Removal Of Organic Pollutants Research Articles

Sulfur-doped CuCo2O4 as a PMS activator: The synergy of oxygen defects and strong Lewis acid sites in boosting the elimination of ciprofloxacin

Herein, the synthesis of sulfur-modified CuCo2O4 (S-CuCo2O4) nanoparticles as a heterogeneous catalyst for peroxymonosulfate (PMS) activation was reported. The S-CuCo2O4 maintained the spinel structure and exhibited rich oxygen vacancies. Also, the presence of S atoms enlarged the specific surface area and created strong Lewis acid sites that both enhanced the adsorption ability toward PMS and CIP. Compared to the corresponding S-doped single oxides and CuCo2O4, the S-CuCo2O4 with the designed molar ratio of S and metal ions to be 10%, i.e., CCS-10, significantly improved the catalytic activity, indicating the synergism between Cu-O-Co bonds, the oxygen vacancies, and the Lewis acid sites. Under the optimal conditions of 0.1g.L-1 CCS-10 dosage, 0.2g.L-1 PMS, and natural pH, the CCS-10/PMS system could remove approximately 87% of CIP and 70% of TOC within 20min at a four-time higher rate than that of the pristine catalyst. This system showed the highest performance in the pH range from weak acidic to weak basic (pH 5.5 - pH 8.5). CCS10/PMS also displayed considerable efficiency in degrading various pollutants belonging to different categories (methylene blue (MB), carbamazepine (CBZ), bisphenol A (BPA), and sulfamethoxazole (SMX)). SO4•–, •OH, O2•–, and 1O2 active species were found to be responsible for CIP elimination. Finally, the PMS residual concentration was recorded to be 0.01g.L-1 after the reaction. Overall, this study could contribute a possible strategy to enhance the heterogeneous catalysts for the removal of organic pollutants.

Full-spectral response of mesoporous Z-scheme nanoheterojunction NaYF4:Yb,Tm@ZnO/BiOI photocatalysts for simultaneous contaminant and pathogen elimination in wastewater

The increasing contamination of water bodies demands effective and economical solutions for wastewater treatment. This study introduces a novel Z-scheme photocatalyst, NaYF4:Yb,Tm@ZnO/BiOI (UZB), synthesized via a simple chemical route. UZB exhibits exceptional photocatalytic degradation efficiencies of 95.1%, 88.7%, and 56.3% for methyl orange under full spectrum, visible, and near-infrared light, respectively. The integration of heterostructures within UZB promotes efficient charge carrier separation, significantly boosting its photocatalytic activity. When applied to actual wastewater, UZB markedly reduces chemical oxygen demand (COD) and total organic carbon (TOC) by 94.1% and 53.2%, respectively, and also effectively decreases turbidity and ammonia concentrations. Additionally, UZB shows strong antibacterial effects against S. aureus and E. coli, with inhibition rates of 93.9% and 92.0%, though some cytotoxicity is noted. These results underscore UZB's potential as a highly efficient photocatalyst for the simultaneous removal of organic pollutants and pathogens from wastewater, supporting its application in industrial water treatment systems.

Enhanced simazine degradation via peroxymonosulfate activation using hemin-doped rice husk biochar as a novel Fe/N–C catalyst

