Removal Of Recalcitrant Pollutants Research Articles

Triazine-based covalent organic framework/ g-C3N4 heterojunction toward highly efficient photoactivation of peroxydisulfate for sulfonamides degradation

Rational design of multifunctional catalysts to realize the synergistic combination of photocatalysis and peroxydisulfate (PDS) activation process is a promising approach for the effective removal of recalcitrant pollutants. Herein, metal-free covalent organic framework/g-C3N4 (COF/CN) van der Waals heterojunction was synthesized by the in-situ polymerization on g-C3N4. The van der Waals force and π-π conjugation effect contributes to promoting the interfacial migration and separation of photoinduced carries. The photocatalytic removal efficiency of sulfamethazine (SMT) by COF/CN was increased by 4.9 and 6.6-folds compared to those of COF and g-C3N4, respectively. In the optimal COF/CN-3/PDS/Vis process, SO4•− and 1O2 were identified as the major contributors to SMT degradation. The relationship between the molecular reactivity of sulfonamides (SAs) and reaction kinetics was elucidated by density functional theory (DFT) calculations at the electron level. The degradation rates and pathways depend on the electronic distribution and reactive sites of SAs with five- or six-membered heterocyclic ring substituents. The nonradical attack on the aniline and the breakage of C-N bond were the common traits of SAs degradation, whereas a unique Smiles-type pathway occurred in SAs with six-membered heterocyclic substituents. This work expected to promote the insight for the interaction between molecular structures of pollutants and reactive species in wastewater purification.

Two-stage treatment of pulp bleaching wastewater by Fenton and biological processes to remove recalcitrant pollutants

In this work, Fenton and aerobic biological processes were successfully coupled to treat pulp bleaching wastewater. The goal was to find a treatment solution to simultaneously maximise the removal of recalcitrant pollutants (adsorbable organic halides – AOX) and organic load (COD) from that wastewater. To that end, two treatment setups were studied: (i) aerobic biological process (activated sludge) followed by Fenton; and (ii) Fenton followed by aerobic biological process. Treatment by biological process followed by Fenton allowed for an overall removal of AOX and COD of 89.5 % and 82.5 %, respectively, at the optimised Fenton conditions determined by Response Surface Methodology: 489 mM H2O2, 9.3 mM Fe2+, and 49.2 min of treatment. Under the inverse treatment setup, an overall removal of 89.6 % AOX and 71.9 % COD was attained. Moreover, it was proven that the microbiological activity was not greatly affected by neither the initial organic load, nor the existence of Fenton chemicals and transformation products in the wastewater composition. Although the treatment sequence Biological → Fenton presented maximum overall performance, operating costs associated with this solution were over 2-fold higher than the inverse sequence, owing to the higher demand of chemicals.

0D/1D CuWO4/Mn0.3Cd0.7S S-scheme heterojunctions for full-spectrum bifunctional photocatalytic degradation and hydrogen production

Integrating photocatalytic oxidation for pollutant removal with hydrogen production via photocatalysis presents a promising approach for sustainable water purification and renewable energy generation, circumventing the sluggish multi-electron transfer inherent in photocatalytic water oxidation. This study introduces novel zero-/one-dimensional (0D/1D) CuWO4/Mn0.3Cd0.7S step-scheme (S-scheme) heterojunctions that exhibit exceptional bifunctional capabilities in photocatalytic degradation and hydrogen production under full-spectrum illumination. The degradation efficiency for tetracycline (TC) using 5 %-CuWO4/Mn0.3Cd0.7S reaches 94.3 % and 94.5 % within 60 min and 6 h, respectively, under ultraviolet–visible (UV–Vis) and near-infrared (NIR) light. Notably, these 0D/1D CuWO4/Mn0.3Cd0.7S S-scheme heterojunctions demonstrate superior hydrogen production, achieving rates of 12442.03 μL g-1h−1 and 2418.54 μL g-1h−1 under UV–Vis light and NIR light irradiation, respectively—these rates are 2.3 times and 55.2 times higher than that of Mn0.3Cd0.7S alone. This performance enhancement is attributed to the intrinsic dimensional effects, transitions of transition metal d-d orbitals, and S-scheme hole/electron (h+/e−) separation characteristics. Additionally, experimental results and density functional theory (DFT) calculations have clarified the modulation of electronic configurations, band alignment, and interfacial interactions via 0D/1D S-scheme heterojunction engineering. This study sheds light on the electron transfer mechanism within S-scheme heterojunction and enhances the effectiveness, economy, and sustainability of recalcitrant pollutant removal and hydrogen production.

