Covalent organic frameworks as robust materials for mitigation of environmental pollutants

Novel solid-phase microextraction fiber coatings: A review

The materials used for the fabrication of solid-phase microextraction fiber coatings in the past five years are summarized in the current review, including carbon, metal-organic frameworks, covalent organic frameworks, aerogel, polymer, ionic liquids/poly (ionic liquids), metal oxides, and natural materials. The preparation approaches of different coatings, such as sol-gel technique, in-situ growth, electrodeposition, and glue methods, are briefly reviewed together with the evolution of the supporting substrates. In addition, the limitations of the current coatings and the future development directions of solid-phase microextraction are presented.

Current Status and Future Perspectives of Supports and Protocols for Enzyme Immobilization

The market for industrial enzymes has witnessed constant growth, which is currently around 7% a year, projected to reach $10.5 billion in 2024. Lipases are hydrolase enzymes naturally responsible for triglyceride hydrolysis. They are the most expansively used industrial biocatalysts, with wide application in a broad range of industries. However, these biocatalytic processes are usually limited by the low stability of the enzyme, the half-life time, and the processes required to solve these problems are complex and lack application feasibility at the industrial scale. Emerging technologies create new materials for enzyme carriers and sophisticate the well-known immobilization principles to produce more robust, eco-friendlier, and cheaper biocatalysts. Therefore, this review discusses the trending studies and industrial applications of the materials and protocols for lipase immobilization, analyzing their advantages and disadvantages. Finally, it summarizes the current challenges and potential alternatives for lipases at the industrial level.

Applications of covalent organic frameworks and their composites in the extraction of pesticides from different samples

Pesticides are used extensively in a wide range of applications and due to their high rate of consumption, they are ubiquitous in the different media and samples like environment, water sources, air, soil, biological materials, wastes (liquids, solids or sludges), vegetables and fruits, where they can persist for long periods. Pesticides often have hazardous side effects and can cause a range of harmful diseases like Parkinson, Alzheimer, asthma, depression and anxiety, cancer, etc, even at low concentrations. To this end, extraction, pre-concentration and determination of pesticides from various samples presents significant challenges caused by sample complexity and the low concentrations of them in many samples. Often, direct extraction and determination of pesticides are impossible due to their low concentrations and the complexity of samples. The main goals of sample preparation are removing interfering species, pre-concentrating target analyte/s and converting the analytes into more stable forms (when needed). The most popular approach is solid-phase extraction due to its simplicity, efficiency, ease of operation and low cost. This method is based on using a wide variety of materials, among which covalent organic frameworks (COFs) can be identified as an emerging class of highly versatile materials exhibiting advantageous properties, such as a porous and crystalline structure, pre-designable structure, high physical and chemical stability, ease of modification, high surface area and high adsorption capacity. The present review will cover recent developments in synthesis and applications of COFs and their composites for extraction of pesticides, different synthesis approaches of COFs, possible mechanisms for interaction of COFs-based adsorbents with pesticides and finally, future prospects and challenges in the fabrication and utilization of COFs and their composites for extraction of pesticides.

Study on the efficiency of a covalent organic framework as adsorbent for the screening of pharmaceuticals in estuary waters

Herein, we demonstrate, for the first time, that covalent organic frameworks (COFs) can be efficient adsorbents for the screening of pharmaceuticals in real water samples, obtaining highly representative data on their occurrence and avoiding the cost of carrying high volume samples and tedious and costly clean-up and preconcentration steps. Of the 23 pharmaceuticals found present in the water samples from the Tagus river estuary using state-of-the-art solid-phase extraction (SPE), 22 were also detected (adsorbed and recovered for analysis) using a COF as the adsorbent material with adsorption efficiency of over 80% for nearly all compounds. In specific cases, acidification of the water samples was identified to lead to a dramatic loss of adsorption efficiency, underlining the effect of sample pre-treatment on the results. The COF efficiently adsorbed (>80%) 19 pharmaceuticals without acid treatment of the sample, highlighting the potential of this class of materials for representative in situ passive adsorption of pharmaceuticals, making this material suitable for being used in water monitoring programs as a simple and cost-efficient sample preparation procedure. In the case of α-hydroxyalprazolam and diclofenac, the COF outperformed the SPE procedure in the recovery efficiency. Although further efforts should be made in tailoring the desorption of the pharmaceuticals from the COF by using different solvents or solvent mixtures, we propose COFs as convenient adsorbent for broad-scope screening and as an efficient adsorbent material to target specific classes of pharmaceuticals. To the best of our knowledge, this is the first study on the use of COFs for contaminant screening in real, naturally contaminated water samples.

