Degradation of 2,4-dichlorophenoxyacetic acid in water by ozonehydrogen peroxide process

This study reports an investigation into the degradation of 2,4-dichlorophenoxyacetic acid in bubble contactor column by O2/H2O2 process, which is widely used as a principal advanced oxidation process. The degradation of 2,4-dichlorophenoxyacetic acid was studied under different H202/O3 molar ratio and pH value. Meanwhile, TOC removal was investigated both in distilled water and tap water. The influences of ozone transfer and consumed hydrogen peroxide were also discussed. The degradation products and oxidation intermediates were identified by GC-MS and LC-MS. A possible reaction mechanism was thus proposed.

Selective removal of 2,4-dichlorophenoxyacetic acid from water by molecularly-imprinted amino-functionalized silica gel sorbent

A molecularly-imprinted amino-functionalized sorbent for selective removal of 2,4-dichlorophenoxyacetic acid （2,4-D） was prepared by a surface imprinting technique in combination with a sol-gel process. The 2,4-D-imprinted amino-functionalized silica sorbent was characterized by FT-IR, nitrogen adsorption and static adsorption experiments. The selectivity of the sorbent was investigated by a batch competitive binding experiment using an aqueous 2,4-D and 2,4-dichlorophenol （2,4-DCP） mixture or using an aqueous 2,4-D and 2,4- dichlorophenylacetic acid （DPAC） mixture. The largest selectivity coefficient for 2,4-D in the presence of 2,4-DCP was found to be over 18, the largest relative selectivity coefficient between 2,4-D and 2,4-DCP over 9. The static uptake capacity and selectivity coefficient of the 2,4-D-imprinted functionalized sorbent are higher than those of the non-imprinted sorbent. The imprinted functionalized silica gel sorbent offered a fast kinetics for the extraction/stripping of 2,4-D, 73% of binding capacity （200 mg/L 2,4-D onto 20 mg of imprinted sorbent） was obtained within 5 min and the adsorbed 2,4-D can be easily stripped by the mixture solution of ethanol and 6 mol/L HC1 （V：V =1：1）. In a test of five extraction/stripping cycles, the adsorption capacity of the sorbent was all above 93% of that of the fresh sorbent. Experimental result showed the potential of molecularly-imprinted amino-functionalized sorbent for selective removal of 2,4-D.

Synthesis,Structural,Spectroscopic Characterization and Biological Properties of the Zn(Ⅱ),Cu(Ⅱ),Ni(Ⅱ),Co(Ⅱ),and Mn(Ⅱ)Complexes With the Widely Used Herbicide 2,4-Dichlorophenoxyacetic Acid

2,4-Dichlorophenoxyacetic acid(2,4-D)is a board-leaf selective herbicide and globally used in agricultural activities.Complexation mode,spectroscopic investigations and biological properties of complexes formed between 2,4-D(C_(6)H_(3)Cl_(2)OCH_(2)·COOH;HL)with Zn(Ⅱ),Cu(Ⅱ),Ni(Ⅱ),Co(Ⅱ),and Mn(Ⅱ)metal ions were investigated.To characterize the binding mode between 2,4-D and the metal ions,many physicochemical approaches were employed.The complexes obtained are characterized quantitatively and qualitatively by using micro elemental analysis,FTIR spectroscopy,UV-Vis spectroscopy,1H-NMR,and magnetic susceptibility measurements.Results of these approaches suggested that the gross formula of the complexes obtained with the metal ions were[ZnL_(2)](2H_(2)O(1),[CuL_(2)(H_(2)O)_(2)](2),[NiL_(2)](3H_(2)O(3),[CoL_(2)(H_(2)O)_(2)](4),and[MnL_(2)(H_(2)O)_(2)](5).In all complexes,two L-anion were coordinated the metal ion by their bidentate carboxylate groups.From the spectral study,all the complexes obtained as monomeric structure and the metals center moieties are six-coordinated with octahedral geometry except Ni(Ⅱ)and Zn(Ⅱ)complexes which existed as a tetrahedral and square pyramidal geometry respectively.The complexes were screened in vitro against several microbes(fungi and bacteria)using Kirby-Bauer disc diffusion method,and data has demonstrated that complex 3 showed excellent antifungal activity.

Insight into the mode of action of 2,4-dichlorophenoxyacetic acid(2,4-D) as an herbicide

2,4-Dichlorophenoxyacetic acid （2,4-D） was the first synthetic herbicide to be commercially developed and has commonly been used as a broadleaf herbicide for over 60 years. It is a selective herbicide that kills dicots without affecting monocots and mimics natural auxin at the molecular level. Physiological responses of dicots sensitive to auxinic herbicides include abnormal growth, senescence,and plant death. The identification of auxin receptors, auxin transport carriers, transcription factors response to auxin, and cross-talk among phytohormones have shed light on the molecular action mode of 2,4-D as a herbicide. Here, the molecular action mode of 2,4-D is highlighted according to the latest findings, emphasizing the physiological process, perception, and signal transduction under herbicide treatment.

