Catalytic degradation of recalcitrant pollutants by Fenton-like process using polyacrylonitrile-supported iron (II) phthalocyanine nanofibers: Intermediates and pathway

Bio-electrochemical degradation of carbamazepine (CBZ): A comprehensive study on effectiveness, degradation pathway, and toxicological assessment

Recent attention on the detrimental effects of pharmaceutically active compounds (PhACs) in natural water has spurred researchers to develop advanced wastewater treatment methods. Carbamazepine (CBZ), a widely recognized anticonvulsant, has often been a primary focus in numerous studies due to its prevalence and resistance to breaking down. This study aims to explore the effectiveness of a bio-electrochemical system in breaking down CBZ in polluted water and to assess the potential harmful effects of the treated wastewater. The results revealed bio-electro degradation process demonstrated a collaborative effect, achieving the highest CBZ degradation compared to electrodegradation and biodegradation techniques. Notably, a maximum CBZ degradation efficiency of 92.01% was attained using the bio-electrochemical system under specific conditions: Initial CBZ concentration of 60 mg/L, pH level at 7, 0.5% (v/v) inoculum dose, and an applied potential of 10 mV. The degradation pathway established by identifying intermediate products via High-Performance Liquid Chromatography-Mass Spectrometry, revealed the complete breakdown of CBZ without any toxic intermediates or end products. This finding was further validated through in vitro and in vivo toxicity assays, confirming the absence of harmful remnants after the degradation process.

Efficient elimination of carbamazepine using polyacrylonitrile-supported pyridine bridged iron phthalocyanine nanofibers by activating peroxymonosulfate in dark condition

The monoaminotrinitro iron phthalocyanine (FeMATNPc) is used to connect with isonicotinic acid (INA) for amide bonding and axial coordination to synthetic a unique catalyst FeMATNPc-INA, which is loaded in polyacrylonitrile (PAN) nanofibers by electrospinning. The introduction of INA destroys the π-π conjugated stack structure in phthalocyanine molecules and exposes more active sites. The FeMATNPc-INA structure is characterized by X-ray photoelectron spectroscopy and UV-visible absorption spectrum, and the FeMATNPc-INA/PAN structure is characterized by Fourier transform infrared spectroscopy and X-ray diffraction. The FeMATNPc-INA/PAN can effectively activate peroxymonosulfate (PMS) to eliminate carbamazepine (CBZ) within 40 minutes (PMS 1.5 mmol/L) in the dark. The effects of catalyst dosage, PMS concentration, pH and inorganic anion on the degradation of CBZ are investigated. It has been confirmed by electron paramagnetic resonance, gas chromatography-mass spectroscopy and free radical capture experiments that the catalytic system is degraded by •OH, SO4•- and Fe (IV) = O are the major active species, the singlet oxygen (1O2) is the secondary active species. The degradation process of CBZ is analyzed by ultra-high performance liquid chromatography-mass spectrometry and the aromatic compounds have been degraded to small molecular acids.

Recent advances in electrospinning-nanofiber materials used in advanced oxidation processes for pollutant degradation

Electrospun nanofiber membranes have emerged as a novel catalyst, demonstrating exceptional efficacy in advanced oxidation processes (AOPs) for the degradation of organic pollutants. Their superior performance can be attributed to their substantial specific surface area, high porosity, ease of modification, rapid recovery, and unparalleled chemical stability. This paper aims to comprehensively explore the progressive applications and underlying mechanisms of electrospun nanofibers in AOPs, which include Fenton-like processes, photocatalysis, catalytic ozonation, and persulfate oxidation. A detailed discussion on the mechanism and efficiency of the catalytic process, which is influenced by the primary components of the electrospun catalyst, is presented. Additionally, the paper examines how concentration, viscosity, and molecular weight affect the characteristics of the spinning materials and seeks to provide a thorough understanding of electrospinning technology to enhance water treatment methods. The review proposes that electrospun nanofiber membranes hold significant potential for enhancing water treatment processes using advanced oxidation methods. This is attributed to their advantageous properties and the tunable nature of the electrospinning process, paving the way for advancements in water treatment through AOPs.

Porous organic semiconductor/PET composite fibre for the synergistic removal of hexavalent chromium and organic pollutants under sunlight

In this study, the porous graphite phase carbon nitride photocatalyst (P-g-C3N4) is prepared by the CaCO3 template method, and then P-g-C3N4/T-polyethylene terephthalate (T-PET) catalytic fibre is prepared by the padding method. P-g-C3N4 can provide more active sites than g-C3N4 as proved by the Brunauer-Emmett-Teller and the UV-Visible diffuse reflectance test. P-g-C3N4 powder catalyst successfully supports PET fibre as proved by scanning electron microscope, Fourier infrared spectroscopy and X-ray diffraction spectroscopy. The photocatalytic performance of P-g-C3N4/T-PET catalytic fibre is tested by constructing a single hexavalent chromium or hexavalent chromium/organic pollutant binary pollution system. The potential application value of P-g-C3N4/T-PET catalytic fibre is further explored by simulating the complex actual water environment. After five recycles, P-g-C3N4/T-PET catalytic fibre shows good catalytic performance. The mechanism of P-g-C3N4/PET photocatalytic degradation of organic pollutants is proposed through the capture agent experiment and electron paramagnetic resonance spectroscopy. Among them, •O2- is the most important active species of P-g-C3N4 catalytic fibre, which is used for the oxidation of organic pollutants. At the same time, photoelectrons generated by the catalytic fibre are used to reduce hexavalent chromium. The efficiency of P-g-C3N4 to remove pollutants is improved by using PET fibre as a carrier, which not only solves the problem of difficult recovery of powder catalysts but also provides more active sites.