H*ads dynamics engineering via bimetallic Pd–Cu@MXene catalyst for enhanced electrocatalytic hydrodechlorination

Electrocatalytic hydrodechlorination (EHDC) is a promising approach to safely remove halogenated emerging contaminants (HECs) pollutants. However, sluggish production dynamics of adsorbed atomic H (H*ads) limit the applicability of this green process. In this study, bimetallic Pd–Cu@MXene catalysts were synthesized to achieve highly efficient removal of HECs. The alloy electrode (Pd–Cu@MX/CC) exhibited better EHDC performance in comparison to Pd@MX/CC electrode, resulting in diclofenac degradation efficiency of 93.3 ± 0.1%. The characterization analysis revealed that the Pd0/PdII ratio decreased by forming bimetallic Pd–Cu alloy. Density functional theory calculations further demonstrated the electronic configuration modulation of the Pd–Cu@MXene catalysts, optimizing binging energies for H* and thereby facilitating H*ads production and tuning the reduction capability of H*ads. Noteably, the amounts and reduction potential of H*ads for Pd–Cu@MXene catalysts were 1.5 times higher and 0.37 eV lower than those observed for the mono Pd electrode. Hence, the introduction of Cu into the Pd catalyst optimized the dynamics of H*ads production, thereby conferring significant advantages to EHDC reactions. This augmentation was underscored by the successful application of the alloy catalysts supported by MXene in EHDC experiments involving other HECs, which represented a new paradigm for EHDC for efficient recalcitrant pollutant removal by H*ads.

Exploring the roles of ascorbic acid/L-cysteine in boosted carbamazepine degradation by biochar-CuFe2O4/Fe2O3/CuO/peroxymonosulfate: Taguchi optimization and mechanistic studies

The present research aimed to improve the efficiency of a novel walnut shell biochar-CuFe2O4/Fe2O3/CuO (BC-CuFeO) nanocomposite for the activation of peroxymonosulfate (PMS) for the degradation of carbamazepine (CBZ), as a recalcitrant organic pollutant. Ascorbic acid (H2A) and L-cysteine (LC) were utilized to significantly increase CBZ removal efficiency in the BC-CuFeO/PMS system. An L-16 Taguchi design was applied to identify the relative significance of the operating parameters for the degradation of CBZ. In addition, both the BC-CuFeO/PMS/H2A and BC-CuFeO/PMS/LC systems demonstrated outstanding CBZ degradation performance in the presence of humic acid, sodium chloride, and sodium nitrate, respectively. The scavenging experiments indicated that 1O2, ·OH, O2•−, and SO4•− were responsible for CBZ degradation in the BC-CuFeO/PMS/H2A system, while O2•−, 1O2, and ·OH contributed to CBZ degradation in the BC-CuFeO/PMS/LC system. Furthermore, the intermediates and pathways of CBZ degradation were determined via Q-TOF-MS analysis, and the potential toxicity of the products was assessed via Toxicity Estimation Software Tool analysis. The practicality of the nanocomposites was also evaluated through the fabrication of catalytic balls and catalytic membranes, followed by the study of their stability for wastewater treatment. In conclusion, this study provides novel and promising PMS activation methods for the efficient removal of recalcitrant pollutants from wastewater.

Efficient piezo-photocatalysis of Bi2O2(OH)NO3/BiOI heterojunction: Collaboration of piezoelectric polarization and interface electric field

