher than system without Mo introduction). Probe experiments and 57Fe Mossbauer indicated that BPA degradation was dominated by SO4•- and FeIV = O converted from SO4•- (Fe(II)-PDS → Fe(III)-SO4•-→FeIV = O-HSO4-). This finding broke down the boundary between radical and non-radical, proposing a new path from SO4•- to FeIV = O. As Density functional theory (DFT) calculations revealed, Mo in FeMo@CN promoted PDS adsorption and reduced generation energy barrier of SO4•- and FeIV = O, achieving a dual improvement. Besides, the stable and efficient BPA degradation in dynamic degradation experiment demonstrated the application potential of FeMo@CN. This work provides a novel method to solve blocked Fe(II)/Fe(III) cycle and re-reveals FeIV = O generation mechanism in SR-AOPs.

Copper-doped orange peel biochar activated peroxydisulfate for efficient degrading tetracycline: The critical role of C-OH and Cu

The usage of biomass waste has aroused great concern in water purification. In this study, copper-doped orange peel biochar (Cu-OPB) prepared by one-step carbonization was firstly used to activate peroxydisulfate (PDS) to eliminate tetracycline (TC). The optimized Cu-OPB showed great activation ability for PDS and could degrade 93.7% of TC at pH 9.07. The presence of H2PO4−, Cl−, and HCO3− did not affect the degradation, while HA and SO42− inhibited TC degradation. SO4•−, •OH and 1O2 were confirmed as the primary active oxygen species in the Cu-OPB/PDS system. Moreover, Cu and the C-OH functional groups on the surface of Cu-OPB played a critical role in the activation by accelerating the electronic migration between Cu-OPB and PDS in the catalytic system. 15 possible intermediate products were found and three feasible degradation pathways were proposed. The toxicity of aquatic organisms of TC was reduced. Furthermore, Cu-OPB could be used as an economically efficient and environmentally friendly catalyst for PDS activation to degrade organic pollutants.

Overturned doping inert Ce into mesoporous CuO for enhanced peroxydisulfate activation and bisphenols degradation

Transition metal oxides have been recently investigated as excellent catalyst for peroxydisulfate (PDS) activation, but suffers from slow redox cycle of metal species. In this work, a novel avenue for facilitating valence cycles of Cu2+/Cu+ was proposed by overturned doping inert Ce into mesoporous CuO. Increased formation of active sites (Cu-Ce interface) and oxygen vacancy was achieved, resulting in accelerated interfacial electron transfer and facilitated valence cycles of Cu2+/Cu+. The Ce-doped mesoporous CuO (CeCuOx) exhibited greatly enhanced activity toward PDS activation and efficient removal of different bisphenols in a wide pH working range. The degradation of bisphenols followed a nonradical oxidation pathway based on electron transfer process (ETP), and CeCuOx@PDS complex was proved to be the primary reactive species. The CeCuOx/PDS system exhibited good stability and superior catalytic performance in complicated water matrix, and would be a promising catalyst for wastewater purification. This work provides a new prospect for boosting the redox behavior of metal active sites for environmental remediation.

The optimized magnetic ball-hinged iron-based hydrothermal carbon for catalytic removal of pharmaceutical pollutant by different peroxides with mechanical sonolysis：Comparisons in performance, mechanism, and application

The application of micro/nano iron-carbon micro-electrolysis (ICME) coupling advanced-oxidation-processes has been overlooked. In this study, the optimal activation systems of the ball-hinged reduced-iron-based hydrothermal-carbons (rFCs, 0.02 g L−1) with micro/nano-ICME activating different peroxides (hydrogen peroxide (HP) or peroxo-disulfate (PDS), 0.75 mM) under low-frequency ultrasonic (US, 28 kHz) driving were constructed to rapidly remove >90 % antibacterial-gentian violet (genV), especially under protonation role within 15 min. The synthetic rFCs with different preparation conditions were selective towards different peroxides. After detection and kinetics calculation, besides •OH and high-valent iron-oxo species, the differently dominant active species between HP and PDS was SO4•−. During the removal of genV, the generated intermediate products existed differences as well, e.g., the possible emergence of dimers in activating PDS. Resumptively, the US mechanical excitation, the micro/nano-ICME effect, and the forced friction of micro/nano-motors (US to rFCs) all contributed to activating peroxides. Furtherly, the construction of the US/ICME/different peroxides by continuous flow reactor (k at 0.117−0.200 min−1) suggested the reliability of enlarging application. Overall, this study not only provided an efficient activation method of physical field-driven catalyst for water treatment but also presented the differential comparisons in mechanism and application between activating HP and PDS.

