4-nitrophenol Research Articles

Rational construction of g-C3N4/SnO2/CoFe2O4 dual Z-scheme system as a potential scaffold for fluorescence sensing and visible light driven photocatalytic degradation of lethal pollutants

Mimicking the natural photosynthesis process, novel direct dual Z-scheme CN/SnO2/CoFe2O4 heterostructures with different weight ratios (CN/SnO2:CoFe2O4 be 1:1, 2:1 and 1:2; namely CSnCo-1, CSnCo-0.5 and CSnCo-2, respectively) were successfully fabricated and employed for photocatalytic degradation of anthracycline drug, doxorubicin (DXR) and aromatic compound, p-nitrophenol (PNP) and fluorescence detection of heavy metal ion, Hg2+; DXR and PNP. CSnCo-0.5 displayed exceptional photocatalytic capability having pseudo first order rate constant values 5.60, 3.02, 1.23 and 1.38 times higher for DXR; and 4.2, 3.0, 1.18 and 1.12 times higher for PNP in comparison to CN, CSn-20, CSnCo-1 and CSnCo-2, respectively. UV–vis DRS study, photoluminescence spectra and electrochemical impedance results inveterate the formation of direct dual Z-scheme charge transfer, which is beneficial for boosting photocatalytic performance of the system. Additionally, CSnCo-0.5 proved to be highly selective and sensitive for the FL sensing of Hg2+, DXR and PNP with detection limits as low as 0.57 µM, 0.05 µM and 0.63 µM, respectively. Further, sensor provided good analytical performance in real water samples.

Simple preparation of monolithic N-doped electrode for efficient EF remediation of petrochemical wastewater: Performance, degradation pathways, and mechanism of different N-doped positions

Developing metal-free N-doped electrode for efficient electro-Fenton (EF) application is significant for petrochemical wastewater treatment considering the serious water pollution problem that caused by petrochemical industry. Herein, a robust monolithic N-doped electrode was fabricated by simple physical mixing and heating methods using accessible raw materials, and applied in EF system for wastewater treatment. The prepared 3D NC-650 electrode was used as cathode, showing excellent catalytic activity and stability for degradation of typical p-nitrophenol (PNP) pollutant and remediation of petrochemical wastewater. During the EF process, the PNP was completely decomposed via the substitution, oxidation, and ring-opening reactions under the attack of ·OH. The degradation pathways of organics in real wastewater matrix were also revealed based on liquid chromatography-mass spectrometry and three-dimensional fluorescence analysis. According to the degradation experiments, microstructure analysis, and theoretical calculation (molecular electrostatic potential, bond length, and adsorption energy), the possible mechanism of different N-doped positions on the monolithic 3D NC-650 electrode was revealed, in which the graphitic N, edge pyridinic N, and edge pyrrolic N all contribute to enhance the EF activity by accelerating the O2 adsorption, facilitating the H2O2 formation by promotion of *–OOH bond breaking, and promoting the adsorption of organics on electrode surface, respectively. This work illustrates insights into the EF reaction mechanism with the monolithic N-doped electrode, and thus accelerates its application for actual wastewater remediation.

Electrochemical sensing of 4‐nitrophenol through heteroleptic complexes of Ag(I) and Hg(II) based on 2‐thiazoline‐2‐thiol: Synthesis, crystal structures, and Hirshfeld analysis

In pursuit of a more effective electro‐sensor for environmentally hazardous nitro phenols detection at the trace level, we have developed two novel complexes [Ag(μ‐S‐thzt)(Hthzt)(PPh3)]2·2CH3CH2OH (1) and [Hg (thzt)2(o‐phen)](2) based on 2‐thiazoline‐2‐thiol (Hthzt). In complexes 1 and 2, triphenylphosphine and o‐phen were used as co‐ligands, respectively. Both the synthesizedcomplexes have been characterized by single crystal X‐ray diffraction data,UV–vis., infrared, and NMR spectrometry. Geometry around both the metal ion complexes is distorted tetrahedral. Noticeably, in complex 1, the Hthzt acts as a bridging as well as terminal ligand. The intermolecular interaction found in complexes 1 and 2 have been further investigated through Hirshfeld surface analysis. On comparing fluorescence intensities of Hthzt, complex 1, and complex 2, the order of fluorescence behavior was found to be Hthzt > complex 1 > complex 2. The electrochemical performance of both complexes 1 and 2 and their ability to sense 4‐nitrophenol (NP) have been evaluated through modified glassy carbon electrodes and were detected by the differential pulse voltammetry (DPV) and cyclic voltammetry (CV) methods. Based on electrochemical responses, complex 1 shows more effective performance as anelectro‐sensor than complex 2. With a relatively low detection limit of 0.19 μM, great selectivity, and acceptable sensitivity, the complex 1/GCE sensor demonstrated an exceptional linear plot between the oxidation peak current and NP concentration in the ranges of 0.5–500 μM.

