Equilibrium, kinetic and thermodynamic studies on the adsorption of 2-nitroaniline onto activated carbon prepared from cotton stalk fibre

Ectopic expression of an Old Yellow Enzyme (OYE3) gene from Saccharomyces cerevisiae increases the tolerance and phytoremediation of 2-nitroaniline in rice

2-nitroaniline (2-NA) is an environmental pollutant and has been extensively used as intermediates in organic synthesis. The presence of 2-NA in the environment is not only harmful for aquatic life but also mutagenic for human beings. In this study, we constructed transgenic rice expressing an Old Yellow Enzyme gene, ScOYE3, from Saccharomyces cerevisiae. The ScOYE3 transgenic plants were comprehensively investigated for their biochemical responses to 2-NA treatment and their 2-NA phytoremediation capabilities. Our results showed that the rice seedlings exposed to 2-NA stress, showed growth inhibition and biomass reduction. However, the transgenic plants exhibited strong tolerance to 2-NA stress compared to wild-type plants. Ectopic expression of ScOYE3 could effectively protect transgenic plants against 2-NA damage, which resulted in less reactive oxygen species accumulation in transgenic plants than that in wild-type plants. Our phytoremediation assay revealed that transgenic plants could eliminate more 2-NA from the medium than wild-type plants. Moreover, omics analysis was performed in order to get a deeper insight into the mechanism of ScOYE3-mediated 2-NA transformation in rice. Altogether, the function of ScOYE3 during 2-NA detoxification was characterized for the first time, which serves as strong theoretical support for the phytoremediation potential of 2-NA by Old Yellow Enzyme genes.

Fabrication of silver nanoparticles within chitosan based microgels for catalysis

Chitosan based monodisperse poly[chitosan-N-isopropylmethacrylamide-acrylic acid] [P(CNA)] microgels were produced via precipitation polymerization. Resulting crosslinked P(CNA) micro particles were used as micro-reactors to prepare silver nanoparticles within the polymeric network by chemical reduction of Ag⁺ ions with sodium borohydride. Various techniques including transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and ultraviolet-visible (UV-vis) spectroscopy were used to analyze P(CNA) microgels and Ag-P(CNA) hybrid microgels. Catalytic potential of Ag-P(CNA) hybrid system towards individual and simultaneous reduction of various nitroarenes like p-nitrophenol (pNP), o-nitrophenol (oNP), p-nitroaniline (pNA) and o-nitroaniline (oNA) into corresponding aminoarenes using sodium borohydride as a reductant in aqueous medium was evaluated. The catalytic activity of Ag-P(CNA) system towards both the individual and simultaneous reduction of nitroarenes was examined at various concentrations of catalyst. The values of pseudo first order rate constant (k₁) for reduction of individual nitroarene and multiple nitroarenes were determined for comparison. The Ag-P(CNA) hybrid microgel system was found to be stable, economical and efficient catalyst for rapid individual and simultaneous reduction of nitroarenes.

Bio-mineralized tin/bismuth oxide nanoparticles with silk fibroins for efficient electrochemical detection of 2-nitroaniline in river water samples

In recent years, the usage of nitroaniline has played a vital role in pharmaceutical formulations as it is a crucial ingredient in the synthesis of pesticides and dyes. However, the level of nitroaniline existing in industrial waste keeps rising the environmental contamination. Thus, monitoring of active nitro-residuals becomes more significant in reducing the toxicity of the ecosystem. Therefore, we have taken an attempt to evaluate the hazardous pollutant 2-nitroaniline (2-NA) using the electrocatalyst viz., tin-doped bismuth oxide inserted on a biopolymer silk fibroin composite modified glassy carbon electrode (Sn-Bi₂O₃/SF@GCE). The Sn-Bi₂O₃/SF nanocomposite was synthesized through hydrothermal and co-precipitation methods. The physicochemical properties of the prepared Sn-Bi₂O₃/SF hybrid composite were examined by conventional microscopy and spectroscopic techniques like FE-SEM, HR-TEM, XRD, FTIR, Raman, and XPS. Furthermore, the bio-mineralized Sn-Bi₂O₃/SF@GCE displayed a wide linear range (0.009 μM-785.7 μM) and a lower detection limit (3.5 nM) with good sensitivity for 2-NA detection under the optimum conditions. The result shows that the Sn-Bi₂O₃/SF-modified GCE has good reproducibility, repeatability, and excellent selectivity for 2-NA detection in the presence of other co-interfering compounds. Moreover, the practical applicability of Sn-Bi₂O₃/SF@GCE sensors was investigated for the effective detection of 2-NA in real river water samples, revealing good recovery results.