Effective removal of recalcitrant pollutants is crucial for environmental protection. Tetracycline hydrochloride, as a representative recalcitrant organic pollutant, poses a potential threat to environmental integrity when present in aquatic ecosystems. Coupling piezoelectric polarization, capable of considerably promoting the photocharge separation, acts as a very prevalent and attractive strategy to improve the photocatalytic activity. In this study, an efficient piezo-photocatalytic system was developed in Bi2O2(OH)NO3/BiOI heterojunction by collaborating with interfacial electric field and vibration-induced piezoelectric polarization. The construction of type II heterojunction allows an interfacial electric field to propel the photogenerated electrons from BiOI to Bi2O2(OH)(NO3) under visible light irradiation. The introduction of vibration-induced piezoelectric polarization field strengthens the interfacial electric field, which further promote the separation and migration of photogenerated charges. Profiting from the above advantages, Bi2O2(OH)(NO3)/BiOI heterojunction exhibited a remarkable piezo-photocatalytic performance, achieving an over 80% degradation efficiency of tetracycline hydrochloride within 10 min, which far surpasses that under individual photocatalysis or ultrasound-induced piezocatalysis and also exceeds most of the previously reported piezo-photocatalysts. The combination of electron paramagnetic resonance, piezoresponse force microscopy, COMSOL simulation, and photoelectrochemical tests are conducted to probe the synergistically-catalytic mechanism. This work not only elucidates the comprehensive impact of interfacial electric field and piezoelectric polarization on charge separation, but also highlights the tremendous potential of piezo-photocatalysis for environmental remediation.

Immobilized-laccase bioreactors for wastewater treatment.

Laccases have shown to be efficient biocatalysts for the removal of recalcitrant pollutants from wastewater. Thus, they catalyze the oxidation of a wide variety of organic compounds by reducing molecular oxygen to water. However, the use of free laccases holds several drawbacks such as poor reusability, high cost, low stability and sensitivity to different denaturing agents that may occur in wastewater. Such drawbacks can be circumvented by immobilizing laccase enzymes in/on solid carriers. Hence, during the last decades different approaches considering various techniques and solid carriers to immobilize laccase enzymes have been developed and tested for the removal of pollutants from wastewater. To scale up wastewater treatment bioprocesses, immobilized laccases are placed in different reactor configurations.

Novel bifunctional in-based metal–organic gel/bacterial cellulose composite gels for effective tetracycline antibiotics removal: Synergistic behavior and mechanism insight of adsorption-photocatalysis

The widespread pollution by tetracycline antibiotics has been proved to be a serious problem to human health and biological systems. Synergistic adsorption-photocatalysis method has demonstrated satisfactory miraculous results for the removal of recalcitrant pollutants. Here we constructed a novel bifunctional In-MOG with hierarchical pore structures, large specific areas and abundant active sites via room-temperature synthesis, achieving 92.93% and 95.58% removal of chlortetracycline (CTC) and tetracycline (TTC) in 60 min, respectively. The excellent removal performance was attributed to the synergistic adsorption-photocatalysis process that resembled a repetitive assembly line work of “enriching and destroying” pollutants. Briefly, CTC/TTC molecules in the aqueous environment were rapidly adsorbed by In-MOG through pore filling, electrostatic interaction, hydrogen bonding interaction, complexation and π-π stacking interaction to accomplish enrichment of pollutants; meanwhile, the generated h+ and •O2− were involved as the main active species in the rapid in-situ photodegradation of pollutants to complete their destruction. Furthermore, In-MOG exhibited excellent anti-interference ability and reusability. Afterwards, in order to address the drawback of easy agglomeration and difficult recycle of powdered In-MOG, In-MOG/BC with the advantages of good removal performance and fine stability was constructed by immobilizing In-MOG into bacterial cellulose (BC) flexible substrate. Further exploration of In-MOG/BC in a self-built reactor for CTC/TTC removal from dynamic systems was carried out to assess the prospect for large-scale applications. Overall, the facile rational design for In-MOG/BC with synergistic adsorption-photocatalysis and the continuous flow reactor provides worthwhile insights in the water purification field.

Hydrodynamic cavitation and photocatalysis for effluent treatment: Key operating parameters and synergistic effects

A combination of hydrodynamic cavitation and photocatalysis (HC-PC) is a promising water treatment technology for the removal of recalcitrant pollutants. In this work, we investigated influence of key parameters of this hybrid technology such as initial concentration, catalyst loading, pH, re-circulating flow rate and cavitation device/scale on degradation of three model pollutants (coumarin, paracetamol and dichloroaniline). Unlike previous HC-PC studies, the individual and combined systems were investigated for each parameter to determine their effect on system performance and overall synergy. We report a dependence of logKow for both systems, with highest removal (100% in 20 min with AC-PC, 37% in 120 min, or 350 passes, with HC-PC) and synergy (Synergistic index of 2.8 and 1.2 for AC-PC and HC-PC, respectively) associated with the more hydrophobic compound, dichloroaniline. HC-PC performance increased and synergy decreased with increasing catalyst loading, and the inverse effect was found with initial concentration (C0: 17.5 to 70 ppm). Similarly, pH decreased performance but increased synergy and low re-circulating flow rate increased performance but decreased synergy. Detailed analysis of these results indicated the utilisation of in-situ generated H2O2 from recombined OH radicals is the main contributor of the observed synergy, and not physical interactions between cavities and photocatalyst particles. Following this, for the first time, influence of cavitation device type (based on linear flows and swirling flows) and device scale on overall performance of HC-PC system was quantified. Vortex based cavitation device was found to provide a 20% and 25% higher performance and synergy compared to a linear flow based cavitation device like orifice. The results presented here provide valuable insights into the synergy of HC and photocatalytic systems.