The presence of herbicides, including simazine (SIM), in aquatic environments pose significant threats to these ecosystems, necessitating a method for their removal. In this study, a hemin-doped rice husk-derived biochar (RBC@Hemin20%) was synthesized using a simple, one-step pyrolysis, and its degradation efficiency towards SIM via peroxymonosulfate (PMS) was assessed. Under optimized conditions (hemin loading = 20 wt%, SIM = 0.5 ppm, RBC@Hemin20% catalyst = 0.2 g L−1, PMS = 2.0 mM, and pH = 5.84 [unadjusted]), RBC@Hemin20%, as an Fe/N–C catalyst, could activate PMS to achieve >99% degradation of SIM. Based on radical scavenger and electron spin resonance spectroscopy (ESR) experiments, both radical (•OH and SO4•−) and non-radical (such as singlet oxygen, 1O2) mechanisms and electron transfer were involved in the degradation system. Significant mineralization (97.3%) and reusability efficiency (∼74.1% SIM degradation after 4 applications) were exhibited by the RBC@Hemin20%/PMS system, which also maintained a remarkable degradation efficiency in tap-, river-, and ground-water. Additionally, the RBC@Hemin20%/PMS system exhibited rapid degradation of tetracycline (TC) and diclofenac (DCF), indicating its prospects in the degradation of other organic pollutants of aquatic environments. The plausible degradation mechanism pathways of SIM are proposed based on identified intermediates. Finally, the toxicity of these intermediate products is analysed using the Ecological Structure Activity Relationship (ECOSAR) software. It is expected that this study will expand the current knowledge on the synthesis of efficient biomass-based Fe/N–C composites for the removal of organic pollutants in water.

Selective degradation of organic pollutants in the aquatic environment by microplastic-derived dissolved organic matter through molecular photoresponse sequence transformation

The photochemical behavior of microplastics (MPs)-dissolved organic matter (PDOM) has received considerable attention, the molecular mechanism by which it undergoes photoresponsive transformation to generate reactive oxygen species (ROS) for the removal of organic pollutants remains unclear. This study combines fluorescence, mass spectrometry, and theoretical models to analyse the differences in the molecular mechanisms of PDOM, biochar-DOM (BDOM) and soil-DOM (SDOM) photoresponsive releasing ROS for selective degradation of organic pollutants. During the photoresponse process, molecular compounds in DOMs mainly undergo demethylation, decarboxylation, deoxygenation reactions to selectively degrade organic pollutants. However, differences in DOMs’ molecular structure composition and transformation patterns lead to varying ROS production. BDOMs containing higher proportion of aromatic compounds (26.68 %) exhibit stronger photoreactivity, resulting in better degradation efficiency of pollutants (>90 %). The high selectivity of PDOM for degradation of organic pollutants stems from the interconversion mode between its high and low oxygen compounds. PDOM degrades large molecular pollutants into less biotoxic small molecular intermediates through both radical and non-radical pathways, thereby reducing environmental hazards (1.5–948 times) posed by pollutants. The results show that although MPs is harmful to aquatic environment, it plays a positive role in regulating the structure of organic carbon pool and reducing environmental risks of other pollutants.

Construction of Visible light Driven Z-Scheme 1D/1D p-CuBi2O4/n-CdWO4 Heterojunction Nanocomposite for Effective Degradation of Organic Pollutants

The effective separation and harnessing of photoinduced charge carriers in photocatalysis are significant challenges. The present study aims to overcome this obstacle by developing a Z-Scheme heterojunction between a p-type CuBi2O4 (CBO) and a n-type CdWO4 (CWO) through a straightforward heat treatment method. The powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and High-resolution transmission electron microscopy (HRTEM) results revealed the successful formation of heterostructures. The photocatalytic efficiency of the materials was assessed by selecting an anionic methyl orange (MO) and cationic Rhodamine-B (Rh-B) dyes under visible light irradiation. Among all the materials, 85 wt.% CBO+ 15 wt.% CWO (CBO/CWO-15) heterostructure exhibited superior photocatalytic activity (90%) corresponding to 90 and 45 times higher than the pristine CBO and CWO, respectively. The positively charged photocatalyst surface attracts a greater number of MO dye molecules than Rh-B, thereby enhancing the degradation of MO over Rh-B. The scavenger results confirmed the involvement of hydroxy ( and superoxide () radicals in the degradation of MO. The rate constant of CBO/CWO-15 (0.01061 min-1) was 64 and 39 times higher than those of CBO (0.00016 min-1) and CWO (0.00027 min-1), respectively. The photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) analyses substantiated the improved charge separation in the CBO/CWO-15 composite, establishing the Z-scheme mechanism. Cycling experiments over four cycles demonstrated consistent stability of the CBO/CWO-15 composite. The study provides an in-detail plausible mechanism of MO degradation. This type of Z-scheme composite material has potential applications in environmental remediation for the effective removal of organic pollutants and antibiotics from wastewater.

