Toxic Water Pollutants Research Articles

Polyoxometalate Derived Materials as Laccase‐Mimic Nanozyme and Reduction Catalyst for p‐Nitrophenol Remediation in Water

Abstractp‐Nitrophenol (PNP), a highly toxic water pollutant, poses significant risks to human health and the environment. For detecting PNP, a colorimetric method utilizing a nanozyme that mimics laccase activity presents a viable approach. In this study, PV14@MIL‐88A, a robust nanozyme with superior laccase‐mimic capabilities, was synthesized by incorporating Na7H2[PV14O42] (PV14) into MIL‐88A, a metal‐organic framework (MOF). This nanozyme demonstrates optimal laccase‐mimicking activity, enabling effective PNP detection via colorimetry and digital image colorimetry using smartphones. Theoretical analyses suggest that the outstanding laccase‐mimic activity of PV14@MIL‐88A is derived from the optimized d‐band center in PV14. Upon calcination with dicyandiamide (DCDA), PV14@MIL‐88A transforms into Fe2O3/VO2@NCNF. In the presence of NaBH4, Fe2O3/VO2@NCNF facilitates the conversion of PNP to p‐aminophenol (PAP), an essential precursor in paracetamol synthesis. The interaction between Fe2O3 and VO2 in Fe2O3/VO2@NCNF enhances adsorption and subsequent reduction of PNP. The saturation magnetization of Fe2O3/VO2@NCNF reaches 25 emu g−1, which supports efficient magnetic separation in the reduction process. This study not only advances an effective method for PNP detection but also facilitates its transformation from a hazardous pollutant into a valuable chemical precursor.

Green Synthesis of Cobalt-Doped CeFe2O5 Nanocomposites Using Waste Gossypium arboreum L. Stalks and Their Application in the Removal of Toxic Water Pollutants.

Currently, there is an increasing need to find new ways to purify water by eliminating bacterial biofilms, textile dyes, and toxic water pollutants. These contaminants pose significant risks to both human health and the environment. To address this issue, in this study, we have developed an eco-friendly approach that involves synthesizing a cobalt-doped cerium iron oxide (CCIO) nanocomposite (NC) using an aqueous extract of Gossypium arboreum L. stalks. The resulting nanoparticles can be used to effectively purify water and tackle the challenges associated with these harmful pollutants. Nanoparticles excel in water pollutant removal by providing a high surface area for efficient adsorption, versatile design for the simultaneous removal of multiple contaminants, catalytic properties for organic pollutant degradation, and magnetic features for easy separation, offering cost-effective and sustainable water treatment solutions. A CCIO nanocomposite was synthesized via a green co-precipitation method utilizing biomolecules and co-enzymes extracted from the aqueous solution of Gossypium arboreum L. stalk. This single-step synthesis process was accomplished within a 5-h reaction period. Furthermore, the synthesis of nanocomposites was confirmed by various characterization techniques such as Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and energy dispersive X-ray (EDX) technology. CCIO NCs were discovered to have a spherical shape and an average size of 40 nm. Based on DLS zeta potential analysis, CCIO NCs were found to be anionic. CCIO NCs also showed significant antimicrobial and antioxidant activity. Overall, considering their physical and chemical properties, the application of CCIO NCs for the adsorption of various dyes (~91%) and water pollutants (chromium = ~60%) has been considered here since they exhibit great adsorption capacity owing to their microporous structure, and represent a step forward in water purification.