Highly efficient and selective heterogeneous catalytic reduction of 2-nitroaniline by cerium oxide nanocatalyst under microwave irradiation

Efficient nanocatalyst with incredible performance is highly demanding in a heterogeneous catalysis system. Herein, we report the facile fabrication of uniform and highly stable Cerium Oxide nanoparticles (CeO₂ NPs), through chemical precipitation method using sodium hydroxide as reducing agent. The synthesized material is characterized through highly sophisticated techniques including UV-Visible, FT-IR, SEM, AFM, XRD, and Zeta Sizer- Potential to check the particle formation, surface morphology, topography, crystalline nature, size, and surface potential. The heterogeneous catalytic performance of CeO₂ NPs has been accomplished for the reduction of 2-nitroaniline from the aqueous media. The CeO₂ nanocatalyst displayed excellent reusability, while the reduction in several repetitive catalytic cycles against 2-nitroaniline under optimized conditions. The CeO₂ nanocatalyst shows 99.12% efficiency within 60s reaction time under a greener source of microwave radiation.

Removing ammonium from contaminated water using Purolite C100E: batch, column, and household filter studies

Ammonium removal from drinking water to protect human and environmental health is one of the major global concerns. This study evaluates the performance of Purolite C100E, a commercial cation exchange resin, in eliminating ammonium in synthetic and real contaminated groundwater. The results demonstrate that the pH operation range of the resin for better ammonium removal is 3 to 8. Lower ammonium removal at low and high pH occurred due to competition from H⁺ and loss of ammonium as ammonia gas, respectively. Equilibrium data of ammonium removal fitted both the Langmuir and Freundlich isotherm models with the maximum Langmuir ion exchange capacities for initial ammonium concentrations of 10-200 mg/L and 50-2000 mg/L, reaching 18.37 mg/g and 40.16 mg/g, respectively. The presence of co-ions in the water reduced the ammonium removal efficiencies slightly (< 12%) in the order Mg²⁺ > Ca²⁺ > K⁺. The higher affinity of ammonium to adsorbent is due to its lower hydrated ionic radius and H-bonding. The maximum exchange capacity in the fluidized bed studies of the original Purolite C100E (bed height 27 cm, resin weight 75 g, initial ammonium concentration 17.4 mg/L, filtration velocity 0.5 m/h) was 10.48 mg/g. It progressively reduced slightly after three regeneration cycles to 8.79 mg/g. The column breakthrough data satisfactorily fitted the Thomas model. A household filter cartridge packed with 4 kg Purolite C100E (80 cm height) and operated at a filtration velocity of 1.9 m/h in Vietnam successfully reduced the initial 6 mg NH₄⁺/L in groundwater (after sand filter pre-treatment) to well below the Vietnam drinking water standard (3 mg/L-QCVN 01:2009/BYT) continuously for 1 week, suggesting that such a filter can be adopted in rural areas to successfully remove ammonium from groundwater.

Biomass magnetic porous carbon prepared from mangosteen shell for the preconcentration of 3 bisphenols from beverages followed by liquid chromatographyquadrupoleorbitrap high-resolution mass spectrometry determination

Natural biomass magnetic porous carbon was successfully prepared via a cost-effective and green route using mangosteen shell as raw material. The prepared magnetic porous carbon was used as a magnetic solid phase extraction adsorbent for bisphenols enrichment from beverages followed by high-performance liquid chromatographyquadrupole Orbitrap high-resolution mass spectrometry. Parameters affecting extraction efficiency including sample solutionpH, adsorbent amount, extraction time, eluent type and volume were optimized. Results showed that biomass magnetic porous carbon had excellent adsorption properties for bisphenols due to its large specific surface area and abundant functional groups, which could form hydrogen bonding and π-π stacking with bisphenols. The enrichment factor of 3 bisphenolswere in the range of15∼19. Under optimum conditions, favorable linearity for all analytes was obtained with correlation coefficients higher than 0.998. Recoveries of spiked samples were in the range of 88.5%∼105.1% with relative standard deviation of 3.4%∼5.5%. These results demonstrated thatmagnetic porous carbon may be a promising adsorbent for enrichment of aromatic compounds. This article is protected by copyright. All rights reserved.