Higher-valent nickel oxides with enhanced two-electron oxygen reduction in advanced electro-Fenton system for organic pollutants degradation

A higher-valent NiO catalyst, enriched with trivalent Ni (Ni3+) and exposed {111} crystal facets, was developed to enhance selective two-electron oxygen reduction (2e– ORR) for electrochemical hydrogen peroxide (H2O2) production, leading to highly efficient organic pollutant removal. The catalyst was synthesized via a precipitation method, incorporating crystal facet and cation vacancy engineering to expose active sites. It demonstrated 96 % selectivity and 59 A g−1 mass activity, attributed to weakened *OOH binding, as shown by density functional theory. Integrated into an advanced electro-Fenton (EF) flow cell, the system achieved 100 % removal of 200 mL of 50 ppm bisphenol A (BPA) in 4 minutes, with 93 % total organic carbon removal within 2 hours. This study provides a scalable and efficient solution for decentralized environmental remediation and wastewater treatment.

Biodegradation of <i>n</i>-Alkanes in Oil-Contaminated Bottom Sediments under Bioelectrochemical Stimulation

Degradation of oil hydrocarbons artificially introduced into bottom sediments in a bioelectrochemical system of a membrane-free (silt) type was studied. Passive bioelectrochemical stimulation by means of electrodes connected by an external circuit with a resistance of 1 kΩ, with an average electric current of ~85 µA was found to cause an increase in degradation during two months from 23.0 to 57.9%. Contamination of bottom sediments with oil (1.32 g/kg) slightly decreased the current in the external circuit of the bioelectrochemical system. The relationship was revealed between the degree of oil degradation and predominant utilization of the lighter n-alkanes in the C14H30–C30H62 series, compared with both the original oil and the residual hydrocarbons of the control. An increase in the representation of the alkB alkane monooxygenase genes relative to the 16S rRNA gene in the total DNA isolated from the sediments was induced by the introduction of hexadecane, both in the case of electrochemical stimulation and in the control. The results may be of interest for the development of new methods of bioelectrochemical removal of organic pollutants from anaerobic environments.

Using Nanozymes in the Removal of Persistent Organic Pollutants from Water Environments

The Article Abstract is not available.

Porous polylactide membranes with high piezo-catalytic efficiency for organic wastewater treatment

Piezo-catalysis has been emerged as a green and promising wastewater treatment technology for efficient removal of persistent organic pollutants (POPs), such as 4-nitrophenol (4-NP). However, it remains challenging to achieve advanced materials with combined advantages of high piezo-catalytic efficiency, good hydrophilicity, and environmental friendliness. In this work, highly crystalline porous polylactide (PLA) membranes possessing such exceptional advantages have been successfully prepared from biodegradable poly(L-lactide)/poly(D-lactide)/polyethylene glycol/polyoxyethylene-polyoxypropylene block copolymer (PLLA/PDLA/PEG/PEO-PPO-PEO) blends by melt processing and subsequent water etching. During the melt-processing, the two PLA enantiomers co-crystallize into stereocomplex (SC) crystals and simultaneously the PEG used as a porogen is expelled from the crystalline regions. The results show that the prepared PLA membranes have not only abundant micro-porous structures but also good hydrophilicity due to the preferential localization of PEO-PPO-PEO copolymer on the pore walls, thus giving rise to an extremely high water flux of 2400 L/m2h. More interestingly, the PLA membranes exhibit remarkable piezoelectric activity and the piezo-catalytic degradation efficiency of 4-NP can reach as high as 96 % under the triggering of water flow involved in vacuum filtration. In addition, the membranes show excellent reusability and the high catalytic efficiency can be well-maintained after five repeated uses. These findings suggest broad application prospects of our porous SC-PLA membranes in organic wastewater treatment.

