Evaluation of the genotoxic and cytotoxic effects of exposure to the herbicide 2,4-dichlorophenoxyacetic acid in Astyanax lacustris (Pisces, Characidae) and the potential for its removal from contaminated water using a biosorbent.

The genotoxic and cytotoxic effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on specimens of Astyanax lacustris were evaluated using different biomarkers. Additionally, this study evaluated the efficiency of an activated carbon filter made from the husks green coconut, which was used as a biosorbent to remove 2,4-D dissolved in the water, and the potential effectiveness of this procedure for the reduction of the toxic effects of this compound on A. lacustris. Three sublethal concentrations of 2,4-D (10, 20, and 40 mg L-1) were tested over 24, 48, and 72 h, and their effects on Astyanax lacustris were evaluated using chromosomal aberration test, the mitotic index, the frequency of micronuclei and nuclear alterations, and the comet assay. Exposure to 2,4-D increased the frequency of chromosomal aberrations, reduced the mitotic index, and caused significant levels of nuclear modification in some of the treatments, in comparison with the negative control. The comet assay revealed DNA damage (classes 1-3) at all 2,4-D concentrations, reaching significant levels in the 20 mg L-1 (48 h) and 40 mg L-1 (72 h) treatments. The coconut husk biosorbent was highly effective for the removal of 2,4-D and the fish exposed to the water decontaminated by this filter had low levels of cellular alteration. The findings of the present study demonstrated, for the first time, the genotoxic and cytotoxic effects of 2,4-D in Astyanax lacustris, as well as suggests the potential application of a biosorbent for the effective decontamination of water contaminated with pesticides.

Clinical study and observation on the effect of hemoperfusion therapy treatment on central nervous system injury in patients with 2,4-dichlorophenoxyacetic acid poisoning.

OBJECTIVE: To evaluate the curative effect of hemoperfusion therapy on central nervous system injury in patients with 2,4-dichlorophenoxyacetic acid poisoning. PATIENTS AND METHODS: A total of 60 patients with 2,4-dichlorophenoxyacetic acid poisoning were enrolled in this study. They were admitted to the Emergency Department of Qinghai Provincial People's Hospital from 2015 to 2018 and were randomly divided into two groups by random number table method. One group was control group (routine treatment group), and the other group was the treatment group (hemoperfusion therapy was added on the basis of routine treatment). Glasgow coma score (GCS), APACHE II score, and MMSE score were used to evaluate the effects before treatment and 7 days after treatment. The results were statistically analyzed. RESULTS: After treatment, GCS in the treatment group was higher than that in the control group, while APACHE II score was lower than that in the control group, and MMSE score was significantly higher than that in the control group, with statistically significant difference (p<0.05). The effective rate in the control group was only 26.67%, and that in the treatment group was 86.67%, with statistically significant difference (c2=19.62, p<0.001). CONCLUSIONS: Hemoperfusion therapy can promote the recovery of central nervous system in patients with 2,4-dichlorophenoxyacetic acid poisoning, reduce the injury of other organs, and significantly reduce the mortality of patients.

High-performance of activated biocarbon based on agricultural biomass waste applied for 2,4-D herbicide removing from water: adsorption, kinetic and thermodynamic assessments.

Activated biocarbons were prepared using biomass wastes: sugarcane bagasse, coconut shell and endocarp of babassu coconut; as a renewable source of low-cost raw materials and without prior treatments. These activated biocarbons were characterized by textural analysis, solid-state 13C nuclear magnetic resonance spectroscopy, X-ray diffraction and scanning electronic microscopy. Textural analysis results revealed that those activated biocarbons were microporous, with specific surface area values of 547, 991 and 1,068 m2 g-1 from sugarcane bagasse, coconut shell and endocarp of babassu coconut, respectively. The innovation of this work was to evaluate which biomass residue was able to offer the best performance in removing 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from water by adsorption. Adsorption process of 2,4-D was investigated and the Langmuir and Redlich-Peterson models described best the adsorption process, with R2 values within 0.96-0.99. The 2,4-D removal performance were 97% and 99% for the coconut and babassu biocarbons, respectively. qM parameter values obtained from Langmuir model were 153.9, 233.0 and 235.5 mg g-1 using sugarcane bagasse, coconut shell and endocarp of babassu, respectively. In addition, the adsorption kinetics were described nicely by the second-order model and the Gibbs free energy parameter values were negative, pointing to a spontaneous adsorption, as well.