Chemically Tailored Metal‐Organic Frameworks for Enhanced Capture of Short‐ and Long‐Chain Per‐ and Polyfluoroalkyl Substances from Water

AbstractPer‐ and polyfluoroalkyl substances (PFAS) are emerging as bioaccumulative and toxic water pollutants, posing a large threat to human and aquatic organisms. This threat is aggravated by their extreme persistence to common degradation methods. Adsorption is regarded as the most conventional method to treat these contaminants, however, existing sorbents present considerable limitations on performance. The development of more efficient PFAS adsorbents is therefore of urgent need. The class of metal‐organic frameworks (MOFs) can hold great promise for these purposes, featuring porous materials with high tailoring potential. Herein, a series of functionalized Zr‐MOFs have been designed with boosted capacities for the adsorption of short‐ and long‐chain perfluorinated carboxylic acids of environmental interest. The approach relies on chemistry‐based concepts to introduce targeted post‐synthetic modifications that promote PFAS···MOF interactions, specifically through coordinative bonding and hydrophobic effects. In particular, the framework TFA‐MOF‐808 (TFA = trifluoroacetic acid) displays the highest capture capacities reported for MOF materials in this pollutant class. Mechanistic studies, assisted by advanced synchrotron characterization techniques and theoretical calculations, support a ligand exchange process occurring during the adsorption phenomena. The results demonstrate the potential of this design approach in developing advanced PFAS sorbents with optimal performance.

Design of Phytic Acid Crosslinked Xerogels as Organic Photocatalysts for Visible Light‐Assisted Degradation of Dyes

AbstractExtensive research is being carried out on the degradation of water pollutants using various strategies to overcome the global water crisis. In the present study, xerogels as a better alternative is utilized to metal oxides for the photocatalytic degradation of toxic water pollutants such as dyes. Xerogels of polyaniline (PANI) and polypyrrole (PPy) are synthesized using phytic acid as a dopant as well as cross‐linker in the weight ratios of 1:1, 1:2, and 2:1 via simple chemical oxidative polymerization. The synthesized xerogels are analyzed for their spectral, morphological, thermal, and optical properties using FTIR, UV–vis, XRD, SEM, and TGA techniques. The xerogels are also tested for their photocatalytic activity against textile dyes – Methylene Blue (MB), Alizarin Red S, (ARS), Rhodamine B (RhB), and Methyl Orange (MO). Among all the composite xerogels, PANI/PPy‐2/1 showed excellent degradation efficiency of 91% for MB dye, 88% for RhB dye, 96% for ARS dye, and 92% for MO dye respectively. The composite PANI/PPy xerogels showed better degradation efficiency than their pristine counterparts. The fragments of the degraded dyes are examined using the LCMS technique and a tentative dye degradation mechanism is proposed.

One pot synthesis of multi-functional B doped g-C3N4-praseodymium oxide nanocomposites for colorimetric detection of Hg2+ ion and solar photocatalytic removal of toxic water pollutants

A novel praseodymium oxide-boron co-doped graphitic carbon nitride composite was synthesized via one-step solid-state thermal condensation of urea, orthoboric acid and praseodymium nitrate precursors. The prepared composites were characterized by various methods. All the prepared composites demonstrated multi-functional activities towards peroxidase-mimetic based colorimetric detection of Hg2+ ions and superior photocatalytic efficiency towards photodegradation of textile colorants, photoreduction of hexavalent chromium and nitro aromatics like para-nitro phenol (PNP) and para-nitro aniline (PNA). The superior photocatalytic activity can be attributed to the formation of type II heterojunction which facilitates charge separation and increases the lifetime of photogenerated charge pairs. As evident from the scavenger studies, these charge pairs are involved in the formation of superoxide and hydroxyl radicals. The superior activity of the optimum composite can be attributed to the porous flaky morphology, decreased optical band gap, heterojunction mediated charge separation, and praseodymium oxide's conductive nature. A linear range of about 0.25–800 nM of Hg2+ ions can be detected with a limit of detection (LOD) of 42.4 nM using the colorimetric strategy. The as-synthesized composite is thus a unique, efficient, economically viable, and excellent candidate for detecting and degrading various hazardous water pollutants.

