A carboxyl-functionalized covalent organic polymer for the efficient adsorption of saxitoxin

Investigation of adsorption parameters of saxitoxin onto loblolly pine-derived biochar synthesized at various pyrolysis temperature

This study highlights the use of loblolly pine derived biochar for the removal of harmful algal bloom toxin, Saxitoxin (STX), from water. Biochar samples were prepared at varying pyrolysis temperatures (400, 600 and 800 °C) for 60 min. As pyrolysis temperature increases, enhancement in surface porosity was observed (SBET = 7.26 ± 0.2 m2/g to 408.15 ± 6.19 m2/g) while a decline in oxygen-containing functional groups was observed (1517.80 ± 14.98 μmol/g to 823.01 ± 7.72 μmol/g). This study aimed to discover the effects of adsorption parameters such as biochar dosage amount, contact time, initial concentration and initial pH on Saxitoxin adsorption. These studies revealed impressive results with >90 % toxin removal with dosage rate of 0.01 g/L, contact time of 30 min, and increasing percent removal with increasing initial STX concentration and initial pH in water. Maximum uptake was calculated for P400 with adsorption capacity of 314.37 μg/g. This showed that surface functionality showed higher affinity for STX uptake, which may be possible due to hydrogen bonding, electrostatic interactions, ion-exchange, and π-π interactions. Applied kinetic models indicated both physisorption and chemisorption interactions with best fit supporting the Elovich models. Complementary, adsorption isotherm analysis confirmed the multilayer adsorption behavior of the Freundlich model. Therefore, these findings support the viable use of biochar material for the remediation of STX waters.

A magnetic carboxyl-functionalized covalent organic framework for the efficient enrichment of foodborne heterocyclic aromatic amines prior to UPLC-MS analysis

Foodborne heterocyclic aromatic amines (HAAs) are potent mutagens and carcinogens, posing significant health risks. Existing enrichment methods for HAAs need better adsorption selectivity and capacity for daily exposure assessment. This study hypothesized that introducing carboxylic groups into magnetic covalent organic frameworks (m-COFs) would improve HAAs adsorption by providing additional binding sites. Hence, we prepared a novel magnetic adsorbent, termed as Fe3O4@DOPA-TpPa-(COOH)2 capable of enhancing the HAAs detection through magnetic solid-phase extraction (MSPE) coupled with UPLC-MS. This sorbent demonstrated a large specific surface area (130.7 m2/g), high magnetic responsivity (21.05 emu/g), and robust stability, with an adsorption capacity (Qm[cal]: 81.82 mg/g) driven by electrostatic, LP - π/C-H - π interactions, and hydrogen bonding. Optimal MSPE conditions provided sensitive detection with a broad linear range (5-500 ng/mL), low limits of detection (0.01-7.01 ng/g), and excellent repeatability. Application to Cantonese mooncake samples showed satisfactory recoveries (62.12%-126.86%). This method offers a more accurate tool for detecting HAAs.

Boosting Photoconductivity by Increasing the Structural Complexity of Multivariate Covalent Organic Frameworks

The assessment of the photoconductivity of Donor-Acceptor (D-A) ordered bulk heterojunctions is gaining attention for the development of innovative organic semiconductors in optoelectronics. Here, the synthesis of pyrene-based (D) Covalent Organic Frameworks, achieve through a multivariate reaction involving two distinct acceptors is reported (A). The products are characterized using powder x-ray diffraction, N2 sorption isotherms, electronic microscopy, and in silico calculations, among other techniques. These characterizations reveal that the multicomponent synthesis enables the modification of properties (e.g., bandgap) of the framework while preserving its structural features, such as crystallinity and porosity. The ordered D-A arrays position these materials as promising candidates for photoconductive semiconductors, particularly regarding the variation in the composition of isotopological frameworks. Photoconductivity experiments demonstrate a volcano-type correlation with respect to the A moiety content, with the optimal value reaching 7.9 × 10-5 cm2 V-1 s-1 for the bare NIP25%-COF. This study illustrates how introducing diverse acceptor units through multivariate synthesis can enhance the photoconductivity of these materials via "defect" engineering, without sacrificing their crystalline or porous characteristics and avoiding the need for de novo synthesis.