Floating metal phthalocyanine@polyacrylonitrile nanofibers for peroxymonosulfate activation: Synergistic photothermal effects and highly efficient flowing wastewater treatment

Highly efficient floating photocatalysis has potential applications in organic pollutant treatment but remains limited by low degradation efficiency in practical applications. By introducing the photothermal effect into a peroxymonosulfate (PMS) coupled photocatalysis system, tetracycline hydrochloride (TCH) degradation could be significantly enhanced using floating metal phthalocyanine@polyacrylonitrile (MPc@PAN) nanofiber mats. MPc@PAN nanofibers with different metal centers showed similar photothermal conversion performance but different activation energies for PMS activation, resulting in metal-center-dependent synergistic photothermal effects, i.e., light-enhanced dominated, thermal-enhanced dominated, and conjointly light-thermal dominated mechanisms. The porous structures and floating ability of the FePc@PAN nanofibers provided a fast mass transfer process, with higher solar energy utilization and superior photothermal conversion performance than the FePc nanopowders. Meanwhile, the FePc@PAN nanofibers showed excellent TCH removal stability within 10 cycles (>92%) and extremely low Fe ion leaching (<0.055 mg/L) in a dual-channel flowing wastewater treatment system. This work provides new insight into PMS activation via photothermal effects for environmental remediation.

Iron (II) phthalocyanine loaded tourmaline efficiently activates PMS to degrade pharmaceutical contaminants under solar light

Iron (II) phthalocyanine (FePc) is loaded on the surface of the tourmaline (TM) by the reflow method to obtain FePc/TM. This research effectively prevents the π-π stacking of FePc, increased the effective utilization rate of PMS activation under solar light, and further improved the catalytic performance of the catalytic system. The catalytic oxidation efficiency of FePc/TM on carbamazepine (CBZ) and sulfadiazine (SD) can reach 99% under solar light for 15 and 5 min, the total organic carbon (TOC) removal rate can reach 58% and 69% under solar light for 120 min. After 6 cycles, the CBZ removal rate remained above 95%. In addition, the FePc/TM catalytic system has an excellent removal rate for other pharmaceuticals. The results of spin-trapped electron paramagnetic resonance and classical quenching experiments show that FePc/TM can effectively activate PMS to generate active species under solar light, including superoxide radical (•O2-), singlet oxygen (1O2), hydroxyl radicals(•OH), and sulphate radicals (SO4•-). The intermediates of CBZ were identified by Ultra-high performance liquid chromatography and high resolution mass spectrometry, and the degradation pathway was proposed. As the reaction progresses, all CBZ and intermediates are reduced and converted into small acids, or mineralized to H2O, CO2. This work provides an alternative method for the design of efficient activation of PMS activation catalysts under solar light to eliminate residual pharmaceuticals in actual water bodies.

Fabrication of an S-Scheme Heterojunction Photocatalyst MoS2/PANI with Greatly Enhanced Photocatalytic Performance

As a promising catalyst, MoS2 has been widely studied owing to its high chemical reactivity, excellent electrical carrier mobility, good optical properties, and narrow band gap. However, the high recombination rate of photoinduced charge carriers limits its practical application in photocatalysis. In this study, MoS2 was coupled with PANI to fabricate an S-scheme heterojunction MoS2/PANI. The synthesized products were characterized systematically, and their photocatalytic properties were evaluated by photocatalytic degradation of norfloxacin (NOR) and rhodamine B (RhB). The obtained results indicated that the fabricated MoS2/PANI inorganic-organic heterojunction displayed tremendously enhanced photocatalytic activity. The degradation efficiencies for 60 mg L-1 of NOR and RhB are 86 and 100% under the simulated sunlight irradiation for 1 h with 10 mg of catalyst, which are 13 and 47 times higher than those of pure MoS2, respectively. Interestingly, it is superior to the previously reported related materials. The remarkably enhanced photocatalytic activity of MoS2 is assigned to the high charge conductivity feature of PANI and the formed S-scheme heterojunction that result in a steric separation of holes and electrons and conserve the initial powerful redox ability of the parent catalysts. This study provides a facile method to greatly improve the photocatalytic activity of MoS2 and facilitates its application for highly efficient removal of organic pollutants, such as antibiotic drugs and organic dyes, utilizing solar energy.