Facile fabrication of Au nanoparticles loaded Ce doped ZnO nanorods for efficient catalytic and photocatalytic decomposition of toxic pollutants in water

Plasmonic Au nanoparticles (NPs) have been deposited onto Ce doped ZnO nanorods prepared through wet chemical route to enhance their photodecomposition performance. The catalytic and photocatalytic performances were evaluated using a series of model pollutants such as 4-nitrophenol, antibiotic levofloxacin, cationic and anionic dyes under sunlight illumination. Various characterization tools such as XRD, Raman, FESEM, TEM, SAED, EDX, XPS, PL and UV–vis spectroscopy were used to examine the structure and physico-chemical properties of the fabricated photocatalysts. XRD, TEM, SAED, EDX, XPS and Raman analyses confirmed the existence of Ce doped ZnO and Au nanostructures while UV–visible absorption studies revealed the presence of SPR of Au NPs in the visible region. The results illustrated that decoration of Au NPs on Ce doped ZnO nanorods makes them outstanding catalyst as well as photocatalyst compared to pure Ce doped ZnO nanorods. The plasmonic nanohybrids with higher Au concentration exhibited superior degradation capability towards reduction and detoxification of 4-NP, decomposition of antibiotic levofloxacin and synthetic dyes, respectively. In addition, detailed study of possible mechanisms behind 4-NP reduction and photodegradation process have been explored. Furthermore, the quenching experiments elucidating ·O2- radicals as the main active species in the degradation mechanism have also been discussed. Moreover, the prepared Ce doped ZnO-Au hybrid plasmonic nanorods maintained high stability and stunning photoactivity even after four cycles which highlights it as a promising material for wastewater treatment.

A comparative study on green synthesis and characterization of Mn doped ZnO nanocomposite for antibacterial and photocatalytic applications

Biological and green synthesis of nanomaterial is a superior choice over chemical and physical methods due to nanoscale attributes implanted in a green chemistry matrix, have sparked a lot of interest for their potential uses in a variety of sectors. This research investigates the growing relevance of nanocomposites manufactured using ecologically friendly, green technologies. The transition to green synthesis correlates with the worldwide drive for environmentally sound procedures, limiting the use of traditional harsh synthetic techniques. Herein, manganese was decorated on ZnO NPs via reducing agent of Withania-extract and confirmed by UV-spectrophotometry with highest peak at 1:2 ratio precursors, and having lower bandgap energy (3.3 eV). XRD showed the sharp peaks and confirms the formation of nanoparticles, having particle size in range of 11–14 nm. SEM confirmed amorphous tetragonal structure while EDX spectroscopy showed the presence of Zn and Mn in all composition. Green synthesized Mn-decorated ZnO-NPs screened against bacterial strains and exhibited excellent antimicrobial activities against gram-negative and gram-positive bacteria. To check further, applicability of synthesized Mn-decorated Zn nanocomposites, their photocatalytic activity against toxic water pollutants (methylene blue (MB) dye) were also investigated and results showed that 53.8% degradation of MB was done successfully. Furthermore, the installation of green chemistry in synthesizing nanocomposites by using plant extract matrix optimizes antibacterial characteristics, antioxidant and biodegradability, helping to build sustainable green Mn decorated ZnO nanomaterial. This work, explains how biologically friendly Mn-doped ZnO nanocomposites can help reduce the environmental impact of traditional packaging materials. Based on these findings, it was determined that nanocomposites derived from biological resources should be produced on a wide scale to eradicate environmental and water contaminants through degradation.

Controlled construction of 2D hierarchical core-shell ZnO/MnO2 nanosheets on Nitinol fiber with enhanced adsorption performance for selective solid-phase microextraction of trace polycyclic aromatic hydrocarbons in water samples

