Recalcitrant Pollutants Research Articles

First full-scale application of electron beam technology for treating dyeing wastewater (30,000 m3/d) in China

Electron beam technology has been widely investigated for the degradation of recalcitrant organic pollutants in water and wastewater in laboratory scale. However, it needs verification in practical application for long-term operation. Strikingly, for the first time, we have successfully applied electron beam technology to treat the actual dyeing wastewater in capacity of 30,000 m3/d in Jiangmen city, Guangdong Province, China. The continuous monitoring data of the effluent water quality showed that electron beam technology can be used as advanced treatment process to effectively improve the removal efficiency of COD and color. The effluent COD of electron beam unit stayed between 20 and 50 mg/L when the influent COD ranged from 180 to 280 mg/L, and the color of the treated dyeing wastewater decreased to about 10 times. The operational cost of whole wastewater treatment processes was about 2.0–2.5 ¥/m3, including electron beam unit. Based on the monitoring data of more than one year's operation, it can be concluded that electron beam technology could provide a solution for refractory industrial wastewater treatment, which is a high efficient and cost-effective advanced treatment process.

Spent waste from edible mushrooms offers innovative strategies for the remediation of persistent organic micropollutants: A review

Urgent and innovative strategies for removal of persistent organic micropollutants (OMPs) in soil, groundwater, and surface water are the need of the hour. OMPs detected in contaminated soils and effluents from wastewater treatment plants (WWTPs) are categorized as environmentally persistent pharmaceutical pollutants (EPPPs), and endocrine disrupting chemicals (EDCs), their admixture could cause serious ecological issues to the non-target species. As complete eradication of OMPs is not possible with the extant conventional WWTPs technology, the inordinate and reckless application of OMPs negatively impacts environmental regenerative and resilience capacity. Therefore, the cardinal focus of this review is the bioremediation of persistent OMPs through efficient application of an agro-waste, i.e. spent mushroom waste (SMW). This innovative, green, long-term strategy embedded in the circular economy, based on state of the art information is comprehensively assessed in this paper. SMW accrues ligninolytic enzymes such as laccase and peroxidase, with efficient mechanism to facilitate biodegradation of recalcitrant organic pollutants. It is vital in this context that future research should address immobilization of such enzymes to overcome quantitative and qualitative issues obstructing their widespread use in biodegradation. Therefore, dual benefit is gained from cultivating critical cash crops like mushrooms to meet the escalating demand for food resources and to aid in biodegradation. Hence, mushroom cultivation has positive environmental, social, and economic implications in developing countries like India.

Combination of MoS2 nanopetals with Ag nanoparticles decorated graphene oxide for boosting photocatalytic abatement of recalcitrant pollutants under visible light irradiation

Herein, various weight ratios (1:1, 1:3, and 3:1) of MoS2/GO composites decorated with Ag nanoparticles (named as MAG) have been prepared by microwave-assisted route. XRD and XPS investigations indicated the catalyst crystallinity and elemental oxidation states. Morphological analysis revealed presence of small MoS2 nanopetals scattered on GO sheets with Ag NPs dispersed on surface whereas BET-analysis disclosed its excellent surface area (∼88 m2/g). Optical properties of MAG catalysts revealed that they were highly visible-light active, with a bandgap of 2.15 eV and a lower charge recombination rate. Excellent efficiency was observed for TC (90.7%; 0.0186 min−1) and FIP-degradation (85.2%; 0.0177 min−1) with 4 mg MAG (3:1) catalyst at neutral pH under visible-light irradiation owing to high synergistic interaction (∼2.21) in the composite. Effects of catalyst amount, pH, and effective area of illumination on degradation were investigated. High reusable nature of the catalyst (65% (TC) and 58% (FIP) efficiency after 5 cycles) was supported by post-photocatalytic characterization studies. Photodegradation products of TC were determined via LC-MS studies. Holes and hydroxyl radicals were majorly involved in degradation process revealed by trapping studies. High COD (70.4%) and TOC (55.1%) removal rates confirm high photo-mineralization of real-wastewater without any pre-treatment. The current investigation, combined with comparative literature, illustrates real-world potential of MAG catalysts for eradication of resistant pollutants.

