Adsorption Of Dimethyl Methylphosphonate Research Articles

Adsorption of DMMP and water vapor on granular activated carbon: An experimental and molecular simulation study

The adsorption behavior of Dimethyl methylphosphonate (DMMP), as a simulant of sarin nerve agent, especially in the presence of water vapor, is crucial for the design of efficient chemical protection equipment. Experimental results reveal DMMP's adsorption isotherm on granular activated carbon (GAC) as a typical type I. The adsorption process was a spontaneous and exothermic physical adsorption process, and the adsorption mechanism was in accordance with Dubinin's micropore filling theory. In the relative humidity range of 10 % ∼ 90 %, the isotherm remained I-type, and the effect of water vapor on the equilibrium adsorption capacity and apparent adsorption rate was weak. Molecular simulations also show that DMMP adsorption on GAC follows a type I isotherm, primarily driven by van der Waals forces of physical adsorption. The adsorption potential energy between DMMP and GAC surpasses that of water molecules, resulting in negligible effects from water vapor on DMMP adsorption equilibrium. Meanwhile, water molecules had minimal effect on the diffusion of DMMP molecules in the GAC pores, and the positional distribution of DMMP multilayer adsorption was consistent under different relative humidity conditions. Furthermore, the presence of polar functional groups such as hydroxyl groups significantly affects the adsorption equilibrium of DMMP.

Decontamination coupled with dynamic adsorption of sulfur mustard (CEES) and nerve agent-sarin simulants (DMMP) on synthesized zeolite-alpha with its metal oxide composites

Chemical warfare agents (CWAs) are the most feared toxic chemicals intended to debilitate the general human population and regional civilians. Therefore, prompt and urgent decontamination is needed to protect millions of lives and the associated hazardous implications. In this present study, our main goal is to evaluate the performance of Zeolite-Alpha and its various metal oxide composites as novel adsorbents for the decontamination of CWA simulants, 2-chloroethyl ethyl sulfide (CEES), and dimethyl methyl phosphonate (DMMP). Synthesized Zeolite-Alpha and their composites were characterized by XRD, FTIR, SEM-EDS, and BET analysis techniques. The CWA simulants’ decontamination (adsorption and desorption) was monitored using GC-FID and GC-MS analysis techniques. A possible reaction mechanism toward the adsorption and destruction of CWA simulants, CEES, and DMMP was also proposed. Nanocrystalline Zeolite-Alpha and its metal oxide composites are powerful adsorbents, and they showed more significant decontamination potential toward the above CWA simulants. The Cr-O-Alpha and Ag-O-Alpha showed promising results (93–98% decontamination) among all other synthesized metal oxide composites.

Adsorptive degradation of dimethyl methylphosphonate over Zr-based metal–organic framework built from 3,3′,5,5′-azobenzenetetracarboxylic acid

Chemical warfare agents (CWAs) pose a significant threat to humans because of their high toxicity. Zirconium-based metal–organic frameworks (Zr-MOFs) are promising candidates for the purification and detoxification of CWAs. In this study, we prepared a Zr6O4(OH)8(H2O)4(abtc)2 denoted to Zr-abtc (abtc = 3,3′,5,5′-azobenzene-tetracarboxylate) under eco-friendly hydrothermal reflux conditions and investigated its detoxification performance. Dimethyl methylphosphonate (DMMP) was used as a simulant of a nerve agent to evaluate the adsorption performance of Zr–abtc. The Zr–abtc MOF was constructed from an 8-connected Zr6 cluster [Zr6(µ3-O)4(µ3-OH)4] with abtc as a linker, resulting in the generation of abundant surface hydroxyl groups, high porosity, and remarkable structural robustness under high moisture and high temperature conditions. The results of the breakthrough (BT) test of DMMP under dry and humid conditions reveal that Zr–abtc displays high DMMP adsorption performance with the adsorption capacity of 1.74 and 1.60 mmol/g under dry and humid condition, respectively. The high performance of Zr–abtc can be attributed to not only the strong interaction between the surface hydroxyl group of Zr–abtc MOF and DMMP but also the catalytic activity of the surface hydroxyl group to form the decomposed product of DMMP, as demonstrated using Fourier transform infrared spectroscopy (FTIR).

