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AbstractThis study reports a sensor using a bimetallic metal-organic framework combined with 1,3,5-benzenetricarboxylic acid (BTC) (ZrCuBTC MOFs) functionalized graphene oxide (GO) and cetyltrimethylammonium bromide (CTAB) to determine the concentration of 2,4-dichlorophenol (2,4-DCP) in industrial wastewater. ZrCuBTC/GO was cast on a bare glassy carbon electrode followed by CTAB for analyte adsorption to produce the CTAB/ZrCuBTC/GO@GCE. The ZrCuBTC/GO was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD), and N2 adsorption–desorption analysis. The electrochemical properties of these materials and 2,4-DCP on the CTAB/ZrCuBTC/GO were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The ZrCuBTC/GO had particle sizes from 20 to 40 nm, a pore diameter of 2.71 nm, a pore volume of 0.793 cm3 g−1, and a surface area of 1227 m2 g−1. Under the optimized conditions, the sensor had excellent electrocatalytic activity and high selectivity for 2,4-DCP. Linear ranges from 0.01 to 0.1, 0.1 to 1.5, and 1.5 to 30 µM were obtained with a low detection limit of 8 nM and excellent reproducibility of 2.71%. Wastewater before and after spiking was analyzed using the sensor and high-performance liquid chromatography (HPLC). The results were comparable with recoveries from 94.9 to 110.3 and 88.6 to 100.2%, respectively. Therefore the developed approach was suitable for the determination of 2,4-DCP in environmental samples. [ABSTRACT FROM AUTHOR]

The dechlorination of 2,4-dichlorophenol (2,4-DCP) by a nanoscale Fe/Ni material was investigated at room temperature. 2,4-DCP can be removed more quickly by an Fe/Ni material with 2% Ni. Fe/Ni exhibited excellent adsorption and reduction efficiency toward 2,4-DCP in an aqueous solution over a wide range of pH values. The removal rate of 2,4-DCP exceeded 95% in 60 min in the pH range of 3.0–9.0, and more than 75% was dechlorinated to phenol (CA). The degradation pathway of 2,4-DCP was confirmed based on analysis of the intermediate and end products. A portion of 2,4-DCP was first dechlorinated with a chlorine atom to produce 2-chlorophenol and 4-chlorophenol, and then dechlorination was performed sequentially to form CA. The other portion of 2,4-DCP was dechlorinated to remove two chlorine atoms simultaneously to generate CA. The investigations are essential to the application of iron-based remediation technology. [ABSTRACT FROM AUTHOR]

Biotreatment of triclosan is mainly performed in conventional activated sludge systems, which, however, are not capable of completely removing this antibacterial agent. As a consequence, triclosan ends up in surface and groundwater, constituting an environmental threat, due to its toxicity to aquatic life. However, little is known regarding the diversity and mechanism of action of microbiota capable of degrading triclosan. In this work, an immobilized cell bioreactor was setup to treat triclosan-rich wastewater. Bioreactor operation resulted in high triclosan removal efficiency, even greater than 99.5%. Nitrogen assimilation was mainly occurred in immobilized biomass, although nitrification was inhibited. Based on Illumina sequencing, Bradyrhizobiaceae, followed by Ferruginibacter, Thermomonas, Lysobacter and Gordonia, were the dominant genera in the bioreactor, representing 38.40 ± 0.62% of the total reads. However, a broad number of taxa (15 genera), mainly members of Xanthomonadaceae, Bradyrhizobiaceae and Chitinophagaceae, showed relative abundances between 1% and 3%. Liquid Chromatography coupled to Quadrupole Time-Of-Flight Mass Spectrometry (LC-QTOF-MS) resulted in the identification of catabolic routes of triclosan in the immobilized cell bioreactor. Seven intermediates of triclosan were detected, with 2,4-dichlorophenol, 4-chlorocatechol and 2-chlorohydroquinone being the key breakdown products of triclosan. Thus, the immobilized cell bioreactor accommodated a diverse bacterial community capable of degrading triclosan. [ABSTRACT FROM AUTHOR]

