In-situ self-assembly of robust Fe (III)-carboxyl functionalized polyacrylonitrile polymeric bead catalyst for efficient photo-Fenton oxidation of p-nitrophenol

Recent advances in advanced oxidation processes (AOPs) for the treatment of nitro- and alkyl-phenolic compounds

The presence of phenolic compounds in the aquatic environment has posed severe risks due to their toxicity. Among the phenolic families, nitro- and alkyl-phenolic compounds have been categorized as precedence contaminants by the United States Environmental Protection Agency (US EPA). Therefore, efficient treatment methods for wastewater containing nitro- and alkyl-phenolic compounds are urgently needed. Due to the advantages of creating reactive species and generating efficient degradation of hazardous contaminants in wastewater, advanced oxidation processes (AOPs) are well-known in the field of treating toxic contaminants. In this review paper, the recent directions in AOPs, catalysts, mechanisms, and kinetics of AOPs are comprehensively reviewed. Furthermore, the conclusion summarizes the research findings, future prospects, and opportunities for this study. The main direction of AOPs lies on the optimization of catalyst and operating parameters, with industrial applications remain as the main challenge. This review article is expected to present a summary and in-depth understanding of AOPs development; and thus, inspiring scientists to accelerate the evolution of AOPs in industrial applications.

N-doped graphene aerogel cathode with internal aeration for enhanced degradation of p-nitrophenol by electro-Fenton process

A columnar N-doped graphene aerogel (NGA) was successfully fabricated by one-step hydrothermal synthesis using L-hydroxyproline as reductant, N-doping, and swelling agent, and it was used as the cathode with internal aeration mode for the electro-Fenton degradation of p-nitrophenol. Owing to the stable solid-liquid-gas three-phase interface, more active defects, and modulated nitrogen dopants, the NGA cathode exhibited enhanced electrocatalytic activity. H₂O₂ could be continuously electro-generated via a two-electron oxygen reduction, and the yield of H₂O₂ was 153.3 mg·L^-1·h^-1 with the low electric energy consumption of 15.3 kWh kg^-1. Simultaneously, the NGA cathode had better charge transfer capability with N-doping, which was conducive to the conversion of Fe³⁺/Fe²⁺. Under the optimal condition, nearly 100% removal of p-nitrophenol and 84% removal of TOC were obtained within 60 and 120 min, respectively. The NGA cathode also presented good stability and versatile applicability in different water matrices. Therefore, the NGA is a cost-effective cathode material in electro-Fenton system with adequate activity and reuse stabilization.

Clearance of methylene blue by CdS enhanced composite hydrogel materials

Hydrogel material is considered to be one of the effective adsorbents widely used to remove organic pollutants. However, the poor mechanical properties of some hydrogels limit their applications. Herein, we prepared composite hydrogels, for which acrylic acid (AA) and acrylamide (AM) were cross-linked and polymerised as the main substrate with adsorption function, while CdS nanoparticles were mainly used as reinforced material. Scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), two-dimensional infrared vibrational echo spectroscopy (2D-IR), and thermal gravimetric analyzer (TGA) were used to determine the physical and chemical structures of the hydrogels. The effects of the composition of AA, AM, and CdS on the mechanical properties and adsorption behaviours of the hydrogels were investigated. Besides, based on the great potential photocatalytic application value for wastewater remediation under the sunlight of CdS, the influence of the CdS doping amount on the photocatalytic property was also studied. As a result, when the mass ratio of AA to AM was 5:5, the hydrogel showed the best mechanical properties, and along with increasing the amount of CdS, the mechanical strength of the hydrogel was significantly enhanced from 0.445 MPa to 1.014 MPa. Besides, the composite hydrogels showed high adsorption and photocatalytic degradation synergistic clearance effect on methylene blue. Thus, the introduction of CdS photocatalytic nanoparticles may be an efficient and economical approach towards bifunctional hydrogel materials with enhanced mechanical property and photocatalytic degradation for wastewater remediation.

