Photocatalytic Degradation of 2,4,6-Trichlorophenol by MgO–MgFe2O4 Derived from Layered Double Hydroxide Structures

Electrochemical sensors based on molecularly imprinted polymers for the detection of chlorophenols as emergent distributing chemicals (EDCs): a review

Environmental pollutants like chlorophenol chemicals and their derivatives are commonplace. These compounds serve as building blocks in the production of medicines, biocides, dyes, and agricultural chemicals. Chlorophenols enter the environment through several different pathways, including the breakdown of complex chlorinated hydrocarbons, industrial waste, herbicides, and insecticides. Chlorophenols are destroyed thermally and chemically, creating dangerous chemicals that pose a threat to public health. Water in particular is affected, and thorough monitoring is required to find this source of pollution because it can pose a major hazard to both human and environmental health. For the detection of chlorophenols, molecularly imprinted polymers (MIPs) have been incorporated into a variety of electrochemical sensing systems and assay formats. Due to their long-term chemical and physical stability as well as their simple and affordable synthesis process, MIPs have become intriguing synthetic alternatives over the past few decades. In this review, we concentrate on the commercial potential of the MIP technology. Additionally, we want to outline the most recent advancements in their incorporation into electrochemical sensors with a high commercial potential for detecting chlorophenols.

Molecularly imprinted polymer-based electrochemical sensors for monitoring the persistent organic pollutants chlorophenols

Because of the serious risks they pose to the environment and public health, chlorophenols (CPs), a typical class of the most persistent organic pollutants, have drawn increasing attention. Monitoring CPs effectively has become a pressing and difficult problem. The rapidly increasing need for onsite and real-time CP detection has led to the consideration of electrochemical sensing as a workable solution. Molecularly imprinted polymer (MIP)-based electrochemical sensing has emerged as a promising area for environmental monitoring in response to this analytical problem. MIPs, in conjunction with miniature electrochemical transducers, provide the opportunity to detect target analytes in situ. These devices have the advantages of great chemical and physical stability, cheap production costs, good selectivity, and quick response times. Most studies suggest that these sensors use nanoparticles to improve their analytical properties, especially sensitivity. Furthermore, these sensors have successfully used real water samples without the need for time-consuming pretreatment procedures. This article provides an overview of electrochemical MIP-based sensors reported to detect CPs in water samples. To obtain the highest sensitivity, special consideration is given to the fabrication of the sensors, which includes the use of various functional monomers, sensing platforms, and materials. Several other parameters are also discussed, including the linear concentration range, limit of detection, and the types of water samples that were examined.

Polypyrrole-induced active-edge-S and high-valence-Mo reinforced composites with boosted electrochemical performance for the determination of 2,4,6-trichlorophenol in the aquatic environment

With the extensive application of halogenated aromatic compounds, including 2,4,6-Trichlorophenol (2,4,6-TCP), improper treatment or discharge contribute to persistently harmful effects on humans and the ecosystem, rendering the identification and monitoring of 2,4,6-TCP in the aquatic environment urgently required. In this study, a highly sensitive electrochemical platform was developed using active-edge-S and high-valence-Mo rich MoS₂/polypyrrole composites. MoS₂/PPy illustrates superior electrochemical performance and catalytic activity and has not been explored for detecting chlorinated phenols previously. The local environment of polypyrrole induces the richness of active edge S and a high oxidation state of Mo species in the composites, both of which endorse a sensitive anodic current response due to the favored oxidation of 2,4,6-TCP through nucleophilic substitution. Also, the higher complementarity between pyrrole and 2,4,6-TCP with respective electron-rich and electron-poor features through π-π stacking interactions enhances the specific detection capability of 2,4,6-TCP by the MoS₂/polypyrrole-modified electrode. The MoS₂/polypyrrole-modified electrode achieved a linear range of 0.1-260 μM with an ultralow limit of detection of 0.009 μM. Additionally, the structural stability boosted by the linkage of polypyrrole and MoS₂ results in good resistance and satisfactory recovery in real water samples. The compiled results demonstrate that the proposed MoS₂/polypyrrole composite opens up a new potential to advance a sensitive, selective, facile fabrication, and low-cost platform for the on-site determination of 2,4,6-TCP in aquatic systems. The sensing of 2,4,6-TCP is important to monitor its occurrence and transport, and can also serve to track the effectiveness and adjust subsequent remediation treatments applied to contaminated sites.