Halophilic Martelella sp. AD-3 enhanced phenanthrene degradation in a bioaugmented activated sludge system through syntrophic interaction

Polycyclic aromatic hydrocarbons (PAHs) are a group of common recalcitrant pollutant in industrial saline wastewater that raised significant concerns, whereas traditional activated sludge (AS) has limited tolerance to high salinity and PAHs toxicity, restricting its capacity to degrade PAHs. It is therefore urgent to develop a bioaugmented sludge (BS) system to aid in the effective degradation of these types of compounds under saline condition. In this study, a novel bioaugmentation strategy was developed by using halophilic Martelella sp. AD-3 for effectively augmented phenanthrene (PHE) degradation under 3% salinity. It was found that a 0.5∼1.5% (w/w) ratio of strain AD-3 to activated sludge was optimal for achieving high PHE degradation activity of the BS system with degradation rates reaching 2.2 mg⋅gVSS−1⋅h−1, nearly 25 times that of the AS system. Although 1-hydroxy-2-naphthoic acid (1H2N) was accumulated obviously, the mineralization of PHE was more complete in the BS system. Reads-based metagenomic coupled metatranscriptomic analysis revealed that the expression values of ndoB, encoding a dioxygenase associated with PHE ring-cleavage, was 5600-fold higher in the BS system than in the AS system. Metagenome assembly showed the members of the Corynebacterium and Alcaligenes genera were abundant in the strain AD-3 bioaugmented BS system with expression of 10.3±1.8% and 1.9±0.26%, respectively. Moreover, phdI and nahG accused for metabolism of 1H2N have been annotated in both above two genera. Degradation assays of intermediates of PHE confirmed that the activated sludge actually possessed considerable degradation capacity for downstream intermediates of PHE including 1H2N. The degradation capacity ratio of 1H2N to PHE was 87% in BS system, while it was 26% in strain AD-3. These results indicated that strain AD-3 contributed mainly in transforming PHE to 1H2N in BS system, while species in activated sludge utilized 1H2N as substrate to grow, thus establishing a syntrophic interaction with strain AD-3 and achieving the complete mineralization of PHE. Long-term continuous experiment confirmed a stable PHE removal efficiency of 93% and few 1H2N accumulation in BS SBR system. This study demonstrated an effective bioaugmented strategy for the bioremediation of saline wastewater containing PAHs.

Environmentally friendly synthesis of silicon dioxide nanoparticles and their application for the removal of emerging contaminants in aqueous media

The highly detrimental potential effects that emerging contaminants have for the environment and human health demand the development of sustainable technologies to eliminate these pollutants. In this work, an eco-friendly approach was followed to synthesize S1O2 nanoparticles to be used to remove caffeine and triclosan from synthetic waters. Rice husk was the precursor used, which was subjected to acid leaching treatments using acetic and oxalic acids, and pyrolysis for 2 h at 700 °C. The resulting powders were characterized by X-ray diffraction, Raman and infrared spectroscopies, the Brunauer-Emmett-Teller method, and scanning and transmission electron microscopy. The particles synthesized were amorphous, had an average size between 4.6 and 9.6 nm, and specific surface areas between 208 and 223 m2/g. The adsorptive performance of the nanosilica obtained using acetic acid was studied by batch tests. The optimum dosage, maximum removal efficiencies and maximum adsorption capacities were 8 g/L, 76%, and 2.74 mg/g, and 24 g/L, 48%, and 0.75 mg/g for triclosan and caffeine, respectively. The data collected fitted the Sips isotherm model, and the pseudo-second and -first order kinetics models, for triclosan and caffeine, respectively. The promising results obtained open the possibility of using the synthesized nanomaterials for removing a variety of toxic and recalcitrant pollutants.

Organic photoredox catalysts for wastewater remediation: Beyond the established advanced oxidation processes

Contaminants of emerging concern (CECs) constitute a wide class of organic molecules, which are found dissolved in wastewaters. Chemical properties of CECs are as wide as their chemical structures; nevertheless, most of the CECs can be removed from wastewaters using Advanced Oxidation Processes (AOPs). However, there are examples of CECs that have proven recalcitrant to AOPs. In such cases, Advanced Reduction Processes (ARPs) include those techniques able to achieve degradation of contaminants by producing highly reactive reducing radicals.Organic photocatalysts have demonstrated to be an efficient alternative to other types of photocatalysts in AOPs. Moreover, several organic photocatalysts, according to their redox properties, could also act as reductants under appropriate scenarios, a process that has been much less explored than oxidation. As an example, Riboflavin (RF) is a natural water-soluble molecule, well-known as vitamin B2. The photophysical and redox properties of RF have been extensively applied for the oxidative photodegradation of contaminants in water. More recently, the potential of RF has been expanded to the photoreduction of more recalcitrant pollutants. For instance, benzotriazoles UV-stabilizers (BUVSs) constitute a vast family of recalcitrant contaminants, which have been successfully degraded in the presence of a commercially available derivative of RF (2′,3′,4′,5′-tetraacetylated riboflavin, RFTA) and visible light, assisted by an amine, which acts as electron donor to the excited states of RFTA, generating the RFTA.−. This species ultimately produces the reduction of the selected BUVSs. Photophysical experiments demonstrated the key role of the radical anion RFTA.−, and allowed determining the rate constants that were correlated to the observed photodegradations.