Insight into the nonradical selective oxidation mechanism for versatile organic pollutants removal by perovskite activated peroxymonosulfate system

The heterogeneous catalysis of peroxymonosulfate (PMS) through nonradical pathway has shown many advantages in environmental remediation. It is necessary to unveil the factors affecting oxidation routes and selectivity toward different organic pollutants. Herein, a series of ABO3-type BiFexCo1-xO3 perovskite catalysts were fabricated via simple hydrothermal process to realize the changeover of catalytic activity and mechanism in PMS activation and pollutants oxidation. The as-prepared BiFe0.5Co0.5O3 (BFCO-3) achieved a 98 % removal efficiency of SMZ with a high kinetic constant (kobs = 0.334 min−1) in 10 min. The superior catalytic performance was ascribed to the introduction of bimetals at B-site, which enhanced electron donating capacity to PMS, confirming by d-band center calculations. Several parameters such as inorganic anions and humic acids affected the SMZ degradation slightly, owing that singlet oxygen was verified to be the primary reactive species in the BFCO-3/PMS system. Moreover, twelve organic pollutants including amoxicillin crystalline (AMX), cephalexin hydrate (CFX), ciprofloxacin (CIP), levofloxacin (LFX), Sulfadiazine (SDZ), sulfamethoxazole (SMZ), 4-acetamidophenol (ACP), benzoic acid (BA), bisphenol A (BPA), carbamazepine (CBZ), metronidazole (MNZ) and naproxen (NPX) were utilized to investigate the selective oxidation mechanism. A linear correlation between lnkobs and their half-wave potential (φ1/2) values (except for BA and MNZ) suggesting the dominant role of nonradical catalysis where phenolic compounds with lower anodic potential tend to lose electrons are more easily degraded. Furthermore, the reactive sites of representative SMZ for electrophilic species attack were precisely identified based on the Fukui index. And the degradation intermediates of SMZ were further determined by LC-MS/MS technology for proposing their degradation pathway and predicting ecotoxicity. This study not only provides an efficient advanced oxidation system for organic pollutants removal but also advances our understanding of the selective oxidation mechanism in nonradical-dominated catalytic process.

High-strength TiO2/TPU composite fiber based textiles for organic pollutant removal

Effective integration of nanostructured photocatalysts into polymer matrices is crucial for the broad practical application of fiber-based photocatalytic composite textiles. Herein, highly durable TiO2/TPU composite fibers with high TiO2 content (>30 wt. %) were prepared through wet spinning using 1D electrospun TiO2 nanofibers (TNFs). Due to the fiber reinforcement principle, the TNF/TPU composite fibers exhibited superior mechanical properties compared with pure TPU fibers. Furthermore, the TNF/TPU composite fibers with a ratio of 1:2 process impressive degradation efficiency for rhodamine B (RhB). The orientation of 1D TNFs and stronger interface between TNF and TPU matrices not only enable the excellent load sharing and transfer effects following fiber pullout and crack bridging mechanisms, but also improve photogenerated charge transfer efficiency, resulting in high strength and high photocatalytic activity. In addition, enhanced TNF exposure on the fiber is due to the hollow and porous structures of composite fibers, which is advantageous for photocatalytic degradation. Notably, when the RhB concentration exceeded 15 ppm, the TNF/TPU composite fibers exhibited higher degradation efficiency than the TNF powder. Therefore, TNF/TPU composite fiber–based textiles with high photocatalytic activity and strength are promising for overcoming the separation and recovery issues of nanostructured catalysts in practical wastewater treatment applications.

Proton vs Electron: The Dual Role of Redox-Inactive Metal Ions in Permanganate Oxidation Kinetics.