Glutathione S-transferases (GSTs) play important roles in many biochemical processes, including the detoxification of xenobiotics, herbicides and pesticides, as well as enhancing stress tolerance in plants. 2,4-Dichlorophenol (2,4-DCP), an extremely toxic chlorophenolic, is a pollutant used as raw material in many industries, including the production of most herbicides and insecticides. This study investigated the response of GST for the phytoremediation of 2,4-DCP in Datura stramonium L., Amaranthus retroflexus L., and Sinapis arvensis L., plants with high phytoremediation potential following 2,4-DCP application. The seedlings grown in a hydroponic system were exposed to various solutions of 2,4-DCP in a concentration range from 75 to 275 ppm for 4 days. The GST activity was evaluated in the seedling roots and leaves. The activities in roots and leaves of D. stramonium increased to 125 ppm but decreased at 150 ppm and its higher doses compared to controls. In A. retroflexus, the GST activity increased to 175 ppm in leaves and 125 ppm in roots but decreased in both in parallel with higher doses of 2,4-DCP. In S. arvensis, on the other hand, all doses of 2,4-DCP decreased GST activity in leaves and roots compared to controls. Our results show that D. stramonium and A. retroflexus respond to 2,4-DCP toxicity with high GST activity, whereas S. arvensis is able tolerate the same toxicity, possibly by a different mechanism. [ABSTRACT FROM AUTHOR]

Herein, we report on the development of an effective, environmentally benign and facile method for visible light driven photo-degradation of Rhodamine 6 G and 2,4-dichlorophenol using Zn-5-p-carboxyphenyl-10,15,20-(tris-4-pyridyl)-porphyrin (2) linked to graphitic carbon nitride quantum dots (g-C3N4 QDs) and anchored on TiO2 fibers (represented as 2@g-C3N4 QDs-TiO2 fibers). The results suggest that the porphyrin acts as a photosensitizer, g-C3N4 QDs function as both photosensitizer and electron mediator, whereas the TiO2 fibers supporting matrix is a photocatalyst and a stabilizer. Anchoring 2@g-C3N4 QDs onto TiO2 fibers resulted in enhanced catalytic activity and thermal stability. Singlet oxygen (1O2) was the main reactive species responsible for degradation of Rhodamine 6 G and 2,4-dichlorophenol. The degradation kinetic studies follow pseudo first-order kinetics. The results demonstrate 2@g-C3N4 QDs-TiO2 fibers ternary hybrid catalyst to be a catalyst for visible light driven photo-degradation of refractory organic water pollutants. [ABSTRACT FROM AUTHOR]

The interactions within microbial, chemical and electronic elements in microbial fuel cell (MFC) system can be crucial for its bio-electrochemical activities and overall performance. Therefore, this study explored polynomial models by response surface methodology (RSM) to better understand interactions among anode pH, cathode pH and inoculum size for optimising MFC system for generation of electricity and degradation of 2,4-dichlorophenol. A statistical central composite design by RSM was used to develop the quadratic model designs. The optimised parameters were determined and evaluated by statistical results and the best MFC systematic outcomes in terms of current generation and chlorophenol degradation. Statistical results revealed that the optimum current density of 106 mA/m2 could be achieved at anode pH 7.5, cathode pH 6.3–6.6 and 21–28% for inoculum size. Anode–cathode pHs interaction was found to positively influence the current generation through extracellular electron transfer mechanism. The phenolic degradation was found to have lower response using these three parameter interactions. Only inoculum size-cathode pH interaction appeared to be significant where the optimum predicted phenolic degradation could be attained at pH 7.6 for cathode pH and 29.6% for inoculum size. [ABSTRACT FROM AUTHOR]