Facile chemical blowing synthesis of interconnected N-doped carbon nanosheets coupled with Co3O4 nanoparticles as superior peroxymonosulfate activators for p-nitrophenol destruction: Mechanisms and degradation pathways

Peroxymonosulfate (PMS)-based advanced oxidation processes are attractive candidates for removal of recalcitrant pollutants, whereas the insufficiency of simple strategies to fabricate low-cost and efficient PMS activators has interfered with the practical application of such technologies. In this study, we have synthesized three-dimensional interconnected N-doped carbon nanosheet frameworks (NCNF) coupled with uniformly distributed cobalt oxide nanoparticles (NPs) (Co3O4-NCNF) through one-pot polymer-chemical-blowing and subsequent thermal oxidation. The achieved Co3O4-NCNF exhibits a high performance toward p-nitrophenol (PNP) degradation through activating PMS with about 98% removal efficiency and apparent rate constant of 0.137 min−1. The degradation process undergoes both radical (SO4•−, •OH and O2•−) and nonradical (1O2) pathways, where SO4•− and 1O2 paly the dominant roles. The PNP degradation has two pathways including the reduction/oxidation and direct oxidation. The structural interconnectivities with highly opened freeway for mass/electron transfer, abundant active surfaces, and synergistic effect of Co3O4 NPs and NCNF in the Co3O4-NCNF provide rich reactive oxidative species for highly efficient PNP degradation. This study offers a gateway to fabricate reactive PMS activator for removal of emerging organic pollutants.

Bone/muscle-inspired polymer porous matrix toughened carbon nanofibrous catalytic membranes for robust emerging contaminants removal

Catalytic membranes are able to conquer the hurdles of common heterogeneous catalysts via facilitated convection/diffusion–reaction process, which efficiently eliminate emerging contaminants (ECs) without secondary contamination. It is challenging to maintain steady advanced oxidation efficiency via rationally designing the robust nano-architectures of catalytic membranes. Inspired by tenacious bone/muscle structure, we for the first time synthesized polyvinylidene fluoride shells and micro-webs intensified carbon catalytic nanofibrous membranes (PVDF-CCNM) using a flash freezing route, achieving instantaneous ECs degradation (e.g. 98.9 ± 0.5% of tetracycline) and producing a massive water throughput (e.g. 29.4 × 103 L m−2) in 84 h under continuous cross-flow filtration, superior to state-of-the-art catalytic membranes. The resulted membrane showed a much higher apparent reaction constant value (1353.5 μmol g−1 min−1) during the dynamic filtration system than that (4.9 μmol g−1 min−1) in batch system, ascribing to forced convection and facilitated diffusion–reaction. Moreover, the resulted membrane exhibited strong resistance to various anions and broad pH range due to the 1O2 dominated catalytic degradation mechanism, which allows for remediating actual high-salinity coal chemical wastewater. This work highlights an innovative catalytic membrane design for robust and practical treatment of recalcitrant pollutants.

Visible-light-driven photocatalytic activation of peroxymonosulfate by K+-reformed polymeric carbon nitride for effective sulfamethoxazole decomposition