Sunlight-driven intimately coupled photocatalysis and biodegradation (SDICPB): A sustainable approach for enhanced detoxification of triclosan

Triclosan is considered as recalcitrant contaminant difficult to degrade from the contaminated wastewater. Thus, promising, and sustainable treatment method is necessary to remove triclosan from the wastewater. Intimately coupled photocatalysis and biodegradation (ICPB) is an emerging, low-cost, efficient, and eco-friendly method for the removal of recalcitrant pollutants. In this study BiOI photocatalyst coated bacterial biofilm developed at carbon felt for efficient degradation and mineralization of triclosan was studied. Based on the characterization of BiOI prepared using methanol had lower band gap 1.85 eV which favors lower recombination of electron-hole pair and higher charge separation which ascribed to enhanced photocatalytic activity. ICPB exhibits 89% of triclosan degradation under direct sunlight exposure. The results showed that production of reactive oxygen species hydroxyl radical and superoxide radical anion played crucial role in the degradation of triclosan into biodegradable metabolites further the bacterial communities mineralized the biodegradable metabolites into water and carbon dioxide. The confocal laser scanning electron microscope results emphasized that interior of the biocarrier shows a large number of live bacterial cells existing in the photocatalyst-coated carrier, where the little toxic effect on bacterial biofilm occurred on the exterior of the carrier. The extracellular polymeric substances characterization result remarkable confirms that which could act as sacrificial agent of photoholes further helped by preventing the toxicity to the bacterial biofilm from the reactive oxygen species and triclosan. Hence, this promising approach can be a possible alternative method for the wastewater treatment polluted with triclosan.

Ultrafast degradation of tetracycline by PMS activation over perfect cubic configuration MnCo2O4.5: New insights into the role of metal-oxygen bonds in PMS activation

The rapid electron transfer to accelerate the redox cycle of the multi-valent metal is the key factor to enhance PMS activation. Here, MnCo2O4.5 possessing perfect cubic configuration, was successfully synthesized by a simple hydrothermal method. Benefiting from metal-oxygen bridge bonds (Mn-O-Co) accompanied by higher electron cloud overlap of Mn-O/Co-O, the as-obtained MnCo2O4.5 exhibited excellent activation of peroxymonosulfate (PMS) for ultrafast elimination of tetracycline (TC) with high mineralization capacity by breaking the thermodynamic limitation of Mn(IV) reduction to Mn(III). Moreover, the stronger bonding ability of Mn-O/Co-O, Mn-O-Co, and asymmetric electron spin orbits between Mn 3d and Co 3d endowed the as-prepared MnCo2O4.5 with trace Mn/Co leaching and could realize decent recovery capacity by magnetic assisted separation. In addition, this catalyst exhibited good resistance to inorganic anions and natural organic matter, as well as satisfactory treatment efficiency for simulated wastewater and ultra-high inactivation efficiency for Escherichia coli. Competitive radical scavenging tests and electron spin resonance (ESR) revealed the primary role of ·O2–, 1O2 and OH in TC removal. The TC degradation pathway was proposed by intermediate analysis and theoretical calculation. This work offered a new insight for the design of highly active PMS activators to achieve efficient removal of recalcitrant pollutant.