The degradation of persistent organic pollutants (POPs) in the simulated wastewaters was investigated by Fe-C micro-electrolysis system. With phenanthrene (PHE) and 2,4-dichlorophenol (2,4-DCP) as target pollutants, different iron-carbon (Fe-C) micro-electrolysis systems have been established. The effects of initial pH, Fe/C mass ratio, and intake air flow on the degradation and mineralization of PHE and 2,4-DCP were studied. At the initial pH of 5.0, Fe/C of 1.5:1, and an aeration flow rate of 1.5 L/min, after 120 min of reaction, the removal efficiency of FHE and COD was 94.3% and 73%, respectively. Under the conditions of initial pH is 3.0, Fe/C is 1:2, aeration flow rate of 1.5 L/min, and reaction time of 90 min, the best removal efficiency of 2,4-DCP can be obtained in the Fe-C micro-electrolysis system as 97% and COD removal efficiency can reach 76%. The results of kinetic studies show that the Fe-C micro-electrolysis process of PHE and 2,4-DCP follows pseudo-first-order kinetics. Commercial activated carbon (AC) was used for comparison under the same condition. The results indicated that the removal rate of organic pollutants and chemical oxygen demand (COD) of Fe-C micro-electrolysis were superior to that of AC. Analyze the structure of iron after reaction by SEM and XRD. The degradation pathway and mechanism for PHE and 2,4-DCP were proposed based on LC-MS analyses of treated wastewater. [ABSTRACT FROM AUTHOR]

Nanostructured ZnS/C was synthesized by a facile approach via calcination of Zn-based zeolite imidazole framework (ZIF-11) with adsorptive sublimed sulfur and was used to fabricate a modified glassy carbon electrode (GCE) for detection of 2,4-dichlorophenol (2,4-DCP). The morphology, structure, and composition of this ZnS/C were characterized by PXRD, Raman spectra, SEM and TEM. The electrochemical performances of the prepared sensor proved that the material has good electrical conductivity and strong catalytic ability. Under optimal conditions, the proposed sensor showed a wide linear range over 2,4-DCP concentration from 0.05 to 3.0 µM with detection limit of 6.4 × 10−8 mol/L. [ABSTRACT FROM AUTHOR]

In this paper, laccase was immobilized with the adsorption-crosslinking method in which biochar was used as the carrier and glutaraldehyde was used as the crosslinking agent. Firstly, the optimal immobilization conditions and optimal operating conditions were investigated, and then the stability of both free laccase and immobilized laccase was compared. Finally, the 2,4-dichlorophenol contaminated soil was remedied with both free laccase and immobilized laccase, and the improvement on the remediation of the contaminated soil by immobilized laccase was analysed through the ecological evaluation. The results showed that in the optimal immobilization condition, the biochar with a particle size of 30 mesh should be selected, and glutaraldehyde with a volume fraction of 4% and 20 mL of laccase solution should be added to complete the 6-hour adsorption operation and 4-hour crosslinking operation. The stability of immobilized laccase was better than that of free laccase, and the thermal deactivation kinetic equation for the free laccase was lnA = −0.7657t + 0.4344 and the thermal deactivation kinetic equation for the immobilized laccase was lnA = −0.1048t + 0.0608, respectively. The degradation ability of immobilized laccase for 2–4 dichlorophenol was better than that of free laccase. The degradation rate of 2,4-dichlorophenol was 44.4% in the free laccase group and 64.6% in the immobilized laccase group. The ecological evaluation showed that the biochar-immobilized laccase had a positive effect on the soil ecological environment in the remediation process of the soil and can improve the remediation of the contaminated soil to some extent. [ABSTRACT FROM AUTHOR]