Conversion of waste paper sludge into magnetic biochar for activation of peroxydisulfate for tetracycline removal

ABSTRACT The Fe2+-peroxydisulfate (PDS) process is an effective method to enhance paper sludge dewaterability. However, the generated waste of iron-rich sludge cake needs to be disposed of properly. Converting sludge cake into magnetic biochar catalysts can help to shorten its environmental risks, recover resources, and reduce catalyst costs. In this work, the magnetic sludge biochar (Fe-SBC) was prepared and applied as a PDS activator to remove tetracycline (TC). Results showed that the Fe-SBC pyrolyzed at 600 °C presented excellent catalytic activity for PDS to degrade TC (rate of 74.89%) under the optimum conditions (intrinsic pH, 10 mM PDS, 0.5 g/L Fe-SBC, and 50 mg/L TC). It was found for the first time that the addition sequences of the biochar catalyst and PDS were insignificant on TC removal. Furthermore, the TC removal mechanism was proposed to be free radicals (·OH, SO4·−, and O2−·) and non-radical (1O2) pathways working together for TC removal, for which 1O2 was dominated. In addition, coexisting ions (Cl− and CO32−) had an inhibitory effect on TC degradation. This work will provide a new recycling approach for waste paper sludge in wastewater treatment.

Hydroxyl Defects-Mediated Hydrolytic Activation of Peroxydisulfate Under Nanoconfinement: Role of Lewis Basic Sites for Altering the Photosensitized Species and Pathways.

Herein, the pivotal mechanism of defect engineering-mediated triazine-based conjugated polymers (TCPs) is comprehensively elucidated for photosensitized activation of peroxydisulfate (PDS) under nanoconfinement by encapsulating the defective polymer framework into the nanochannel of SBA-15 (d-TCPs@SBA-15). The incorporated hydroxyl defects (-OH defects) substantially accelerate the accumulation of electrons at -OH defects, forming the Lewis basic sites. Due to the facilitated elongation of the S─O bond and reduced energy barrier of SO5* generation, the captured PDS undergo prehydrolysis process, oxidized into O2 - and 1O2 by surrounding h+, thereby setting apart from the conventional reductive activation of SO4 -/•OH generation occurred in pristine TCPs (p-TCPs). Crucially, this work represents a pioneering effort in exploring the PDS activation pathway upon the defective polymer under the nanoconfinement to leverage kinetic merits of slow photon effect and reactive oxygen species (ROSs) enrichment, and the novel prehydrolysis activation mechanism involved may catalyze the rational design of photocatalysts featuring Lewis-acid/base centers.

Enhanced synergistic catalysis of bisphenol A in river water using an anti-aging photocatalytic membrane

Bisphenol A (BPA), as an endocrine disruptor, poses a potential threat to ecosystems and human health in aquatic environments. Membrane catalytic systems can accelerate the degradation of BPA and facilitate its conversion into harmless compounds. Nevertheless, the complex nature of the water environments and the limited stability of catalysts often result in challenges such as catalyst aging and deactivation. Herein, an anti-aging multifunctional AgFeO2 catalytic material with electron transfer membrane support was prepared for synergistic catalysis of low-energy LED light (12 W) excitation and peroxydisulfate (PDS) activation. The anti-aging photocatalytic membrane completely degraded 10 ppm of BPA within 30 min, and did not show significant aging after the long-term synergistic catalytic process. In addition, actual river water was employed to assess the aging process and catalytic efficiency in a practical environment. A 60.79 cm2 photocatalytic membrane completely purified 10 L of BPA polluted river water, while the total organic carbon content decreased by 50 %. This was mainly due to the synergistic catalytic effect of the membrane, which boosted photoelectron transfer through electron transfer shortcuts, thereby enhancing persulfate activation. Overall, the multifunctional membrane provides an effective strategy for achieving a long-lasting catalytic effect and controlling photocatalyst aging in practice.

Sonocatalytic degradation of furazolidone using a heterogeneous triple ion synergy system of ZnFe2O4@ZIF-67 nanostructures: Physicochemical Characterization and degradation pathway

Heterogeneous sonocatalysis coupled with peroxydisulfate (PDS) activation is considered as a rapid advanced oxidation process for the degradation of emerging pharmaceutical pollutants. ZnFe2O4@ZIF-67 nanostructures (NSs) with commendable features including a high crystallinity, a narrow bandgap, and an outstanding specific surface, showed excellent sonocatalytic performance, PDS activation and stability. A novel triple ion synergistic system was used for the swift degradation of 60 mg/L furazolidone (FZD) from real contaminated water sources. A superior sonocatalytic degradation performance of FZD (94 %) by ZnFe2O4@ZIF-67/PDS/Ultrasound system was achieved under the optimal conditions of 20 mmol/L PDS and 0.4 g/L of the nanocomposite within 60 min. The e-/h+ pairs produced as a result of the sonoluminescence phenomenon in the ZnFe2O4@ZIF-67 NSs, with a bandgap of 1.86 eV, accelerated the redox reduction transform cycle of the Zn2+ /Zn, Fe3+/ Fe2+ and Co3+/ Co2+ pairs by generating a large number of oxidative radicals, leading to the enhanced degradation efficiency. Quenching tests illustrated that SO4•-,1O2, •OH radicals and surface oxidation–reduction reactions played a crucial role during FZD degradation. FZD degradation by-products were put forward using the LC-MS technique, and a plausible degradation pathway was suggested. The mineralization tests and the toxicity of generated intermediates of FZD degradation were also examined. Also, the stability and reusability results underscored the substantial proficiency of the above system to remediate real-pharmaceutical-contaminated-water sources, providing a practical approach for its industrial applications.