Ferrate(VI)/Periodate System: Synergistic and Rapid Oxidation of Micropollutants via Periodate/Iodate-Modulated Fe(IV)/Fe(V) Intermediates

The presence of organic micropollutants in water sources worldwide has created a need for the development of effective and selective oxidation methods in complex water matrices. This study is the first report of the combination of ferrate(VI) (Fe(VI)) and periodate (PI) for synergistic, rapid, and selective elimination of multiple micropollutants. This combined system was found to outperform other Fe(VI)/oxidant systems (e.g., H₂O₂, peroxydisulfate, and peroxymonosulfate) in rapid water decontamination. Scavenging, probing, and electron spin resonance experiments showed that high-valent Fe(IV)/Fe(V) intermediates, rather than hydroxyl radicals, superoxide radicals, singlet oxygen, and iodyl radicals, played a dominant role in the process. Further, the generation of Fe(IV)/Fe(V) was evidenced directly by the ⁵⁷Fe Mössbauer spectroscopic test. Surprisingly, the reactivity of PI toward Fe(VI) is rather low (0.8223 M^-1 s^-1) at pH 8.0, implying that PI was not acting as an activator. Besides, as the only iodine sink of PI, iodate also played an enhanced role in micropollutant abatement by Fe(VI) oxidation. Further experiments proved that PI and/or iodate might function as the Fe(IV)/Fe(V) ligands, causing the utilization efficiency of Fe(IV)/Fe(V) intermediates for pollutant oxidation to outcompete their auto-decomposition. Finally, the oxidized products and plausible transformation pathways of three different micropollutants by single Fe(VI) and Fe(VI)/PI oxidation were characterized and elucidated. Overall, this study proposed a novel selective oxidation strategy (i.e., Fe(VI)/PI system) that could efficiently eliminate water micropollutants and clarified the unexpected interactions between PI/iodate and Fe(VI) for accelerated oxidation.

Solar-driven zinc-doped graphitic carbon nitride photocatalytic fibre for simultaneous removal of hexavalent chromium and pharmaceuticals

The current environmental problems urgently require researchers to seek an environmentally friendly, effective and easy to operate sewage treatment method. Graphite carbon nitride (g-C₃N₄), which has the advantages of simple preparation, safety, non-toxicity and chemical resistance, was expected to become a photocatalyst for solving environmental pollution. However, the performances of g-C₃N₄ still have some limitations that the electron hole recombination is fast and the powder is not easy to recover. In this study, zinc-doped graphite carbon nitride photocatalyst (Zn-g-C₃N₄) was mixed with polyacrylonitrile (PAN) to produce photocatalyst fibres by electrospinning. It not only solves the problem that the powder catalyst is difficult to recycle, but also effectively inhibits the recombination of photoelectron-hole pairs. Zn-g-C₃N₄/PAN has good photocatalytic activity for the simultaneous reduction of hexavalent chromium and degradation of pharmaceuticals. When organic pollutants are present, the reduction efficiency of hexavalent chromium was improved without affecting its own removal efficiency. The potential application value of Zn-g-C₃N₄/PAN catalytic fibre was further explored by simulating the complex actual water environment. The composite fibre can be easily reused and keep its superior photocatalytic performance. The mechanism of pharmaceuticals degradation was proposed, in which ∙O2- is the most important active species, which leads to the oxidation of pharmaceuticals. Besides, the photoelectrons generated by the catalyst can reduce the toxic hexavalent chromium. The efficiency of Zn-g-C₃N₄ to remove pollutants is improved by PAN fibre as a carrier, which not only solves the problem of difficult recovery of powder catalysts, but also provides more active sites.

Oxidative Degradation of Pharmaceuticals: The Role of Tetrapyrrole-Based Catalysts

Nowadays, society’s widespread consumption of pharmaceutical drugs and the consequent accumulation of such compounds or their metabolites in effluents requires the development of efficient strategies and systems that lead to their effective degradation. This can be done through oxidative processes, in which tetrapyrrolic macrocycles (porphyrins, phthalocyanines) deserve special attention since they are among the most promising degradation catalysts. This paper presents a review of the literature over the past ten years on the major advances made in the development of oxidation processes of pharmaceuticals in aqueous solutions using tetrapyrrole-based catalysts. The review presents a brief discussion of the mechanisms involved in these oxidative processes and is organized by the degradation of families of pharmaceutical compounds, namely antibiotics, analgesics and neurological drugs, among others. For each family, a critical analysis and discussion of the fundamental roles of tetrapyrrolic macrocycles are presented, regarding both photochemical degradative processes and direct oxidative chemical degradation.

Efficient Catalytic Degradation of Phenol with Phthalocyanine-Immobilized Reduced Graphene-Bacterial Cellulose Nanocomposite

In this report, phthalocyanine (Pc)/reduced graphene (rG)/bacterial cellulose (BC) ternary nanocomposite, Pc-rGBC, was developed through the immobilization of Pc onto a reduced graphene-bacterial cellulose (rGBC) nanohybrid after the reduction of biosynthesized graphene oxide-bacterial cellulose (GOBC) with N₂H₄. Field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FT-IR) were employed to monitor all of the functionalization processes. The Pc-rGBC nanocomposite was applied for the treatment of phenol wastewater. Thanks to the synergistic effect of BC and rG, Pc-rGBC had good adsorption capacity to phenol molecules, and the equilibrium adsorption data fitted well with the Freundlich model. When H₂O₂ was presented as an oxidant, phenol could rapidly be catalytically decomposed by the Pc-rGBC nanocomposite; the phenol degradation ratio was more than 90% within 90 min of catalytic oxidation, and the recycling experiment showed that the Pc-rGBC nanocomposite had excellent recycling performance in the consecutive treatment of phenol wastewater. The HPLC result showed that several organic acids, such as oxalic acid, maleic acid, fumaric acid, glutaric acid, and adipic acid, were formed during the reaction. The chemical oxygen demand (COD) result indicated that the formed organic acids could be further mineralized to CO₂ and H₂O, and the mineralization ratio was more than 80% when the catalytic reaction time was prolonged to 4 h. This work is of vital importance, in terms of both academic research and industrial practice, to the design of Pc-based functional materials and their application in environmental purification.