A pulsed switching peroxi-coagulation process to control hydroxyl radical production and to enhance 2,4-Dichlorophenoxyacetic acid degradation

The aim of this study was to develop a new pulsed switching peroxi-coagulation system to control hydroxyl radical(∙OH)production and to enhance 2,4-Dichlorophenoxyacetic acid(2,4-D)degradation.The system was constructed with a sacrifice iron anode,a Pt anode,and a gas diffusion cathode.Production of H_(2)O_(2) and Fe^(2+)was controlled separately by time delayers with different pulsed switching frequencies.Under current densities of 5.0 mA/cm^(2)(H_(2)O_(2))and 0.5 mA/cm^(2)(Fe^(2+)),the∙OH production was optimized with the pulsed switching frequency of 1.0 s(H_(2)O_(2)):0.3 s(Fe^(2+))and the ratio of H_(2)O_(2) to Fe^(2+)molar concentrations of 6.6.Under the optimal condition,2,4-D with an initial concentration of 500 mg/L was completely removed in the system within 240 min.The energy consumption for the 2,4-D removal in the system was much lower than that in the electro-Fenton process(686 vs.13610 kWh/kg TOC).The iron consumption in the system was~20 times as low as that in the peroxi-coagulation process(19620 vs.3940400 mg/L)within 240 min.The system should be a promising peroxi-coagulation method for organic pollutants removal in wastewater.

Effects of humic acid fractions with different polarities on photodegradation of 2,4-D in aqueous environments

Four fractions(A,B,C,and D)of humic acids(HAs)were separated based on the polarity from weak to strong.UV-vis absorption and Fourier transform infrared spectroscopy(FTIR)analysis show that the fractions C and Dpossessedmore aromatic C5C content.The influences of HAs and their fractions on the photolysis were investigated by the photodegradation of 2,4-D solutions under simulated solar light irradiation.The degradation rate of 2,4-D was found to decrease in the presence of bulk HAs or their fractions especially at high HAs concentration.The fractions of strong polarity C and D retarded the degradation rate more than the fractions of weak polarity A and B.This could be attributed to the different absorption intensity of the four HAs fractions in the order of D≥C>A>B,and the stronger π-π electron donor-acceptor interactions between the strong polar fractions and 2,4-D.

Photochemical degradation of typical halogenated herbicide 2,4-D in drinking water with UV/H_(2)O_(2)/micro-aeration

UV/H2O2/micro-aeration is a newly developed process based on UV/H2O2. Halogenated pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) photochemical degradation in aqueous solution was studied under various solution conditions. The UV intensity,initial 2,4-D concentrations and solution temperature varied from 183.6 to 1048.7 μW·cm-2,from 59.2 to 300.0 μg·L-1 and from 15 to 30℃,respectively. The concentration of hydrogen peroxide (H2O2) and pH ranged from 0 to 50 mg·L-1 and 5 to 9,and different water quality solutions (tap water,distilled water and deionized water) were examined in this study. With initial concentration of about 100 μg·L-1,more than 95.6% of 2,4-D can be removed in 90 min at intensity of UV radiation of 843.9 μW·cm-2,H2O2 dosage of 20 mg·L-1,pH 7 and room temperature. The removal efficiency of 2,4-D by UV/H2O2/micro-aeration process is better than UV/H2O2 process. The photodecomposition of 2,4-D in aqueous solution follows pseudo-first-order kinetics. 2,4-D is greatly affected by UV irradation intensity,H2O2 dosage,initial 2,4-D concentration and water quality solutions,but it appears to be slightly influenced by pH and temperature. There is a linear relationship between rate constant k and UV intensity and initial H2O2 concentration,which indicates that higher removal capacity can be achieved by the improvement of these factors. Finally,a preliminary cost analysis reveals that UV/H2O2/micro-aeration process is more cost-effective than the UV/H2O2 process in the removal of 2,4-D from drinking water.

Effects of variations in culture media and hormonal treatments upon callus induction potential in endosperm explant of Barringtonia racemosa L.

