Covalent organic frameworks-based smart materials for mitigation of pharmaceutical pollutants from aqueous solution

Lignocellulosic biomass for biochar production: A green initiative on biowaste conversion for pharmaceutical and other emerging pollutant removal

Lignocellulosic waste generation and their improper disposal has accelerated the problems associated with increased greenhouse gas emissions and associated environmental pollution. Constructive ways to manage and mitigate the pollution associated with lignocellulosic waste has propelled the research on biochar production using lignocellulose-based substrates. The sustainability of various biochar production technologies in employing lignocellulosic biomass as feedstock for biochar production not only aids in the lignocellulosic biomass valorization but also helps in carbon neutralization and carbon utilization. Functionalization of biochar through various physicochemical methods helps in improving their functional properties majorly by reducing the size of the biochar particles to nanoscale and modifying their surface properties. The usage of engineered biochar as nano adsorbents for environmental applications like dye absorption, removal of organic pollutants and endocrine disrupting compounds from wastewater has been the thrust areas of research in the past few decades. This review presents a comprehensive outlook on the up-to-date research findings related to the production and engineering of biochar from lignocellulosic biomass and their applications in environmental remediation especially with respect to wastewater treatment. Further a detailed discussion on various biochar activation methods and the future scope of biochar research is presented in this review work.

New sulfonated covalent organic framework for highly effective As(III) removal from water

The goal of taking out As(III) from water is to reduce the detriment that poisonous metals can do to people and nature. A substance that can absorb As(III), TFPOTDB-SO3H, was made by combining 2,5-diaminobenzenesulfonic acid and 2,4,6-tris-(4-formylphenoxy)-1,3,5-triazine in a reaction that joins molecules together. This substance can adsorb As(III) very well and has excellent qualities like being easy to use again, separate substances, and filter out liquids. At pH = 8 and at room temperature, TFPOTDB-SO3H adsorbed a lot of As(III). It achieved a removal rate of 97.1 % within 10 min and could adsorb up to 344.8 mg/g. A research was conducted to investigate the effect of co-existing anions on the elimination of arsenic. The findings indicated that the presence of anions had a minimal adverse impact, reducing As(III) uptake by approximately 1-7 %. The kinetics of the uptake process were found to be controlled by the quasi-second order kinetic model, while the Langmuir isotherm model validated that the mechanism for As(III) removal was monolayer chemisorption. According to the thermodynamic analysis, the adsorption process was endothermic and occurred spontaneously. Moreover, even after 4 successive adsorption-desorption cycles, the adsorbent preserved a substantial uptake productivity of 88.86 % for As(III). The results collectively indicate that TFPOTDB-SO3H holds considerable promise for the efficient adsorption and elimination of As(III) ions from wastewater.

Theoretical design of transition metal-doped oxo-triarylmethyl as a disposable platform for adsorption of ibuprofen

Emerging environmental contaminants have become a crucial environmental issue because of the highly toxic effluents emitted by factories. Ibuprofen (IBP), as a typical anti-inflammatory drug, is frequently detected in water sources. Therefore, its removal using various adsorbents has drawn great interest. Herein, the structural, electronic, energetic, and optical properties of pristine oxo-triarylmethyl (oxTAM) and transition metal-doped oxo-triarylmethyl (TM@oxTAM, TM = Sc, Ti, V, Cr, and Mn) for adsorption of the IBU drug were investigated using density functional theory (DFT) calculations implemented in Gaussian and VASP codes. Frontier molecular orbital (FMO), density of states (DOS), and electronic band structure results demonstrated that transition metal-doped oxTAM causes a significant reduction in the energy band gap (Eg) value of pristine oxTAM, with the highest decrease (30.14 %) in the case of Mn@oxTAM. It was found that transition metal doping onto oxTAM leads to an increase in the adsorption energies (1.20-2.64 eV) and charge density between transition metal and IBU. Natural bond orbital (NBO) analysis revealed that charge was effectively transferred from the IBU towards the transition metal, which was further analyzed by charge decomposition analysis (CDA). Furthermore, quantum theory of atoms in molecules (QTAIM), interaction region indicator (IRI), electron localization function (ELF), and radial distribution function (RDF) analyses revealed that the IBU is adsorbed on the Sc@oxTAM surface via covalent interactions, while electrostatic with partially covalent interactions are dominated in other IBU/TM@oxTAM complexes. The results suggest that TM doping on the oxTAM provides a new insight for developing photocatalyst-based covalent organic frameworks (COFs) to remove emerging pollutants in wastewater.