The degradation pathways of carbamazepine in advanced oxidation process: A mini review coupled with DFT calculation

Degradation pathway is important for the study of carbamazepine (CBZ) removal in advanced oxidation processes (AOPs). Generally, degradation pathways are speculated based on intermediate identification and basic chemical rules. However, this semiempirical strategy is sometimes time-consuming and baseless. To improve the situation, a mini meta-analysis was first conducted for the degradation pathways of CBZ in AOPs. Then, the rationality of the pathways was analyzed by Density Functional Theory (DFT) calculation. Results show that the degradation pathways of CBZ in various AOPs has high similarity, and the reactive sites predicted by Fukui function fitted well with the data retrieved from literatures. In addition, molecule configuration of degradation intermediates was found to play a very important roles on degradation pathway. The study reveals that computational chemistry is a useful tool for degradation pathway speculation in AOPs.

Tailoring spatial structure of electroactive biofilm for enhanced activity and direct electron transfer on iron phthalocyanine modified anode in microbial fuel cells

Electroactive biofilm (EAB) has been considered as the core determining electricity generation in microbial fuel cells (MFCs), and its spatial structure regulation for enhanced activity and selectivity is of great concern. In this study, iron phthalocyanine (FePc) was introduced into a carbon cloth (CC) electrode, aiming at improving the affinity between the anode and outer membrane c-type cytochromes (OM c-Cyts) and achieving a highly active EAB. The FePc modified CC anode (FePc-CC) effectively improved the viability of EAB and enriched the Geobacter species up to 44.83% (FePc-CC) from 6.97% (CC). The FePc-CC anode achieved a much higher power density of 2419 mW m^-2 than the CC (560 mW m^-2) and a remarkable higher biomass loading of 2477.2 ± 84.5 μg cm^-2 than the CC (749.3 ± 31.3 μg cm^-2). As the charge transfer resistance was decreased by 58.6 times from 395.2 Ω (CC) to 6.74 Ω (FePc-CC), the interfacial reaction rate was accelerated and the direct electron transfer via OM c-Cyts was promoted. This work provides an effective method to improve the EAB activity by regulating its spatial structure, and opens the door toward the development of highly active EAB using metal phthalocyanines in MFCs.

Synergistic catalysis of BiOIO3 catalyst for elimination of organic pollutants under simultaneous photo-irradiation and ultrasound-vibration treatment

Development of efficiently catalytic strategy for oxidative purification of organic pollutants is of great significance. Photocatalysis has become one of the most important technologies in the past half a century, but the inefficiency of photocatalysts drastically suppresses its practical application. This work proposes a synergistic photopiezocatalysis of BiOIO₃ under simultaneous photo-irradiation and ultrasound-vibration treatment to degrade various organic pollutants. Different from the high recombination of photo-excited charges in photocatalysis, the ultrasound-induced stress deforms the pyroelectric BiOIO₃ to form a piezoelectric potential that drives photo-/thermo-generated free electrons and holes in catalyst to diffuse along opposite directions. In comparison with the single photocatalysis and piezocatalysis, the photopiezocatalysis possesses a synergistic effect, presenting evidently enhanced catalytic performance for decomposing a variety of organic dyes and a persistent organic pollutant 2,4-DCP. No apparent decrease in activity during successive five runs demonstrates that the photopiezocatalysis of BiOIO₃ has a high stability and reusability. Finally, a plausible photopiezocatalysis mechanism is proposed based on the determination of active species produced on catalyst and intermediates during pollutant degradation. Our findings provide a new insight to promote charge separation and meanwhile develop an efficient synergistic photopiezocatalysis for environment remediation.

Oxidation of diclofenac in the presence of iron(II) octacarboxyphthalocyanine

This paper presents the results of the research on the influence of catalytic activity of iron(II) octacarboxyphthalocyanines (FePcOC) on the transformation of diclofenac (DCF) which is the most popular anti-inflammatory analgesic. Diclofenac poses a serious threat to the natural environment. The paper demonstrates that diclofenac, in the presence a monomeric form of iron octacarboxyphthalocyanine and hydroxyl radicals (HO^•) (from H₂O₂), undergoes a transformation into diclofenac-2,5-iminoquinone (DCF-2,5-IQ), causing distinct changes in the UV-Vis absorption spectrum. In the presence of iron octacarboxyphthalocyanine and H₂O₂, the previously colourless diclofenac solution becomes intense orange. As a result, a new band at approx. 450 nm appears in the absorption spectrum. HPLC analysis has shown that the concentration of diclofenac decreases with time. TD-DFT calculations using the CAM-B3LYP/6-31+G (d, p) method have been conducted to confirm experimental data concerning the formation of a new band at λ_max = 450 nm.

Artificial light-harvesting 2D photosynthetic systems with iron phthalocyanine/graphitic carbon nitride composites for highly efficient CO2 reduction

Fabricating high-efficient 2D artificial photosynthetic systems for CO2 reduction based on phthalocyanine/graphitic carbon nitride composites.