Objective: To induce callus from the medicinally valuable species, Barringtonia racemosa L.(B. racemosa) whereby the formation of callus is essential for micropropagation studies and in vitro plant secondary metabolites production.Methods: The callus induction potential in B. racemosa was assessed from endosperm explant cultured on different culture media and plant hormonal treatments. Lloyd and Mc Cown's woody plant medium and Murashige and Skoog's medium were used in the study as culture media. On the other hand, various concentrations and combinations of2,4-dichlorophenoxyacetic acid(1.0–2.0 mg/L) and kinetin(0.5–2.5 mg/L) had been incorporated in the culture media to exert the effects of auxin and cytokinin on callus induction.Results: From the present study, it was found that the profuse [(1.681 ± 0.770) g fresh weight,(0.239 ± 0.239) g dry weight] and friable callus formation was optimally produced with desirable morphology and considerable percentage of callus induction(56.70%) in endosperm explants cultured on 1.0 mg/L 2,4-dichlorophenoxyacetic acid and 1.5 mg/L kinetin in Murashige and Skoog's medium.Conclusions: A reliable protocol for inducing callus formation of profuse and friable morphology in endosperm explant of B. racemosa had therefore been successfully established.

Proline and Glutamine Improve in vitro Callus Induction and Subsequent Shooting in Rice

This study was conducted to evaluate the effects of proline and glutamine on in vitro callus induction and subsequent regeneration and to develop a reproducible and highly efficient plant regeneration protocol in four rice genotypes, viz. Pawana, Jaya, Indrayani and Ambemohar. Considerable variation in response to plant growth regulators and amino acid supplements used was observed in all the four genotypes. Medium supplemented with proline and glutamine was shown to be superior to medium without proline and glutamine. The best callusing from mature embryo was observed on Murashige and Skoog （MS） medium supplemented with 2.0 mg/L 2,4-dichlorophenoxyacetic acid （2,4-D）, 500 mg/L proline and 500 mg/L glutamine. Shoot induction was higher in the callus obtained from medium supplemented with 500 mg/L proline and 500 mg/L glutamine. The highest shoot regeneration frequency （83.2%） was observed on MS medium with 2.0 mg/L benzylaminopurine, 0.5 mg/L 1-naphthaleneacetic acid, 500 mg/L proline, and 500 mg/L glutamine in the callus obtained from MS medium supplemented with 2.0 mg/L 2,4-D, 500 mg/L proline and 500 mg/L glutamine. Among the four genotypes, Pawana has the highest regeneration efficiency （83.2%）, whereas the regeneration efficiency of the rest three rice genotypes was in the range of 32.0% to 72.3%. This optimized regeneration protocol can be efficiently used for Agrobacterium mediated genetic transformation in rice.

Qualitative and Quantitative Changes in Biochemical Constituents in the Rice Plant Treated with Different Xenobiotics

Experiments were conducted at Entomology division of Directorate of Rice research to study the qualitative and quantitative changes in biochemical constituents in the rice plant treated with different xenobiotics, viz. insecticides like deltamethrin, imidacloprid, herbicide like 2,4-Dichlorophenoxyacetic acid, fungicide like carbendazim, green manure Calotropis gigantea leaves, botanicals like Neem Seed Powder and fertilizer urea along with control plants of TN1, PTB33 and Swama varieties comprising of total 15 treatments. Application of butachlor, carbendazim, deltamethrin and excessive nitrogen fertilization resulted in increased population build up of brown plant hopper （BPH）. Significantly, lower honeydew excretion （13 mme area） in the BPH nymphs was observed on resistant PTB33 variety compared to susceptible TN1 and Swarna varieties （116 and 110 mm2 respectively）. In susceptible TN1 variety, the sucrose content was significantly higher （9.35 mg/g tissue） compared to BPH resistant PTB33 （5.32 mg/g tissue）. The BPH resistant PTB33 variety exhibited significantly lower free amino acid content （1.23 mg/g tissue） as compared to TN1 （2.51 mg/g）. The C/N ratio was comparatively high in the resistant PTB33 alone （4.32）, but was low in PTB33 applied with 2,4-D ＋ carbendazim （2.73）, 2,4-D ＋ imidacloprid ~ carbendazim （2.3）, excess urea fertilizer （2.18）. The total phenol contents measured in resistant PTB33 （7.5 mg/g dry wt）, susceptible TN1 （5.865 mg/g dry wt） and the popular variety Swarna （5.57 mg/g dry wt） were almost same and no statistical difference was observed. Further, treatment of these varieties with different xenobiotics and botanicals also did not significantly alter their total phenol content. However, the phenol content of the resistant PTB 33 alone and treated with xenobiotics was higher compared to the susceptible TN 1 and Swarna varieties alone and treated with xenobiotics. The plant biochemical constituents such as free amino acids, sucrose were lower in untreated resistant PTB33 compared to susceptible TN1, and PTB33 treated with urea and deltamethrin. The high feeding rate and population build up on the susceptible variety TN1 is positively correlated with high quantities of sucrose, free amino acids and lower quantities of phenols and low C/N ratio.