Visible light photo-Fenton catalytic properties of starch functionalized α-FeOOH/β-FeOOH/Cu2O p-n-p heterojunction nanostructures

Photocatalysts with p-n-p heterojunctions can result in efficient charge separation. This idea motivated the synthesis of starch functionalized α-FeOOH/β-FeOOH/Cu2O heterojunction nanocomposites. All components in the composite have visible range band gaps. In a step-wise procedure, Cu2O nanostructures were precipitated on starch functionalized α-FeOOH/β-FeOOH nanocomposites. Mott Schottky plots confirmed p-n-p heterojunction formation. It enhanced charge separation and slowed down recombination resulting in efficient visible-light photocatalytic activity. The activity of this photocatalyst was evaluated for the photo-Fenton degradation of p-nitrophenol (PNP) and methyl orange (MO). Both degradation reactions follow zero-order kinetics. The photocatalyst remained stable during the organic pollutant degradation process even after repeated use.

N-doped carbon nanoflakes coordinate with amorphous Fe to activate ozone for degradation of p-nitrophenol

Due to their high catalytic performance, metal nitrogen-doped carbon materials are widely used in the field of environmental restoration of polluted water but there is limited research on metal nitrogen doped carbon composite materials as ozone catalysts. Herein, we report the preparation of amorphous iron-coordinated nitrogen-doped carbon nanosheets as a catalyst for ozone by the coordination of Fe-metal ions at the end of phenol chain in the lignin network. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (Raman), powder X-ray diffraction (XRD) and element mapping were used to characterize the Fe/D-NC composite material and investigate its morphology and composition. Highly uniform distribution of iron species was found through characterization. By exploring the degradation performance of composite materials of Fe/D-NC-T (700，800，900 ℃) prepared at different temperatures, it was found that the optimal Fe/D-NC-800 could effectively degrade p-nitrophenol (PNP) within 30 min. Quenching experiments and ESR analysis showed that both free and non-free radicals (•OH, O2•− and 1O2) and intrinsic Lewis acid sites (LAS) of the composite material Fe/D-NC-800 were involved and responsible for the degradation of PNP. This work not only offers new platforms for catalytic ozonation and may drive the development of metal-lignin-based catalytic ozonation for effective water treatment but also opens new avenues toward lignin valorization and biomass economy.

Enhanced microbial degradation mediated by pyrogenic carbon toward p-nitrophenol: Role of carbon structures and iron minerals

Pyrogenic carbon (PC) including black carbons and engineered carbons can mediate the extracellular electron transfer to facilitate the biogeochemical reaction with organic pollutants. Yet, the role of carbon structures and iron minerals on PC-mediated microbial degradation is still lacking of understanding. Herein, we studied the electrochemical properties of PCs produced from varied feedstock with regards to the mediated degradation of p-nitrophenol (PNP) by Shewanella putrefaciens CN32 in anoxic system. Mediated degradation by PCs was enhanced by facilitating extracellular electron transfer through oxygenated group and graphitic structure. Graphitic crystallites improved the electron-accepting capacity (as suggested by ID/IG and EAC) and diminished the electrochemical impedance (as suggested by Rct), contributing to PNP degradation under the anoxic system. Furthermore, more interfacial adsorption was conducive to the mediated reduction by the graphitic structure on PCs of high-temperature. In the presence of iron minerals, both hematite and goethite significantly facilitated PC-mediated degradation, which could be ascribed to the enhancement of the electron-donating capacity of microorganism and the accumulation of the reductive-state PCs by the interaction with generated Fe(II). This work paves a feasible way to the technical design on the remediation of phenolic contaminants by PC-mediated microbial degradation in environment.