Simultaneous Removal of Antibiotics and Heavy Metals with Poly(Aspartic Acid)-Based Fenton Micromotors

The discharge of diverse pollutants has led to a complex water environment and posed a huge health threat to humans and animals. Self-propelled micromotors have recently attracted considerable attention for efficient water remediation due to their strong localized mass transfer effect. However, a single functionalized component is difficult to tackle with multiple contaminants and requires to combine different decontamination effects together. Here, we introduced a multifunctional micromotor to implement the adsorption and degradation roles simultaneously by integrating the poly(aspartic acid) (PASP) adsorbent with a MnO₂ -based catalyst. The as-prepared micromotors are well propelled in contaminated waters by MnO₂ catalyzing hydrogen peroxide. In addition, the catalytic ramsdellite MnO₂ (R-MnO₂ ) inner layer is decorated with Fe₂ O₃ nanoparticles to improve their catalytic performance, contributing to an excellent degradation ability with 90% tetracycline (TC) removal in 50 minutes by enhanced Fenton-like reactions. Combining the attractive adsorption capability of poly (aspartic acid) (PASP), the composite micromotors offer an efficient removal of heavy metal ions in short time. Moreover, the designed micromotors are able to simultaneously remove antibiotic and heavy metals in mixed contaminants circumstance just in single treatment. This multifunctional micromotor with distinctive decontamination ability exhibits a promising prospective in treating multiple pollutants in the future.

Highly efficient and stable FeIIFeIII LDH carbon felt cathode for removal of pharmaceutical ofloxacin at neutral pH

The traditional electro-Fenton (EF) has been facing major challenges including narrow suitable range of pH and non-reusability of catalyst. To overcome these drawbacks we synthesized Fe^IIFe^III-layered double hydroxide modified carbon felt (Fe^IIFe^III LDH-CF) cathode via in situ solvo-thermal process. Chemical composition and electrochemical characterization of Fe^IIFe^III LDH-CF were tested and analyzed. The apparent rate constant of decay kinetics of ofloxacin (OFC) with Fe^IIFe^III LDH-CF (0.18 min^-1) at pH 7 was more than 3 times higher than that of homogeneous EF (0.05 min^-1) at pH 3 with 0.1 mM Fe²⁺ under same current density (9.37 mA cm^-2). Also, a series of experiments including evolution of solution pH, iron leaching, OFC removal with trapping agent and quantitative detection of hydroxyl radicals (OH) were conducted, demonstrating the dominant role of OH generated by surface catalyst via ≡ Fe^II/Fe^III on LDH cathode for degradation of organics as well contributing to high efficiency and good stability at neutral pH. Besides, formation and evolution of aromatic intermediates, carboxylic acids and inorganic ions (F^-, NH₄⁺ and NO₃^-) were identified by High-Performance Liquid chromatography, Gas Chromatography-Mass Spectrometry and ionic chromatography analyses. These findings allowed proposing a plausible degradation pathway of OFC by OH generated in the heterogeneous EF process.

Biogenesis of Prism-Like Silver Oxide Nanoparticles Using Nappa Cabbage Extract and Their p-Nitrophenol Sensing Activity

The present study aimed to explore the eco-friendly synthesis of prism-like silver oxide nanoparticles (Ag₂ONPs) from nappa cabbage extract and its p-nitrophenol sensing activity. The prepared Ag₂ONPs were characterized by X-ray diffraction (XRD), field-emission scanning spectroscopy (FESEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and ultraviolet (UV)-visible light spectral analysis (UV-Vis). p-Nitrophenol sensing properties of the prepared nanoparticles were also determined using a simple I-V method. The results showed that the as-prepared Ag₂ONPs have a face-centered cubic (fcc) crystalline nature and a prism-like morphology with particle size in the range 21.61-92.26 nm. The result also showed a high intensity of the (111) facet, making the Ag₂ONP-carbon black/nickel foam electrode (Ag₂ONP-C/NFE) exhibit a high-performance response to p-nitrophenol spanning a wide range of concentrations from 1.0 mM to 0.1 pM and a response time of around 5 s, indicating a high potential for water treatment applications.