In this paper, laccase is immobilized by the cross-linking method, using organic fertilizer as a carrier and glutaraldehyde as a cross-linking agent. Here, the optimal conditions of laccase immobilization were explored and the optimal operating conditions and stabilities of free laccase and immobilized laccase were also studied. Then, free laccase and immobilized laccase were applied to the soil remediation. Meanwhile, the effect of soil improvement treated with immobilized laccase was studied through ecological evaluation. The results showed that the optimal conditions for laccase immobilization were: the volume fraction of glutaraldehyde was 5%, the amount of enzyme added was 15 mL, and the immobilization time was 6 h. Under the same conditions, thermal stability and acid-base stability of immobilized laccase were better than free laccase. Under the optimal conditions, using laccase to treat 2,4-dichlorophenol in the soil, it was found that the free laccase group degraded 44.4% within 5 days, while the immobilized laccase group degraded 58.6%. Although both the degradation trends and route are the same, the degradation effect of the latter is obviously better. Ecological evaluation showed that organic fertilizer carrier had an impact on soil physical and chemical properties and soil enzymes, playing a positive role in soil ecological security and improving the soil. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks have received interest in many fields due to their fascinating properties. In this work, a flower-like covalent organic framework was prepared by a simple solvothermal method and used as an adsorbent for the removal of bisphenol A and 2,4-dichlorophenol from lake water. Due to the inherent hydrophobicity and large delocalized π-electron system, the proposed flower-like covalent organic framework forms π-π staking interactions with the aromatic ring-related compounds. Furthermore, the advantages of flower-like covalent organic framework, such as the porous structure and large specific surface area, facilitate the adsorption of phenolic compounds. Therefore, the flower-like covalent organic framework exhibited a relatively high affinity for bisphenol A and 2,4-dichlorophenol with adsorption capacity values of 56.8 mg/g and 36.6 mg/g, respectively. Furthermore, this material was successfully applied to remove bisphenol A and 2,4-dichlorophenol from lake water samples. [ABSTRACT FROM AUTHOR]

Various poly(alkylene sulfide)s have been synthesized and used as catalysts to enhance the para-regioselectivity in chlorination of phenol and 2-chlorophenol using freshly distilled sulfuryl chloride in the presence of AlCl3 as an activator. Poly(alkylene sulfide)s having alternating spacers, one having three methylene groups and the second having three, six or nine methylene groups were the most para-regioselective catalysts in chlorination of both phenol and 2-chlorophenol. For example, chlorination of phenol and 2-chlorophenol in the presence of optimal examples of such poly(alkylene sulfide)s gave 4-chlorophenol and 2,4-dichlorophenol as the major products in 94.8 and 95.4% yields, respectively, compared with 75.4 and 55.0% yields in the absence of catalysts. In addition, double chlorination of phenol in the presence of poly(alkylene sulfide)s gave 2,4-dichlrophenol in up to 97.1% yield compared with only 58.6% in the absence of catalysts. [ABSTRACT FROM AUTHOR]

Olfaction is a key sensory mechanism in humans. Deficits in this chemosensory function have wide-ranging impacts on overall health and quality of life. This study examines the role of environmental phenols as risk factors for olfactory dysfunction among a random sample of 839 middle-aged and older U.S. adults. Olfactory function assessment was carried out using a short 8-item test, scores on which were used to classify subjects into normal or impaired olfactory function groups. Logistic regression models were used to test for associations between olfactory impairment and creatinine-adjusted urinary levels of 8 common environmental phenols, adjusting for potentially confounding covariates. A statistically significant association between 2,4-dichlorophenol levels and olfactory impairment (OR = 1.02 [95 % CI: (1.003, 1.04)];p = 0.02) was found. 2,4-dichlorophenol is a hazardous pollutant with widespread exposure via industrial and indoor air pollution, diet, and the use of pesticides and herbicides. This study is the first to reveal its role in olfactory impairment. [ABSTRACT FROM PUBLISHER]

The degradation of 2,4-dichlorophenol (2,4-DCP) in wastewater is widely concerned in recent years because of its toxicity, carcinogenic and mutagenic properties. Generally, the pH values vary during the process of photocatalytic degradation, effecting UV-Vis absorbance spectral of 2,4-DCP. In this paper, we utilized the Na2CO3-NaHCO3buffer solution to eliminate the impact of pH changes caused by the acidic intermediates. As a result, the removal efficiency of 2,4-DCP and the reaction rate are significantly elevated. It can be concluded that the buffer solution can promote the photocatalytic degradation of 2,4-DCP effectively. [ABSTRACT FROM PUBLISHER]

A magnetic graphene nanocomposite (Fe3O4-GNC) was prepared and used for the solid phase extraction (SPE) and removal of 2,4-dichlorophenol from aqueous solutions. The physicochemical properties were investigated using SEM, EDX, FTIR, and TGA. Different factors affecting sorption capacity were studied systematically. Results for kinetics studies revealed that 2,4-dichlorophenol sorption followed pseudo-second-order kinetics and theqevalue (987.45 mg/g) was in close agreement with experimental value (1000 mg/g). Thermodynamic study showed that the sorption is endothermic (∆Hº = +56.116 kJ/mol) and spontaneous. The desorption studies were carried out for the reusability and extraction of 2,4-dichlorophenol from aqueous samples and 94% recoveries were obtained. The method was found feasible for the removal and preconcentration of trace analysis of 2,4-dichlorophenol in environmental water samples. [ABSTRACT FROM AUTHOR]