The SO4•– radical based advanced oxidation process (SR-AOP) is the effective remediation strategy for addressing the concern of severe pollution risk caused by recalcitrant pollutants. In this study, we report the visible-light-driven photocatalytic activation (VL-PCA) of PMS by using K+-induced structure remodeling high crystallinity of (KPCN). The degradation of sulfamethoxazole (SMX) by KPCN+PMS+VL system (the corresponding kinetic constant is 0.1452 min–1) was enhanced remarkably compared with PCN+PMS+VL system (0.0263 min–1). •O2–, 1O2, •OH and SO4•– radicals were the dominant reactive species for the enhanced decomposition of SMX, evidently demonstrated by reactive species scavenger and electron paramagnetic resonance (EPR) experiments. The KPCN crystalline semiconductors maintain the properties of long-range atomic order configuration and nonlinear optical (NLO) response of pristine PCN. The unique NLO effects of KPCN enable it to produce more photogenerated carriers and minimize the electron-hole pair recombination, which exhibit superior VL-PCA performance of PMS toward SMX degradation. This study gives a proof-in-concept demonstration of the increased activity of the C3N4-based PMS photocatalytic-activator by regulating the disordered structure and phase defects of PCN, shedding light on the development of highly efficient VL-PCA catalysts based on carbon nitride.

Photosensitized Thermoplastic Nano-Photocatalysts Active in the Visible Light Range for Potential Applications Inside Extraterrestrial Facilities.

Among different depollution methods, photocatalysis activated by solar light is promising for terrestrial outdoor applications. However, its use in underground structures and/or microgravity environments (e.g., extraterrestrial structures) is forbidden. In these cases, there are issues related to the energy emitted from the indoor lighting system because it is not high enough to promote the photocatalytic mechanism. Moreover, microgravity does not allow the recovery of the photocatalytic slurry from the depolluted solution. In this work, the synthesis of a filmable nanocomposite based on semiconductor nanoparticles supported by photosensitized copolyacrylates was performed through a bulk in situ radical copolymerization involving a photosensitizer macromonomer. The macromonomer and the nanocomposites were characterized through UV-Vis, fluorescence and NMR spectroscopies, gel permeation chromatography and thermogravimetric analysis. The photocatalytic activity of the sensitized nanocomposites was studied through photodegradation tests of common dyes and recalcitrant xenobiotic pollutants, employing UV-Vis and visible range (λ > 390 nm) light radiations. The sensitized nanocomposite photocatalytic performances increased about two times that of the unsensitized nanocomposite and that of visible range light radiation alone (>390 nm). The experimental data have shown that these new systems, applied as thin films, have the potential for use in indoor deep underground and extraterrestrial structures.

Bioremediation of Perfluoroalkyl Substances (PFAS) by Anaerobic Digestion: Effect of PFAS on Different Trophic Groups and Methane Production Accelerated by Carbon Materials.

Per- and polyfluoroalkyl substances (PFAS) are recalcitrant pollutants which tend to persist in soils and aquatic environments and their remediation is among the most challenging with respect to organic pollutants. Anaerobic digestion (AD) supplemented with low amounts of carbon materials (CM), acting as electron drivers, has proved to be an efficient process for the removal of organic compounds from wastewater. This work explores the impact of PFAS on different trophic groups in anaerobic communities, and the effect of carbon nanotubes (CNT), activated carbon (AC), and oxidized AC (AC-HNO3), as electron shuttles on the anaerobic bioremoval of these compounds, based on CH4 production. The inhibition of the specific methanogenic activity (SMA) exerted by perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), at a concentration of 0.1 mg L−1, was below 10% for acetoclastic and below 15%, for acetogenic communities. Hydrogenotrophic methanogens were not affected by the presence of PFAS. All CM reduced the negative impact of PFAS on the CH4 production rate, but AC was the best. Moreover, the methanization percentage (MP) of sewage sludge (SS) increased 41% in the presence of PFOS (1.2 g L−1) and AC. In addition, AC fostered an increase of 11% in the MP of SS+PFOS, relative to the condition without AC. AC promoted detoxification of PFOA- and PFOS-treated samples by 51% and 35%, respectively, as assessed by Vibrio fischeri assays, demonstrating the advantage of bringing AD and CM together for PFAS remediation.

Assessment of Levonorgestrel Leaching in a Landfill and Its Effects on Placental Cell Lines and Sperm Cells

