Metal-organic framework-based biosensing platforms for the sensitive determination of trace elements and heavy metals: A comprehensive review

Heavy metals in food and water sources are potentially harmful to humans. Determination of these pollutants is critical for improving safety. Effective recognition systems are a contemporary challenge; several novel technologies for the quick, easy, selective, and sensitive determination of these compounds are in demand. Metal-organic framework (MOF)-based sensors and biosensors have crucial applications in identifying these potentially harmful substances. Here, we review electrochemical and optical biosensors for in situ sensing that are sensitive and cost effective, with a simple protocol and wide linear range. Despite the abundance of articles in this field, we assessed and checked out various basic features of MOFs as porous compounds that include clusters or ions, and some of the ligands connected to these clusters have a variety of useful properties. Afterward, we also assessed various electrochemical and optical sensing assays, which have recently gathered interest because of their potential applications for recognizing certain compounds in the environment. Their operation and approaches are dependent on their structures, the materials and component types used, and the substances they are targeting

Toward Green Synthesis of Graphene Oxide Using Recycled Sulfuric Acid via Couette-Taylor Flow

Developing eco-friendly and cost-effective processes for the synthesis of graphene oxide (GO) is essential for its widespread industrial applications. In this work, we propose a green synthesis technique for GO production using recycled sulfuric acid and filter-processed oxidized natural graphite obtained from a Couette-Taylor flow reactor. The viscosity of reactant mixtures processed from Couette-Taylor flow was considerably lower (???200 cP at 25 ??C) than that of those from Hummers' method, which enabled the simple filtration process. The filtered sulfuric acid can be recycled and reused for the repetitive GO synthesis with negligible differences in the as-synthesized GO qualities. This removal of sulfuric acid has great potential in lowering the overall GO production cost as the amount of water required during the fabrication process, which takes a great portion of the total production cost, can be dramatically reduced after such acid filtration. The proposed eco-friendly GO fabrication process is expected to promote the commercial application of graphene materials into industry shortly

Potential of Adsorption of Diverse Environmental Contaminants onto Microplastics

Microplastics are regarded as vectors of hazardous contaminants due to their ability to adsorb xenobiotic chemicals. This has led to increased interest in the risk of previously neglected microplastic contaminants in the aquatic environment. Here, we assessed the possibility of transferring chemical contaminants to microplastics by evaluating the adsorption performance of (in)organic pollutants on various types of microplastics (polystyrene, PS; polyethylene terephthalate, PET; high-density polyethylene, HDPE; and low-density polyethylene, LDPE;). Considering the toxicity and polarity of each pollutant, dyes (BB9 and RR120) and heavy metals (Cd(II), Pb(II), As(III), and As(V)) were selected for the adsorption experiments. Dye was found to be adsorbed through physical adsorption. The adsorption capacity of microplastics for RR120 and BB9 was the highest for HDPE-1 and LDPE-1, respectively. Additionally, the smaller the size of the microplastics, the higher the adsorbed amounts. The main adsorption mechanism of heavy metals was found to be through physical and chemical adsorption. And adsorption mechanism of dye depends on physical adsorption. Thus, the adsorption of microplastic contaminants was affected more by the condition than by the type of microplastics

Comparing Graphene Oxide and Reduced Graphene Oxide as Blending Materials for Polysulfone and Polyvinylidene Difluoride Membranes

Graphene is a single atomic plane of graphite, and it exhibits unique electronic, thermal, and mechanical properties. Exfoliated graphene oxide (GO) contains various hydrophilic functional groups, such as hydroxyl, epoxide, and carboxyl groups, that can modify the hydrophobic characteristics of a membrane surface. Though reduced graphene oxide (rGO) has fewer functional groups than GO, its associated sp2 structures and physical properties can be recovered. A considerable amount of research has focused on the use of GO to obtain a pristine graphene material via reduction processes. In this study, polysulfone (PSf) and polyvinylidene fluoride (PVDF) membranes that were blended with GO and rGO, respectively, were fabricated by using the immersion phase inversion method and an n-methylpyrrolidone (NMP) solvent. Results showed that the graphene nanomaterials, GO and rGO, can change the pore morphology (size and structure) of both PSf and PVDF membranes. The optimum content of both was then investigated, and the highest flux enhancement was observed with the 0.10 wt% GO-blended PSf membrane. The presence of functional groups in GO within prepared PSf and PVDF membranes alters the membrane characteristics to hydrophilic. An antifouling test and rejection efficiency evaluation also showed that the 0.10 wt% membrane provided the best performance