Marine toxins in environment: Recent updates on depuration techniques

Marine toxins pose a significant safety risk, leading to human intoxications and causing substantial economic losses in seafood-producing regions. The development of rapid, cost-effective, efficient, and reliable approaches for the containment of these substances is therefore crucial in order to mitigate the adverse impact of marine toxins. This research conducted a comprehensive review on the toxicity and influencing factors of marine toxins production. Additionally, depuration technologies, including adsorption, advanced oxidation processes, biodegradation, heating treatment, temporary maintenance and purification, and drug inhibition, were systematically summarized. The study also provided a comparative analysis of the advantages and disadvantages of various depuration technologies and proposed strategies for future development.

Exploring Advanced Oxygen Reduction Reaction Electrocatalysts: The Potential of Metal-Free and Non-Pyrolyzed Covalent Organic Frameworks

Oxygen reduction reaction (ORR) electrocatalysis is an area of increasing interest for the in-situ production of H2O2 or the development of energy-related devices such as hydrogen fuel cells. Although pyrolyzed catalysts still offer the best performances to date with reference to the organic-based catalysts, metal-free and non-pyrolyzed covalent organic frameworks (COFs) stands out as promising alternatives candidates due to their favourable characteristics such as crystallinity, porosity, and organic composition, allowing the study of structural-property relationships. Herein, we present the design principles and recent advances in COFs-based ORR electrocatalysts, demonstrating how composition influences the activity and electronic pathway of the oxygen reduction process.

Room-Temperature Synthesis of Covalently Bridged MOP@TpPa-CH3 Composite Photocatalysts for Artificial Photosynthesis

The conversion of CO2 into useful chemicals via photocatalysts is a promising strategy for resolving the environmental problems caused by the addition of CO2. Herein, a series of composite photocatalysts MOP@TpPa-CH3 based on MOP-NH2 and TpPa-CH3 through covalent bridging have been prepared via a facile room-temperature evaporation method and employed for photocatalytic CO2 reduction. The photocatalytic performances of MOP@TpPa-CH3 are greater than those of TpPa-CH3 and MOP-NH2, where the CO generation rate of MOP@TpPa-CH3 under 10% CO2 still reaches 119.25 μmol g-1 h-1, which is 2.18 times higher than that under pure CO2 (54.74 μmol g-1 h-1). To investigate the structural factors affecting the photocatalytic activity, MOP@TBPa-CH3 without C═O groups is synthesized, and the photoreduction performance is also evaluated. The controlling experimental results demonstrate that the excellent photoreduction CO2 performance of MOP@TpPa-CH3 in a 10% CO2 atmosphere is due to the presence of C═O groups in TpPa-CH3. This work offers a new design and construction strategy for novel MOP@COF composites.

Influence of biochar on the removal of Microcystin-LR and Saxitoxin from aqueous solutions

The present study assessed the effective use of biochar for the adsorption of two potent HAB toxins namely, Microcystin-LR (MCLR) and Saxitoxin (STX) through a combination of dosage, kinetic, equilibrium, initial pH, and competitive adsorption experiments. The adsorption results suggest that biochar has excellent capabilities for removing MCLR and STX, with STX reporting higher adsorption capacities (622.53-3507.46 µg/g). STX removal required a minimal dosage of 0.02 g/L, while MCLR removal needed 0.4 g/L for > 90%. Similarly, a shorter contact time was required for STX removal compared to MCLR for > 90% of toxin removed from water. Initial pH study revealed that for MCLR acidic conditions favored higher uptake while STX favored basic conditions. Kinetic studies revealed that the Elovich model to be most suitable for both toxins, while STX also showed suitable fittings for Pseudo-First Order and Pseudo-Second Order in individual toxin systems. Similarly, for the Elovich model the most suited kinetic model for both toxins in presence of each other. Isotherm studies confirmed the Langmuir-Freundlich model as the best fit for both toxins. These results suggest adsorption mechanisms including pore filling, hydrogen bonding, π-π interactions, hydrophobic interactions, electrostatic attraction, and dispersive interactions.