The Buenavista landfill is located east of the city of Medellín, but it has a slope steeper than 30% and is less than 600 m away from the Piedras River, possibly influencing the quality of the drinking water in the city. Many complex residues are disposed of in this landfill, including pharmaceuticals and personal care products (PPCPs) such as levonorgestrel (LNG), which may reach water bodies via runoff and leaching. We assessed the levels of LNG in the effluent of an upflow anaerobic sludge blanket (UASB) reactor from the Buenavista landfill by uHPLC–DAD, as well as the endocrine disruptor effect of LNG on placental cell lines (BeWo) and human sperm cells. Additionally, the potential leaching of LNG was assayed under laboratory conditions using soil layers that were sampled from the Buenavista landfill. LNG was detected at levels of 315 μg·L−1 in the effluents of the UASB reactor. Thus, the UASB reactor is not an efficient treatment method for the removal of recalcitrant pollutants. Additionally, we found that a layer of soil used as a cover material may adsorb more than 90% of LNG pollutants, but small amounts may still be leached, which means that a cover material is not a strong enough barrier to fully prevent the leaching of LNG. Finally, our results show that the leachate fraction decreased the levels of β-human chorionic gonadotropin, but not sperm motility or viability. Thus, leached LNG could trigger reproduction disorders, but further studies should be carried out to investigate its potential effects in more detail.

Investigating the role of ultrasound in improving the photocatalytic ability of CQD decorated boron-doped g-C3N4 for tetracycline degradation and first-principles study of nitrogen-vacancy formation

Graphitic carbon nitride (CN) is recognized as a promising photocatalyst for energy and environmental remediation. However, challenges persist due to limited CN surface-active sites and poor electronic properties. To overcome such challenges, we have synthesized Carbon Quantum Dots decorated Boron-doped Exfoliated CN (CQD@B-ECN) via ultrasound-assisted thermal polycondensation method. The substitutional boron doping favored nitrogen-vacancy as evident from experimental results and DFT calculations, which accelerated the charge separation/transfer and the CQD incorporation broadens the light-harvesting ability through photon upconversion. Moreover, the specific surface area of 2CQD-2B-ECN (685 m2/g) was significantly greater than CN providing enormous active sites. 2CQD-2B-ECN were evaluated using Tetracycline (TC) antibiotic, where photocatalysis and sonocatalysis showed 68% and 0.2% degradation in 120 min, respectively. Remarkably, sonophotocatalysis exhibited 84% TC degradation with a synergy index of 1.2 and complete degradation within 180 min. This work reveals an insight into CQD-B-ECN as a novel sonophotocatalyst for the degradation of diverse recalcitrant pollutants.

Visible-Light Driven Photocatalytic Degradation of 4-Chlorophenol Using Graphitic Carbon Nitride-Based Nanocomposites

4-chlorophenol (4-CP), a hydroxylated aromatic compound (HAC), is a recalcitrant and toxic organic pollutant found in industrial wastewater and various environmental media. In this paper, visible-light-activated photocatalysis using graphitic carbon nitride (GCN) was used to treat 4-CP in an aqueous media. Graphitic carbon nitride from different precursors (dicyanamide, urea, and melamine), as well as GCN/silver nanocomposites (AgBr, Ag3PO4, Ag2CrO4, and Ag), were successfully synthesized and characterized by BET, XRD, SEM, EDS, and UV-Vis DRS. The band gaps of the photocatalysts were estimated using the UV-Vis DRS characterization results and Tauc plots. The evaluation of the efficacy of the GCN-based catalysts in degrading 4-CP was conducted with different photoreactors such as a royal blue light-emitting diode (LED), a UV-A LED, LUZCHEM cool white lamps, and a solar simulator. The results showed that GCNs with royal blue LED can effectively degrade 4-CP from aqueous media. Among the different precursors, urea-derived GCN showed the best performance in degrading 4-CP due to its large surface area. GCN/0.3Ag2CrO4 nanocomposite showed a synergistic effect for the enhanced photocatalytic degradation of 4-CP. The degradation of 4-CP with a rate constant of 2.64 × 10−2 min−1 was achieved with a GCN/0.3Ag2CrO4 nanocomposite under royal blue LED irradiation.

Electrospun CuS nanoparticles/chitosan nanofiber composites for visible and near-infrared light-driven catalytic degradation of antibiotic pollutants