Synthesis of FePcS-PMA-LDH Cointercalation Composite with Enhanced Visible Light Photo-Fenton Catalytic Activity for BPA Degradation at Circumneutral pH

(1) Background: Iron tetrasulfophthalocyanine with a large nonlinear optical coefficient, good stability, and high catalytic activity has aroused the attention of researchers in the field of photo-Fenton reaction. Further improvement of the visible light photo-Fenton catalytic activity under circumneutral pH conditions for their practical application is still of great importance. (2) Methods: In this paper, iron tetrasulfophthalocyanine (FePcS) and phosphomolybdic acid (PMA) cointercalated layered double hydroxides (LDH) were synthesized by the ion-exchange method. All samples were fully characterized by various techniques and the results showed that FePcS and PMA were successfully intercalated in layered double hydroxides and the resulted compound exhibited strong absorption in the visible light region. The cointercalation compound was tested as a heterogeneous catalyst for the visible light photo-Fenton degradation of bisphenol A (BPA) at circumneutral pH. (3) Results: The results showed that the degradation and total organic carbon removal efficiencies of bisphenol A were 100% and 69.2%, respectively. (4) Conclusions: The cyclic voltammetry and electrochemical impedance spectroscopy measurements demonstrated that the main contribution of PMA to the enhanced photo-Fenton activity of FePcS–PMA–LDH comes from the acceleration of electron transfer in the reaction system. Additionally, the possible reaction mechanism in the photo-Fenton system catalyzed by FePcS–PMA–LDH was also proposed.

Facile Production of a Fenton-Like Photocatalyst by Two-Step Calcination with a Broad pH Adaptability

A novel heterogeneous Fenton-like photocatalyst, Fe-doped graphitic carbon nitride (Fe-g-C₃N₄), was produced by facile two-step calcination method. This Fe–g–C₃N₄ catalyzed rhodamine B degradation in the presence of H₂O₂ accompanied with visible light irradiation. transmission electron microscopy(TEM), x-ray diffraction (XRD), FT-IR, x-ray photoelectron spectroscopy (XPS), and photoluminescence fluorescent spectrometer (PL) characterization analysis methods were adopted to evaluate the physicochemical property of samples. It can be observed that the Fe-g-C₃N₄ exhibited excellent photocatalytic Fenton-like activity at a wide pH range of 3–9, with rhodamine B(RhB) degradation efficiency up to 95.5% after irradiation for 45 min in the presence of 1.0 mM H₂O₂. Its high activity was ascribed to the formation of Fe–N ligands in the triazine rings that accelerated electron movement driving the Fe(III)/Fe(II) redox cycle, and inhibited photo-generated electron hole re-combinations for continuous generation of reactive oxygen species by reactions between Fe(II) and H₂O₂. The main active oxygen species were hydroxyl radicals, followed by superoxide radicals and hole electrons. This produced catalyst of Fe–g–C₃N₄ shows excellent reusability and stability, and can be a promising candidate for decontamination of wastewater.

Application of response surface methodology for optimization of oxytetracycline hydrochloride degradation using hydrogen peroxide/polystyrene-supported iron phthalocyanine oxidation process

Inspired by metalloporphyrin-based enzymes, a biomimetic catalyst, R-N-Fe, was prepared by grafting iron phthalocyanine (FePc) covalently onto a macroporous chloromethylated polystyrene-divinylbenzene resin (R), which was pre-functionalized using 4-aminopyridine (4-ampy) as an axial ligand. The novel catalyst was used for the degradation of oxytetracycline hydrochloride (OTCH). The response surface methodology was employed to optimize the independent operating parameters, including temperature, catalyst amount, H₂O₂ dosage, and initial pH value. The results displayed that the initial pH and temperature had the most significant effect on the removal efficiency. Under optimum conditions, the OTCH removal efficiency was 93.98%. Additionally, the classical quenching experiment and electron paramagnetic resonance (EPR) test indicated that R-N-Fe could generate hydroxyl radicals by decomposing H₂O₂, which was the main active species for eliminating OTCH. Furthermore, R-N-Fe can be easily recycled and can maintain high stability in the reusability test, rendering it a good potential for practical application.

Kinetic study of the degradation of rhodamine B using a flow-through UV/electro-Fenton process with the presence of ethylenediaminetetraacetic acid

An UV enhanced electro-Fenton (EF) process was conducted in a flow-through system to remove rhodamine B (RhB) in the presence of ethylenediamine tetraacetate (EDTA). The process was denoted as UV/EDTA/EF where EDTA formed complexes with iron ions, thus keeping them soluble at high pH values. The process was very efficient as it could initiate the fast reduction of Fe^III to Fe^II and thus the decomposition of H₂O₂. The influence of Fe dose, the ratio of EDTA:Fe, aeration rate, flow rate, current, initial RhB concentration and pH on the RhB removal in the UV/EDTA/EF process was investigated. The best RhB removal was obtained as 89.9% at [Fe]₀ = [EDTA]₀ = 0.2 mM, current = 50 mA, aeration rate = 20 mL min^-1, flow rate = 7 mL min^-1, pH = 7 and [Na₂SO₄]₀ = 0.05 M. The degradation of EDTA during the process was also studied. Radical scavenging experiments indicated that OH was the dominant radical for RhB removal. While, the photolysis of Fe^IIIEDTA was mainly responsible for EDTA degradation. RhB and EDTA removal in different systems was compared. The stability test proved that in the presence of EDTA, the UV/EF process could remove RhB with high efficiency in the first two runs. While, the efficiency dropped remarkably after EDTA's complete depletion. The mechanisms of the UV/EDTA/EF process were proposed. UV/EDTA/EF conducted in the flow-through system was able to efficiently remove RhB as well as EDTA in a wide pH range and proposed as a promising approach for wastewater treatment.