BackgroundPolycyclic aromatic hydrocarbons (PAHs) are an important class of potentially toxic persistent organic pollutants in environmental water. Their concentrations are usually too low to allow for direct determination with analytical instruments, and the preconcentration is required prior to instrumental analysis. Solid phase microextraction (SPME) is considered as a high-performance green sample preparation technique for volatile and non-volatile organic compounds due to its high enrichment factor. In fact, the nature of SPME coatings governs the adsorption performance. Therefore, more efforts have devoted to the controlled construction of novel long-life SPME fibers with enhanced adsorption performance and improved adsorption selectivity. Results2D hierarchical core-shell ZnO/MnO2 nanosheets (NSs) were constructed on a Nitinol (NiTi) fiber substrate by layer-by-layer assembly for enhanced and selective SPME of PAHs. Firstly, hexagonal ZnO NSs were electrodeposited on the NiTi substrate. Subsequently smaller secondary MnO2 NSs were uniformly grown on the surface of ZnO NSs by a facile hydrothermal oxidation process. ZnO NSs were well protected by the chemically stable MnO2 shell, making the coating highly durable and efficient for SPME application. Meanwhile, the ZnO/MnO2 NSs coating demonstrated superior adsorption performance for PAHs. After the optimization of SPME conditions, the proposed SPME-HPLC-UV method exhibited good analytical performance for preconcentrating and determining trace PAHs with wide linear ranges (0.03–200 μg L−1) and low LODs (0.005–0.112 μg L−1) as well as good repeatability (1.4%-6.9%) and fiber-to-fiber reproducibility (5.3%-7.1%). Moreover, the proposed method showed good precision and recovery in the preconcentration and determination of target PAHs in real water samples. SignificanceAs compared with representative commercially available fibers, the NiTi@ZnO/MnO2 NSs fiber showed enhanced adsorption efficiency and improved adsorption selectivity for PAHs. The constructed fiber can be used as an alternative to commercial fibers for the adsorption and preconcentration of target PAHs in the environmental water samples. Moreover, the preparation strategy is expected to provide new insights into the precisely controlled construction of the efficient and stable core-shell bimetallic oxide nanostructures on the superielastic NiTi-based fibers.

Asymmetric response of transition metal cationic orbitals to applied electric field

Understanding the quantum mechanical mechanisms underlying atomic/ionic interfacial processes and phenomena, particularly their dependence on the electronic orbital rearrangement of atoms/ions in an external electric field, remains a significant challenge. This study investigated the asymmetric response of transition metal (TM) cationic orbitals when subjected to an applied electric field. Quantum mechanical calculations were employed to quantify the newly formed hybrid orbitals and evaluate the corresponding orbital energies of the TM cations. Analysis of the quantitative contribution of asymmetric orbital hybridization to TM–surface interactions showed a significant change in orbital energy and increased effective charges of TM cations at the charged surface. This asymmetric response, induced by a negative external electric field generated from the structural charges of clay minerals (e.g., montmorillonite), repels electrons from the outer-shell orbital. This repulsion consequently increases the electron binding energy of the inner-shell orbitals, leading to new surface reactions, polarization-enhanced induction force, and polarization-induced covalent bonding between the TM cations and the charged surface. Our theoretical predictions regarding TM–clay mineral interactions are consistent with the experimental observations of TM cation adsorption. This finding has significant implications for the adsorptive removal of TM cations from wastewaters and for enhancing the catalytic efficiency of TM–surface catalysts. The unique physical and chemical characteristics exhibited by TMs at charged particle surfaces, resulting from their asymmetric response, can play pivotal roles in environmental and chemical engineering.

Preferential separation of a radioactive TcO4- surrogate from a mixture of oxoanions by a cationic MOF.

Preferential trapping of a selected metal-oxoanion from a mixture of other metal-oxoanionic toxic pollutants in water has been demonstrated by implementing energy-efficient adsorption followed by the ion-exchange method, utilizing a hydrolytically stable cationic metal-organic framework (MOF). The cationic MOF exhibits ultrafast and selective extraction efficiency towards ReO4- (a surrogate anion of radioactive TcO4-) over other metal-oxoanions in contaminated water systems.

Green synthesis of an ionic porous organic polymer for efficient capture of environmentally toxic MnO4- and I3- from water.