Marine toxins in seafood: Recent updates on sample pretreatment and determination techniques

Marine toxins can lead to varying degrees of human poisoning, often resulting in fatal symptoms and causing significant economic losses in seafood-producing regions. To gain a deeper comprehension of the role of marine toxins in seafood and their impact on the environment, it is imperative to develop rapid, cost-effective, environmentally friendly, and efficient methods for sample pretreatment and determination to mitigate adverse impacts of marine toxins. This review presents a comprehensive overview of advancements made in sample pretreatment and determination techniques for marine toxins since 2017. The advantages and disadvantages of various technologies were critically examined. Additionally, the current challenges and future development strategies for the analysis of marine toxins are provided.

Quaternary ammonium-functionalized rosin-derived resin for the high-performance capture of caramels: Experiments and quantum chemical theory simulations

Water contamination caused by discharge of spent washes containing colorants remains controversial. In this study, rosin-derived strongly basic macroporous anion-adsorption resin (RSBMAR) was designed as an advanced adsorbent for scavenging caramel, the most recalcitrant colorant in spent washes. Toxicity tests suggest that RSBMAR is environmentally friendly and hardly threatens aquatic organisms. RSBMAR exhibits outstanding caramel capture efficiency because of its rich target quaternary ammonium (-R4N+) and protonated tertiary amine (-R3NH+) groups, abundant porous structure, large specific surface area, excellent thermal stability, and good sphericity. The caramel adsorption capacity of RSBMAR was 165.86 mg/g and the decolorization efficiency reached 96.75%. After five cycles, the spent RSBMAR maintained a high decolorization rate, indicating excellent renewability. Multiple characterizations indicated that caramel capture was largely mediated by charge interaction between -R4N+/-R3NH+ (RSBMAR) and -RCOO-/-RCOOH (caramel), followed by H-bonds. Quantum chemical theory simulations, including electrostatic potential, local ionization energy, frontier molecular orbitals, and independent gradient model analyses, further visualized caramel capture mechanisms at atomic level. Hirshfeld surface analysis revealed that RSBMAR acts as both an H-bond donor and acceptor during caramel uptake. Dynamic adsorption was performed to treat real wastewater, laying the foundation for the industrial application of RSBMAR.

New insights on the preparation of amine covalent organic polymer and its adsorption properties

Dye pollution is becoming increasingly severe. This study used the Schiff base reaction to synthesize a polyaromatic ring covalent organic polymer material with amide bonds and high electronegativity named SLEL-9 to adsorb Methylene Blue (MB) and Rhodamine B (RhB). SLEL-9 was characterized by Fourier transform infra-red spectra, X-ray photoelectron spectra, Brunauer-Emmett-Teller (BET), zeta potential analysis, and other techniques. It was found that SLEL-9 material contains C-C, CN, C-N, and CO. SLEL-9 had a zeta potential of about -45 mV under neutral conditions, which proved that the material had been synthesized successfully. The BET and Langmuir surface areas of SLEL-9 were 35.187 m2 g-1 and 56.419 m2 g-1, respectively. The adsorptions of SLEL-9 on low concentration (10 mg L-1) Methylene Blue and Rhodamine B reached equilibrium within 48 h. The results showed that SLEL-9's adsorption of dye molecules are more consistent with pseudo-second-order kinetic and Langmuir isotherm model. The adsorption experiments showed that the adsorption process is a spontaneous endothermic reaction, mainly chemisorption. The maximum adsorption capacity of SLEL-9 for MB and RhB were 132.45 mg g-1 and 101.94 mg g-1. In addition, this study investigated to determine the optimal reaction parameters. The primary mechanisms of SLEL-9 adsorption of two dyes are n→π* interaction, π-π EDA interaction and electrostatic attraction. Selective adsorb ability experiment results showed that SLEL-9 could selectively adsorb MB and RhB to a certain extent. Finally, it was found that SLEL-9 can maintain over 70% adsorption capacity after five reuses and can maintain stability after soaking in different pH water and organic solvents for 120 h. SLEL-9 proved to be a promising organic covalent polymer adsorption material for the removal of Methylene Blue and Rhodamine B in water.