Novel polypropylene-TiO2:Bi spherical floater for the efficient photocatalytic degradation of the recalcitrant 2,4,6-TCP herbicide

In this work, spherical photocatalytic floaters were fabricated by depositing TiO₂:Bi (TBi) particles on polypropylene (PP) spheres (recycled from beer cans). These particles were deposited on the sphere (TBi-sphere) by the spray coating technique and evaluated their performance for the photocatalytic degradation of 2,4,6-trichlorophenol (2,4,6-TCP) herbicide. SEM images demonstrated that the BTi powders consisted in conglomerated grains with sizes of 20-80 nm and the analysis by X-ray diffraction confirmed the presence of rutile and anatase phases in the BTi. The photocatalytic experiments showed that the TBi and TBi-sphere produced maximum degradation of 90 and 97% for 2,4,6-TCP, respectively, after 4 h under UV-Vis light. The photocatalytic powders/composites were reused 3 times and the loss of degradation efficiency was 3 and 16% for the TBi powder and TBi-sphere, respectively. This means that the TBi-sphere is more stable for the continuous degradation of the 2,4,6-TCP contaminant. The TiO₂:Bi powder was compared with the commercial TiO₂ (P25) and found that the TiO₂:Bi powder had higher light absorption (≈42%) and higher surface area (≈105%) than the P25. Therefore, the degradation percentage for the 2,4,6-TCP was 52% higher in the sample doped with Bi. Also, scavenger experiments were carried out and found that the main oxidizing agents produced for the degradation of 2,4,6-TCP were •OH^- radicals and •O₂^- anions. Other species such as h⁺ were also produced at lower amount. Hence, our results demonstrated that spherical/floatable photocatalytic composites are a viable option to remove herbicide residuals from the water, which is of interest in water-treatment-plants.

Biomass chemical looping gasification for syngas production using modified hematite as oxygen carriers

Syngas is a clean energy carrier and a major industrial feedstock. In this paper, syngas was produced via biomass chemical looping gasification (CLG) process. Hematite, the most common Fe-based oxygen carrier (OC), was modified with different metal oxides (CeO₂, CaO and MgO) by the impregnation method. The hematite modified by CeO₂, CaO and MgO was namely as CeO₂-hematite (CeO₂-H), CaO-hematite (CaO-H) and MgO-hematite (MgO-H), respectively. The introduction of CeO₂, CaO and MgO enhanced the reactivity of lattice oxygen of hematite. The optimum condition for syngas production had been explored as the mass ratio of oxygen carrier to biomass (O/B) of 0.2, the mass ratio of steam to biomass (S/B) of 0.75 and temperature of 800°C in the biomass CLG process. The CeO₂-H exhibited the most wonderful performance compared to that for CaO-H and MgO-H. The crystal composition of OC influenced greatly in the CLG process. CeFeO₃ had a good oxygen mobility property and lattice oxygen releasing capacity due to the most oxygen vacancy distributed on the OC surface and the most active lattice oxygen, which is conducive to the biomass chemical looping gasification process for syngas production, leading to the highest gasification efficiency of 95.86% and gas yield of 1.20 m³/kg of the three. Cyclic test proved that CeO₂-H had well sintering resistance and cyclic performance.

Preparation of MnO2-Carbon Materials and Their Applications in Photocatalytic Water Treatment

Water pollution is one of the most important problems in the field of environmental protection in the whole world, and organic pollution is a critical one for wastewater pollution problems. How to solve the problem effectively has triggered a common concern in the area of environmental protection nowadays. Around this problem, scientists have carried out a lot of research; due to the advantages of high efficiency, a lack of secondary pollution, and low cost, photocatalytic technology has attracted more and more attention. In the past, MnO₂ was seldom used in the field of water pollution treatment due to its easy agglomeration and low catalytic activity at low temperatures. With the development of carbon materials, it was found that the composite of carbon materials and MnO₂ could overcome the above defects, and the composite had good photocatalytic performance, and the research on the photocatalytic performance of MnO₂-carbon materials has gradually become a research hotspot in recent years. This review covers recent progress on MnO₂-carbon materials for photocatalytic water treatment. We focus on the preparation methods of MnO₂ and different kinds of carbon material composites and the application of composite materials in the removal of phenolic compounds, antibiotics, organic dyes, and heavy metal ions in water. Finally, we present our perspective on the challenges and future research directions of MnO₂-carbon materials in the field of environmental applications.