Quick catalytic responsive chitosan flakes@Ag/CuO nanocomposites in organic synthesis and environmental remediation

This report deals with polymeric microgel of chitosan flakes (CF) for catalytic applications of bimetallic Ag/CuO nanoparticles (NPs). Nanocomposites, based on fabricated chitosan flakes, act as nanocatalyst and are used for swift chemical reduction of methylene blue (MB), para-nitro phenol (PNP) and dimethyl amino-benzaldehyde (DMAB) in presence of sodium borohydride or UV light. In our present work N-hydroxyl methyl acrylamide, instead of the traditional divinylic cross linker, has been employed as monomer as well as cross linker for the synthesis of chitosan flakes. The fabricated chitosan flakes have been doped with Ag/CuO NPs to yield nanocomposites. Three grades of nanocomposites have been synthesized by varying the amounts of N-hydroxyl methyl acrylamide, to optimize the crosslinking and suitable network, to yield stabilized NPs. FT-IR, XRD, TGA, SEM, TEM, EDX, DLS and Ultraviolet-Visible (UV-Vis.) spectroscopic characterization techniques have been performed to establish the polymeric chitosan flakes and nanocomposites. When the nanocomposites are employed as catalysts, the percentages of reduction of MB, PNP and DMAB, using sodium borohydride (NaBH4) or presence of UV-light, are over 90%, with lesser reaction time. The catalytic reduction in case of NaBH4 exhibits pseudo first order kinetics and the corresponding rate constant (kapp) values have been determined.

Source apportionment of gaseous Nitrophenols and their contribution to HONO formation in an urban area

Nitrophenols (NPs) have significant impacts on human health, climate, and atmospheric chemistry. Despite numerous measurements of particulate NPs, still little is known about their gaseous atmospheric abundances, sources, and fate. Here, four gaseous NPs [2,4-dinitrophenol (2,4-DNP), 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), and 2-Methyl-4-nitrophenol (2-Me-4-NP)] were continuously monitored during late Spring at an urban site in Houston, Texas. Among the four NPs, 4-NP showed the highest abundance, followed by 2-Me-4-NP, 2-NP, and 2,4-DNP with average concentrations of 1.07 ± 0.19 ppt, 0.47 ± 0.12 ppt, 0.41 ± 0.16 ppt, and 0.27 ± 0.09 ppt, respectively. The positive matrix factorization (PMF) model identified seven sources: industrial NPs, secondary formation, phenol sources, acetonitrile source, natural gas/crude oil, traffic, and petrochemical industries/oil refineries. A zero-dimensional photochemical box model was used to simulate the observed 2-NP and 2,4-DNP. A 50.0% and 70.0% jNO2 was found to be consistent with the measured 2-NP and 2,4-DNP. This yields a nitrous acid (HONO) production of 7.5 ± 2.5 ppt/h from 06:00 to 18:00 Central Standard Time (CST) from both NPs. An extrapolation including other known NPs suggests a maximum HONO formation of 13.8 ppt/h. The results of this study suggest that using PMF analysis supplemented by photochemical box model provides identification of the NPs sources and their atmospheric implication to HONO formation.

A Turn-On Fluorescent Assay for Glyphosate Determination Based on Polydopamine-Polyethyleneimine Copolymer via the Inner Filter Effect

The threat of glyphosate to food safety has attracted widespread attention. Consequently, it is highly urgent to develop a sensitive and accurate method for glyphosate detection. Herein, a turn-on fluorescent method for glyphosate detection using polydopamine-polyethyleneimine (PDA-PEI) copolymer as a fluorescent probe and p-nitrophenylphosphate (PNPP)/alkaline phosphatase (ALP) as a fluorescence quenching system is developed. The PDA-PEI copolymer was prepared by a one-pot method under mild condition, and its fluorescence kept almost unchanged after storing in a refrigerator for one month. ALP catalyzed the hydrolysis of PNPP to p-nitrophenol (PNP) that caused the fluorescence quenching of PDA-PEI copolymer via the inner filter effect. However, glyphosate inhibited ALP activity, thereby preventing the formation of PNP and restoring the fluorescence signal. Under the optimized conditions, the fluorescence of PDA-PEI copolymer depended on glyphosate concentrations ranging from 0.2 to 10 μg/mL with a detection limit of 0.06 μg/mL. Moreover, this assay was applied to detect glyphosate in real samples using the standard addition method. The recoveries were in the range from 88.8% to 107.0% with RSD less than 7.78%. This study provides a novel insight for glyphosate detection and expands the applications of fluorescent copolymer.