Covalent organic frameworks: Pioneering remediation solutions for organic pollutants

Covalent Organic Frameworks (COFs) have emerged as a promising class of crystalline porous materials with customizable structures, high surface areas, and tunable functionalities. Their unique properties make them attractive candidates for addressing environmental contamination caused by pharmaceuticals, pesticides, industrial chemicals, persistent organic pollutants (POPs), and endocrine disruptors (EDCs). This review article provides a comprehensive overview of recent advancements and applications of COFs in removing and remedying various environmental contaminants. We delve into the synthesis, properties, and performance of COFs and their potential limitations and future prospects.

Organic Covalent Interaction-based Frameworks as Emerging Catalysts for Environment and Energy Applications: Current Scenario and Opportunities

The term "covalent organic framework" (COF) refers to a class of porous organic polymeric materials made from organic building blocks that have been covalently bonded. The preplanned and predetermined bonding of the monomer linkers allow them to demonstrate directional flexibility in two- or three-dimensional spaces. COFs are modern materials, and the discovery of new synthesis and linking techniques has made it possible to prepare them with a variety of favorable features and use them in a range of applications. Additionally, they can be post-synthetically altered or transformed into other materials of particular interest to produce compounds with enhanced chemical and physical properties. Because of its tunability in different chemical and physical states, post-synthetic modifications, high stability, functionality, high porosity and ordered geometry, COFs are regarded as one of the most promising materials for catalysis and environmental applications. This study highlights the basic advancements in establishing the stable COFs structures and various post-synthetic modification approaches. Further, the photocatalytic applications, such as organic transformations, degradation of emerging pollutants and removal of heavy metals, production of hydrogen and Conversion of carbon dioxide (CO₂ ) to useful products have also been presented. Finally, the future research directions and probable outcomes have also been summarized, by focusing their promises for specialists in a variety of research fields.

Occurrence, distribution, and ecological risk assessment of pharmaceuticals and personal care products in the surface water of the middle and lower reaches of the Yellow River (Henan section)

Pharmaceuticals and personal care products (PPCPs) are commonly seen emerging organic contaminants in aquatic environments. The transects for the occurrence and distribution of 24 PPCPs along the middle and lower reaches of the Yellow River (Henan section) were investigated in this study. All 24 targeted compounds were detected in surface water, with concentrations in the range from not detected (ND) to 527.4 ng/L. Among these PPCPs, caffeine is found to have the highest concentration and its detection frequency is 100%. The total PPCP concentration ranged from 136 ng/L to 916 ng/L (median, 319.5 ng/L). Spatial analysis showed that the pollution level of PPCPs in the trunk stream was lower than that in most tributaries in the middle and lower reaches of the Yellow River (Henan section). The ecotoxicological risk assessment indicated that norfloxacin, azithromycin, estrone, and triclosan posed high risks to aquatic organisms (RQ > 1), roxithromycin and oxytetracycline imposed moderate risks (0.1 ≤ RQ < 1), and the tributary Jindi River had the highest mixed risk (MRQ = 222).

Zinc hydroxystannate/zinc-tin oxide heterojunctions for the UVC-assisted photocatalytic degradation of methyl orange and tetracycline

Partial phase modification of zinc hydroxystannate (ZHS) is an effective technique for improving its light absorption capacity. In this study, a zinc hydroxystannate/zinc-tin oxide (ZHS/ZTO) heterostructure was synthesized via chemical co-precipitation followed by annealing. The as-prepared heterostructure revealed cubic crystal morphology along with high-intensity diffraction peaks in the XRD pattern. The XPS analysis of ZHS/ZTO heterostructures demonstrated the presence of key elements (Zn, Sn, and O) in their most stable ionic forms. The photocatalytic degradation efficiencies of the prepared samples were tested against methyl orange (MO) and tetracycline (TC) in an aqueous medium under UVC (254 nm) radiation. Under optimized conditions, maximum degradation efficiencies of 99% for MO and 97% for TC were observed in 120 and 180 min, respectively. Further, the predominant role of OH˙ radicals in the photocatalytic removal of MO and TC was evident through scavenging experiments. 2nd order kinetic model was outperformed in simulating the degradation mechanism of both targets over 1st and zero-order kinetic models. Finally, a photocatalytic degradation mechanism is proposed based on the energy values estimated for the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) using UPS analysis.