The syntheses of ionic porous organic polymers (iPOPs) via an ionothermal strategy or using solvents with high boiling points are not environmentally friendly approaches. Furthermore, green synthesis of an ionic porous organic polymer has not been reported to date. The azo-coupling reaction is considered a green synthetic strategy and has been used to obtain a new ionic porous organic polymer (iPOP-6) wherein water is used as a solvent. iPOP-6 turns out to be a useful adsorbent that can scavenge toxic water pollutants (MnO4- and I3-) in an energy efficient manner via an ion exchange based adsorption process. The distribution coefficients (Kd) associated with the removal of MnO4- and I3- are greater than 105 mL g-1 - a desirable feature observed in a superior adsorbent. iPOP-6 can remove such pollutants from water samples collected from different water bodies with good capture efficiency. The removal mechanism was also ratified by theoretical studies. Overall, this work presents a new ionic POP with improved features and performance for water purification applications.

Surface plasmon resonance effect of silver decorated on BiOCl and its enhanced sunlight-active photodegradation of rhodamine B (RhB) dye and ofloxacin (OFL) antibiotic

Fast electron-hole recombination rate is the major problem concerning low photocatalytic performance of the UV-active BiOCl photocatalyst. To overcome this drawback, decoration of noble metals on the surface of semiconducting photocatalysts can be regarded as one of the promising strategies to improve the photoactivity due to a synergy of heterojunction formation and surface plasmon resonance effect. However, the huge dosage (larger than 10 wt%) of the noble metal incorporated on photocatalyst surface causes high cost in production of the final product. In this work, solvothermally grown BiOCl photocatalyst was decorated with low silver metal loading of 2.5–10 wt%. The tetragonal 2.5 wt%Ag/BiOCl photocatalyst exhibited complete photodegradation of Rhodamin B (RhB) dye and ofloxacin (OFL) antibiotic under natural solar light. The enhancement of the resultant photocatalytic efficiency is possibly due to increasing of charge carrier separation efficiency at the interface together with the formation of the Schottky barrier at the Ag/BiOCl interface so that an improvement in quantum efficiency and an increase in the photocatalytic activity are expected. In addition, well dispersion of silver on BiOCl also leads to red shift in the absorption of light toward visible regime. This is due to the local surface plasmon resonance (LSPR) effect of Ag on BiOCl surface. The synthesized Ag/BiOCl photocatalyst displays enhanced photocatalytic activity with great structural stability after five times of use indicating its excellent cycling ability. The present finding offers a new pathway to create a silver decorated BiOCl for complete removal of harmful dye and antibiotic in aqueous solution. The treatment of toxic organic pollutants in the natural water can be done very easily by utilization of the green technology based on photocatalytic method with the beneficial of abundant solar energy.

A sustainable approach for the removal of chlorpyrifos pesticide from aqueous phase using novel nano magnetized biochar

In last two decades, organophosphate pesticides have become a prominent class of toxic water pollutants. Besides, these are not only poisonous for living beings, but their decomposition is also a time-taking process. For the first time, our study reports the application of nano-magnetized and carbonaceous adsorbents, obtained from orange peels (bio-waste), for the removal of chlorpyrifos from water resources. The -nano magnetized orange peels (NMOPs) were synthesized by the co-precipitation method with the use of iron salts. The competency of orange peels for chlorpyrifos adsorption was further enhanced by converting untreated orange peels (UOPs) into carbonaceous orange peels (COPs). The adsorbents were analyzed with FT-IR, SEM, EDX, XRD and VSM. The peak at 540 cm−1 in FTIR spectra corresponded to the Fe-O bond and confirmed the successful doping of iron salts on orange peels. Biosorption studies carried out by varying different parameters showed that these adsorbents are efficient for the uptake of chlorpyrifos. The effects of adsorbent dose, contact time, chlorpyrifos initial concentration, and pH were investigated to assess the adsorbents’ efficiency via biosorption studies. It was noted that the adsorbents showed maximum adsorption with adsorbent dose = 0.4 g, contact time = 50 mins, chlorpyrifos concentration = 150 ppm, pH = 4 and temperature = 30 °C. The adsorption maximum values (qmax) were found to be 68, 108 & 100 mg g−1 for the UOPs, COPs and NMOPs, respectively. Kinetic studies indicate that the removal of chlorpyrifos followed the pseudo-second-order model of adsorption. The adsorption results were effectively described by the Langmuir isotherm and Freundlich isotherm models.