Multivalent Effect of Defect Engineered Ag2S/g-C3N4 3D Porous Floating Catalyst with Enhanced Contaminant Removal Efficiency

Chlorophenols, as a major environmental pollutant, enter water systems through industrial wastewater, agricultural runoff and chemical spills, and they are stable, persistent under natural conditions, and highly hazardous to water resources. The objective of this article is to prepare Ag2S-modified C3N4 three-dimensional network photocatalyst by calcination method to use photocatalysis as an efficient, safe, and environmentally friendly method to degrade chlorophenols. Ag2S/C3N4 has an excellent visible light absorption range, low band gap, effective separation of photogenerated charges, and active free radicals production, all of which make for the enhancement of photocatalytic degradation performance of the Ag2S/C3N4 system. Under the light irradiation (λ ≥ 420 nm), the photocatalytic degradation efficiency of 2,4,6-Trichlorophenol reach 95% within 150 min, and the stable photocatalytic degradation activity can still be maintained under different pH water environment and four degradation cycles. When Ag2S is loaded on ACNs, more photogenerated electrons are generated and subsequent reactions produce highly reactive groups such as •O2- and •OH that will originally be able to continuously attack TCP molecules to degrade pollutants. Therefore, this study shows that the photocatalyst provides a novel research approach for realizing the application in the field of pollutant degradation.

Dual function Mg-doped binary metal ferrite: Photocatalytic degradation of trichlorophenol, bactericidal activity and molecular docking analysis

A new Mg-doped Zn_0.5Ni_0.5Fe₂O₄ (Mg-FZN) photocatalyst was synthesised using a simple co-precipitation-doping technique to develop a dual-function material with the ability to degrade hazardous and refractory pollutants and inactivate bacterial strains. The characterization results revealed that Mg-FZN is an n-type semiconductor with a conduction band of -0.413 eV, an average pore width of 2.32 nm, and a crystal size of 31.45 nm. The photocatalytic activity of Mg-FZN was assessed based on the degradation of 2,4,5-trichlorophenol and achieved 83.8% degradation efficiency under optimised conditions. The radical quenching results revealed that h⁺ significantly contributed to the photodegradation process while ^•OH, and ^•O₂^- played key roles. Additionally, within 60 min, 25 mg of Mg-FZN had bactericidal effects on the bacteria E. coli and S. aureus in both the presence and absence of UV light. Mg-FZN showed H-bonding, electrostatic, and metal-contact interactions with the amino acid residues of the bacterial protein with high binding scores (-4.711 kcal/mol and -5.872 kcal/mol), according to molecular docking.

Self-assembled nanorods with reduced graphene oxide as efficient nano-catalyst for dual modality sensing of hazardous phenolic compound

The modern development in the agricultural production has huge influential factors being highly beneficial and also includes some health hazards. Under the class of chlorophenols, 2,4,6-trichlorophenol is a widely used chemical which remains as a major pollutant in the environment. The detection of 2,4,6-trichlorophenol was initiated as a controlling measure to decrease the seriousness prevailing in the ecosystem. The electrochemical and UV-vis absorption sensing platform are simple and low-cost detection techniques with precise and sensitive analysis. Cadmium tin oxide integrated with the reduced graphene oxide was employed as a nanohybrid for the construction of the working electrode. The structural and morphological analysis confirmed the high degree of crystallinity of the nanocomposite with nanorod formation. The high surface area, with high charge carrier mobility, and increased electrical conductivity of the material boosted the 2,4,6-trichlorophenol detection. The active surface area was calculated to be 0.068 cm^-1, 0.089 cm^-1, 0.118 cm^-1 and 0.146 cm^-1 for all the modified electrodes. The resistance of the electrodes was about 91.4 Ω, 72.9 Ω, 48.8 Ω and 41.6 Ω. The linear range of 2,4,6-trichlorophenol was 0.019 μM-0.299 μM and 1.299 μM-1678.97 μM in electrochemical sensing and 10.99 μM-24.84 μM in UV detection. The obtained limit of detection with the formulation 3σ/SD was about 3.05 nM and 80 nM with sensitivity about 14.01 μA μM^-1 cm^-2. The real sample detection in environmental real samples showed good recovery results. The specific selectivity, good repeatability, reproducibility and stability analysis proves the good sensing parameters. Thus, the fabricated electrode is highly sufficient of sensing 2,4,6-trichlorophenol. These excellent features of the material can be applied for several other applications which will provide good performances.