Microplastics in water systems: A review of their impacts on the environment and their potential hazards

Microplastics, the microscopic plastics, are fragments of any type of plastic that are being produced today as plastic waste originating from anthropogenic activities. Such microplastics are discharged into the environment, and they enter back into the human body through different means. The microplastics spread in the environment due to environmental factors and the inherent properties of microplastics, such as density, hydrophobicity, and recalcitrance, and then eventually enter the water environment. In this study, to better understand the behavior of microplastics in the water environment, an extensive literature review was conducted on the occurrence of microplastics in aquatic environments categorized by seawater, wastewater, and freshwater. We summarized the abundance and distribution of microplastics in the water environment and studied the environmental factors affecting them in detail. In addition, focusing on the sampling and pretreatment processes that can limit the analysis results of microplastics, we discussed in depth the sampling methods, density separation, and organic matter digestion methods for each water environment. Finally, the potential hazards posed by the behavior of aging microplastics, such as adsorption of pollutants or ingestion by aquatic organisms, due to exposure to the environment were also investigated

Ultrasonic-assisted photocatalytic degradation of various organic contaminants using ZnO supported on a natural polymer of sporopollenin

Water resource pollution by organic contaminants is an environmental issue of increasing concern. Here, sporopollenin/zinc oxide (SP/ZnO) was used as an environmentally friendly and durable catalyst for sonophotocatalytic treatment of three organic compounds: direct blue 25 (DB 25), levofloxacin (LEV), and dimethylphtalate (DMPh). The resulting catalyst had a 2.65 eV bandgap value and 9.81 m2/g surface area. The crystalline structure and functional groups of SP/ZnO were confirmed by X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FTIR) analyses. After 120 min of the sonophotocatalysis, the degradation efficiencies of DB 25, LEV, and DMPh by SP/ZnO were 86.41, 75.88, and 62.54%, respectively, which were higher than that of the other investigated processes. The role of reactive oxygen species were investigated using various scavengers, enhancers, photoluminescence, and o-phenylenediamine. Owing to its stability, the catalyst exhibited good reusability after four consecutive cycles. In addition, the high integrity of the catalyst was confirmed by scanning electron microscopy (SEM), XRD, and FTIR analyses. After four consecutive examinations, the leaching of zinc in the aqueous phase was < 3 mg/L. Moreover, gas chromatography-mass spectrometry (GC–MS) analyses indicated that the contaminants were initially converted into cyclic compounds and then into aliphatic compounds, including carboxylic acids and animated products. Thus, this study synthesized an environmentally friendly and reusable SP/ZnO composite for the degradation of various organic pollutants using a sonophotocatalytic process

Evaluation of the formation of oxidants and by-products using Pt/Ti, RuO₂/Ti, and IrO₂/Ti electrodes in the electrochemical process

<div><p>The aim of this study was to evaluate the formation of oxidants and by-products by using different electrode materials, such as Pt/Ti, RuO₂/Ti, and IrO₂/Ti, in the electrochemical process. The harmful by-products and were formed during the electrolysis of a Cl⁻ electrolyte solution, as well as active chlorine, which is the most common water disinfectant. With regard to drinking water treatment, the most efficient electrode was defined as that leading to a higher formation of active chlorine and a lower formation of hazardous by-products. Overall, it was found that the Pt/Ti electrode should not be used for drinking water treatment applications, while the IrO₂/Ti and RuO₂/Ti electrodes are ideal for use.</p></div