• Electrospun CuS nanoparticles/chitosan nanofiber composites (ENFCs) were developed. • The removal mechanism of tetracycline includes adsorption and catalytic degradation. • Visible and near-infrared light-driven photo-Fenton degradation of tetracycline. • The degradation intermediates and possible transformation pathways were evaluated. In the present study, copper sulfide nanoparticles (CuS NPs)/chitosan nanofiber composites with photo-Fenton catalytic and photothermal activities were developed to enhance the removal of recalcitrant biomedical pollutants such as tetracycline (TC). CuS NPs were encapsulated in CS nanofibers by an electrospinning technique (CS ENFs) to obtain CuS@CS ENF composite (CuS@CS ENFC) membranes with high porosity and large surface areas. An investigation of the mechanism of TC removal revealed the complementary performances between adsorption of TC by CS ENFs and the Fenton-like reaction of TC with CuS NPs during the degradation of TC. The ENFCs were cross-linked with genipin (GP) to improve the stability of CuS NPs in long-term storage and the availability of the ENFCs over a wide pH range. CuS@CS ENFCs generated electron-hole pairs and local hyperthermia under near infrared (NIR) laser irradiation, which caused the H 2 O 2 -involved catalytic reaction on ENFCs to take place at a faster rate than in the dark. Compared to pristine CuS NPs, ENFCs were more easily separated from the reaction mixture, and the adsorption sites on ENFCs could be regenerated by the photo-Fenton catalytic degradation of TC. The ENFCs also exhibited antibacterial activity. ENFCs are eco-friendly and easily recyclable, so they have the potential for chemical engineering, biomedical, and environmental applications.

One-pot synthesis of mesoporous silicas supported Cu single-atom and CuO nanoparticles for peroxymonosulfate-activated degradation of tetracycline over a wide pH range

Peroxymonosulfate activated heterogeneous Fenton-like catalytic reactions are promising in degradation of recalcitrant pollutants. Mesoporous silicas supported high-dispersion Cu species, as a kind of conventional heterogeneous catalysts for extensive applications, are rarely studied for their degradation efficiency in peroxymonosulfate-triggered reactions. In this work, one-pot incorporation method was employed to generate simultaneously Cu single-atom, Cu nanoparticles in mesoporous silicas (like the sample of Cu/Si-3 with 0.68 wt% of Cu) using sodium copper chlorophyllin as Cu source by calcining directly in air atmosphere. Several characterizations confirm the coexistence of Cu single-atom, Cu nanoparticles and mesopore with uniform size distribution. Activated by peroxymonosulfate, Cu/Si-3 was found to be efficient in degradation of tetracycline throughout a wide pH range of 2–11. The radicals of S O 4 g − , ⋅ O H and O 1 2 played their role in the degradation reaction. The underlying catalytic mechanism of the Fenton-like reaction was speculated on the basis of analysis of reactive oxygen species. This work has important implication in reasonable design and fabrication of catalysts with high-dispersion metal and controllable synthesis of functional mesoporous materials, as well as in proper disposal of recalcitrant pollutants including tetracycline. • Composite of Cu single-atom and CuO nanoparticles simultaneously generated by one-pot synthesis under air atmosphere. • Successful preparation of mesoporous materials with uniform size distribution. • Cu single-atom catalysts obtained by calcination without protection of inert gas. • The obtained highly dispersed Cu species favourable in degradation of tetracycline. • The catalyst's wide working pH window of 2–11.

Surface confinement of per-fluoroalkyl substances on an iron-decorated clay-cyclodextrin composite enables rapid oxidation by hydroxyl radicals

The removal and oxidation of seven perfluorinated compounds were studied in the presence of an iron-clay-cyclodextrin polymer composite (Fe-MMT-βCD-DFB). The iron-clay backbone served as a heterogeneous Fenton catalyst, and the cyclodextrin polymer, cross-linked with polyfluorinated aromatic molecules, was used to promote removal and surface-confinement of the perfluorinated compounds. The composite exhibited superior adsorption (∼90%) and efficient oxidation (>70%) towards the high molecular weight PFAS: PFHpA, PFOA, PFNA, PFDA, and PFOS. The lower molecular weight PFAS: PFBA and PFHxA, showed lower adsorption affinity towards the composite but were almost completely degraded once adsorbed to the surface (>90%). The oxidation was very rapid, reaching over 65% degradation of PFOA and PFOS within the first 10 min. EPR and probe measurements revealed that hydroxyl radicals were responsible for the high degradation rates. In addition, fluoride ion measurements coupled with TOC and LC/MS analysis showed high defluorination and mineralization rates of PFOA and PFOS (73.2% and 73.5%, respectively). The composite also displayed excellent performance in a mixed solution with the seven different PFAS, especially towards the degradation of high MW compounds. Furthermore, the composite’s degradation activity remained stable even after five cycles of adsorption and degradation. Taken together, the results suggest that composites that promote surface confinement of the pollutants near the catalytic active sites can be used to efficiently remove and destroy highly recalcitrant pollutants under benign environmental conditions.

