Adsorptive removal of organic pollutants from aqueous solutions using novel GO/bentonite/MgFeAl-LTH nanocomposite.

The contamination of water with organic pollutants such as dyes and phenols is a serious environmental problem, requiring effective treatment methods. In the present study, a novel nanocomposite was synthesized by intercalating graphene oxide and bentonite clay into MgFeAl-layered triple hydroxide (GO/BENT/LTH), which was characterized using different techniques. The adsorption efficacy of the GO/BENT/LTH nanocomposite was assessed via the removal of two harmful organic water pollutants, namely methyl orange (MO) and 2-nitrophenol (2NP). The obtained results revealed that the maximum adsorption capacities (qmax) of MO and 2NP reached 3106.3 and 2063.5 mg/g, respectively, demonstrating the excellent adsorption performance of the nanocomposite. Furthermore, this study examined the effects of contact time, initial MO and 2NP concentrations, pH, and temperature of the wastewater samples on the adsorptive removal of MO and 2NP by the GO/BENT/LTH nanocomposite. The pH, zeta potential, and FTIR investigations suggested the presence of more than one adsorption mechanism. Thermodynamic investigations elucidated the exothermic nature of the adsorption of MO and 2NP onto the GO/BENT/LTH nanocomposite, with MO adsorption being more sensitive to temperature change. Additionally, regeneration studies revealed a marginal loss in the MO and 2NP removal with the repetitive use of the GO/BENT/LTH nanocomposite, demonstrating its reusability. Overall, the findings of this study reveal the promise of the GO/BENT/LTH nanocomposite for effective water decontamination.

Olfactory responses of Amblyomma maculatum to rumen fluid and other odourants that attract blood-seeking arthropods.

Amblyomma maculatum Koch (Ixodida: Ixodidae) has emerged as a significant vector of human and companion animal diseases in the U.S.A. When expanding in range, A. maculatum can be difficult to collect in the field and control on livestock. A novel method is needed to improve the field collection of A. maculatum, as well as to control their effects as ectoparasites of livestock and companion animals. The present study aimed to test the effects of known volatiles on the activation and selection choices of A. maculatum in a laboratory-based Y-tube assay and field-based assays. Although the majority of adult A. maculatum were activated to move by five of the seven semiochemicals tested, only rumen fluid significantly attracted ticks to make a selection in the Y-tube apparatus. Rumen fluid attracted the most A. maculatum in the laboratory, with 56% (84/150) making it to the rumen Y-tube arm, although the results were not replicated in semi-field experiments. These studies highlight the need for continued work to identify attractants for tick vectors that will assist field collections. These attractants could also be incorporated into management strategies that lead to prevention technologies to reduce tick burdens on cattle or in risk areas of humans.

Two anthracene-based zirconium metal-organic frameworks with fcu and hcp topologies as versatile fluorescent sensors for detection of inorganic ions and nitroaromatics.

Two anthracene-based zirconium metal-organic frameworks (UiO-68-AN-fcu and UiO-68-AN-hcp) with blue emission were synthesized by the solvothermal reaction of ZrCl4 with anthracene-based ligand 4,4'-(9,10-anthracenediyl)dibenzoic acid. The two MOFs inherited the luminescence properties of anthracene-based ligand and exhibited different topologies due to the change of connection mode of Zr-O clusters. The two stable anthracene-based zirconium MOFs served as luminescent sensors for selectively detecting 2-nitrophenol, Fe3+ and Cr2O72-. UiO-68-AN-hcp with flower morphology exhibited stronger quenching effect for 2-nitrophenol, Fe3+ and Cr2O72- by comparing to UiO-68-AN-fcu. Adsorption tests, fluorescence lifetime and spectroscopy studies demonstrated that the fluorescence responses of MOFs for analytes can be primarily attributed to the dynamic quenching mechanism involving energy and electron transfer. These results revealed that the combination of luminescent anthracene-based ligand and Zr-O clusters is a feasible strategy to construst MOFs-based fluorescent sensors.