Modeling and simulation of external electric field application for diisopropyl methylphosphonate sensing through B12N12 fullerene

The external electric field can effectually enhance the electronic and optical features of low dimensional systems. Hence, the corresponding atomic structure and adsorption feature changes of a B12N12 fullerene under different applied external electric fields for dimethyl methylphosphonate (DMMP) detection were evaluated. The adsorption of DMMP on the B12N12 surface has been calculated using density functional theory (DFT) and time dependent density functional theory (TDDFT) by the PBE (Perdew-Burke-Ernzerhof) functional to study the effects of the parallel (EX) and transverse (EY) external electric fields on the structural and optoelectronic features of the pure fullerene. Through the analysis of the binding energy it is found that B12N12 fullerenes, in the presence of a parallel external electric field (EX = 0.15 a.u.), are energetically favored when compared to B12N12 fullerenes in the presence of a transverse external electric field (EY = 0.15 a.u.). The results demonstrate that a transverse external electric field ranging from 0.005 a.u. to 0.015 a.u. could enhance the DMMP sensitivity of the B12N12 fullerene (with a significant reduction of energy band gap), which potentially could aid in the development of a room temperature DMMP gas sensor. The adsorption and desorption of DMMP could be controlled by external electric field too, which has the potential for applications in itself, relative to DMMP collection and storage.

Dynamic adsorption of dimethyl methyl Phosphonate and 2-chloroethyl ethyl sulfide on zeolite-MOR and its nanocomposites monitored by gas chromatography flame ionized detector (GC-FID)

Present paper highlights the adsorption performances of mordenite (MOR), polyaniline-mordenite (PANI/MOR), copper oxide-mordenite (CuO/MOR) and silver oxide-mordenite (AgO/MOR) nanocomposites toward decontamination of toxic chemical warfare agent’s (CWA)simulant 2-chloroethyl ethyl sulfide (CEES, blistering agent simulant) and dimethyl methyl phosphonate (DMMP, nerve agent simulant) at normal condition of temperature (30 ± 2 °C) and pressure. Composite of MOR zeolite with polyaniline (PANI) was prepared by oxidative polymerization using ammonium per sulfate as an initiator. The composites of MOR zeolite and metal oxide (CuO/MOR) and (AgO/MOR) were prepared by taking aqueous solution of corresponding metal nitrates using ion exchange technique. Adsorption experiments were monitored by gas chromatography – flame ionize detector (GC-FID) to detect ions concentration. Nanocomposites were characterized by techniques such as XRD, FTIR, FESEM-EDX, TGA, UV-Vis and BET. X-ray diffraction (XRD) pattern shows the crystalline nature of parent zeolite and its nanocomposites. Field emission scanning electron microscopy (FESEM) analysis reveals that mordenite, PANI/MOR and AgO/MOR have polyhedron, agglomerated rough and fibrous elongated surfaces, respectively. From SEM analysis, obtained particle size was in the range of 2 to 14.5 μm. Brunauer–Emmett–Teller (BET) analysis depicts that the surface area of MOR, PANI/MOR, AgO/MOR and CuO/MOR were 93.07, 166.49, 120.31and 93.51 m2/g, respectively. AgO/MOR and PANI/MOR nanocomposites were found good adsorbent candidate. The nanocomposite of AgO/MOR was able to decontaminate ∼ 100% in 6 h. We are also able to remove DMMP by PANI/MOR up to ∼ 100%.

Kinetics of Dimethyl Methylphosphonate Adsorption and Decomposition on Zirconium Hydroxide Using Variable Temperature In Situ Attenuated Total Reflection Infrared Spectroscopy.

The decomposition mechanisms of dimethyl methylphosphonate (DMMP), a widely used simulant for organophosphorus chemical warfare agents (CWAs), are relatively well understood from previous studies. However, there still lacks a quantitative description of DMMP decomposition kinetics under ambient conditions that is relevant for sequestration applications. We investigated adsorption and decomposition kinetics of DMMP on amorphous zirconium hydroxide (ZH) using variable-temperature in situ attenuated total reflection (ATR) infrared spectroscopy. We demonstrate that quantifying DMMP decomposition kinetics using conventional methods, where the integrated absorbance of P-O vibrational modes is monitored, can be inaccurate because these spectra are also convoluted with C-O vibrational modes from transient surface methoxy species that are not proportional to DMMP decomposition due to methanol desorption. Here, we propose to use the ρ(PCH3) modes as an alternative way to track DMMP adsorption and decomposition reactions. On the basis of density functional theory (DFT) simulations and comparisons to relatively unreactive monoclinic zirconia (m-ZrO2), we assign the deconvoluted components of the ρ(PCH3) region and use it to monitor decomposition products over time at various temperatures. Because the PCH3 group is present in many toxic organophosphorus compounds, tracking the PCH3 bands in time-dependent IR spectra is useful for measuring surface kinetics of CWAs and their simulants on various decontamination materials.

Toward Efficient Toxic-Gas Detectors: Exploring Molecular Interactions of Sarin and Dimethyl Methylphosphonate with Metal-Centered Phthalocyanine Structures.