Solar heterogeneous photocatalytic degradation of phenol on TiO2/quartz and TiO2/calcite: a statistical and kinetic approach on comparative efficiencies towards a TiO2/glass system.

Phenol is a widely used synthetic organic compound, which according to global estimations, is discharged into the environment at a rate of 10 tons/year through industrial waste. Phenol is a recalcitrant pollutant, and human exposure to water containing phenolic substances can lead to health issues. It has been found both in drinking water and wastewater. Solar heterogeneous photocatalytic phenol degradation, measured through chemical oxygen demand, was performed on a thin film tilted plate reactor with TiO2 immobilized onto different support materials. A full factorial experimental design (4 × 3 × 3) was carried out to statistically evaluate if the independent variables' effects were significant. Four advanced oxidation processes (photolysis, photolysis + H2O2, heterogeneous photocatalysis, and heterogeneous photocatalysis + H2O2), three support materials (quartz, calcite, and glass), and three pH levels (3, 5.4, and 9) were evaluated. Reaction kinetics were fitted to the pseudo-first-order reaction rate and data was analyzed with an ANCOVA and means test, considering solar light intensity as a covariate. Photolysis/calcite at pH 5.4 and heterogeneous photocatalysis + H2O2/glass plate at pH 3 gave the best results, with a reaction rate constant kph = 3.047 × 10-3min-1 and kphC = 4.498 × 10-3min-1, respectively. The three independent variables and their interactions had a significant effect in the phenol degradation (p < 0.05).

Lignin peroxidase-catalyzed direct oxidation of trace organic pollutants through a long-range electron transfer mechanism: Using propranolol as an example

In this work, lignin peroxidase (LiP) was extracted for the in vitro degradation of a persistent compound (propranolol, PPN). The results showed that 94.2% of PPN was degraded at 30 U L−1 LiP activity and 10 mg L−1 PPN. The PPN degradation rate increased from 33.5% to 94.2% when the veratryl alcohol (VA) concentration varied from 0 to 180 µM, but decreased to 73.1% with further VA addition. This phenomenon confirmed that VA was indispensable, however, it also acted as a competitive inhibitor of PPN oxidation. Computational analysis revealed that the Trp171…iron porphyrin (TRP-FeP) path was responsible for specific substrate (e.g., VA) transformation, and another long-range electron transfer (LRET) path through His–Asp…FeP (HSP-FeP) was discovered for non-specific substrate (e.g., PPN) degradation. These two electron-transfer routes shared one catalytic center, and VA protected the enzyme from H2O2-dependent inactivation. The HSP-FeP path transformed PPN through single electron transfer or H abstraction mechanisms. In addition, hydroxyl radicals generated in the LiP/H2O2 system were involved in the hydroxylation of the PPN intermediates. Possible degradation pathways were deduced using these degradation mechanisms and mass-spectrometry analysis. The multipath degradation mechanism endowed LiP with a remarkable capacity for removing various recalcitrant pollutants in environmental remediation.

Microbial Debromination of Polybrominated Diphenyl Ethers by Dehalococcoides-Containing Enrichment Culture.

Polybrominated diphenyl ethers (PBDEs), commonly used as flame retardants in a wide variety of consumer products, are emerging persistent pollutants and ubiquitously distributed in the environment. The lack of proper bacterial populations to detoxify these recalcitrant pollutants, in particular of higher brominated congeners, has confounded the attempts to bioremediate PBDE-contaminated sites. In this study, we report a Dehalococcoides-containing enrichment culture, PB, which completely debrominates 0.44 μM tetra-brominated diphenyl ether (BDE) 47 to diphenyl ether within 25 days (0.07 μM Br–/day) and extensively debrominates 62.4 ± 4.5% of 0.34 μM hepta-BDE 183 (0.006 μM Br–/day) with a predominant generation of penta- through tri-BDEs as well as small amounts of diphenyl ether within 120 days. Later, a marked acceleration rate (0.021 μM Br–/day) and more extensive debromination (87.7 ± 2.1%) of 0.38 μM hepta-BDE 183 was observed in the presence of 0.44 μM tetra-BDE 47, which is achieved via the faster growth rate of responsible bacterial populations on lower BDE-47 and debromination by expressed BDE-47 reductive dehalogenases. Therefore, the PB enrichment culture can serve as a potential candidate for in situ PBDE bioremediation since both BDE-47 and BDE-183 are dominant and representative BDE congeners and often coexist in contaminated sites.