Novel biochar and hydrochar for the adsorption of 2-nitrophenol from aqueous solutions: An approach using the PVSDM model.

Two new adsorbents, namely avocado-based hydrochar and LDH/bone-based biochar, were developed, characterized, and applied for adsorbing 2-nitrophenol. The pore volume and surface diffusion model (PVSDM) was numerically solved for different geometries and applied to interpret the adsorption decay curves. Both adsorbents presented interesting textural and physicochemical characteristics, which achieved maximum adsorption capacities of 761 mg/g for biochar and 562 mg/g for hydrochar. The adsorption equilibrium data were well fitted by Henry isotherm. Besides, thermodynamic investigation revealed endothermic adsorption with the occurrence of electrostatic interactions. PVSDM predicted the adsorption decay curves for different adsorbent geometries at different initial concentrations of 2-nitrophenol. The surface diffusion was the main intraparticle mass transport mechanism. Furthermore, the external mass transfer and surface diffusion coefficients increased with the increase of 2-nitrophenol concentration.

Electrochemical Detection of 2-Nitrophenol Using a Glassy Carbon Electrode Modified with BaO Nanorods.

Here, an electrochemical detection approach (differential pulse voltammetry) was employed to develop a 2-nitrophenol (2-NP) sensor probe using a glassy carbon electrode (GCE) coated by wet-chemically synthesized nanorods (NRs) of BaO. The prepared BaO NRs were characterized by field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (XRD) analysis. The peak currents by differential pulse voltammetric (DPV) analysis of 2-NP are plotted against the concentration to obtain the calibration curve of the 2-NP detection. It was found to be linear from 1.5 to 9.0 µM, defined as the dynamic range (LDR) for 2-NP detection in phosphate buffer solution. The sensor sensitivity was calculated from the slope of LDR by considering the active surface area of NRs coated on GCE (0.0316 cm2 ) and found as 17.6 µAµM-1 cm-2 . The limit of detection (LOD) was calculated as 0.50±0.025 µM from the signal/noise (S/N) ratio of 3. Moreover, the sensor analytical parameters such as reproducibility, long-term performing ability (stability), response time and validity in real environmental samples were found acceptable and to give satisfactory results. The development of a nanomaterial-based electrochemical chemical sensor might be an effective approach to sensor technology to detect carcinogenic and hazardous toxins for environmental safety and healthcare fields in a broad scale.

New approach for the assessment of the contribution of adsorption, biodegradation and self-bioregeneration in the dynamic process of biologically active carbon functioning.

This work developed an effective model of the cooperative removal process of organic compounds on biologically active carbon. This model involves the determination of the dynamics of adsorption efficiency and degradation of specific classes of target organic substances but also the dynamics of non-target filling of pores with products of vital microbial activity. It is possible to quantitatively assess the contributions of adsorption, biodegradation and self-bioregeneration in the process of biologically active carbon functioning and the changes in the activated carbon porous properties during the process. The model developed was applied to assess the efficiency of filtration of 2-nitrophenol through a biologically active carbon bed for 38 months. The activated carbon adsorption capacity for removing 2-nitrophenol was preserved after three years of the bed service due to the effective biodegradation that resulted in self-bioregeneration of the sorbent. Nontarget losses of porosity (filling with bioproducts) increased with increasing duration of system operation, and by the end of the experiment, these losses amounted to 61% of the pore volume of the fresh sorbent.

Bacilli-Mediated Degradation of Xenobiotic Compounds and Heavy Metals.