Biosynthesis of silver nanoparticles using Onosma sericeum Willd. and evaluation of their catalytic properties and antibacterial and cytotoxic activity

In this study, silver nanoparticle (AgNP) synthesis was carried out using Onosma sericeum Willd. aqueous extract for the first time, with a simple, economical, and green method without the need for any other organic solvent or external reducing or stabilizing agent. A variety of AgNPs, all of different particle sizes, were synthesized by controlling the silver ion concentration, extract volume, temperature, and pH. It was determined that the optimum conditions for AgNP synthesis were 1 mM AgNO3, pH 8, 25 °C, 20 g/200 mL extract, silver nitrate, and extract ratio 5:1 (v/v). The AgNPs were defined using UV-Vis spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The particle size distribution and zeta potential measurements of the AgNPs were measured using the dynamic light scattering (DLS) technique. It was determined that the AgNPs with a particle size of less than 10 nm showed a higher catalytic effect in the reduction of 2-nitrobenzenamine. It was also found that these nanoparticles had a cytotoxic effect on the MCF-7 breast cancer cell line depending on dosage and time. The resulting IC50 values were between 76.63 µg/mL and 169.77 µg/mL. Furthermore, the biosynthesized AgNPs showed effective antibacterial activity against the Acinetobacter baumannii bacteria. The results of the study showed that synthesized AgNPs can have a promising role in biomedical and nanobiotechnology applications.

Recent progress in controlling the synthesis and assembly of nanostructures: Application for electrochemical determination of p-nitroaniline in water

The development of nanoparticle research has grown considerably in recent years. One of the reasons for the considerable current interest in nanoparticles is because such materials frequently display unusual physical (structural, electronic, magnetic, and optical) and chemical (catalytic) properties. The development of nanomaterials is of interest to the scientific community and industrial companies. Different methods (physical, chemical, and biological) allow their manufacture. In particular, a major effort has been devoted to the development and improvement of synthesis methods in order to obtain nano-objects of controlled size and shape, a necessary pre-requisite to their organization, and to the study of their intrinsic and collective properties. Reviews play an important role in keeping interested parties up to date on the current state of the research in any academic field. This review aims to focus on the development of nanoparticles and stabilization with adsorbed/covalently attached ligands in solution phase since these factors are deeply related to the origins of the particles' stability, the media to which they are exposed, and the involved applications. This study also examines the factors that influence the synthesis of nanoparticles. It aims to provide an overview of existing electrochemical sensors, particularly those that operate with nanomaterial-based electrode modifications for p-nitroaniline (PNA) determination and to propose guidelines for related research and development activities. Emphasis was placed on the procedure for the analysis of PNA in water samples using nanosilver-based electrodes.

Reduction of 4-nitrophenol and 2-nitroaniline using immobilized CoMn2O4 NPs on lignin supported on FPS

In the present work, fibrous phosphosilicate (FPS) is functionalized by using octakis[3(3-aminopropyltriethoxysilane)propyl]octasilsesquioxane (APTPOSS) groups.