Tartaric acid coupled with gibberellin improves remediation efficiency and ensures safe production of crops: A new strategy for phytoremediation

Phytoremediation is the direct use of living green plants and it is an effective, inexpensive, non-invasive, and environmentally friendly technique used to transfer or stabilize all the toxic metals and environmental pollutants in polluted soil or ground water. To study the effect of tartaric acid, gibberellin, and tartaric acid coupled with gibberellin on rape-kenaf or rape-sweet sorghum rotation, a field experiment was carried out on a farmland combined polluted with Cd and Pb in eastern Hunan Province, China. The results showed that these two rotation systems coupled with superposition measure has potential to enhance yield and biomass of rape (Brassica napus L.), kenaf (Hibiscus cannabinus) and sweet sorghum (Sorghum dochna (F.) Snowden), as well as to increase Cd and Pb uptake of the three crops, thus accelerating phytoextraction. The Cd and Pb annual removal by rape-kenaf rotation in one year under different treatments were 269–438 and 112–149 g·hm−2, respectively. And the Cd and Pb annual removal by rape-sweet sorghum rotation in one year under different treatments were 68.0–111 and 43.8–92.3 g·hm−2, respectively. Under the two rotation systems, these integrated management measures can remove Cd and Pb up to 438 g·hm−2·year−1 and 149 g·hm−2·year−1, respectively. The Cd and Pb content in rape seeds or sweet sorghum stems and leaves were lower than the food or forage standard, indicating that we can use this rotation system for both remediation and safety production. Furthermore, the two rotation systems also generated considerable economic value. These results showed that the combination of phytoremediation and agricultural production is a feasible technical mode in the field of Cd and Pb co-contamination, and also provides useful information for further study of the interaction mechanism between rotation crops and enhancement measures. In subsequent experiments we can set concentration gradients for tartaric acid and gibberellin, and we can also select other crops for rotation, with a view to finding the optimal auxiliary measure and crop rotation modern.

Microcystin-LR-induced autophagy via miR-282–5p/PIK3R1 pathway in Eriocheir sinensis hepatopancreas

With the intensifying climate warming, blue-green algae blooms have become more frequent and severe, releasing environmental hazards such as microcystin that pose potential threats to human and animal health. Autophagy has been shown to play a crucial role in regulating immune responses induced by environmental hazards, enabling cells to adapt to stress and protect against damage. Although microcystin-LR (MC-LR) has been identified to affect autophagy in mammalian, its impact on aquatic animals has been poorly studied. To investigate the toxicological effects of MC-LR in aquatic ecosystems, we constructed a microRNA profile of acute MC-LR stress in the hepatopancreas of the Chinese mitten crab. Interestingly, we found the MC-LR exposure activated autophagy in the hepatopancreas based on the following evidence. Specifically, mRNA expression level of ATG7, Beclin1 and Gabarap was significantly up-regulated, autophagy regulatory pathways were significantly enriched, and numerous autolysosomes and autophagosomes were observed. Additionally, we found that miR-282–5p and its target gene PIK3R1 played important regulatory roles in autophagy by in vivo and in vitro experiments. Overexpression of miR-282–5p mimicked MC-LR-induced autophagy by inhibiting PIK3R1 expression, while miR-282–5p silencing inhibited autophagy by promoting PIK3R1 expression. Altogether, our findings suggest that MC-LR increases miR-282–5p, which then targets inhibition of PIK3R1 to stimulate autophagy. This study focused on the stress response regulatory mechanisms of juvenile crabs to toxic pollutants in water, offering a potential target for alleviating the toxicity of MC-LR. These findings lay a foundation for reducing the toxicity of MC-LR and environmental hazards in organisms.