Batch and Continuous Column Adsorption of p-Nitrophenol onto Activated Carbons with Different Particle Sizes

The study focused on investigating the solvent adsorption of p-Nitrophenol (PNP) onto activated carbons for wastewater treatment. It explored the influence of adsorbate concentration and adsorbent size on equilibrium isotherms and removal rates to develop efficient adsorption processes. The study examined adsorption isotherms under equilibrium conditions utilizing both the Langmuir and Double-Langmuir models and the Dubinin–Radushkevich equation. Remarkably, all the models demonstrated equally excellent fitting to the experimental data. Kinetics of PNP adsorption were investigated using pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models. This provided insights into the dominant adsorption mechanism and mass transfer phenomena, aiding the design of efficient wastewater treatment processes. Strong correlations (correlation coefficients > 0.9) were found between the models and experimental data for three types of activated carbons under batch conditions. This validation enhances the reliability and applicability of the models, supporting their practical use. The study also observed a slight increase in maximum adsorption capacity (qmax) with decreasing particle size, although there is not a significant difference: 340, 350, and 365 mg·g−1, for CB-L, CB-M, and CB-S, respectively. This insight helps in selecting appropriate activated carbon for effective PNP removal, considering both adsorption capacity and particle size. Furthermore, the analysis of PNP adsorption under dynamic conditions in fixed-bed columns highlighted the significance of inlet velocity and carbon mass in determining breakthrough time, with particle size playing a secondary role. This information aids in optimizing the design and operation of fixed-bed adsorption systems for efficient PNP removal. In summary, this study’s significant contributions lie in enhancing our understanding of PNP adsorption in wastewater treatment. By investigating equilibrium isotherms, kinetics, and mass transfer phenomena, it provides validated models, insights into adsorption capacity and particle size, and practical guidance for dynamic adsorption systems. These findings contribute to the development of efficient and sustainable wastewater treatment methods.

Green synthesized nano-silver/cellulose aerogel as a robust active and recyclable catalyst towards nitrophenol hydrogenation

Water contamination by hazardous aromatic nitro compounds is a serious problem, and reduction in p-nitrophenol (PNP) by combining a catalyst and a reductant has been a topic of intense interest in recent years. Although several methods have been explored for generating effective metal nanoparticle composites, the nano-size makes it challenging to recover after wastewater treatment, thus restricting its practical use. Additionally, the previously described approaches had critical disadvantages, including high material synthesis costs and secondary environmental contamination. Herein, nontoxic and low-cost materials were employed. A novel green technique for the synthesis of silver nanoparticles (AgNPs) decorated on 3D cellulose aerogel (CA) derived from water hyacinth was demonstrated using an aqueous extract ofJasminum subtriplinerve Blumeleaves as a stabilising and reducing agent for high-performance towards PNP reduction in the presence of NaBH4 in an aqueous medium. The as-prepared composites were investigated by powder X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Batch experiments of PNP hydrogenation were conducted to evaluate the catalytic performance. At room temperature, the reaction could be completed in about 10 min using the 1.5Ag/CA2.0 catalyst, with the catalytic activity almost unchanged. Moreover, the structure has no apparent deterioration after five cycles. Strikingly, the 26.15 nm-average size of AgNPs with even distribution on CA correlates with the good kinetic characterisation/feature (k = 0.34 min−1). In particular, the reduction rates of the three isomers of nitrophenol were examined and found to follow the following order: PNP > o-nitrophenol (ONP) > m-nitrophenol (MNP). This study provides some valuable insights into developing easily separated robust green catalysts for heterogeneous catalytic reactions in the environmental remediation field.