Adsorption of Methylene Blue and Pb2+ by using acid-activated Posidonia oceanica waste

Dead leaves of seagrass Posidonia oceanica were activated by using one mol L-1 acetic acid and used as an eco-adsorbent for the removal of methylene blue (MB) and Pb2+ from aqueous solutions. The seagrass was characterized by chemical and physical measurements that confirmed the acid-activation of seagrass. The favourable conditions for MB and Pb2+ adsorption onto the activated seagrass (SGa) were determined to be a pH range of 2-12 and ≥6, an adsorbent dosage of 3.0 and 0.5 g L-1, respectively, and a shaking time of 30 min, which are suitable for a wide range of wastewaters. The equilibrium data were analysed using the Langmuir, Freundlich and Dubinin-Raduskavich-Kaganer (DRK) adsorption isotherm models. The Freundlich and DRK models best describe the adsorption processes of MB and Pb2+, on SGa with capacities of 2681.9 and 631.13 mg g-1, respectively. The adsorption isotherm fitting and thermodynamic studies suggest that the adsorption mechanism of MB may combine electrostatic and physical multilayer adsorption processes, in which MB may be present as monomers as well as dimers and trimers which were confirmed from UV spectroscopy whereas Pb2+ is chemically adsorbed onto SGa. The pseudo-2nd-order kinetic model was utilized to investigate the kinetics of adsorption processes. The removal process was successfully applied for MB-spiked brackish waste water from Manzala Lake, Egypt, with removal efficiencies of 91.5-99.9%.

Equilibrium and kinetic studies of ferricyanide adsorption from aqueous solution by activated red mud

In this study, activated red mud (ARM) was used as a new adsorbent for the removal of ferricyanide anions from aqueous solution. Based on the percentage of ferricyanide removal and ferricyanide adsorption capacity, optimum conditions were evaluated using the response surface method (RSM) and central composite design (CCD). In optimum conditions (pH = 5.6, adsorbent dosage of 2.59 g, ferricyanide concentration of 60 ppm and contact time of 60 min), the percentage of ferricyanide removal and ferricyanide adsorption capacity were obtained as 79.6% and 1.8 mg/g, respectively. The kinetics and equilibrium studies were evaluated by considering the effective parameters including pH and ferricyanide concentration. Kinetic studies were evaluated by kinetic models of pseudo first-order, pseudo-second-order (four different linearized forms), Elovich and intraparticle diffusion. The results of the kinetic study indicated that the mechanism of ferricyanide adsorption onto the ARM adsorbent is a chemisorption interaction by a fast ferricyanide adsorption onto ARM and subsequently the slow diffusion of ferricyanide ions into the ARM inner adsorption sites. The equilibrium studies showed that the adsorption process followed the Langmuir model in which ferricyanide adsorption onto ARM was homogeneous with monolayer adsorption. The results indicated that the activation process of red mud improved adsorbent efficiency and increased the adsorption capacity.

Tea waste derived activated carbon for the adsorption of sodium diclofenac from wastewater: adsorbent characteristics, adsorption isotherms, kinetics, and thermodynamics

The present experimental study reports the performance of tea waste (TW) derived adsorbent for the adsorption of sodium diclofenac (SD) from aqueous solution (SD concentration = 10-50 mg/L). The waste-derived activated carbon was prepared by chemical activation process of raw waste using H₂SO₄, KOH, ZnCl₂, and K₂CO₃ as activating agents (TW: activating agent = 1:1 by weight). Subsequently, the oven-dried material was carbonized at 600-°C temperature for 2 h. The synthesized adsorbents were porous and their Brunauer-Emmett-Teller (BET) surface area was ranged 115-865 m²/g. Among all synthesized adsorbents, the adsorbent activated by ZnCl₂ exhibited the highest adsorption capacity (= 62 mg/g), though it was much lower compared to 91 mg/g obtained with commercial activated carbon (CAC) (SD concentration = 30 mg/L, adsorbent dose = 300 mg/L and initial wastewater pH = 6.47). SD equilibrium data could be described by Langmuir isotherm adequately, while pseudo-second-order rate model showed better fit to the time based adsorption data. Low activation energy of the adsorption process suggests the reaction to be temperature independent. Thermodynamic parameters showed the spontaneous and endothermic nature of adsorption process conducted in the presence of waste derived adsorbent.