Efficient Degradation of Phenoxyalkanoic Acid Herbicides by the Alkali-Tolerant Cupriavidus oxalaticus Strain X32.

Phenoxyalkanoic acid (PAA) herbicides are mainly metabolized by microorganisms in soils, but the degraders that perform well under alkaline environments are rarely considered. Herein, we report Cupriavidus oxalaticus strain X32, which showed encouraging PAA-degradation abilities, PAA tolerance, and alkali tolerance. In liquid media, without the addition of exogenous carbon sources, X32 could completely remove 500 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) or 4-chloro-2-methylphenoxyacetic acid within 3 days, faster than that with the model degrader Cupriavidus necator JMP134. Particularly, X32 still functioned at pH 10.5. Of note, with X32 inoculation, we observed 2,4-D degradation in soils and diminished phytotoxicity to maize (Zea mays). Furthermore, potential mechanisms underlying PAA biodegradation and alkali tolerance were then analyzed by whole-genome sequencing. Three modules of tfd gene clusters involved in 2,4-D catabolism and genes encoding monovalent cation/proton antiporters involved in alkali tolerance were putatively identified. Thus, X32 could be a promising candidate for the bioremediation of PAA-contaminated sites, especially in alkaline surroundings.

Retention Modelling of Phenoxy Acid Herbicides in Reversed-Phase HPLC under Gradient Elution.

Phenoxy acid herbicides are used worldwide and are potential contaminants of drinking water. Reversed phase high-performance liquid chromatography (RP-HPLC) is commonly used to monitor phenoxy acid herbicides in water samples. RP-HPLC retention of phenoxy acids is affected by both mobile phase composition and pH, but the synergic effect of these two factors, which is also dependent on the structure and pKa of solutes, cannot be easily predicted. In this paper, to support the setup of RP-HPLC analysis of phenoxy acids under application of linear mobile phase gradients we modelled the simultaneous effect of the molecular structure and the elution conditions (pH, initial acetonitrile content in the eluent and gradient slope) on the retention of the solutes. In particular, the chromatographic conditions and the molecular descriptors collected on the analyzed compounds were used to estimate the retention factor k by Partial Least Squares (PLS) regression. Eventually, a variable selection approach, Genetic Algorithms, was used to reduce the model complexity and allow an easier interpretation. The PLS model calibrated on the retention data of 15 solutes and successively tested on three external analytes provided satisfying and reliable results.

2,4-dichlorophenoxyacetic acid (2,4-D) micropollutant herbicide removing from water using granular and powdered activated carbons: a comparison applied for water treatment and health safety.

Activated carbons are well-known porous materials as an effective adsorbent used for the removal of emerging contaminants, such as herbicides, which are increasingly present in water bodies. Most water treatment plants, specially in Brazil, are unable to completely remove such contaminants by the conventional process and advanced treatment using activated carbons is required. The aim of this paper was to verify the influence of the activated carbons granulometry and specific surface area on the 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide removal efficiency using distilled-deionized water and filtered water collected from a conventional Water Treatment Plant. Commercial activated carbons samples used in this work were obtained from two different manufacturers. Activated carbons were analyzed by the specific surface area, pore size and volume distribution, nuclear magnetic resonance, infrared and x-ray spectroscopy, moisture, volatile matter and ash contents. Batch adsorption isotherms experiments were used and performed by Langmuir and Freundlich models. Granular and powdered activated carbons removed over 99% of 2,4-D in distilled water and near to 99% using filtered water. The activated carbons evaluated in this work presented high performance and played a key role in water treatment by removing 2,4-D herbicide, ensuring the protection of human health and the ecosystem.

Monodisperse cobalt(II) based metal-organic coordination polymer beads as a sorbent for solid-phase extraction of chlorophenoxy acid herbicides prior to their quantitation by HPLC.