S,N-rich luminous covalent organic frameworks for Hg2+ detection and removal

The challenge for simultaneous detection and removal of Hg²⁺ is the design of bifunctional materials bearing abundant accessible chelating sites with high affinity. Covalent-organic frameworks (COFs) are attracting more and more attention as potential bifunctional materials for Hg²⁺ detection due to their large specific surface area, ordered pores, and abundant chelating sites. Here, a new luminous S,N-rich COF_BTT-AMPD based on hydrophilic block unit of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AMPD) was constructed, which improved the solubility and affinity for Hg²⁺ greatly. Another S-rich fused-ring unit of benzotrithiophene tricarbalaldehyde (BTT) enhanced the conjugation of COF_BTT-AMPD, and the methyl-rich chains block unit of AMPD effectively suppressed the aggregation-caused quenching. Thus, the COF_BTT-AMPD emitted strong fluorescence at 546 nm in liquid and solid as well as different solvent with a wide pH range, which was used for the visual detection and removal of Hg²⁺ (detection limit: 2.6 nM, linear range: 8.6 × 10^-3-20 μM, monolayer adsorption capacity: 476.19 mg g^-1) successfully. COF_BTT-AMPD-based fabric and light-emitting diode coatings were further constructed to realize the visual detection of Hg²⁺ vapor. The results reveal the potential of S,N-rich luminous COF_BTT-AMPD for Hg²⁺ detection and remediation in the environment.

Covalent organic frameworks as promising adsorbent paradigm for environmental pollutants from aqueous matrices: Perspective and challenges

Covalent organic frameworks (COFs) are an emerging class of new porous crystalline polymers materials having robust framework, outstanding structural regularity, highly ordered aperture size, inherent porosity, and chemical stability with designer properties, making them an ideal material for adsorbing a variety of contaminants from water bodies. Presented study focusses on the current advances and progress of pristine COFs as well as COFs based composites as an emerging substitute for the adsorption and removal of a variety of pollutants including water desalination technique, heavy metals, pharmaceuticals, dyes and organic pollutants. The absorption capabilities of COFs-derived architecture are evaluated and equated with those of other commonly used adsorbents. The interaction between sorption ability and structural property as well as some regularly utilized ways to improve the adsorption performance of COFs-based materials are also reviewed. Finally, perspective and a summary about the challenges and opportunities of COFs and COFs-derived materials are discussed to deliver some exciting data for fabricating and designing of COFs and COFs-derived materials for remediation of environmental pollutants.

Robust strategies to eliminate endocrine disruptive estrogens in water resources

The widespread occurrence and ubiquitous distribution of estrogens, i.e., estrone (E1), estradiol (E2), and estriol (E3) in our water matrices, is an issue of global concern. Public and regulatory authorities are concerned and placing joint efforts to eliminate estrogens and related environmentally hazardous compounds, due to their toxic influences on the environmental matrices, ecology, and human health, even at low concentrations. However, most of the available literature is focused on the occurrence of estrogens in different water environments with limited treatment options. Thus, a detailed review to fully cover the several treatment processes is needed. This review comprehensively and comparatively discusses many physical, chemical, and biological-based treatments to eliminate natural estrogens, i.e., estrone (E1), estradiol (E2), and estriol (E3) and related synthetic estrogens, e.g., 17α-ethinylestradiol (EE2) and other related hazardous compounds. The covered techniques include adsorption, nanofiltration, ultrafiltration, ultrasonication, photocatalysis of estrogenic compounds, Fenton, Fenton-like and photo-Fenton degradation of estrogenic compounds, electro-Fenton degradation of estrogenic compounds, ozonation, and biological methods for the removal of estrogenic compounds are thoroughly discussed with suitable examples. The studies revealed that treatment plants based on chemical and biological approaches are cost-friendly for removing estrogenic pollutants. Further, there is a need to properly monitor and disposal of the usage of estrogenic drugs in humans and animals. Additional studies are required to explore a robust and more advanced oxidation treatment strategy that can contribute effectively to industrial-scale applications. This review may assist future investigations, monitoring, and removing estrogenic compounds from various environmental matrices. In concluding remarks, a way forward and future perspectives focusing on bridging knowledge gaps in estrogenic compounds removal are also proposed.

Nano-remediation technologies for the sustainable mitigation of persistent organic pollutants

The absence of novel and efficient methods for the elimination of persistent organic pollutants (POPs) from the environment is a serious concern in the society. The pollutants release into the atmosphere by means of industrialization and urbanization is a massive global hazard. Although, the eco-toxicity associated with nanotechnology is still being debated, nano-remediation is a potentially developing tool for dealing with contamination of the environment, particularly POPs. Nano-remediation is a novel strategy to the safe and long-term removal of POPs. This detailed review article presents an important perspective on latest innovations and future views of nano-remediation methods used for environmental decontamination, like nano-photocatalysis and nanosensing. Different kinds of nanomaterials including nanoscale zero-valent iron (nZVI), carbon nanotubes (CNTs), magnetic and metallic nanoparticles, silica (SiO₂) nanoparticles, graphene oxide, covalent organic frameworks (COFs), and metal organic frameworks (MOFs) have been summarized for the mitigation of POPs. Furthermore, the long-term viability of nano-remediation strategies for dealing with legacy contamination was considered, with a particular emphasis on environmental and health implications. The assessment goes on to discuss the environmental consequences of nanotechnology and offers consensual recommendations on how to employ nanotechnology for a greater present and a more prosperous future.