Seasonal characteristics of phosphorus sorption by sediments from plain lakes with different trophic statuses

Phosphorus (P) sorption in sediments plays a significant role in trophic status of a lake. This study investigated the characteristics of P sorption in sediments from three lakes with different trophic statuses (moderately eutrophic, lightly eutrophic and moderately trophic) through kinetic, batch equilibrium and thermodynamic experiments. Results show that pseudo-second-order kinetics best describe P sorption in sediments from the three lakes. Fitting by modified Langmuir and Freundlich isotherms indicates that the moderately trophic lake sediment has higher sorption capacity (maximum of 0.848 mg g-1 at 35°C) than the sediments of the other two lakes at different temperatures (5, 15, 25 and 35°C). Thermodynamic results indicate that the processes of P sorption of the three sediments are spontaneous, entropy-driven and endothermic reactions. The risk of P release in sediments was analysed according to the calculated results of isotherms combined with the change in P fraction. Sediments from the moderately eutrophic lake act as a source in summer. The lightly eutrophic and moderately trophic lakes act as sources in spring and winter, and a pool in summer and autumn, respectively. Furthermore, the amounts of reductant-soluble P, calcium-bound P and iron-bound P are significantly related to the sorption capacity of sediments from the three lakes (p < 0.05). The different sediments have different P release risk, and P fraction in sediment is one of the significant factors of P sorption.

Evaluation and mechanism of ammonia nitrogen removal using sediments from a malodorous river

Malodorous rivers are among the major environmental problems of cities in developing countries. In addition to the unpleasant smell, the sediments of such rivers can act as a sink for pollutants. The excessive amount of ammonia nitrogen (NH₃-N) in rivers is the main factor that causes the malodour. Therefore, a suitable method is necessary for sediment disposition and NH₃-N removal in malodorous rivers. The sediment in a malodorous river (PS) in Beijing, China was selected and modified via calcination (PS-D), Na⁺ doping (PS-Na) and calcination-Na⁺ doping (PS-DNa). The NH₃-N removal efficiency using the four sediment materials was evaluated, and results indicated that the NH₃-N removal efficiency using the modified sediment materials could reach over 60%. PS-DNa achieved the highest NH₃-N removal efficiency (90.04%). The kinetics study showed that the pseudo-second-order model could effectively describe the sorption kinetics and that the exterior activated site had the main function of P sorption. The results of the sorption isotherms indicated that the maximum sorption capacities of PS-Na, PS-D and PS-DNa were 0.343, 0.831 and 1.113 mg g^-1, respectively, and a high temperature was favourable to sorption. The calculated thermodynamic parameters suggested that sorption was a feasible or spontaneous (ΔG < 0), entropy-driven (ΔS > 0), and endothermic (ΔH > 0) reaction.

A simple approach for the sonochemical synthesis of Fe3O4-guargum nanocomposite and its catalytic reduction of p-nitroaniline

In this present study, a facile and green method to synthesize highly stable Fe₃O₄-guar gum nanocomposite using ultrasound was reported. Thermal gravimetric analysis, fourier transform infrared spectroscopy, X-ray diffractometry, field emission scanning electron microscopy, energy dispersive spectroscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy were used to characterize the crystal structure, size and morphology, elemental composition, metal-metal and metal-oxygen bonds of the synthesized nanocomposites. Fe₃O₄-guar gum nanocomposite with a size of ∼48nm was obtained as from TEM. The physicochemical characterization supports the feasibility of guar gum as an efficient stabilizing agent for the formation of nanocomposite; guar gum acts as a capping agent with a zeta potential value of -34.8 which was found to be beneficial for achieving lower particle size. Guar gum serves as a matrix for both reduction and stabilization of nanocomposite. The HR-TEM and XPS shows that Fe₃O₄ nanoparticles are encapsulated by the guar gum polymeric networks or Fe₃O₄-guar gum core-shell structure. The guar gum encapsulated magnetite nanocomposite has performed better in terms of catalytic activity for the liquid phase reduction of p-nitroaniline. The simple catalytic reduction of p-nitroaniline showed an efficiency of 47% and further exceptional improvement of up to 98% reduction within 60min with the addition of sodium borohydride was achieved. The sonochemical synthesis of Fe₃O₄-guar gum nanocomposite does not require stringent experimental conditions or any toxic agents, and thus, a straightforward, rapid, efficient and green method for the fabrication of highly active catalysts for treating environmental pollutants.