Xenobiotic compounds are man-made compounds and widely used in dyes, drugs, pesticides, herbicides, insecticides, explosives, and other industrial chemicals. These compounds have been released into our soil and water due to anthropogenic activities and improper waste disposal practices and cause serious damage to aquatic and terrestrial ecosystems due to their toxic nature. The United States Environmental Protection Agency (USEPA) has listed several toxic substances as priority pollutants. Bacterial remediation is identified as an emerging technique to remove these substances from the environment. Many bacterial genera are actively involved in the degradation of toxic substances. Among the bacterial genera, the members of the genus Bacillus have a great potential to degrade or transform various toxic substances. Many Bacilli have been isolated and characterized by their ability to degrade or transform a wide range of compounds including both naturally occurring substances and xenobiotic compounds. This review describes the biodegradation potentials of Bacilli toward various toxic substances, including 4-chloro-2-nitrophenol, insecticides, pesticides, herbicides, explosives, drugs, polycyclic aromatic compounds, heavy metals, azo dyes, and aromatic acids. Besides, the advanced technologies used for bioremediation of environmental pollutants using Bacilli are also briefly described. This review will increase our understanding of Bacilli-mediated degradation of xenobiotic compounds and heavy metals.

Investigation of nitrogen content effect in reducing agent to prepare wavelength controllable fluorescent silicon nanoparticles and its application in detection of 2-nitrophenol.

Fluorescent silicon nanoparticles (SiNPs) displayed different emission wavelengths have been synthesized, but it has not been reported that the preparation of wavelength controllable SiNPs by adjusting the nitrogen content of reducing agents. In this paper, the wavelength-controlled fluorescent SiNPs were prepared by selecting the dopamine (DA) with nitrogen content between catechol and 2-aminophenol as the reducing agent and N-[3-(trimethoxysilyl) propyl]-ethylenediamine (DAMO) as the silicon source via one-step hydrothermal method. The emission wavelength of the prepared SiNPs was in direct proportion to the nitrogen content in the reducing agent. To the best of our knowledge, this is the first time for exploring the nitrogen content in reducing agents could affect the optical properties of SiNPs so far. In addition, the obtained SiNPs could be applied to determinate 2-nitrophenol (2-NP). Based on the combination action of inner filter effect (IFE) and static quenching effect (SQE) mechanism, a wide linear range was obtained from 0.1 to 500 µM, and the limit of detection was 0.029 µM for 2-NP, which was comparable to or even lower than some previous reports. This SiNPs probe was also successfully employed for sensing of 2-NP in industrial effluent with satisfactory results (98.6%-103.4%).

Decomposition byproducts induced by gamma radiation and their toxicity: the case of 2-nitrophenol.

The induced degradation and detoxification of 2-nitrophenol (2-NP) in aqueous media by gamma irradiation were carefully evaluated in this study. Gamma radiation at absorbed doses as low as 20 kGy was able to degrade 2-NP to reach a removal of at least 85% across the investigated range of concentration (50-150 ppm). 2-NP breaks down to aromatic-based compounds with increasing number of byproducts upon increasing the radiation treatment from the absorbed dose of 50% decomposition (D50) to the absorbed dose of 90% decomposition (D90), after which no byproducts could be detected, indicating the formation of undetectable aliphatic hydrocarbons, insoluble, or volatile byproducts. Toxicology studies showed that the degradation of 2-NP under absorbed doses up to D90 resulted in a more toxic byproduct than the parent compound, and a remarkable reduction in the toxicity was observed with the irradiated samples with absorbed doses above D90. Varying the pH of the media to acidic or basic conditions did not significantly alter the degradation behavior of 2-NP. However, a notable improvement of the detoxification was associated with the samples of acidic pH. Adding 0.5% of H2O2 to 2-NP solutions had a positive effect by reducing D90 by a factor of nine and diminishing the toxicity by twofolds.

Microwave-activated carbons from tucumã (Astrocaryum aculeatum) seed for efficient removal of 2-nitrophenol from aqueous solutions.