High-Valent Iron-Oxo Complexes as Dominant Species to Eliminate Pharmaceuticals and Chloride-Containing Intermediates by the Activation of Peroxymonosulfate Under Visible Irradiation

Abstract

Generally, the sulfate (SO4·−) and hydroxyl (HO·) radicals are the dominant active species in most catalytic oxidation processes with peroxymonosulfate (PMS). However, the existence of various natural organic and inorganic matters in aquatic environments might influence the oxidation efficiency of these radicals, and/or form more toxic and refractory intermediates than the parent, especially in chlorine-ion-containing conditions. Here, we constructed a novel visible-light catalytic system with PMS based on iron hexadecachlorophthalocyanine-poly (4-vinylpyridine)/polyacrylonitrile nanofibers through pyridine ligands to generate high-valent iron-oxo (Fe(IV)=O) species as the main active species. The coordination structure was characterized by UV–Vis diffuse reflection, X-ray photoelectron spectroscopy, etc. The high-valent iron-oxo generation from peroxysulfate O–O bond heterolytic cleavage was proved by high-definition electrospray ionization mass spectrometer. Ultra-performance liquid chromatography coupled with high-definition mass spectrometry showed that the photocatalytic system was efficient for the degradation of carbamazepine and the chlorinated intermediates by iron-oxo active species in chlorine-ion-containing conditions.

Graphic Abstract

Carbamazepine is degraded by the bacterial strain Labrys portucalensis F11

The occurrence of pharmaceuticals in the environment is a topic of concern. Carbamazepine (CBZ) is a widespread antiepileptic drug and due to its physical-chemical characteristics minimal removal is achieved in conventional water treatments, and thus has been suggested as a molecular marker of wastewater contamination in surface water and groundwater. The present study reports the biotransformation of CBZ by the bacterial strain Labrys portucalensis F11. When supplied as a sole carbon source, a 95.4% biotransformation of 42.69 μM CBZ was achieved in 30 days. In co-metabolism with acetate, complete biotransformation was attained at a faster rate. Following a target approach, the detection and identification of 14 intermediary metabolites was achieved through UPLC-QTOF/MS/MS. Biotransformation of CBZ by the bacterial strain is mostly based on oxidation, loss of -CHNO group and ketone formation reactions; a biotransformation pathway with two routes is proposed. The toxicity of untreated and treated CBZ solutions was assessed using Vibrio Fischeri and Lepidium sativum acute toxicity tests and Toxi-Chromo Test. The presence of CBZ and/or its degradations products in solution resulted in moderate toxic effect on Vibrio Fischeri, whereas the other organisms were not affected. To the best of our knowledge this is the first report that proposes the metabolic degradation pathway of CBZ by a single bacterial strain.

Carbamazepine Degradation Mediated by Light in the Presence of Humic Substances-Coated Magnetite Nanoparticles

The use of iron-based nanomaterials for environmental remediation processes has recently received considerable attention. Here, we employed core-shell magnetite-humic acids nanoparticles as a heterogeneous photosensitizer and iron source in photo-Fenton reaction for the degradation of the psychiatric drug carbamazepine (CBZ). CBZ showed low photodegradation rates in the presence of the magnetic nanoparticles, whereas the addition of hydrogen peroxide at pH = 3 to the system drastically increased the abatement of the contaminant. The measured Fe²⁺ and Fe³⁺ profiles point to the generation of Fe³⁺ at the surface of the nanoparticles, indicating a heterogeneous oxidation of the contaminant mediated by hydroxyl radicals. Products with a higher transformation degree were observed in the photo-Fenton procedure and support the attack of the HO^• radical on the CBZ molecule. Promising results encourage the use of the nanoparticles as efficient iron sources with enhanced magnet-sensitive properties, suitable for applications in photo-Fenton treatments for the purification of wastewater.

Copper-based catalyst from waste printed circuit boards for effective Fenton-like discoloration of Rhodamine B at neutral pH

The carbonized waste printed circuit board (c-PCB) was used as novel copper-based catalyst for Fenton-like discoloration of Rhodamine B (RhB). The elemental ingredients, structure and morphology of the catalyst was investigated by multi-techniques. The catalytic activity of c-PCB for RhB discoloration was evaluated in the presence of H₂O₂, examining the factors of catalyst dosage, H₂O₂ dosage, solution pH, RhB concentration and temperature. RhB discoloration is improved with increasing catalyst dosage (0-2.0 g L^-1), H₂O₂ dosage (0-0.15 mol L^-1), solution pH (4.66-9.36) and temperature (30-50 °C). We found that c-PCB shows excellent catalytic activity for RhB discoloration in a broad pH range. RhB removal of 95.78% is obtained within 6 h at neutral pH (6.70). RhB discoloration is well described by the first-order kinetics, and the activation energy is calculated to be 87 kJ mol^-1. The dominant role of OH radical in the c-PCB/H₂O₂ system is identified by quenching tests. The plausible pathway for RhB discoloration is discussed based on the time-dependent UV-vis spectra. The possible catalytic mechanism in the c-PCB/H₂O₂ system is also presented. Good reusability of c-PCB is verified by three cycles. This work opens a new strategy of "waste treating waste", facilitating management of hazardous solid wastes and cleaner treatment of textile wastewater.

