Thermal degradation of chlorophenoxy acid herbicides

The chlorophenoxy herbicide MCPA (4-chloro-2-methylphenoxyacetic acid), widely used for the control of broad-leaf weeds primarily in cereal and grass seed crops, still remains one of the most often used herbicides in Portugal. As the formation of inclusion complexes with cyclodextrins can improve its solubility properties, the interaction between the herbicide MCPA and β-cyclodextrin was investigated. The stability constants describing the extent of formation of the complexes have been determined by phase-solubility studies. Different analytical techniques [ultraviolet-visible spectroscopy (UV-Vis), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy ( 1 H NMR)] were employed for a thorough investigation of the structural characteristics of the obtained complexes, which exhibited distinct features and properties from both "guest" and "host" molecules. FTIR and 1 H NMR data obtained for the MCPA/β-CD complexes gave information about the interaction between MCPA and the nonpolar cyclodextrin cavity. The dramatic change observed in band frequency and proton displacements of OCH 2 group and H6 aromatic proton confirmed the inclusion of MCPA in β-CD.The formation of an inclusion complex between MCPA and β-CD increased the aqueous solubility of this herbicide which could be a particularly advantageous property for some specific applications, namely to improve commercial formulation and for environmental protection.

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“…[21] In the physical mixture (PM) DSC curves it was possible to clearly distinguish the MCPA fusion endothermic peak around 119.8…”

Section: Differential Scanning Calorimetry (Dsc)mentioning

confidence: 99%

Host-guest complexes of phenoxy alkyl acid herbicides and cyclodextrins. MCPA and β-cyclodextrin

Garrido

Santos

Silva³

et al. 2012

Journal of Environmental Science and Health, Part B

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“…Among the family of CPCs, monochlorophenol and dichlorophenols are most likely to be released into the air because they have the greatest tendency of being gases (large Henry's law constant). Furthermore, release of chlorophenols to the atmosphere also occurs through the incineration of chlorinated wastes from municipal solid waste and hazardous waste incinerations . Conventional methods for detecting CPCs in air comprise of spectrometric and chromatographic techniques that require precision instrumentational analyses .…”

Section: Introductionmentioning

confidence: 99%

Sensing and adsorption study of gaseous phase chlorophenols on functionalized carbon nanotube membrane

Kanchanatip

Tulaphol

Den

et al. 2018

Env Prog and Sustain Energy

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The adsorption equilibrium isotherms as well as gas sensing of three chlorinated phenolic compounds (CPCs) including phenol, 2‐chlorophenol, and 2,4‐dichlorophenol by acid‐functionalized carbon nanotube (CNT) membrane were studied. CNTs were synthesized via floating catalyst chemical vapor deposition method at 800°C and then functionalized with a mixture of HNO3 and H2SO4. The functionalized CNTs were vacuum filtered to form CNT membranes. The adsorption isotherm followed the Langmuir adsorption model better than the Freundlich model, suggesting monolayer adsorption. The maximum adsorption capacities were found to be 61.35, 93.46, and 104.17 mg g−1 for phenol, 2‐chlorophenol, and 2,4‐dichlorophenol, respectively. The desorption energy determined via thermogravimetric analysis indicates that adsorption of all three CPCs onto the CNT membranes belonged to chemisorption type. For the gas sensing test, the CNT membrane showed fast response to the tested CPCs with good stability and repeatability. The sensitivity values obtained were 5.39 × 10−2, 3.35 × 10−2 and 2.58 × 10−2 for 2,4‐dichlorophenol, 2‐chlorophenol, and phenol, respectively. It is noteworthy that the adsorption capacity and sensitivity of the CNT membrane to the target gases increased with the increase in the number of chlorine atoms in the phenolic compounds. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S315–S322, 2019

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“…Furthermore, chlorophenols are also released to the atmosphere through the chlorinated wastes incineration. For instance, 2,4dichlorophenol has been founded in air from the combustion of chlorophenol-based herbicides as well as municipal solid waste and hazardous waste inceneration (Gomez et al, 1988(Gomez et al, , Öberg et al, 1989.…”

Section: List Of Tablesmentioning

confidence: 99%

Synthesis, sorption and sensing capability of carbon nanotube based materials for gas-phase chlorinated phenols

Kanchanatip

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The adsorption equilibrium isotherms as well as gas sensing of three chlorinated phenolic compounds (CPCs) including phenol, 2-chlorophenol, and 2,4-dichlorophenol by acid-functionalized carbon nanotubes (CNT) were studied. CNTs were synthesized via floating catalyst chemical vapor deposition method at 800oC and then functionalized with a mixture of HNO3 and H2SO4. The functionalized CNTs were vacuum filtered to form CNT buckypaper. The adsorption isotherm followed the Langmuir adsorption model better than the Freundlich and Redlich-Peterson models. The maximum adsorption capacities were found to be 61.35, 93.46 and 104.17 mg/g for phenol, 2-chlorophenol and 2,4-dichlorophenol, respectively. The desorption activation energy determined via thermogravimetric analysis indicates that adsorption of all three CPCs onto the CNTs belonged to chemisorption type. For the gas sensing test, the CNT buckypaper showed fast response to the tested CPCs with good stability and repeatability. The sensitivity values obtained were 13.778 × 10-4, 8.835 × 10-4 and 7.122 × 10-4 for 2,4-dichlorophenol, 2-chlorophenol and phenol, respectively. It is noteworthy that the adsorption capacity and sensitivity of the CNT based materials to the target gases increased with the increase in the number of chlorine atoms in the phenolic compounds.

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Thermal degradation of chlorophenoxy acid herbicides

Cited by 7 publications

References 18 publications

Host-guest complexes of phenoxy alkyl acid herbicides and cyclodextrins. MCPA and β-cyclodextrin

Host-guest complexes of phenoxy alkyl acid herbicides and cyclodextrins. MCPA and β-cyclodextrin

Sensing and adsorption study of gaseous phase chlorophenols on functionalized carbon nanotube membrane

Synthesis, sorption and sensing capability of carbon nanotube based materials for gas-phase chlorinated phenols

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