In this work, a saline aqueous solution of phenol, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) was treated by the photo-Fenton process in a falling-film solar reactor. The influence of the parameters such as initial pH (5–7), initial concentration of Fe2+(1–2.5 mM) and rate of H2O2addition (1.87–3.74 mmol min−1) was investigated. The efficiency of photodegradation was determined from the removal of dissolved organic carbon (DOC), described by the species degradation of phenol, 2,4-D and 2,4-DCP. Response surface methodology was employed to assess the effects of the variables investigated, i.e. [Fe2+], [H2O2] and pH, in the photo-Fenton process with solar irradiation. The results reveal that the variables’ initial concentration of Fe2+and H2O2presents predominant effect on pollutants’ degradation in terms of DOC removal, while pH showed no influence. Under the most adequate experimental conditions, about 85% DOC removal was obtained in 180 min by using a reaction system employed here, and total removal of phenol, 2,4- and 2,4-DCP mixture in about 30 min. [ABSTRACT FROM PUBLISHER]

In this study, we have attempted to reveal the physical or mechanistic features of the sonochemical degradation of 2,4-dichlorophenol (2,4-DCP). The principal physical phenomenon underlying sonochemical effects is radial motion of cavitation bubbles and production of radicals from transient collapse of these bubbles. We reveal some important physical facets of sonochemical degradation of 2,4-DCP by adopting dual approach of coupling experimental results with simulations of radial motion of cavitation bubble. First, the location of the degradation is predominantly the interfacial region between bubble and bulk medium, and secondly, the extent of degradation is controlled by conservation - and not the production - of oxidizing radicals that affects the probability of radical-pollutant interaction. [ABSTRACT FROM AUTHOR]

This study aims at comparing the removal of 2,4-dichlorophenol (2,4-DCP) by 3 methods; adsorption using hydrophobic zeolite (faujasite) or activated carbon (S-23 and L-27), conventional ozonation and hybrid adsorption/ozonation treatment. On the one hand, the three materials correctly adsorb 2,4-DCP; however the adsorption kinetics using zeolite is very low. On the other hand, ozonation totally removes 2,4-DCP after 1 h experiment and the simultaneous combination of adsorbent and ozone does not change the 2,4-DCP degradation. But, though ozonation and hybrid process appear to be equivalent for 2,4-DCP removal, activated carbons are able to decompose ozone and to improve chemical oxygen demand (COD) removal, whereas the zeolite does not show this catalytic effect. Similar results were also observed in a former study with nitrobenzene. Adsorbent degradation is evaluated by Brunauer, Emmet and Teller (BET) and differential thermogravimetric (DTG) analysis, which evidence that Faujasite and S-23 activated carbon are resistant to ozone exposure whereas the pore volume and the surface area of L-27 activated carbon decrease during ozonation. [ABSTRACT FROM AUTHOR]

Biological methods of wastewater treatment have been proved very effective for bioremediation of polluted sites. In this study, the degrading abilities of two bacteria Pseudomonas sp. and Staphylococcus xylosus, towards 1,2-dichlorobenzene (1,2-DCB), 2,4-dichlorophenol (2,4-DCP) and 4-Cl-m-cresol, are compared. Culture history and the presence of glucose as carbon source have been used for the optimization of cell's performance. 1,2-DCB showed the higher values of effective concentration (EC50), 1.04 and 0.84 mM with Pseudomonas sp. and S. xylosus respectively, whereas no substrate-inhibition appeared, in contrary to 4-Cl-m-cresol, that was more persistent in biodegradation by both bacteria. 2,4-DCP was less assimilated compared to 1,2-DCB, whereas bacterial specificity was higher, as it was found by the estimation of the half-saturation constant of 0.36 and 0.26 mM with Pseudomonas sp. and S. xylosus, respectively. [ABSTRACT FROM AUTHOR]