Activated carbons (ACs) prepared from tucumã seed (Astrocaryum aculeatum) were used for 2-nitrophenol removal from aqueous solutions. The ACs were characterized by elemental analysis, FTIR, N2 adsorption/desorption isotherms, TGA, hydrophobicity/hydrophilicity balance, and total of acidic and basic groups. The ACs showed to have hydrophilic surfaces and they presented high specific surface areas (up to 1318 m2 g-1). In batch optimization studies, maximum removal was obtained at pH 7, contact time of 30 min, adsorbent dosage 1.5 gL-1 and temperature of 50°C. The general-order kinetic model and Liu isotherm model best fit the kinetic and equilibrium adsorption data with a maximum adsorption capacity of 1382 mg g-1 at 50°C. Effect of temperature and thermodynamic studies revealed that the adsorption processes of 2-nitrophenol onto ACs are dependent on temperature and are exothermic and spontaneous, respectively. About the applicability of the ACs for treating simulated effluents, the tucumã seed-activated carbon showed an excellent outcome in the treatment of simulated effluents, evidencing its high efficiency for phenolic compound adsorption. Tucumã seed-ACs showed to be cost effective and highly efficient adsorbents for efficient removal of 2-nitrophenol from aqueous solutions.

Conversion of Eragrostis plana Nees leaves to activated carbon by microwave-assisted pyrolysis for the removal of organic emerging contaminants from aqueous solutions.

Eragrostis plana Nees leaves, abundant lignocellulosic biomass, was used as carbon source for preparation of activated carbon, by using microwave-assisted pyrolysis and chemical activation. The novel activated carbon (MWEPN) was characterised by FTIR, CHN elemental analysis, Boehm's titration method, TGA, SEM, N2 adsorption/desorption curves and pH of the point of zero charge (pHpzc). Afterwards, the adsorbent was successfully employed for adsorption of the two emerging contaminants (caffeine and 2-nitrophenol). The results indicated that MWEPN had a predominantly mesoporous structure with a high surface area of 1250 m2 g-1. FTIR analysis indicated the presence of carbonyl, hydroxyl and carboxylic groups on the surface of MWEPN. The Boehm analysis showed the existence of the high amount of acid moieties on the surface of activated carbon. Adsorption kinetic indicated that the system followed the Avrami fractional order at the optimal pH of 7. The equilibrium time was attained at 30 min. The Liu isotherm model better described the isothermal data. Based on the Liu isotherm, the maximum sorption capacities (Qmax) of caffeine and 2-nitrophenol adsorbed onto activated carbon at 25 °C were 235.5 and 255.8 mg g-1, respectively.

Recent advances in degradation of chloronitrophenols.

Chloronitrophenols (CNPs) constitute a group of environmental pollutants that are widely distributed in our surrounding environment due to human based activities. This group of chemicals is highly toxic to living beings due to its mutagenic and carcinogenic nature. Examples include 2-chloro-4-nitrophenol, 4-chloro-2-nitrophenol, 2-chloro-5-nitrophenol, 4-chloro-3-nitrophenol and 2,6-dichloro-4-nitrophenol. Several methods including advanced oxidation processes, adsorption and bacterial degradation have been used for degradation of CNPs. Among, bacterial degradation is an eco-friendly and effective way to degrade CNPs. Several bacterial metabolic pathways have been proposed for degradation of CNPs and their genes and enzymes have been identified in bacteria. These bacteria were able to degrade CNPs in broth culture and soil. Therefore, CNPs-degrading bacteria are suitable candidates for bioremediation of CNPs-contaminated sites. Few CNP-degrading bacteria exhibited chemotaxis towards CNPs to enhance their biodegradation. The present review summarizes recent progress in degradation of CNPs.

Ammonia-modified graphene sheets decorated with magnetic Fe3O4 nanoparticles for the photocatalytic and photo-Fenton degradation of phenolic compounds under sunlight irradiation.