Vanadium selenide decorated reduced graphene oxide nanocomposite: A co-active catalyst for the detection of 2,4,6 - Trichlorophenol

Transition metal chalcogenides (TMCs) have great potential in diverse electrochemical technologies owing to their unique characteristics. In the present work, we portray the design and synthesis of Vanadium selenide (V₂Se₉)/reduced graphene oxide (rGO) forming a two-dimensional (2D) hybrid nanocomposite via a simple hydrothermal method. The successfully synthesized nanocomposite underwent in-depth surface and morphological characterizations by XRD, Raman spectroscopy, XPS, TEM, STEM and its potential as an electro catalyst was investigated by using glassy carbon electrode (GCE) for the detection of 2,4,6-trichlorophenol (TCP). The structural features favored a high charge transfer ratio, high surface area as well as excellent conductivity and catalytic activity. The V₂Se₉/rGO/GCE modified electrode showed a low charge transfer resistance (R_ct) of 54.057 Ω cm², a decent detection limit (LOD) of 35.07 nM and a very high sensitivity of 22 μA μM^-1 cm^-2 in a working range of 0.001 μM-1150 μM. This is due to the active proton interaction, surface enhancement, and positive synergistic effect between rGO and V₂Se₉. The proposed sensor has good detection potential in agricultural soil, river water, fish, and beverage samples like wine and apple juice. The obtained results from our investigation would elucidate the application of the catalyst in electrochemical sensors.

Synthesis and characterization of chitosan-supported Fe2O3 nanohybrids for rapid sonophotocatalytic degradation of 2,4,6-trichlorophenol

The present study reports the design of heterogeneous photocatalytic system using Fe₂O₃ with chitosan (CS) as a matrix for the sonophotocatalytic degradation of 2,4,6-trichlorophenol (2,4,6-TCP). CS was chosen as a polymer matrix as it is abundant in nature, eco-friendly, and can be easily processed into microparticles, nanofibers, as well as nanoparticles and shows the tendency of adhesion towards a vast range of solid substrates besides serving as a chelating agent toward metallic oxides. The nanohybrids were characterized via Fourier transformation infrared spectrum (FT-IR), X-ray diffraction (XRD), scanning electron microscopy coupled with electron dispersive spectrum (SEM-EDS), thermogravimetric analysis (TGA), and UV-visible diffuse reflectance (UV-Vis-DRS) analyses. Infrared spectroscopy (IR) studies confirmed synergistic interaction between Fe₂O₃ and CS. The XRD measurements confirmed the crystalline morphology while SEM revealed formation of rod-like structures. The TGA studies confirmed higher thermal stability of CS/Fe₂O₃ as compared to pure CS. The optical band gap for CS and CS/Fe₂O₃ was calculated to be 3 eV and 2.25 eV, respectively, from diffuse reflectance spectral (DRS) studies. Rapid photocatalytic degradation of 2,4,6-TCP was observed under UV light irradiation in presence of CS and CS/Fe₂O₃ nanohybrids which revealed 83.19% and 95.20% degradation within a short span of 60 min. The degraded fragments were identified using liquid chromatography-mass spectrometry (LC-MS). The present study on the development of ecofriendly nanohybrid photocatalyst is expected to provide experimental basis for the future development of CS-based photocatalysts which can be easily processed into membranes/filters for the industrial scale degradation of toxic organic pollutants.

Photoelectrocatalytic Degradation of Congo Red Dye with Activated Hydrotalcites and Copper Anode

Photoelectrocatalysis is a novel technique that combines heterogeneous photocatalysis with the application of an electric field to the system through electrodes for the degradation of organic contaminants in aqueous systems, mainly of toxic dyes. The efficiency of these combined processes depends on the semiconductor properties of the catalysts, as well as on the anodic capacity of the electrode. In this study, we propose the use of active hydrotalcites in the degradation of Congo red dye through processes assisted by ultraviolet (UV) irradiation and electric current. Our research focused on evaluating the degradation capacity of Congo red by means of photolysis, catalysis, photocatalysis, electrocatalysis, and photoelectrocatalysis, as well as identifying the effect of the properties of the active hydrotalcites in these processes. The results show that a maximum degradation was reached with the photoelectrocatalysis process with active hydrotalcites and a copper anode at 6 h with 95% in a half-life of 0.36 h. The degradation is favored by the attack of the OH• radicals under double bonds in the diazo groups where the electrode produces Cu2+ ions, and with the photogenerated electrons, the recombination speed of the electron–hole in the hydrotalcite catalyst is reduced until the complete degradation.

Catalysis for Global Development. Contributions around the Iberoamerican Federation of Catalysis

Following biennial meetings held since 1968, the Iberoamerican Federation of Catalysis Societies (FISoCat), the Portuguese Chemical Society (SPQ) and the University of Coimbra jointly organized the XXVI Iberoamerican Congress on Catalysis (CICat 2018), which took place in the historic city of Coimbra, Portugal, between the 9th and 14th of September 2018 [...]