Covalent Organic Frameworks-Based Membranes as Promising Modalities from Preparation to Separation Applications: An Overview

Covalent organic frameworks (COFs) are a promising class of porous crystalline materials made up of covalently connected and periodically protracted network topologies through organic linkers. The tailorability of organic linker and intrinsic structures endow COFs with a tunable porosity and structure, low density, facilely-tailored functionality, and large surface area, attracting increasing amount of interests in variety of research areas of membrane separations. COF-based membranes have spawned a slew of new research projects, ranging from fabrication methodologies to separation applications. Herein, we tried to emphasis the major developments in the synthetic approaches of COFs based membranes for a variety of separation applications such as, separation of gaseous mixtures, water treatment as well as separation of isomeric and chiral organic compounds. The proposed methods for fabricating COF-based continuous membranes and columns for real world applications are also thoroughly explored. Finally, a viewpoint on the future directions and remaining challenges for COF research in the area of separation is provided.

Persistence, environmental hazards, and mitigation of pharmaceutically active residual contaminants from water matrices

Pharmaceutical compounds are designed to elicit a biological reaction in specific organisms. However, they may also elicit a biological response in non-specific organisms when exposed to ambient quantities. Therefore, the potential human health hazards and environmental effects associated with pharmaceutically active compounds presented in aquatic environments are being studied by researchers all over the world. Owing to their broad-spectrum occurrence in various environmental matrices, direct or indirect environmental hazardous impacts, and human-health related consequences, several pharmaceutically active compounds have been categorized as emerging contaminants (ECs) of top concern. ECs are often recalcitrant and resistant to abate from water matrices. In this review, we have examined the classification, occurrence, and environmental hazards of pharmaceutically active compounds. Moreover, because of their toxicity and the inefficiency of wastewater treatment plants to remove pharmaceutical pollutants, novel wastewater remediation technologies are urgently required. Thus, we have also analyzed the recent advances in microbes-assisted bioremediation as a suitable, cost-effective, and eco-friendly alternative for the decontamination of pharmaceutical pollutants. Finally, the most important factors to reach optimal bioremediation are discussed.

Covalent organic framework-based porous materials for harmful gas purification

Covalent organic frameworks (COFs) with 2D or 3D networks are a class of novel porous crystalline materials, and have attracted more and more attention in the field of gas purification owing to their attractive physicochemical properties, such as high surface area, adjustable functionality and structure, low density, and high stability. However, few systematic reviews about the application statuses of COFs in gas purification are available, especially about non-CO₂ harmful gases. In this review, the recent progress of COFs about the capture, catalysis, and detection of common harmful gases (such as CO₂, NO_x, SO₂, H₂S, NH₃ and volatile pollutants) were comprehensively discussed. The design strategies of COF functional materials from porosity adjustment to surface functionalization (including bottom-up approach, post-synthetic approach, and blending with other materials) for certain application were summarized in detail. Furthermore, the faced challenges and future research directions of COFs in the harmful gas treatment were clearly proposed to inspire the development of COFs.

Covalent Organic Frameworks: New Materials Platform for Photocatalytic Degradation of Aqueous Pollutants

Covalent organic frameworks (COFs) are highly porous and crystalline polymeric materials, constructed by covalent bonds and extending in two or threedimensions. After the discovery of the first COF materials in 2005 by Yaghi et al., COFs have experienced exciting progress and exhibitedtheirpromising potential applications invarious fields, such as gas adsorption and separation, energy storage, optoelectronics, sensing and catalysis. Because of their tunablestructures, abundant, regular and customizable pores in addition to large specific surface area, COFs can harvest ultraviolet, visible and near-infrared photons, adsorb a large amount of substrates in internal structures and initiate surface redox reactions to act as effective organic photocatalysts for water splitting, CO₂ reduction, organic transformations and pollutant degradation. In this review, we will discuss COF photocatalysts for the degradation of aqueous pollutants. The state-of-the-art paragon examples in this research area will be discussed according to the different structural type of COF photocatalysts. The degradation mechanism will be emphasized. Furthermore, the future development direction, challenges required to be overcome and the perspective in this field will be summarized in the conclusion.