Synthesis and Recognition Properties of Cd(II) Framework for Highly Selective Sensing of Fe3+, Cr2O72− and CrO42− ions

AbstractIn this study, we successfully constructed a high‐performance fluorescent material for the detection of toxic pollutants in water, [Cd(2‐bpmh)(BDC)H2O]n (1) (2‐bpmh=1,4‐bis(2‐pyridyl)‐2,3‐diaza‐1,3‐butadiene, H2BDC=terephthalic acid), which achieved high yield under the condition of solvothermal reaction. Single crystal X‐ray analysis revealed that complex 1 forms a one‐dimensional chain structure, which is further assembled into a three‐dimensional structure through hydrogen bonding interactions. The luminescence sensing research showed that 1 not only displayed excellent luminescence quenching efficiency, but also could specifically recognize Cr2O72−, CrO42− and Fe3+ ions in water.

MOF-Derived Ni/ZIF-8/ZnO Arrays on Carbon Fiber Cloth for Efficient Adsorption-Catalytic Oxidation.

The catalytic oxidation of toxic organic pollutants in water requires enhanced efficiency for commercial applications. A ZnO nanorod array grown on a carbon fiber cloth (CFC) serves as the zinc source to ensure that the Ni/ZIF-8/ZnO nanoreactor is constructed. The Ni/ZIF-8/ZnO/CFC nanoreactor efficiently activates peroxymonosulfate (PMS) for bisphenol A (BPA) degradation owing to its high density of active sites, high adsorbability, and dispersibility structure, which concentrates catalytic and adsorptive sites within a confined space. Experimental and theoretical calculations clearly show that the introduction of Ni is beneficial for improving the adsorption of BPA and the activation of PMS. The synergistic mechanism of BPA adsorption-PMS activation is also investigated, and the degradation pathway of BPA is examined. Moreover, a filter catalytic unit is constructed using Ni/ZIF-8/ZnO/CFC to achieve a continuous zero discharge of BPA, which is convenient for nanocatalyst recycling. This study aims to develop a new strategy for the removal of emerging organic pollutants from water using a system with strong adsorption and catalytic capabilities.

Two-Dimensional Lanthanide Metal-Organic Frameworks as a Platform for Sensing Pollutant and Nitrophenols Reduction.

The discharge of harmful and toxic pollutants in water is destroying the ecosystem balance and human being health at an alarming rate. Therefore, the detection and removal of water pollutants by using stable and efficient materials are significant but challenging. Herein, three novel lanthanide metal-organic frameworks (Ln-MOFs), [La(L)(DMF)2(H2O)2]·H2O (LCUH-104), [Nd(L)(DMF)2(H2O)2]·H2O (LCUH-105), and [Pr(L)(DMF)2(H2O)2]·H2O (LCUH-106) [H3L = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid (H3TZI)] were solvothermally constructed and structurally characterized. In the three Ln-MOFs, dinuclear metallic clusters {Ln2} were connected by deprotonated tetrazol-containing dicarboxylate TZI3- to obtain a 2D layered framework with a point symbol of {42·84}·{46}. Their excellent chemical and thermal stabilities were beneficial to carry out fluorescence sensing and achieve the catalytic nitrophenols (NPs) reduction. Especially, the incorporation of the nitrogen-rich tetrazole ring into their 2D layered frameworks enables the fabrication of Pd nanocatalysts (Pd NPs@LCUH-104/105/106) and have dramatically enhanced catalytic activity by using the unique metal-support interactions between three Ln-MOFs and the encapsulating palladium nanoparticles (Pd NPs). Specifically, the reduction of NPs (2-NP, 3-NP, and 4-NP) in aqueous solution by Pd NPs@LCUH-104 exhibits exceptional conversion efficiency, remarkable rate constants (k), and outstanding cycling stability. The catalytic rate of Pd NPs@LCUH-104 for 4-NP is nearly 8.5 times more than that of Pd/C (wt 5%) and its turnover frequency value is 0.051 s-1, which indicate its excellent catalytic activity. Meanwhile, LCUH-105, as a multifunctional fluorescence sensor, exhibited excellent fluorescence detection of norfloxacin (NFX) (turn on) and Cr2O72- (turn off) with high selectivity and sensitivity at a low concentration, and the corresponding fluorescence enhancement/quenching mechanism has also been systematically investigated through various detection means and theoretical calculations.