A microwave-driven deep-UV ZnI2 light source for degrading organic wastewater: comparison with mercury lamp

The traditional cathode low-pressure Hg lamp is the most mainstream UV light source in degrading organic wastewater but with significant limitations of short lifetime, environmental hazard and poor degradation efficiency. Here, we evaluate a self-designed microwave-driven ZnI2 deep-UV lamp on degrading Rhodamine B (RhB), methylene blue (MB), and p-nitrophenol (PNP). An electrodeless Hg lamp was used as control. First we investigated the emission wavelength, spatial radiation distribution, the effect of power on radiation intensity, and relative permittivity of ZnI2 lamp. Then the degradation rate, kinetics and energy yield on degrading RhB, MB and PNP as well as the cost were studied. ZnI2 lamp showed shorter wavelengths, approaching UVC radiation intensity, approaching attenuation factor and higher microwave coupling capability to Hg lamp. After treatment with ZnI2 lamp for 10, 6 and 15 min, 5 mg/L of RhB, MB and PNP can reach 100% removal rates. Moreover, higher degradation rate and kinetic constants of ZnI2 lamp for 3 compounds than the Hg lamp in this paper and in the literature were achieved. With the assistance of microwave and properties of environmental-friendly and low cost, ZnI2 lamp provides a new alternative to traditional Hg lamp and wastewater photochemical treatment method.

Soybean crop intensification for sustainable aboveground-underground plant–soil interactions

The major challenge of growing soybean, other than unfavorable weather and small farm size, is the non-availability of quality inputs at the right time. Furthermore, in soybean growing regions, crop productivity and soil environment have deteriorated due to the use of traditional varieties and conventional methods of production. Soybean crop intensification or system of crop intensification in soybean (SCI) is an agricultural production system that boosts soybean yields, improves the soil environment, and maximizes the efficiency of input utilization, although the contribution of SCI to crop productivity is not well understood as different genotypes of soybean exhibit different physiological responses. Therefore, a field study was conducted in 2014–2015 and 2015–2016 using three crop establishment methods (SCI at a 45 cm × 45 cm row spacing, SCI at 30 cm × 30 cm, and a conventional method at 45 cm × 10 cm) assisted in vertical strips with four genotypes (Pusa 9,712, PS 1347, DS 12–13, and DS 12–5) using a strip-plot design with three replications. Compared with standard methods of cultivation, the adoption of SCI at 45 cm × 45 cm resulted in a significantly higher stomatal conductance (0.211 mol H2O m−2 s−1), transpiration rate (7.8 mmol H2O m−2 s−1), and net photosynthetic rate (398 mol CO2 m−2 s−1). The implementation of an SCI at 30 cm × 30 cm had significantly greater intercepted photosynthetic active radiation (PAR) (1,249 mol m−2 s−1) than the conventional method system, increasing crop yield from 9.6 to 13.3% and biomass yield from 8.2 to 10.7%. In addition, under an SCI at 30 cm × 30 cm, there were more nodules, significantly larger root volume and surface density, and increased NPK uptake compared with the other methods. Significantly greater soil dehydrogenase activity, alkaline phosphatase activity, acetylene-reducing assay, total polysaccharides, microbial biomass carbon, and soil chlorophyll were found with SCI at 45 cm × 45 cm (13.63 g TPF g−1 soil hr.−1, 93.2 g p-nitro phenol g−1 soil hr.−1, 25.5 n moles ethylene g−1 soil hr.−1, 443.7 mg kg−1 soil, 216.5 mg kg−1 soil, and 0.43 mg g−1 soil, respectively). Therefore, the adoption of an SCI at 30 cm × 30 cm and/or 45 cm × 45 cm could provide the best environment for microbial activities and overall soil health, as well as the sustainable productivity of soybean aboveground.

Porous N-doped carbon converted from protein-rich shrub enables record-high removal of p-nitrophenol: superior performance and mechanism

The complete removal of harmful phenolic contaminants from water remains huge challenge because of the lack of cost-effective and powerful adsorbents. Herein, a sustainable nitrogen self-doped biochar (named KBC750N) with large specific surface area (1398.44 m2/g), high adsorption capacity (606.06 mg/g) and removal ratio (99.99%) for p-nitrophenol (PNP) in real waters (Seawater, Yangtze River water, and Yellow River water) was prepared from a naturally abundant protein-rich psammophyte Caragana korshinskii (CK) by a facile one-step pyrolysis process. The in-situ nitrogen-doped biochar shows much better adsorption removal efficiency of 99.99% toward PNP than expensive commercial adsorbents (only 77.52%). The biochar still keeps high adsorption efficiency after reused more than five times. Site energy distribution analysis revealed that the biochar captures PNP mainly through n–π and π–π electron-donor–acceptor interactions among the electron-rich functional groups (N-containing moieties, –COOH, and –OH), graphite carbon, and PNP. Density functional theory (DFT) calculations confirmed that the nitrogen site in biochar helps to strengthen its adsorption capability to PNP. This work provides a sustainable platform for the development of high-performance, cost-effective materials for efficient elimination of organic pollutants from water.