The treatability of 2,4-dwichlorophenol (DCP) was studied in an anaerobic/aerobic sequential reactor system. Laboratory scale upflow anaerobic sludge blanket (UASB) reactor/ completely stirred tank reactors (CSTR) were operated at constant 2,4-DCP concentrations, and increasing chemical oxygen demand (COD) loading rates. The effect of shock organic loading rates on 2,4-DCP, COD removal efficiencies and methane gas production were investigated in the UASB reactor. When the organic loading rate was increased from 3.6 g l-1 d-1 to 30.16 g l-1 d-1, the COD and 2,4-DCP removal efficiencies decreased from 80 to 25% and from 99 to 60% in the UASB reactor. The optimum organic loading rates for maximum 2,4-DCP (E=99-100%) and COD (E=65-85%) removal efficiencies were 25-30 and 8-20 g-COD l-1 d-1, respectively. The percentage of methane of the total gas varied between 70 and 80 while the organic loadings were 18 g-COD l-1 d-1 and 20.36 g-COD l-1 d-1, respectively. During 80 days of operation, 2,4-DCP concentration was found to be below 0.5 and 0.1 mg l-1 in aerobic reactor effluent resulting in 78 and 100% removal efficiencies. When the hydraulic retention time (HRT) was 18.72 h, the 2,4-DCP removal efficiency was 97% in the aerobic reactor. The optimum COD removal efficiency was 78.83% in anaerobic reactor effluent at an influent COD loading rate of 7.238 g-COD l-1 d-1 while 83.6% maximum COD removal efficiency was obtained in the aerobic reactor, resulting in a total COD removal efficiency of 96.83% in the whole system. The 2,4-DCP removal efficiency was 99% in the sequential anaerobic (UASB)/aerobic (CSTR) reactor system at COD loading rates varying between 11.46 and 30.16 g-COD l-1d-1. [ABSTRACT FROM AUTHOR]

Coconut coir pith, a solid waste generated in coir fibre industries, was carbonized and used as adsorbent for the removal of 2,4-dichlorophenol (2,4-DCP) from water. Varying parameters such as agitation time, 2,4-DCP concentration, adsorbent dose, pH, and temperature were investigated. Adsorption equilibrium reached at 60, 80, 100, and 120 min for 2,4-DCP concentrations of 10, 20, 30, and 40 mg L−1, respectively. Adsorption followed pseudo-second order kinetics. The adsorption equilibrium data moderately obeyed Langmuir and Freundlich isotherms. The adsorption capacity was found to be 19 mg g−1 of carbon. Increase of temperature increased adsorption. Acidic pH was favorable for the adsorption of 2,4-DCP. Studies on pH effect and desorption show that both physisorption and chemisorption were involved in the adsorption process. [ABSTRACT FROM AUTHOR]

Lignite based granular activated carbon of 20×30 mesh size was used to investigate the extent of bioregeneration of phenol and 2,4-DCP in a batch system. The adsorption isotherm fits very well with the Freundlich isotherm and it is apparent that 2,4-DCP is more adsorbable than phenol. The degree of reversible adsorption for phenol and 2,4-DCP were 32.9 and 10.6 %, respectively. The low percentages of their reversibility meant that the adsorption phenomena of both phenol and 2,4-DCP were not fully physicosorption. The microorganisms can regenerate 31.4 % (21.2 mg g−1) of GAC loaded with phenol and 14.3 % (24.8 mg g−1) of GAC loaded with 2,4-DCP over a period of 7–10 days. The bioregeneration of phenols closely followed the first order kinetics with the rate constant of 0.046 day−1 at initial phenol concentration of 100 mg l−1 and biomass concentration of 20 mg l−1 MLVSS. The rate constant was 0.021 day−1 at initial 2,4-DCP concentration of 200 mg l−1 and 200 mg l−1 MLVSS. In addition, the increasing in initial concentration of biomass in the solution shortened the time required to reach the asymptotic limit on the bioregeneration but rendered little impact on the bioregeneration percentage. [ABSTRACT FROM AUTHOR]