Roles of Phosphorus Sources in Microbial Community Assembly for the Removal of Organic Matters and Ammonia in Activated Sludge

Various phosphorus sources are utilized by microbes in WWTPs, eventually affecting microbial assembly and functions. This study identified the effects of phosphorus source on microbial communities and functions in the activated sludge. By cultivation with 59 phosphorus sources, including inorganic phosphates (IP), nucleoside-monophosphates (NMP), cyclic-nucleoside-monophosphates (cNMP), and other organophosphates (OP), we evaluated the change in removal efficiencies of total organic carbon (TOC) and ammonia, microbial biomass, alkaline phosphatase (AKP) activity, microbial community structure, and AKP-associated genes. TOC and ammonia removal efficiency was highest in IP (64.8%) and cNMP (52.3%) treatments. Microbial community structure changed significantly across phosphorus sources that IP and cNMP encouraged Enterobacter and Aeromonas, respectively. The abundance of phoA and phoU genes was higher in IP treatments, whereas phoD and phoX genes dominated OP treatments. Our findings suggested that the performance of WWTPs was dependent on phosphorus sources and provided new insights into effective WWTP management.

Iron-based metal-organic frameworks as novel platforms for catalytic ozonation of organic pollutant: Efficiency and mechanism

Developing new heterogeneous catalysts has attracted much attention and is of significant importance for the efficient catalytic ozonation of organic pollutant. Herein, for the first time, we explored four environmental-benign iron-based MOFs (Fe-MOFs) for the catalytic ozonation reaction. These Fe-MOFs were characterized by PXRD, FT-IR, SEM, XPS, N₂ sorption-desorption isotherms and chemisorbed-pyridine IR. All Fe-MOFs show high catalytic performances with their intrinsic Lewis acid sites (LAS). Furthermore, MIL-53(Fe) demonstrates the highest catalytic activity because of its largest amount of LAS and suitable porosity-derived attractive mass-transfer property. The Rhodamine B (RhB) degradation kinetic rate is calculated to be 5.76 min^-1 with MIL-53(Fe), while 1.82 min^-1 with MIL-88B(Fe), 1.40 min^-1 with MIL-101(Fe), 0.87 min^-1 with MIL-100(Fe) and 0.43 min^-1 of ozonation alone. The TOC removal in MIL-53(Fe)/O₃ system is 4 times higher than that of ozonation alone. MIL-53(Fe) displays acceptable reusability and stability after 5 cycles. Surface LAS of MIL-53(Fe) are the active sites for the ozone decomposition. Moreover, surface-adsorbed hydroxyl radical, superoxide radical and singlet oxygen are confirmed as the reactive oxygen species from ozone decomposition in MIL-53(Fe) suspension. This work offers new platforms for catalytic ozonation and may drive the development of MOFs-based catalytic ozonation for effective water treatment.

Identification of transformation products of carbamazepine in lettuce crops irrigated with Ultraviolet-C treated water

Transformation of organic microcontaminants (OMCs) during wastewater treatments results in the generation of transformation products (TPs), which can be more persistent than parent compounds. Due to reuse of reclaimed wastewater (RWW) for crop irrigation, OMCs and TPs are released in soils being capable to translocate to crops. Furthermore, OMCs are also susceptible to transformation once they reach the soil or crops. The recalcitrant antiepileptic carbamazepine (CBZ) and some of its frequently reported TPs have been found in agricultural systems. However, there is no knowledge about the fate in reuse practices of multiple CBZ TPs that can be formed during wastewater treatment processes. For the first time, this work presents a study of the behavior of CBZ TPs generated after a conventional Ultraviolet-C (UVC) treatment in an agricultural environment. The UVC-treated water was used for the irrigation of lettuces grown under controlled conditions. The latter was compared to the fate of TPs generated in the peat and plant by irrigation with non-treated water containing CBZ. A suspect screening strategy was developed to identify the TPs using liquid chromatography coupled to quadrupole-time-of-flight (LC-QTOF-MS). The results revealed the presence of 24 TPs, 22 in UVC-treated water, 11 in peat and 9 in lettuce leaves. 4 of the TPs identified in peat (iminostilbene, TP 271B, TP 285A-B); and 3 in leaves (10-11 dihydrocarbamazepine, TP 271A-B) were not previously reported in soils or edible parts of crops, respectively. Comparing the TPs found in peat and lettuces derived from both irrigation conditions, no significant differences regarding TPs formation or occurrence were observed. UVC treatment did not contribute to the formation of different TPs than those generated by transformation or metabolism of CBZ in peat or plant material. This research improves the current knowledge on the fate of CBZ TPs in agricultural systems because of reuse practices.

The construction of a Fenton system to achieve in situ H2O2 generation and decomposition for enhanced photocatalytic performance

A photo-Fenton system combining Ni_xFe_yO₄–BiOBr with the in situ generation and decomposition of H₂O₂ was constructed for efficient organic compound degradation.