A novel dual-responsive bio-derived magnetic nanocomposite: An excellent catalyst for efficient photodegradation of contaminants and detection of food additive in wastewater

Industrial development has been a global issue due to massive disposal of pollutants in water bodies. Considering this, many researchers adopt photocatalysis as an efficient technology for coordinated abatement of pollutants from wastewater. However, designing of materials that grant dual applicability in removal as well as detection of pollutant is still a challenge. Thus, demonstrated herein were bio-derived bi-functional hybrid magnetic nanocomposites that presented high photocatalytic degradation and electrochemical detection of noxious contaminants in wastewater. Magnetic nickel ferrite (NF) nanoparticles were organized on bio-derived template constructed from carboxylated cellulose (CCL) and carboxylated graphene oxide (CGO) via facile hydrothermal treatment to fabricate CCL-CGO-NF nanocomposites which were validated through various characterization techniques such as FT-IR, Powder XRD, FE-SEM, HR-TEM, EDX, XPS and VSM studies. The photocatalytic activity was investigated for degradation of three virulent model contaminants: Fast green (FG), Levofloxacin (LV) and p-Nitrophenol (PNP). Results displayed higher degradation efficiency of CCL-CGO-NFx nanocomposites than pure NF with highest degradation of 98%, 75% and 94% for FG, LV and PNP, respectively using CCL-CGO-NF70. Moreover, CCL-CGO-NF70 was employed for electrochemical sensing of FG that exhibited low detection limit of 1 μM in concentration range of 5–1200 μM. The nanocomposite established good stability, repeatability, reproducibility and sensitivity in real samples that certifies its dual practical applicability in environment detoxification as a photocatalyst and an electrochemical sensor. Finally, social implications and future perspectives concerning this proposed method was discussed.

Hidro(solvo)termal destekli silika aerojellerin sentezi, modifikasyonu ve onların adsorpsiyon çalışmalarında kullanımı

The hydro(solvo)thermal synthesis method was used to successfully synthesize bare silica aerogels and nano- and microparticle-embedded silica aerogels containing SiO2 and carbon microparticles in this study. New groups were added to these structures through modification. In the study, first, the effect of the variables was systematically examined to determine the optimum conditions. The most suitable recipe for silica aerogel was created. SiO2 and CP particles were synthesized, and modified silica aerogels were prepared with these particles and agents containing amine. For the characterization of synthesized silica aerogel, particles (SiO2, CP) and particle-embedded silica aerogels, TGA, SEM, DLS and BET-BJH techniques were used. These structures were used as adsorbent in environmental applications such as removing organic pollutants like 4-nitro phenol, methylene blue, Victoria blue, bromophenol blue etc. from aqueous media. In this environmental application, the adsorption capacity (mg/g) was determined by using UV-vis spectroscopy. The prepared structures are good adsorbents, and the adsorption capacity can be increased 18-fold with modification.

Effectual visible light photocatalytic reduction of para-nitro phenol using reduced graphene oxide and ZnO composite

Removing wastewater pollutants using semiconducting-based heterogeneous photocatalysis is an advantageous technique because it provides strong redox power charge carriers under sunlight irradiation. In this study, we synthesized a composite of reduced graphene oxide (rGO) and zinc oxide nanorods (ZnO) called rGO@ZnO. We established the formation of type II heterojunction composites by employing various physicochemical characterization techniques. To evaluate the photocatalytic performance of the synthesized rGO@ZnO composite, we tested it for reducing a common wastewater pollutant, para-nitro phenol (PNP), to para-amino phenol (PAP) under both ultraviolet (UV) and visible light irradiances. The rGOx@ZnO (x = 0.5–7 wt%) samples, comprising various weights of rGO, were investigated as potential photocatalysts for the reduction of PNP to PAP under visible light irradiation. Among the samples, rGO5@ZnO exhibited remarkable photocatalytic activity, achieving a PNP reduction efficiency of approximately 98% within a short duration of four minutes. These results demonstrate an effective strategy and provide fundamental insights into removing high-value-added organic water pollutants.