Redox-inactive metal-ion-driven modulation of the oxidation behavior of high-valent metal-oxo complex has garnered significant interest in biological and chemical synthesis; however, their role in permanganate (Mn(VII)) oxidation for the removal of organic pollutants has been largely neglected. Here, we uncover the impact of six metal ions (i.e., Ca2+, Mg2+, Ni2+, Zn2+, Al3+, and Sc3+) presenting in water environments on Mn(VII) activity. These ions uniformly boost the electron and oxygen transfer capabilities of Mn(VII) while impeding proton transfer, as evidenced by electrochemical tests, thioanisole probe analysis, and the kinetic isotope effect. The observed effects are intricately linked to the Lewis acidity of the metal ions. Further mechanistic insights reveal that Mn(VII) can interact with metal ions without direct reduction. Such interactions modify the electronic configuration of Mn(VII) and create an acidic microenvironment, thus increasing its electrophilicity and the energy barrier for the abstraction of proton from organic substrates. More importantly, the efficacy of Mn(VII) in removing phenolic pollutants is regulated by these ions through changing the driving force for proton and electron transfer, i.e., facilitated at pH > 4.5 and inhibited at lower pH. The contribution of active Mn intermediates is also discussed to reveal the oxidative mechanism of the metal ion/Mn(VII) system. These findings not only facilitate the rational design of Mn(VII) oxidation conditions in the presence of metal ions for water decontamination but also offer an alternative paradigm for enhancing electrophilic oxidation.

Advancing Photocatalysis: Insights from 2D Materials and Operational Parameters for Organic Pollutants Removal

Advancing Photocatalysis: Insights from 2D Materials and Operational Parameters for Organic Pollutants Removal

Selective elimination of organic pollutants and analysis of effects and novel mechanisms of aged microplastics on wavelength-dependent UV-LED/H2O2 system

The selective removal of organic pollutants and potential impact of aged microplastics (MPs) as emerging pollutants in wavelength-dependent UV-LED/H2O2 system are not fully understood. This study found that cefalexin (CFX) degradation efficiency in UV-LED alone system was highly correlated with its UV molar absorbance (R2=0.994), while in UV-LED/H2O2 system, it was correlated with ·OH yield (R2=0.991) across various wavelengths. Quantitative structure-activity relationship (QSAR) analysis showed selective degradation of six pollutants based on their e--donating capabilities (R2=0.748–0.916). The coexistence of aged MPs, introducing C-O/C=O groups and rearranging their surface e-, potentially affected the elimination efficiency of CFX. Aged polystyrene (PS) decreased the degradation efficiency of CFX by shorting the O-O bond length (lO-O) in H2O2 and capturing e- from H2O2, whereas aged polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) had negligible effects as the lO-O elongation balanced the e--donating effect of H2O2. Additionally, phenol released from aged PS, with strong nucleophilicity, competing with CFX for ·OH, further decreasing CFX degradation efficiency. This study provides valuable insights into organic pollutant selective removal and reveals a novel inhibitory mechanism of aged PS on the performance of UV-LED/H2O2 technology.

Sulfur vacancies-engineered CaIn2S4 microspheres for enhanced photocatalytic organic pollutant and antibiotic removal

It is an interesting research topic on construction of defect- rich structures to enhance the performance of photocatalysts. In this study, CaIn2S4 photocatalyst containing sulfur vacancy was successfully synthesized using a straightforward solvothermal method. The sulfur vacancy concentration in CaIn2S4 was controlled by adjusting the amount of thioacetamide added during preparation. Among the prepared samples, CaIn2S4-10 sample with excellent photocatalytic performance exhibits superior degradation efficiency (98.2 %) within 50 minutes when the initial methyl orange (MO) concentration was 20 mg/L. Similarly, it shows the highest degradation performance (94 %) against the antibiotic tetracycline hydrochloride (TCH) (20 mg/L). The phase structure, surface element composition, optical properties and other characteristics of the prepared samples were systematically investigated. The findings demonstrate that the CaIn2S4-10 sample exhibits a decreased band gap width and a negatively shifted conduction band position, which enhances its reduction ability and improves its photocatalytic activity.