Photochemistry of 9-acridinecarboxaldehyde in aqueous media

Dark and photolysis reactions in solution were investigated for 9-acridinecarboxaldehyde (ACL). ACL reacts in the dark at T = 20 °C and pH = 7.0 in an air saturated solution to the main product 9-acridinecarboxylic acid (ACA) and to the minor product 9-acridinemethanol (ACM) with a lifetime of τ = 4.3 days. The dissociation constant of the base ACLH+ was determined to be pKa ± σ = 4.38 ± 0.04. The photolysis of ACL was investigated using a polychromatic Xe-light source. The quantum yield in aqueous solution at T = 20 °C in a concentration range of c0(ACL) = 0.18-16.6 μM for pH > pKa and for nitrogen, air and oxygen aerated solutions was found to be Φ ± σ = (0.015 ± 0.003) mol/mol, independent from concentration. The quantum yield of ACLH+, i.e. for pH ≪ pKa, is by a factor of 2 higher (Φ = 0.029 mol/mol). Quantum yields in methanol and isopropanol are slightly lower compared to water and in acetone lower by about a factor of 20. In acetonitrile ACL was found to be practically photostable. Minimum lifetimes in sunlight for a measurement on September 5, 2017 were in the range of τ = 5-10 minutes. The diurnal photolysis of ACL in sunlight was satisfactory explained using the mean quantum yield, the absorption spectrum and photon fluxes with suitable corrections for cloudiness and the dimensions of the setup. For low concentrations ACR is formed with a yield of practically 100% in the photolysis reaction. However, with increasing concentration of ACL yields of ACR decrease and yields of ACA increase. 9(10H)-Acridinone and ACM were always detected as minor products with yields below 2%. 9-Methylacridine was never detected in any reaction of ACL. Strong indications are presented of a photolysis reaction of ACL in a river located in Lower Saxony (Germany) with a corresponding equimolar formation of ACR. ACL is therefore a direct precursor of ACR in natural surface water.

Catalytic degradation of sulfaquinoxalinum by polyester/poly-4-vinylpyridine nanofibers-supported iron phthalocyanine

Iron (II) phthalocyanine (FePc) supported on electrospun polyester/poly-4-vinylpyridine nanofibers (PET/P4VP NFs) was prepared by stirring in tetrahydrofuran. The resulting product was confirmed and characterized by ultraviolet-visible diffuse reflectance spectroscopy, attenuated total reflection Fourier transform infrared spectra, X-ray photoelectron spectroscopy, gas chromatography/mass spectrometry, and ultra-performance liquid chromatography. More than 95% of sulfaquinoxalinum (SQX) could be removed by the activation of hydrogen peroxide in the presence of FePc-P4VP/PET with a PET and P4VP mass ratio of 1:1. This system exhibited a high catalytic activity across a wide pH and temperature range. The degradation rates of SQX achieved 100, 95, and 78% at a pH of 3, 7, and 9, respectively, and the degradation rates of SQX are more than 80% at the temperature ranging from 35 to 65 °C. DMSO₂ could be detected by gas chromatography/mass spectrometry after the addition of DMSO, suggesting the formation of the high-valent iron intermediates in this catalytic system. In addition, the electron paramagnetic resonance experiments proved that free radicals did not dominate the reaction in our system. Therefore, the high-valent iron intermediates were proposed to the main active species in the FePc-P4VP/PET/hydrogen peroxide system. In summary, the heterogeneous catalytic processes with non-radical catalytic mechanism might have better catalytic performance for the removal of organic pollutants, which can potentially be used in wastewater treatment.

Construction of solid–liquid interfacial Fenton-like reaction under visible light irradiation over etched CoxFeyO4–BiOBr photocatalysts

An in situ H₂O₂ production and Fenton-like system, Co_xFe_yO₄–BiOBr has been constructed. Co and Fe can build two redox cycles for ROSs (˙O₂⁻ and ˙OH radicals) generation and the optimal composites were obtained.

Quantitative Immobilization of Phthalocyanine onto Bacterial Cellulose for Construction of a High-Performance Catalytic Membrane Reactor

We report the fabrication of a tetra-amino cobalt (II) phthalocyanine (CoPc)-immobilized bacterial cellulose (BC) functional nanocomposite, CoPc@BC, by quantitative immobilization of CoPc onto a BC membrane. Lab-cultured BC was oxidized by NaIO₄ to generate aldehyde groups on BC for the subsequent CoPc immobilization, the processing conditions were optimized by monitoring both the generated aldehyde content and the resulting CoPc loading. X-ray photoelectron spectroscopy (XPS) was employed to characterize the change of the element bonding environment during the functionalization processes. The CoPc@BC functional nanocomposite was utilized for the treatment of reactive red X-3B dye wastewater. The CoPc molecules in the CoPc@BC nanocomposite can function as an “antenna” to adsorb the target anionic dye molecules, the adsorption takes place both on the surface and in the interior of CoPc@BC. A catalytic membrane reactor (CMR) was assembled with the CoPc@BC nanocomposite, the performance of CMR was evaluated based on the catalytic oxidation behavior of reactive red X-3B, with H₂O₂ as an oxidant. Highly-reactive hydroxyl radical (OH) was involved in the catalytic oxidation process, as detected by electron paramagnetic resonance (EPR). Under optimal operating conditions of a flow rate of 6 mL/min, a reaction temperature of 50 °C, and an H₂O₂ concentration of 10 mmol/L, the decoloration rate of CMR was as high as 50 μmol⋅min⁻¹⋅g⁻¹.