Recent Advances in the Detection of Food Toxins Using Mass Spectrometry

Edibles are the only source of nutrients and energy for humans. However, ingredients of edibles have undergone many physicochemical changes during preparation and storage. Aging, hydrolysis, oxidation, and rancidity are some of the major changes that not only change the native flavor, texture, and taste of food but also destroy the nutritive value and jeopardize public health. The major reasons for the production of harmful metabolites, chemicals, and toxins are poor processing, inappropriate storage, and microbial spoilage, which are lethal to consumers. In addition, the emergence of new pollutants has intensified the need for advanced and rapid food analysis techniques to detect such toxins. The issue with the detection of toxins in food samples is the nonvolatile nature and absence of detectable chromophores; hence, normal conventional techniques need additional derivatization. Mass spectrometry (MS) offers high sensitivity, selectivity, and capability to handle complex mixtures, making it an ideal analytical technique for the identification and quantification of food toxins. Recent technological advancements, such as high-resolution MS and tandem mass spectrometry (MS/MS), have significantly improved sensitivity, enabling the detection of food toxins at ultralow levels. Moreover, the emergence of ambient ionization techniques has facilitated rapid in situ analysis of samples with lower time and resources. Despite numerous advantages, the widespread adoption of MS in routine food safety monitoring faces certain challenges such as instrument cost, complexity, data analysis, and standardization of methods. Nevertheless, the continuous advancements in MS-technology and its integration with complementary techniques hold promising prospects for revolutionizing food safety monitoring. This review discusses the application of MS in detecting various food toxins including mycotoxins, marine biotoxins, and plant-derived toxins. It also explores the implementation of untargeted approaches, such as metabolomics and proteomics, for the discovery of novel and emerging food toxins, enhancing our understanding of potential hazards in the food supply chain.

Novel vinylene-based covalent organic framework as a promising adsorbent for the rapid extraction of beta-agonists in meat samples

Beta-agonists are potent bronchodilators approved for the treatment of asthma and tocolysis. However, they have been extensively misused as feed additives in the veterinary field to improve feed efficiency. The concern over their potential hazard to health has come to the fore again. In this study, a novel vinylene-based covalent organic framework (V-COF-1) with a two-dimensional structure was developed. The structure shows good tolerance in a variety of mediums, which can be attributed to the low polarity linkage. The high specific surface area and variable interaction with analytes accelerate the extraction time. Furthermore, the swelling resulting from the formation of hydrogen bonds by the protic solvent intercalation with the triazine group also improves the adsorption efficiency. Finally, due to its great reusability, it is economical material in sample preparation application. The V-COF-1 based μ-dSPE approach was coupled with UHPLC-MS/MS to develop a highly sensitive and selective method. The linearity of the method ranged from 0.05 to 20 ng g^-1 with a correlation coefficient (R²) higher than 0.9958, and the limits of detection and quantification fell in the ranges of 0.01-0.10 ng g^-1 and 0.04-0.32 ng g^-1. The proposed method has been successfully applied to determine beta-agonists in meat samples, and the results indicated good recovery of 82.2-116%. The intra-day and inter-day precision were less than 6.61%, indicating the potential for sustainable application in food analysis.