Facile-prepared Fe/Mn co-doped biochar is an efficient catalyst for mediating the degradation of aqueous ibuprofen via catalytic ozonation

The fabrication of efficient, stable, and low-cost catalysts is crucially important for the catalytic ozonation process for the removal of recalcitrant pollutants. In this study, we present a facile impregnation-pyrolysis method for the preparation of novel porous Fe/Mn co-doped biochar (Fe-Mn-C) with excellent catalytic activity and reusability for the catalytic ozonation of ibuprofen (IBP). The incorporation of Fe/Mn heteroatoms into the carbon skeleton of biochar not only produced more defective sites and promoted the charge transfer on the materials surface but also created active Fe/Mn species with multi-valence states for ozone activation. As a result, >95% of IBP (50 mg/L) and 80.5% of total organic carbon can be rapidly removed within 9 min in the Fe-Mn-C/O3 process at a pH of 7, ozone dosage of 4.93 mg/min, and Fe-Mn-C dosage of 0.5 g/L. The catalytic reaction rate in Fe-Mn-C/O3 was 6.58 times higher than that of sole ozonation and 2.3–4.1 times higher than that of catalytic ozonation with other catalysts (e.g., biochar, Fe-doped biochar, Mn-doped biochar, activated carbon, Fe3O4 and MnO2). Moreover, the obtained Fe-Mn-C can be reused for multiple cycles; the performance is not significantly reduced in subsequent cycles, and there is no significant metal leaching. Further studies suggested that the radical pathways (superoxide radicals and hydroxyl radicals) were mainly responsible for the degradation of IBP in the Fe-Mn-C/O3 system. Furthermore, the contributions of the surface functional groups, doped atoms, and delocalized π electrons of Fe-Mn-C to the decomposition of ozone and the formation of reactive species were identified by correlation analysis between the catalytic ozonation rate and the physiochemical properties of Fe-Mn-C to clarify the mechanism underlying the improved performance.

Influence of water matrix components on the UV/chlorine process and its reactions mechanism

The UV/chlorine system has become an attractive alternative Advanced Oxidation Process (AOP) for the removal of recalcitrant pollutants in the last decade due to the simultaneous formation of chlorine and hydroxyl radicals. However, there is no consensus regarding the results and trends obtained in previous micropollutant removal studies by AOPs, highlighting the complexity of the UV/chlorine process and the need for further research. This study investigates the degradation of acetaminophen (ACTP) by UV/chlorine and the effects of the water matrix in the reaction kinetics. In particular, the effects of natural organic matter (NOM), alkalinity and mineral salts on the kinetics and reactive species were elucidated. The complexity of the system was revealed by the analysis of the radical generation and transformation in different water matrices, applying the kinetic modelling approach to complement the scavenger tests.The higher kinetic rates of ACTP at alkaline pH provided new insights into the chlorine reactions under UV radiation, where secondary and tertiary reactive oxygen species including ozone were proven to play the major role in degradation. On the contrary, at acidic pH, reaction kinetic modelling demonstrated that ClO• radical occurs at high concentrations in the order of 10−10 M, being therefore the main oxidant, followed by other chlorine radicals. It is noteworthy that at alkaline pH the presence of typical inorganic ions such as carbonate had little impact on ACTP degradation, contrary to the observed reduction of degradation rates at acidic pH. The expected detrimental effect of the NOM in AOPs was also evidenced, although the use of chlorine as radical source reduces the relevance of the inner filter effect in comparison to UV/H2O2.

Magnetic double-core@shell MnO2@NiFe@DE as a multifunctional scavenger for efficient removal of tetracycline, anionic and cationic dyes

Design and fabrication of core-shell nanomaterials with excellent properties such as multifunctionality, tunability, and stability for the removal of recalcitrant pollutants from wastewater is highly valued. In this work, magnetic MnO2@NiFe@DE nanocomposites with double-core@shell structures were obtained via a two-step hydrothermal method for efficiently removing tetracycline, anionic and cationic dyes through the synergistic effect of oxidation and adsorption. The novel nanomaterial displayed superior removal of methyl orange, methylene blue, and tetracycline in low pH solutions with 100%, 100%, and 83%, respectively. The effects of solution pH, adsorption time, and contaminant concentration on the performance of the nanocomposite were also investigated, and the pseudo-second-order kinetic model well described the data. Physical adsorption including electrostatic adsorption, anion exchange, and hydrogen bonding are the predominant mechanisms for contaminant removal. The oxidation mechanism is mainly hydroxyl radical action. Through the use of permanent magnets, the recovery process of the adsorbent and the adsorbed dyes and antibiotics is energetically and economically sustainable. This as-synthesized nanocomposite as multifunction material has a high removal rate, low cost, and easy separation, and the applicability in treating the solutions with low pH, which is promised to be an efficient organic wastewater remover in practical applications.