Enhanced Pollutant Removal and Antifouling in an Aerobic Ceramic Membrane Bioreactor with Bentonite for Pharmaceutical Wastewater Treatment.

This study examined the impact of adding bentonite clay (concentration of 1.5 to 10 g/L) to a pilot-scale aerobic ceramic membrane bioreactor (AeCMBR) for treating pharmaceutical wastewater (PhWW). The hydraulic retention time (HRT) was maintained at 24 h; the dissolved oxygen was between 2 mg/L (on) and 4 mg/L (off) throughout operation. Organic and nitrogen pollution removal rates and heavy metal (Cu, Ni, Pb, Zn) reduction rates were assessed. The chemical oxygen demand (COD) removal efficiency exceeded 82%. Adsorption improved ammonia (NH4+) removal to 78%; the addition of 5 g of bentonite resulted in a 38% improvement compared with the process without bentonite. The average nitrate concentration decreased from 169.69 mg/L to 43.72 mg/L. The average removal efficiencies for Cu, Ni, Pb and Zn were 86%, 68.52%, 46.90% and 56.76%, respectively. Bentonite at 5 g/L significantly reduced membrane fouling. The cost-benefit analysis enabled us to predict that the process will meet the multiple objectives of durability, treatment performance and economic viability. The combination of an AeCMBR and bentonite adsorption has proven to be a valuable solution for treating highly polluted wastewater.

Non-radical activation of peracetic acid by Fe-Co sulfide modified activated carbon for the degradation of refractory organic matter

Recently, the non radical activation system had attracted much attention due to its strong anti-interference ability. In this study, a novel FeCo2S4/activated carbon (AC) catalyst was prepared and used to construct a non radical dominated degradation system. Due to the electron-donating groups (C-OH) of AC and the conversion of free radicals generated from the activation of PAA by iron (Fe) and cobalt (Co) ions, a large amount of singlet oxygen (1O2) were produced, making the activation system possessed excellent universality and applicability for the removal of organic pollutants. Within 5 min, about 89.87 % of tetracycline hydrochloride (TCH) was removed in FeCo2S4 /AC + PAA. After only 20 min of reaction, the TCH removal efficiency reached 94.12 %, accompany with the reaction rate reached 0.099 min−1. Other organic pollutants including ibuprofen (IBU), sulfamethoxazole (SMX), ciprofloxacin (CIP), p-nitrophenol (PNP) and atrazine (ATZ) were also efficiently removed within 20 min, with the removal efficiencies were 92.0 %, 91.5 %, 89.4 %, 88.3 %, and 84.5 %, respectively. When the solution pH changed from 5.01 to 9.48, FeCo2S4 /AC also showed excellent catalytic performances, with the TCH removal rates were maintained at over 85.18 %. Moreover, the removal rate of TCH still reached 90.23 % after 5 recycles. This study offered an efficient non-radical peracetic acid (PAA) activation system, which can be effectively used to degrade refractory organic pollutants from complex water environment.

Fabrication of modified Sb2O3 nanospheres for the removal of hazardous malachite green organic pollutant and selective NO2 gas sensor

Sb2O3 and Ni modified Sb2O3 (Ni–Sb2O3) nanospheres were synthesized using low cost co-precipitation method and characterised using various instrumental methods such as X-ray Powder Diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared (FT-IR) spectroscopy. The XRD pattern reveals cubic crystal lattice. The average size of Sb2O3 and Ni–Sb2O3 nanoparticles was calculated to be around 41 nm and 29 nm, respectively. The HR-TEM investigation of the Sb2O3 nanomaterial reveals homogeneous spherical balls with a fine dispersion. The random-shaped nanoparticles with porous surfaces and voids were revealed by SEM. EDS examination confirms the elemental composition of Sb (41.79 %) and O (58.21 %) in Sb2O3 and Sb (36.80 %), O (58.95 %), and Ni (4.25 %) in Ni–Sb2O3. Sb2O3 and Ni– Sb2O3 exhibit band gaps of 3.67 eV and 3.51 eV, respectively, according to UV–Vis analysis. The IR peaks 445.47, 642.18, and 745.18 in Sb2O3 and 438.72, 645.07, and 756.92 in Ni– Sb2O3 support the Sb–O bonding in the synthesized nanomaterials. The synthesized nanomaterials have been used for photocatalytic degradation of malachite green (MG) dye and sensing NO2, SO2, CO2, petroleum vapour and LPG gases. The MG dye was degraded 97.67 % in 120 min using Ni–Sb2O3 at optimized conditions (catalyst dose: 0.1 g/L to 0.3 g/L, pH: 7 and MG dye: 10 ppm). The gas sensing study showed that Ni–Sb2O3 sensor has greater sensitivity and selectivity for NO2 gas.