Graphitic carbon nitride modified by 5-sulfonic-8-hydroxyquinoline and Fe (III) ions as visible-light photocatalyst to efficiently reduce nitroaromatic compounds

In this study, a new graphitic carbon nitride (CN) catalyst was synthesized by combining 5-sulfonic-8-hydroxyquinoline (SQ) and Fe (III) ions. Photocatalysis reduction of nitroaromatic compounds was employed to evaluate the catalytic performance of the synthesized catalyst. Compared to the pristine CN, the optimized CN-SQ-2-Fe photocatalyst showed enhanced absorption in visible light region, which promoted photogenerated charge transfer and separation. Herein, we also developed a green and efficient photocatalysis route to convert nitrophenols (NPs) into aminophenols (APs) using CN-SQ-2-Fe photocatalyst. The visible light, separation of photogenerated charges and carrier transportation of the optimized sample CN-SQ-2-Fe were significantly improved in comparison with the pristine CN and the modified samples of CN-Fe and CN-SQ-2. Accordingly, the CN-SQ-2-Fe showed a high conversion (96%) of p-nitrophenol (p-NP) to p-aminophenol (p-AP) under visible light irradiation for 2 h and possessed high photocatalytic durability. Different NP compounds were also studied under the condition of photocatalysis reduction and demonstrated high conversion (>97%). Finally, a possible mechanism was proposed for the photocatalytic reduction of p-NP by CN-SQ-2-Fe. This work provides an effective approach to prepare graphitic carbon nitride (CN) modified by 5-sulfonic-8-hydroxyquinoline (SQ) and Fe (III) ions, which is a potential visible light driven photocatalyst for the reduction of nitrobenzene derivatives.

Ultrasonic-assisted self-assembly of a neodymium vanadate and hydroxylated multi-walled carbon nanotubes composite for electrochemical detection of p-nitrophenol

In recent years, nanocomposites prepared from rare earth metal vanadate and carbon nanomaterials have attracted great attention, and they have shown great promise for electrochemical sensing applications. Herein, a facile ultrasonic-assisted assembly method was adopted to prepare neodymium vanadate/hydroxylated multi-walled carbon nanotubes (NdV/MWCNTs-OH) composite. The morphology, elemental states, crystal structure and functional groups of the composites were investigated through a series of characterizations. Then, a novel electrochemical sensor, NdV/MWCNTs-OH composite modified glassy carbon electrode (GCE), was designed for the detection of p-nitrophenol (PNP). The synergistic effect generated by the combination of NdV and WMCNTs-OH accelerated the charge transfer kinetics and exposed more active sites, which facilitated more effective detection. Under optimized experimental conditions, the as-prepared sensor exhibited a wider linear range (1–200 μM) to PNP, and a lower limit of detection (LOD) of 0.41 μM could be obtained (signal-to-noise ratio of 3; S/N = 3). Furthermore, the sensor was successfully used for the determination of PNP in real samples (industrial wastewater and river samples), and satisfactory recoveries (96.67%−101.88%) with RSDs less than 5% were observed. Herein, the prepared electrochemical sensor has potential application prospect in the analysis and detection of PNP.

Kinetic and Equilibrium Function and Switchable Catalytic Activity of Some Thermo-Responsive Hydrogel Metal Absorbents Based on Modified PNIPAM

Synthesis and identification of some thermo-responsive hydrogel metal absorbents based on Schiff base modified PNIPAM is described. PNIPAM hydrogel is produced through conventional free-radical polymerization method. The hydrogel is amino modified with different amines and then treated with various aldehydes to make polymeric Schiff-bases supposing to utilize as an absorbent for Cu salt. Characterization of the as-prepared hydrogels was performed properly and confirmed the corresponding structures. Kinetic and equilibrium function of the absorbents and the effect of distinct variables like pH, adsorbent amount and contact time in the absorption process are investigated in detail. Kinetic and adsorption isotherm data agreed with pseudo-second order model and Langmuir isotherm, respectively. The maximum value of adsorption capacity of the prepared adsorbent was around 8550 mg g−1. In addition, the corresponding switchable catalytic activity using one of the thermo-responsive hydrogel metal absorbents in the reduction of 4-nitro phenol to 4-amino phenol in the role of model reaction is examined.