Magnetic TiO2/Fe3O4-Chitosan Beads: A Highly Efficient and Reusable Catalyst for Photo-Electro-Fenton Process

Heterogeneous photo-electro-Fenton process is an attractive technology for the removal of recalcitrant pollutants. To better exploit the presence of an irradiation source, a bifunctional catalyst with TiO2 nanoparticles embedded into an iron–chitosan matrix was developed. The catalytic activity of the catalyst was improved by the optimization of the loaded TiO2 content. The prepared composite catalysts based on TiO2, Fe3O4 and chitosan were called TiO2/Fe3O4-CS beads. The best catalyst with an optimal ratio TiO2/Fe = 2 exhibited a high efficiency in the degradation and mineralization of chlordimeform (CDM) insecticide. Under the optimum conditions (concentration of catalyst equal to 1 g L−1 and applied current intensity equal to 70 mA), a real effluent doped with 30 mg L−1 of CDM was efficiently treated, leading to 80.8 ± 1.9% TOC reduction after 6 h of treatment, with total removal of CDM after only 1 h.The generated carboxylic acids and minerals were identified and quantified. Furthermore, the stability and reusability of the developed catalyst was examined, and an insignificant reduction in catalytic activity was noticed for four consecutive cycles of the photo-electro-Fenton process. Analyses using SEM, XRD and VSM showed a good stability of the physicochemical properties of the catalyst after use.

Recent advances on the coconut shell derived carbonaceous material for the removal of recalcitrant pollutants: A review

Recent advances on the coconut shell derived carbonaceous material for the removal of recalcitrant pollutants: A review

Highly porous seeding-free boron-doped ultrananocrystalline diamond used as high-performance anode for electrochemical removal of carbaryl from water

Boron-doped diamond (BDD) electrodes are regarded as the most promising catalytic materials that are highly efficient and suitable for application in advanced electrochemical oxidation processes targeted at the removal of recalcitrant contaminants in different water matrices. Improving the synthesis of these electrodes through the enhancement of their morphology, structure and stability has become the goal of the material scientists. The present work reports the use of an ultranano-diamond electrode with a highly porous structure (B-UNCDWS/TDNT/Ti) for the treatment of water containing carbaryl. The application of the proposed electrode at current density of 75 mA cm−2 led to the complete removal of the pollutant (carbaryl) from the synthetic medium in 30 min of electrolysis with an electric energy per order of 4.01 kWh m−3 order−1. The results obtained from the time-course analysis of the carboxylic acids and nitrogen-based ions present in the solution showed that the concentrations of nitrogen-based ions were within the established maximum levels for human consumption. Under optimal operating conditions, the proposed electrode was successfully employed for the complete removal of carbaryl in real water. Thus, the findings of this study show that the unique, easy-to-prepare BDD-based electrode proposed in this study is a highly efficient tool which has excellent application potential for the removal of recalcitrant pollutants in water.

Enhanced photo-Fenton degradation of tetracycline hydrochloride by 2, 5-dioxido-1, 4-benzenedicarboxylate-functionalized MIL-100(Fe)

Heterogeneous photo-Fenton technology has drawn tremendous attention for removal of recalcitrant pollutants. Fe-based metal-organic frameworks (Fe-MOFs) are regarded to be superior candidates in wastewater treatment technology. However, the central metal sites of the MOFs are coordinated with the linkers, which reduces active site exposure and decelerates H2O2 activation. In this study, a series of 2, 5-dioxido-1, 4-benzenedicarboxylate (H2DOBDC)-functionalized MIL-100(Fe) with enhanced degradation performance was successfully constructed via solvothermal strategy. The modified MIL-100(Fe) displayed an improvement in photo-Fenton behaviors. The photocatalytic rate constant of optimized MIL-100(Fe)-1/2/3 are 2.3, 3.6 and 4.4 times higher compared with the original MIL-100(Fe). The introduced H2DOBDC accelerates the separation and transfer in photo-induced charges and promotes Fe(II)/Fe(III) cycle, thus improving the performance. •OH and •O2− are main reactive radicals in tetracycline (TCH) degradation. Dealkylation, hydroxylation, dehydration and dealdehyding are the main pathways for TCH degradation.

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.

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.