Synthesis of easily separable and eco-friendly efficient catalyst with both photocatalytic and photo-Fenton degradation properties is of great importance for environment remediation application. Herein, ammonia-modified graphene (AG) sheets decorated with Fe3O4 nanoparticles (AG/Fe3O4) as a magnetically recoverable photocatalyst by a simple in situ solution chemistry approach. First, we have functionalized graphene oxide (GO) sheets by amide functional group and then Fe3O4 nanoparticles (NPs) are doped onto the functionalized GO surface. The AG/Fe3O4 nanocomposite showed efficient photocatalytic activity towards degradation of phenol (92.43%), 2-nitrophenol (2-NP) (98%) and 2-chlorophenol (2-CP) (97.15%) within 70-120min. Consequently, in case of photo-Fenton degradation phenomenon, 93.56% phenol, 98.76% 2-NP and 98.06% of 2-CP degradation were achieved within 50-80min using AG/Fe3O4 nanocomposite under sunlight irradiation. The synergistic effect between amide functionalized graphene and Fe3O4 nanoparticles (NPs) enhances the photocatalytic activity by preventing the recombination rate of electron-hole-pair in Fe3O4 NPs. Furthermore, the remarkable reusability of the AG/Fe3O4 nanocomposite was observed up to ten cycles during the photocatalytic degradation of these phenolic compounds.

Fully solar-driven thermo- and electrochemistry for advanced oxidation processes (STEP-AOPs) of 2-nitrophenol wastewater.

The STEP (Solar Thermal Electrochemical Process) for Advanced Oxidation Processes (AOPs, combined to STEP-AOPs), fully driven by solar energy without the input of any other forms of energy and chemicals, is introduced and demonstrated from the theory to experiments. Exemplified by the persistent organic pollutant 2-nitrophenol in water, the fundamental model and practical system are exhibited for the STEP-AOPs to efficiently transform 2-nitrophenol into carbon dioxide, water, and the other substances. The results show that the STEP-AOPs system performs more effectively than classical AOPs in terms of the thermodynamics and kinetics of pollutant oxidation. Due to the combination of solar thermochemical reactions with electrochemistry, the STEP-AOPs system allows the requisite electrolysis voltage of 2-nitrophenol to be experimentally decreased from 1.00 V to 0.84 V, and the response current increases from 18 mA to 40 mA. STEP-AOPs also greatly improve the kinetics of the oxidation at 30 °C and 80 °C. As a result, the removal rate of 2-nitrophenol after 1 h increased from 19.50% at 30 °C to 32.70% at 80 °C at constant 1.90 V. Mechanistic analysis reveals that the oxidation pathway is favorably changed because of thermal effects. The tracking of the reaction displayed that benzenediol and hydroquinone are initial products, with maleic acid and formic acid as sequential carboxylic acid products, and carbon dioxide as the final product. The theory and experiments on STEP-AOPs system exemplified by the oxidation of 2-nitrophenol provide a broad basis for extension of the STEP and AOPs for rapid and efficient treatment of organic wastewater.

Evaluation of sunlight induced structural changes and their effect on the photocatalytic activity of V2O5 for the degradation of phenols.

Despite knowing the fact that vanadium pentoxide is slightly soluble in aqueous medium, its photocatalytic activity was evaluated for the degradation of phenol and its derivatives (2-hydroxyphenol, 2-chlorophenol, 2-aminophenol and 2-nitrophenol) in natural sunlight exposure. The prime objective of the study was to differentiate between the homogeneous and heterogeneous photocatalysis incurred by dissolved and undissolved V2O5 in natural sunlight exposure. V2O5 was synthesized by chemical precipitation procedure using Triton X-100 as morphology mediator and characterized by DRS, PLS, Raman, FESEM and XRD. A lower solubility of ∼ 5% per 100ml of water at 23 °C was observed after calcination at 600 °C. The study revealed no contribution of the dissolved V2O5 in the photocatalytic process. In sunlight exposure, V2O5 powder exhibited substantial activity for the degradation, however, a low mineralization of phenolic substrates was observed. The initial low activity of V2O5 followed by a sharp increase both in degradation and mineralization in complete spectrum sunlight exposure, was further investigated that revealed the decrease in the bandgap and the reduction in the particle size with the interaction of UV photons (<420 nm) as this effect was not observable in the exposure of visible region of sunlight. The role of the chemically different substituents attached to an aromatic ring at 2-positions and the secondary interaction of released ions during the degradation process with the reactive oxygen species (ROS) was also explored.