Selective oxidation of organic pollutants by unactivated and carbonate-activated peroxymonosulfate (PMS): Mechanism, kinetics, and transformation pathway

Although the activation mechanisms of peroxymonosulfate (PMS) by various homogeneous and heterogeneous catalysts have been reported, the chemistry of PMS in catalyst-free systems and its interaction with background oxygenated anions remains poorly understood. In this study, the unactivated PMS and carbonate-activated PMS (CO32–/PMS) systems for removal of various organic pollutant (including oxytetracycline (OTC), metronidazole (MNZ), methylene blue (MB), and acid orange G (OG)) were investigated. The results showed that 74.5 %, 90.21 %, 1.22 %, and 2.25 % of OTC, MB, OG, and MNZ were removed, respectively within 180 min in the unactivated PMS system due to the formation of ·OH and 1O2. 95.88 %, 100 %, 100 %, and 6.09 % of OTC, MB, OG, and MNZ were removed, respectively in the CO32–/PMS system, which is primary due to the generation of 1O2. The removal efficiencies of these four pollutants were significantly improved under alkaline conditions. In addition, the TOC removal rates were 21.88 % for MB and 26.53 % for OTC within 180 min in the CO32–/PMS system. The presence of Cl− and SO42− can greatly enhance the OTC removal efficiency both in the unactivated and CO32–/PMS systems. Through the high performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, OTC degradation products in the unactivated PMS and CO32–/PMS systems were identified, revealing six different reaction mechanisms, including hydroxylation (+16 Da), decarbonylation (−28 Da), demethylation (−14 Da), secondary alcohol oxidation (−2 Da), deamination (−15 Da), and dehydration (−18 Da). This study provides insight into the reaction mechanism of catalyst-free PMS systems and may promote the application of unactivated PMS and CO32–/PMS systems for the remediation of organic contaminated water.

Simultaneous desalination and removal of organic pollutants in a novel bifunctional FCDI system: The enhancement by in-situ reutilization of chloride ions

A new system of flow electrode capacitive deionization coupled with in situ electro-oxidation (FCDI-EO) was constructed to achieve the degradation of organic pollutants while maintaining high desalination efficiency. The effects of different parameters of potential difference, electrolyte, and pH on the chloride removal performance of FCDI-EO and the removal performance of rhodamine B (RhB) were investigated. Under the optimal conditions of potential difference = 4 V, [Cl−] = 500 mg/L, and pH = 4, the removal of chloride ions, RhB and total organic carbon (TOC) was as high as 88.74 %, 99.02 %, and 87.82 %, respectively. The quenching experiments showed that hydroxyl radicals (OH) and reactive chlorine species (RCS) were involved in the FCDI-EO system. The liquid chromatography-mass spectrometry (LC-MS) analysis suggested the possible mineralization pathway of RhB. Furthermore, toxicity assessment analysis showed that the toxicity of the degradation intermediates of RhB decreased during the treatment. Overall, this study provides a promising process that reducing the generation of high-concentration saline water in desalination and in situ utilizing the Cl− gathered from the feed water. The findings of this study could provide useful guidance for the development of flow electrode capacitive deionization technology and organic pollutant control.