Metal-organic coordination polymer beads (MOCBs) are described for use as a sorbent for solid-phase extraction of chlorophenoxy herbides. By applying regulation of Co(II) ions, micro-sized monodisperse MOCBs were obtained through the microwave heating. The MOCBs-based method displays excellent extraction efficiency towards chlorophenoxy herbicides, specifically of 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, 4-chloromethylphenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid and 2-(2,4-dichlorophenoxy)propionic acid. Following extraction, the herbicides were eluted with 8% formic acid in methanol and quantified by HPLC. The method, when applied to analyze spiked cereals, exhibits a wide linear range (from 0.6 to 1000 ng g-1) and low limits of quantification (ranging from 0.10 to 0.25 ng g-1). For a single column, the inter-day and intra-day precisions, expressed as the relative standard deviation are in the range of 2.5-6.8%. The batch-to-batch reproducibility (for n = 3) is <4.6%. For spiked cereal samples, relative recoveries are very good (90.3-102.3%, for n = 4). The extraction efficiency of MOCBs remains unchanged after reusing for 40 times. Graphical abstractSchematic presentation of Co(II)-doped metal-organic coordination polymer beads (Co(II)@MOCB) using for solid-phase extraction (SPE).

A response surface methodology for optimization of 2,4-dichlorophenoxyacetic acid removal from synthetic and drainage water: a comparative study.

The potential of a granular activated carbon (GAC), a rice husk biochar (BRH), and multi-walled carbon nanotubes (MWCNTs) for removing 2,4-dichlorophenoxyacetic acid (2,4-D) from simulated wastewater and drainage water has been evaluated. In this regard, a response surface methodology (RSM) with a central composite design (CCD) (CCD-RSM design) was used to optimize the removal of 2,4-D from simulated wastewater under different operational parameters. The maximum adsorption capacities followed the order GAC > BRH > MWCNTs, whereas the equilibrium time increased in the order MWCNTs < GAC < BRH. In the case of GAC and BRH, the 2,4-D removal percentage increased significantly upon increasing the adsorbent dosage and temperature and decreased upon increasing the initial 2,4-D concentration and pH. The results showed that the contact time and temperature were not important as regards the adsorption efficiency of 2,4-D by MWCNTs, whereas rapid removal of 2,4-D from simulated wastewater was achieved within the first 5 min of contact with the MWCNTs. The results confirmed that the Freundlich isotherm model with the highest coefficient of determination (R2) and the lowest standard error of the estimate (SEE) satisfactorily fitted the 2,4-D experimental data. In addition, successful usage of the three adsorbents investigated was observed for removal of 2,4-D from drainage water from an agricultural drainage system. An economic analysis with a rate of return (ROR) method indicated that BRH could be used as an eco-friendly, low-cost, versatile, and high adsorption capacity alternative to GAC and MWCNTs for the removal of 2,4-D.

Rapid detection and quantification of 2,4-dichlorophenoxyacetic acid in milk using molecularly imprinted polymers-surface-enhanced Raman spectroscopy.

We report the development of a molecularly imprinted polymers-surface-enhanced Raman spectroscopy (MIPs-SERS) method for rapid detection and quantification of a herbicide residue 2,4-dichlorophenoxyacetic acid (2,4-D) in milk. MIPs were synthesized via bulk polymerization and utilized as solid phase extraction sorbent to selectively extract and enrich 2,4-D from milk. Silver nanoparticles were synthesized to facilitate the collection of SERS spectra of the extracts. Based on the characteristic band intensity of 2,4-D (391 cm-1), the limit of detection was 0.006 ppm and the limit of quantification was 0.008 ppm. A simple logarithmic working range (0.01-1 ppm) was established, satisfying the sensitivity requirement referring to the maximum residue level of 2,4-D in milk in both Europe and North America. The overall test of 2,4-D for each milk sample required only 20 min including sample preparation. This MIPs-SERS method has potential for practical applications in detecting 2,4-D in agri-foods.

Integrating fluorescent molecularly imprinted polymer (MIP) sensor particles with a modular microfluidic platform for nanomolar small-molecule detection directly in aqueous samples.

Fluorescent sensory MIP (molecularly imprinted polymer) particles were combined with a droplet-based 3D microfluidic system for the selective determination of a prototype small-molecule analyte of environmental concern, 2,4-dichlorophenoxyacetic acid or 2,4-D, at nanomolar concentration directly in water samples. A tailor-made fluorescent indicator cross-linker was thus designed that translates the binding event directly into an enhanced fluorescence signal. The phenoxazinone-type cross-linker was co-polymerized into a thin MIP layer grafted from the surface of silica microparticles following a RAFT (reversible addition-fragmentation chain transfer) polymerization protocol. While the indicator cross-linker outperformed its corresponding monomer twin, establishment of a phase-transfer protocol was essential to guarantee that the hydrogen bond-mediated signalling mechanism between the urea binding site on the indicator cross-linker and the carboxylate group of the analyte was still operative upon real sample analysis. The latter was achieved by integration of the fluorescent core-shell MIP sensor particles into a modular microfluidic platform that allows for an in-line phase-transfer assay, extracting the analyte from aqueous sample droplets into the organic phase that contains the sensor particles. Real-time fluorescence determination of 2,4-D down to 20nM was realized with the system and applied for the analysis of various surface water samples collected from different parts of the world.