2-Nitrophenol reduction promoted by S. putrefaciens 200 and biogenic ferrous iron: the role of different size-fractions of dissolved organic matter.

The reduction of nitroaromatic compounds (listed as a priority pollutant) in natural subsurface environments typically coexists with dissimilatory reduction of iron oxides effected by dissolved organic matter (DOM). Investigating the impact of the DOM that influences those reduction processes is crucial for understanding and predicting the geochemical fate of these environmental species. This study investigated the impact of different molecular weight DOM fractions (DMWDs) on the 2-nitrophenol (2-NP) reduction by S. putrefaciens 200 (SP200) and α-Fe2O3 with lactate (excluding electron donor interference). Kinetic measurements demonstrated that 2-NP reduction rates were affected by the redox reactivity of active species under DMWDs (denoted as L-DOM, M-DOM, and H-DOM). The enhanced reduction rates are consistent with the negative shifts in peak oxidation potential values, the increases in HA-like/FA-like values, aromaticity index values and electron transfer capacity values. L-DOM acted mainly as ligands to complex Fe(II), whereas the significant role of H-DOM in reductive reactions should be acting as an electron shuttle, transferring electrons from SP200 to Fe(III) and 2-NP and from biogenic Fe(II) to 2-NP, further accelerating the 2-NP reductions. Those observations provide valuable insights into the role of DOM in the biogeochemical redox processes and the remediation of contaminated soil in a natural environment.

Effects of dissolved organic matter on adsorbed Fe(II) reactivity for the reduction of 2-nitrophenol in TiO2 suspensions.

Dissolved organic matter (DOM) is widespread in aquatic and terrestrial environments. Iron is the most abundant transition metal in the Earth's crust. The biogeochemistry of iron and the strength of Fe(II) as a reducing agent while adsorbed on minerals are affected by DOM. This study investigated the effects of Fe(II)/DOM interactions on the reduction of 2-nitrophenol (2-NP) in TiO2 suspensions. Kinetic measurements demonstrated that rates (k) of 2-NP reduction by adsorbed Fe(II) species are affected by adding DOM (denoted O-DOM), and the obtained k values under the impact of the Fe(II)/DOM interaction with different molecular weight DOM fractions [including MW<3500Da (L-DOM), 350014000Da (H-DOM)] showed significant differences. The enhanced rates of 2-NP reduction contributed to increases in the amount of adsorbed Fe(II) species and negative shifts in peak oxidation potential values (EP) in CV tests. For different molecular weight DOM fractions, increases in k (O-DOM

Oxidation of carcinogenic 2-nitroanisole by rat cytochromes P450 - similarity between human and rat enzymes.

2-Nitroanisole (2-NA) is an important industrial pollutant and a potent carcinogen for rodents. Understanding which cytochrome P450 (CYP) enzymes are involved in its metabolism are important to assess an individual's susceptibility to this environmental carcinogen. The aim of this study was to evaluate the efficiency of rat hepatic CYPs to oxidize 2-NA, to examine the metabolites formed during such an oxidation, and to compare such efficiencies of rat CYPs with those of human. 2-NA is oxidized by rat hepatic microsomes to 2-nitrophenol (2-NP) as the major metabolite, and to 2,6-dihydroxynitrobenzene (2,6-DNB) and 2,5-dihydroxynitrobenzene (2,5-DNB) as the minor products. All these metabolites are suggested as detoxication products. Using hepatic microsomes of rats pre-treated with specific CYP inducers and microsomes from Baculovirus transfected insect cells expressing recombinant rat and human CYP enzymes we found that rat recombinant CYP2E1, 2D2, 2B2, 2C6 and 1A1, as well as orthologous human CYP enzymes are the most efficient enzymes metabolizing 2-NA. However, human CYP1A1 oxidize 2-NA with a higher efficiency than the enzyme of rats. The results show the participation of orthologous CYPs in 2-NA oxidation by both species and underline the suitability of rat species as a model to evaluate human susceptibility to 2-NA.