Engineering sulfuric acid-pretreated biochar supporting MnO2 for efficient toxic organic pollutants removal from aqueous solution in a wide pH range

Manganese dioxides (MnO2) and biochar materials are both desirable candidates for environmental remediation of toxic organic pollutants (TOPs) in water due to wide availability and environmental-friendly. In practical application, however, MnO2 suffers from low redox activity owing to deprotonation, while biochar is subject to limited removal capacity. Herein, a difunctional engineering sulfuric acid-pretreated biochar supporting MnO2 composite (MBC-A) was firstly synthesized and optimized to remove various TOPs from aqueous solution. Specifically, sulfuric acid not only served as an active agent to improve the specific surface area of biochar for improvement of adsorption capacity and more MnO2 loading, but also facilitated the introduction of sulfonic acid groups (-SO3H) as an internal proton reservoir to inhibit inactivation of MnO2 due to deprotonation in alkaline. Thanks to adsorption and oxidation, MBC-A showed excellent removal capacity (214.9 mg/g) and fast reaction kinetics (360 min) for tetracycline (TC), exceeding precursor and other materials reported in literature. Importantly, the effective operation pH range of MBC-A was broadened to 1–13 with the help of buffering capacity of –SO3H groups. The dominant driving force of adsorption were π-π interaction and hydrogen bond; while reactive oxidative species were mainly ascribed to singlet oxygen (1O2), hydroxyl radical (·OH) and reactive Mn3+. The possible reactive sites and pathway were investigated by combining experimental results with density functional theory (DFT) calculation. Further, the results of multiple cyclic runs, removal in real river water and toxicity assessment demonstrated well reusability, high environmental security, and excellent practical applicability of MBC-A.

Fe3O4@CMC-Cu magnetic nanocomposite as an efficient catalyst for reduction of toxic pollutants in water

Metallic nanoparticles embedded in the polymer matrix are considered a significant category of heterogeneous catalysts with strong catalytic performance. Functionalized polymers are inexpensive building blocks that make good catalytic platforms for stabilizing metallic nanoparticles. In this study, Fe3O4@CMC-Cu magnetic nanocomposites were successfully synthesized and characterized by XRD, FTIR, BET, XPS, VSM, HR-TEM, and EDX mapping. Morphology observation shows that spherical Fe3O4 magnetic nanoparticles and Cu NPs are distributed uniformly and encapsulated inside the polymer structure with an average diameter of ∼ 11 nm without substantial agglomeration. Additionally, the inclusion of CMC polymer and Cu NPs gradually reduces the magnetic saturation of Fe3O4. The reduction of 4-nitrophenol (4-NP) and the organic dyes Congo red (CR) and acriflavine (ACF) in aqueous medium at room temperature was used to test the nanocomposites' catalytic activity. The effects of reaction parameters, catalyst amount and Cu NPs percentages on the catalytic effectiveness were determined. The induction time of the reaction decreases with increasing the nanocomposite amount and the Cu NPs loading percentages. Excellent catalytic activity was demonstrated by the Fe3O4@CMC-Cu (10 %) nanocomposite for the elimination of all three intended organic contaminants (4-NP, CR and ACF). For the reduction of 4-NP, CR, and ACF, the calculated Kapp values were 1.55 min−1, 0.3 min−1, and 2.3 min−1, respectively. The magnetic nanocomposite was easily separated from the reaction solution and recycled for up to five successive cycles without suffering a substantial decrease in the catalytic activity. Such magnetic nanocomposites provide light on highly effective catalysts for applications in environmental protection.