A 3D-Printed, Portable, Optical-Sensing Platform for Smartphones Capable of Detecting the Herbicide 2,4-Dichlorophenoxyacetic Acid.

Onsite rapid detection of herbicides and herbicide residuals in environmental and biological specimens are important for agriculture, environmental concerns, food safety, and health care. The traditional method for herbicide detection requires expensive laboratory equipment and a long turnaround time. In this work, we developed a single-stripe microliter plate smartphone-based colorimetric device for rapid and low-cost in-field tests. This portable smartphone platform is capable of screening eight samples in a single-stripe microplate. The device combined the advantages of small size (50 × 100 × 160 mm3) and low cost ($10). The platform was calibrated by using two different dye solutions, i.e. methyl blue (MB) and rhodamine B, for the red and green channels. The results showed good correlation with results attained from a traditional laboratory reader. We demonstrated the application of this platform for detection of the herbicide 2,4-dichlorophenoxyacetic acid in the range of 1 to 80 ppb. Spiked samples of tap water, rat serum, plasma, and human serum were tested by our device. Recoveries obtained varied from 95.6% to 105.2% for all of the spiked samples using the microplate reader and from 93.7% to 106.9% for all of the samples using the smartphone device. This work validated that the smartphone optical-sensing platform is comparable to the commercial microplate reader; it is eligible for onsite, rapid, and low-cost detection of herbicides for environmental evaluation and biological monitoring.

Ionic Liquid-Hybrid Molecularly Imprinted Material-Filter Solid-Phase Extraction Coupled with HPLC for Determination of 6-Benzyladenine and 4-Chlorophenoxyacetic Acid in Bean Sprouts.

A new method involving ionic liquid-hybrid molecularly imprinted material-filter solid-phase extraction coupled to high-performance liquid chromatography (IL-HIM-FSPE-HPLC) was developed for the simultaneous isolation and determination of 6-benzyladenine (6-BA) and 4-chlorophenoxyacetic acid (4-CPA) in bean sprouts. Sample preconcentration was performed using a modified filter, with the new IL-HIM as the adsorbent, which shows double adsorption. The first adsorption involves special recognition of molecular imprinting, and the second involves ion exchange and electrostatic attraction caused by the ionic liquid. This method combines the advantages of ionic liquids, hybrid materials, and molecularly imprinted polymers and was successfully applied to determine 6-BA and 4-CPA in bean sprouts. The adsorption of 6-BA to IL-HIM is based on selective imprinted recognition, whereas the adsorption of 4-CPA is mainly dependent on ion-exchange interactions.

Phenoxy herbicide removal from aqueous solutions using fast pyrolysis switchgrass biochar.

The release of herbicides is known to negatively impact humans and the environment. We report the use of a low cost biochar (prepared through fast pyrolysis) to successfully remove phenoxy herbicides from aqueous solutions. The biochar was characterized using: FT-IR, SEM, pHpzc, elemental analysis, and surface area measurements. Sorption experiments were run at pH values from 2 to 10, adsorbate concentrations from 25 to 300 mg/L and temperatures from 25 to 45 °C. Adsorption isotherms were evaluated from 25 to 45 °C using both two parameter (Freundlich and Langmuir) and three parameter (Redlich-Peterson and Toth) adsorption isotherm models. The maximum adsorption capacities for 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) were Q0SGB∼134 mg/g and Q0SGB∼50 mg/g, respectively, at pH 2. This low surface area switchgrass biochar (1.1 m2/g) can adsorb far more MCPA per unit of measured surface area (45 mg/m2) than high surface area commercial activated carbons (1050-1150 m2/g) which absorb only 0.08-0.11 mg/m2, and are also expensive. This indicates that biochar three dimensional swelling occurs in an aqueous environment and adsorbates are imbibed and adsorbed at additional sorption sites.

[Enhanced Removal of Herbicide 2,4-dichlorophenoxyacetic Acid and Simultaneous Power Generation in Microbial Fuel Cells].