The reduction of 4-nitrophenol and 2-nitroaniline by the incorporation of Ni@Pd MNPs into modified UiO-66-NH2 metal–organic frameworks (MOFs) with tetrathia-azacyclopentadecane

UiO-66-NH₂/TTACP/Ni@Pd MNPs exhibited excellent catalytic activity for the reduction of 2-nitroaniline and 4-nitrophenol.

A new V-doped Bi2(O,S)3 oxysulfide catalyst for highly efficient catalytic reduction of 2-nitroaniline and organic dyes

A new type of convenient, and environmentally friendly, Vanadium (V)-doped Bi₂(O,S)₃ oxysulfide catalyst with different V contents was successfully synthesized via a simple and facile method. The obtained V-doped Bi₂(O,S)₃ solid solution catalysts were fully characterized by conventional methods. The catalytic performance of the samples was tested by using the reduction of 2-nitroaniline (2-NA) in aqueous solution. The reduction/decolorization of methylene blue (MB) and rhodamine B (RhB) was also chosen to evaluate the universality of catalysts. It was observed that the introduction of V can improve the catalytic performance, and 20%V-Bi₂(O,S)₃ was found to be the optimal V doping concentration for the reduction of 2-NA, MB, and RhB dyes. For comparative purposes, a related V-free Bi₂(O, S)₃ oxysulfide material was synthesized and tested as the catalyst. The superior activity of V-doped Bi₂(O,S)₃ over pure Bi₂(O,S)₃ was ascribed mainly to an increase in active sites of the material and also due to the presence of synergistic effects. The presence of V⁵⁺ as found from XPS analysis may interact with Bi atoms and enhancing the catalytic activity of the sample. In the catalytic reduction of 2-NA, MB and RhB, the obtained V-doped Bi₂(O,S)₃ oxysulfide catalyst exhibited excellent catalytic activity as compared with other reported catalysts. Furthermore this highly efficient, low-cost and easily reusable V-doped Bi₂(O,S)₃ catalyst is anticipated to be of great potential in catalysis in the future.

Catalytic reduction of 2-nitroaniline: a review

2-nitroaniline (2-NA) is highly toxic and environmental contaminant. It is reduced to less toxic and environmental benign product o-phenylenediamine by using different reducing agents like sodium borohydride, potassium borohydride, or hydrazine hydrate in the presence of various catalytic systems. These catalytic systems have various advantages and drawbacks. Silica-supported gold nanoparticles are frequently reported catalyst for the reduction of 2-nitroaniline in aqueous medium. In this review article, different catalytic systems reported for reduction of o-nitroaniline under various reaction conditions have been discussed. The critical review of the recent research progress for development of novel catalysts used for the reduction of 2-nitroaniline has been provided here.

Removing ammonium from water using modified corncob-biochar

Ammonium pollution in groundwater and surface water is of major concern in many parts of the world due to the danger it poses to the environment and people's health. This study focuses on the development of a low cost adsorbent, specifically a modified biochar prepared from corncob. Evaluated here is the efficiency of this new material for removing ammonium from synthetic water (ammonium concentration from 10 to 100mg/L). The characteristics of the modified biochar were determined by Brunauer-Emmett-Teller (BET) test, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). It was found that ammonium adsorption on modified biochar strongly depended on pH. Adsorption kinetics of NH₄⁺-N using modified biochar followed the pseudo-second order kinetic model. Both Langmuir and Sips adsorption isotherm models could simulate well the adsorption behavior of ammonium on modificated biochar. The highest adsorption capacity of 22.6mg NH₄⁺-N/g modified biochar was obtained when the biochar was modified by soaking it in HNO₃ 6M and NaOH 0.3M for 8h and 24h, respectively. The high adsorption capacity of the modified biochar suggested that it is a promising adsorbent for NH₄⁺-N remediation from water.

Performance and mechanism of hierarchically porous Ce–Zr oxide nanospheres encapsulated calcium alginate beads for fluoride removal from water

Hierarchically porous Ce–Zr metal oxide nanospheres encapsulated calcium alginate millimeter-sized beads showed a high efficiency for fluoride removal from water.

High-performance fish-scale-based porous carbon for the removal of methylene blue from aqueous solution

The fish-scale-based porous carbon shows high performance for the removal of methylene blue from aqueous solution.