Bimetal-organic framework derived single-atom-like Co/Fe catalysts for peroxydisulfate activation: The dual amplification of radical and nonradical pathways

A novel single-atom-like Co/Fe catalyst (i.e., Co/Fe-N-C) was synthesized by pyrolysis of a Zn/Co/Fe zeolitic imidazolate framework, and applied in peroxydisulfate (PDS) activation for removal of organic contaminants from wastewater. The isolated diatomic metal-nitrogen sites were detected by X-ray adsorption fine-structure. The degradation of four contaminants (i.e., phenol, bisphenol A, 2,4-dichlorophenol, and N-methyl-2-pyrrolidone) with a concentration of 100 mg/L could be degraded separately within 20 min by the Co/Fe-N-C system with 10 mmol/L of PDS, 0.5 g/L of catalyst dosage, and initial pH of 3. Besides, 79.2 % of phenol could be mineralized in 120 min, and the turn-over frequency value of the catalyst was calculated to be 27.17 min−1, which was higher than the commonly reported homogeneous PS-AOPs. Moreover, the Co/Fe-N-C exhibited high stability (mineralization rate over 70 % after 5 cycles), a wide initial pH range (3−9), and high catalytic performance at 5–20 mmol/L of PDS concentrations. Based on the analysis of radical scavenging experiments and electron spin resonance spectra, the radical and non-radical pathways for PDS activation were proved in the system, and the contribution of phenol degradation by each pathway was clarified.

Integration of a 3D-printed electrochemical reactor with a tubular membrane photoreactor to promote sulfate-based advanced oxidation processes

This study investigates the integration of an in-house 3D printed electrochemical cell − SERPIC-UCLM® cell – for the in situ generation of peroxymonosulfuric acid (PMSA) witha lab-scale tubular membrane photoreactor (TMPr) to evaluate the effectiveness of sulfate-radical advanced oxidation processes (SR-AOPs) in eliminating contaminants of emerging concern (CECs) from reverse osmosis and nanofiltration concentrates (ROC and NFC, respectively). First, the SERPIC-UCLM® cell was evaluated in terms of mass transport features employing the limiting current technique, demonstrating favorable volumetric mass transport rates (kmA ∼ 10–3 s-1) and Sherwood values (Sh > 300) under the laminar regime (110 < Re < 790). Afterwards, the effect of the electrolyte (sulfuric acid, H2SO4) initial pH in the electrochemical generation of PMSA was studied, with an initial pH of 1 selected as optimal. PMSA is a highly reactive peroxyacid that undergoes self-decomposition at neutral pH mediums (e.g., ROC and NFC with a pH of 7.6 and 7.9, respectively), primarily existing in the form of peroxomonosulfate (PMS). Additionally, the phototreatment of the ROC and NFC was assessed using the electrogenerated PMS and commercial peroxydisulfate (PDS) under the same conditions. The results indicated comparable degradation patterns for CECs in both ROC and NFC. Furthermore, the application of 2.4 mM PMS resulted in removals higher than 60 % for 7 of the 11 CECs identified in the NFC, and ensured compliance with wastewater discharge regulations for pH, chemical oxygen demand (COD), and total suspended solids (TSS) levels. These findings emphasize the importance of this technology, showing its advantages in terms of versatility and logistics.

Self-Assembled Ultra-Long Hybrid Nanowire Formed by Simple Mixing: An Untapped Feature of Peroxydisulfate.

Peroxydisulfate (PDS), a popular molecule that is able to oxidize organic compounds, is garnering attention across various disciplines of chemistry, materials, pharmaceuticals, environmental remediation, and sustainability. Methylene blue (MB) is a model pollutant that can be readily oxidized by PDS-derived radicals. Unlike the conventional degradation process, here a reversible "dissolution-precipitation" phenomenon is discovered, triggered by a simple mixing of PDS and MB, revealing a novel application of PDS in fabricating self-assembled ultra-long nanowires with MB. This phenomenon is unique to PDS and MB, different from the traditional salting out or self-aggregation of dyes. Formation of nanowires facilitated by electrostatic interaction between S+ and O- moieties and π-π stacking is reversible, controlled by temperature and the solvent polarity. MB1-PDS-MB2 configuration (MB: PDS = 2:1) is theoretically predicted by density functional theory (DFT) calculations and further validated by stoichiometric ratios of carbon, sulfur, and nitrogen in the obtained precipitates (MBO). This untapped feature of PDS enables the development of colorimetric quantitative detection of PDS and sustainable dye recycling. Far more than those demonstrated cases, the potentialities of MBO as a nanomaterial merit further exploration.