This study investigated the effects of a widely used herbicide 2,4-dichlorophenoxyacetic acid on power generation, pollutants removal from microbial fuel cells (MFCs) and microbial community changes, and also explored anode pre-aeration for enhanced 2,4-D removal and power generation. The results showed that when 2,4-D was inputted to the anode chamber of MFCs which was previously enriched with acetate sodium as the fuel, the voltage output and power density declined and the internal resistance increased apparently. The maximum power density declined to 0.057 W·m-2 in the presence of 300 mg·L-1 2,4-D comparing to 0.151 W·m-2 obtained with acetate alone (850 mg·L-1), and the internal resistance increased from 524 Ω to 1230 Ω correspondingly. To accelerate 2,4-D removal rate and reduce its inhibition to anode exoelectrogens, 6h pre-aeration was applied to the anode chamber. Fast removal of 2,4-D was achieved during aeration period and simultaneous high maximum voltage output (0.42-0.47 V) was obtained. Anode microbial community changed after 2,4-D addition and several 2,4-D degrading bacteria and 2,4-D tolerant exoelectrogen were enriched. MFCs could be used for 2,4-D removal and simultaneous power generation through anode pre-aeration.

AuNPs-functionalized PANABA-MWCNTs nanocomposite-based impedimetric immunosensor for 2,4-dichlorophenoxy acetic acid detection.

In this work, we developed an impedimetric label-free immunosensor for the detection of 2,4-Dichlorophenoxy Acetic Acid (2,4-D) herbicide either in standard solution and spiked real samples. For this purpose, we prepared by electropolymerization a conductive polymer poly-(aniline-co-3-aminobenzoic acid) (PANABA) then we immobilized anti-2,4-D antibody onto a nanocomposite AuNPs-PANABA-MWCNTs employing the carboxylic moieties as anchor sites. The nanocomposite was synthesized by electrochemical polymerization of aniline and 3-aminobenzoic acid, in the presence of a dispersion of gold nanoparticles, onto a multi-walled carbon nanotubes-based screen printed electrode. Aniline-based copolymer, modified with the nanomaterials, allowed to enhance the electrode conductivity thus obtaining a more sensitive antigen detection. The impedimetric measurements were carried out by electrochemical impedance spectroscopy (EIS) in faradic condition by using Fe(CN)63-/4- as redox probe. The developed impedimetric immunosensor displayed a wide linearity range towards 2,4-D (1-100ppb), good repeatability (RSD 6%), stability and a LOD (0.3ppb) lower than herbicide emission limits.

Adsorption of 2,4-Dichlorophenoxyacetic Acid from an Aqueous Solution on Fly Ash.

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on fly ash was studied. The effects of adsorbent dose, contact time, pH, ionic strength, and temperature on the adsorption were investigated. Adsorption kinetic data were analyzed using pseudo-first and pseudo-second order models, and results showed that adsorption kinetics were better represented by the pseudo-second order model. Adsorption isotherms of 2,4-D on fly ash were analyzed using the Freundlich and Langmuir models. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was spontaneous and endothermic. The negative values of ΔG° and the positive value of ΔH° indicate the spontaneous nature of 2,4-D adsorption on fly ash, and that the adsorption process was endothermic. Results showed that fly ash is an efficient, low-cost adsorbent for removal of 2,4-D from water.

Rapid adsorption of 2,4-dichlorophenoxyacetic acid by iron oxide nanoparticles-doped carboxylic ordered mesoporous carbon.

The ordered mesoporous carbon composite functionalized with carboxylate groups and iron oxide nanoparticles (Fe/OMC) was successfully prepared and used to adsorb 2,4-dichlorophenoxyacetic acid (2,4-D) from wastewater. The resultant adsorbent possessed high degree of order, large specific surface area and pore volume, and good magnetic properties. The increase in initial pollutant concentration and contact time would make the adsorption capacity increase, but the pH and temperature are inversely proportional to 2,4-D uptake. The equilibrium of adsorption was reached within 120 min, and the equilibrated adsorption capacity increased from 99.38 to 310.78 mg/g with the increase of initial concentration of 2,4-D from 100 to 500 mg/L. Notablely, the adsorption capacity reached 97% of the maximum within the first 5 min. The kinetics and isotherm study showed that the pseudo-second-order kinetic and Langmuir isotherm models could well fit the adsorption data. These results indicate that Fe/OMC has a good potential for the rapid adsorption of 2,4-D and prevention of its further diffusion.