Environmental occurrence, toxicity concerns, and remediation of recalcitrant nitroaromatic compounds

Nitroaromatic compounds (NACs) are considered important groups of chemicals mainly produced by human and industrial activities. The large-scale application of these xenobiotics creates contamination of the water and soil environment. Despite applicability, NACs have been caused severe hazardous side effects in animals and human systems like different cancers, anemia, skin irritation, liver damage and mutagenic effects. The effective remediation of the NACs from the environment is a significant concern. Researchers have implemented physicochemical and biological methods for the remediation of NACs from the environment. Most of the applied methods are based on adsorption and degradation approaches. Among these methods, degradation is considered a versatile method for the subsequent removal of NACs due to its exceptional properties like simplicity, easy operation, cost-effectiveness, and availability. Most importantly, the degradation process does not generate hazardous side products and wastes compared to other methods. Hence, the importance of NACs, their remediation, and supreme attributes of the degradation method have encouraged us to review the recent progress and development for the removal of these perilous materials using degradation as a versatile method. Therefore, in this review, (i) NACs, physicochemical properties, and their hazardous side effects on humans and animals are discussed; (ii) Physicochemical methods, microbial, anaerobic bioremediation, mycoremediation, and aerobic degradation approaches for the degradation of NACs were thoroughly vetted; (iii) The possible mechanisms for degradation of NACs were investigated and discussed. (iv) The applied kinetic models for evaluation of the rate of degradation were also assessed and discussed. Finally, (vi) current challenges and future prospects of proposed methods for degradation and removal of NACs were also directed.

Occurrence, removal and mass balance of substituted diphenylamine antioxidants in wastewater treatment plants in Northeast China

Substituted diphenylamine antioxidants (SDPAs) are additives used in various commodities and are commonly found in environmental samples. However, limited information was available on their fate and removal in wastewater treatment plants (WWTPs). This paper reports the results on the occurrence and removal efficiency of ten selected SDPAs in six WWTPs equipped with different treatment processes in Northeast China. Quite similar distributions of different SDPA congeners were shown in the studied WWTPs, with ditertoctyl-diphenylamine (C8/C8-DPA), tertbutyl-tertoctyl-diphenylamine (C4/C8-DPA), and tertoctyl-diphenylamine (C8-DPA) being always dominant in the influent, effluent, and sludge (total > 80%). A cyclic activated sludge system combined with a V-shape filter achieved the highest removal efficiencies of SDPAs among various treatment processes. Styrenated-diphenylamine1 (S-DPA1) (96 ± 10%), C8-DPA (95 ± 5.5%), and distyrenated-diphenylamine1 (DS-DPA1) (94 ± 9.3%) showed high and stable removal efficiencies, whereas C4/C8-DPA (85 ± 31%) and C8/C8-DPA (84 ± 62%) showed considerably varied removal efficiencies. Per-day discharges of SDPAs to the receiving environment through effluent and sludge were estimated as 828 ± 350 and 5578 ± 5196 mg, respectively. A median of 85% of the initial mass loadings of SDPAs was found in the sludge samples, suggesting that the observed removal of SDPAs in the WWTPs was caused by their sorption to the sludge, rather than biodegradation/transformation. This work provides an overall description of the occurrence, fate, and mass balance of SDPAs in WWTPs in Northeast China and highlights a new emission route to the environment via WWTPs.

Recent Advances in Covalent Organic Frameworks for Heavy Metal Removal Applications

Covalent organic frameworks comprise a unique class of functional materials that has recently emerged as a versatile tool for energy-related, photocatalytic, environmental, and electrochromic device applications. A plethora of structures can be designed and implemented through a careful selection of ligands and functional units. On the other hand, porous materials for heavy metal absorption are constantly on the forefront of materials science due to the significant health issues that arise from the release of the latter to aquatic environments. In this critical review, we provide insights on the correlation between the structure of functional covalent organic frameworks and their heavy metal absorption. The elements we selected were Pb, Hg, Cr, Cd, and As metal ions, as well as radioactive elements, and we focused on their removal with functional networks. Finally, we outline their advantages and disadvantages compared to other competitive systems such as zeolites and metal organic frameworks (MOFs), we analyze the potential drawbacks for industrial scale applications, and we provide our outlook on the future of this emerging field.

A novel 2D mesoporous phosphazene-anthraquinone-based covalent organic polymer: synthesis, characterization and supercapacitor applications

A novel phosphazene anthraquinone-based covalent organic polymer (HD-1) was successfully designed and synthesized through a simple polymerization reaction. The as-prepared material was used as an electrode active material for a supercapacitor.