2,4-D adsorption to biochars: effect of preparation conditions on equilibrium adsorption capacity and comparison with commercial activated carbon literature data.

Batch isotherm experiments were conducted with chars to study adsorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Chars generated from corncobs, bamboo and wood chips in a laboratory pyrolyzer at 400-700 °C were compared with traditional kiln charcoals collected from villages in S/SE Asia and with activated carbons (ACs). 2,4-D uptake by laboratory chars obtained from bamboo and wood chips after 14 h of pyrolysis at 700 °C, from wood chips after 96 h of pyrolysis at 600 °C, and one of the field-collected chars (basudha) was comparable to ACs. H:C and O:C ratios declined with pyrolysis temperature and duration while surface area increased to >500 m(2)/g. Increasing pyrolysis intensity by increasing temperature and/or duration of heating was found to positively influence adsorption capacity yield (mg(2,4-D/g(feedstock))) over the range of conditions studied. Economic analysis showed that high temperature chars can be a cost-effective alternative to ACs for water treatment applications.

Small (13)C/(12)C fractionation contrasts with large enantiomer fractionation in aerobic biodegradation of phenoxy acids.

Phenoxy acid herbicides are important groundwater contaminants. Stable isotope analysis and enantiomer analysis are well-recognized approaches for assessing in situ biodegradation in the field. In an aerobic degradation survey with six phenoxyacetic acid and three phenoxypropionic acid-degrading bacteria we measured (a) enantiomer-specific carbon isotope fractionation of MCPP ((R,S)-2-(4-chloro-2-methylphenoxy)-propionic acid), DCPP ((R,S)-2-(2,4-dichlorophenoxy)-propionic acid), and 4-CPP ((R,S)-2-(4-chlorophenoxy)-propionic acid); (b) compound-specific isotope fractionation of MCPA (4-chloro-2-methylphenoxyacetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid); and (c) enantiomer fractionation of MCPP, DCPP, and 4-CPP. Insignificant or very slight (ε = -1.3‰ to -2.0‰) carbon isotope fractionation was observed. Equally small values in an RdpA enzyme assay (εea = -1.0 ± 0.1‰) and even smaller fractionation in whole cell experiments of the host organism Sphingobium herbicidovorans MH (εwc = -0.3 ± 0.1‰) suggest that (i) enzyme-associated isotope effects were already small, yet (ii) further masked by active transport through the cell membrane. In contrast, enantiomer fractionation in MCPP, DCPP, and 4-CPP was pronounced, with enantioselectivities (ES) of -0.65 to -0.98 with Sphingomonas sp. PM2, -0.63 to -0.89 with Sphingobium herbicidovorans MH, and 0.74 to 0.97 with Delftia acidovorans MC1. To detect aerobic biodegradation of phenoxypropionic acids in the field, enantiomer fractionation seems, therefore, a stronger indicator than carbon isotope fractionation.

Fabrication of In2S3 nanoparticle decorated TiO2 nanotube arrays by successive ionic layer adsorption and reaction technique and their photocatalytic application.

In2S3 nanoparticle (NP) decorated self-organized TiO2 nanotube array (In2S3/TiO2 NT) hybrids were fabricated via simple successive ionic layer adsorption and reaction (SILAR) technique. The In2S3 NPs in a size of about 15 nm were found to deposit on the top surface of the highly oriented TiO2 NT while without clogging the tube entrances. The loading amount of In2S3 NPs on the TiO2 NT was controlled by the cycle number of SILAR deposition. Compared with the bare TiO2 NT, the In2S3/TiO2 NT hybrids showed stronger absorption in the visible light region and significantly enhanced photocurrent density. The photocatalytic activity of the In2S3/TiO2 NT photocatalyst far exceeds that of bare TiO2 NT in the degradation of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) under simulated solar light. After 160-min irradiation, almost 100% 2,4-D removal is obtained on the 7-In2S3/TiO2 NT prepared through seven SILAR deposition cycles, much higher than 26% on the bare TiO2 NT. After 10 successive cycles of photocatalytic process with total 1,600 min of irradiation, In2S3/TiO2 NT maintained as high 2,4-D removal efficiency as 95.1% with good stability and easy recovery, which justifies the potential of the photocatalytic system in application for the photocatalytic removal of organic pollutants such as herbicides or pesticides from water.