The rapid and reliable detection of lethal agents such as sarin is of increasing importance. Here, density-functional theory (DFT) is used to compare the interaction of sarin with single-metal-centered phthalocyanine (MPc) and MPc layer structures to a benign model system, i.e., the adsorption of dimethyl methylphosphonate (DMMP). The calculations show that sarin and DMMP behave nearly identical to the various MPcs studied. Among NiPc, CuPc, CoPc, and zinc phthalocyanine (ZnPc), we find the interaction of both sarin and DMMP to be the strongest with ZnPc, both in terms of interaction energy and adsorption-induced work function changes. ZnPc is thus proposed as a promising sensor for sarin detection. Using X-ray photoelectron spectroscopy, the theoretically predicted charge transfer from DMMP to ZnPc is confirmed and identified as a key component in the sensing mechanism.

Chitosan-Derived Porous Activated Carbon for the Removal of the Chemical Warfare Agent Simulant Dimethyl Methylphosphonate.

Methods for the rapid removal of chemical warfare agents are of critical importance. In this work, a porous activated carbon material (C-PAC) was prepared from chitosan flakes via single-step potassium carbonate (K2CO3) activation for the prompt adsorption of dimethyl methylphosphonate (DMMP). C-PAC samples were prepared using different carbonization temperatures (350, 550, and 750 °C) at a constant K2CO3/chitosan ratio (1:2) and using different activator ratios (K2CO3/chitosan ratios of 1:0.5, 1:1, 1:2, and 1:3) at 750 °C. Furthermore, we evaluated the effect of preparation conditions on the adsorption capacities of the various C-PAC materials for DMMP under ambient conditions (25 °C). Notably, for the C-PAC material prepared at 750 °C using a K2CO3/chitosan ratio of 1:2, the DMMP adsorption was saturated at approximately 412 mg·g−1 carbon after 48 h. The good performance of this material makes it a potential candidate for use in remedial applications or protective gear.

Positive Effects of Impregnation of Fe-oxide in Mesoporous Al-Oxides on the Decontamination of Dimethyl Methylphosphonate

Dimethyl methylphosphonate (DMMP) is an important simulant of organophosphates pesticides and chemical warfare nerve agents. Here, we investigated the catalytic decontamination of DMMP on Fe-oxide impregnated mesoporous Al2O3. Fe-oxide/Al2O3 sample was prepared via the temperature regulated chemical vapor deposition of Fe-oxide on mesoporous Al2O3 and post-annealing at 750 °C. The Fe-oxide/Al2O3 and bare Al2O3 samples were exposed to DMMP-containing dry air at room temperature to study the effects of Fe-oxide impregnation on the reactive adsorption of DMMP. The facilitation of DMMP degradation into CO2 and methanol at room temperature in the presence of nano-dispersed Fe-oxide was evidenced by gas-chromatograph and Fourier transform-infrared (FT-IR) absorption spectroscopy. In addition, temperature programmed oxidation (TPO) experiments and gas chromatography (Agilent, 6890) equipped with mass spectrometer (Agilent, 5973N) (GC/MS) analyses revealed that the minimum temperature that was required for total oxidation of DMMP into CO2 can also be lowered by Fe-oxide impregnation in mesoporous Al2O3.

Coupling Ambient Pressure X-ray Photoelectron Spectroscopy with Density Functional Theory to Study Complex Surface Chemistry and Catalysis

Ambient pressure X-ray photoelectron spectroscopy (APXPS) experiments narrow the pressure and materials gaps between UHV surface science experiments and applications. Upon closing these gaps, ambiguity can enter the analysis of the spectra due to overlapping peaks from different elements or functional groups of both the sample and the gas phase. Additionally, reaction intermediates and mechanisms are often inaccessible from interpretation of APXPS data alone. In many cases, these issues can be overcome with the aid of density functional theory (DFT) calculations. Here, we outline our process of combining DFT calculations with APXPS experiments by describing our recent investigations of the adsorption of dimethyl methylphosphonate (DMMP) on MoO3 and CuO. We begin by showing the importance of the characterization of the isolated gas phase molecule before adsorption onto a surface. In particular, strong agreement between theory and experiment helps identify plausible decomposition pathways of the isolated molecule and provides a baseline for interpretation of spectra showing evidence of DMMP interaction with surfaces. The intact adsorption of DMMP on MoO3 offers an illustration of how moving beyond pristine single crystalline surfaces in calculations can enable better modeling of experimental trends that result from surface defects. Studies of DMMP adsorption on CuO exemplify the powerful synergy of APXPS combined with DFT for elucidation of complex reaction mechanisms on surfaces.

Molecular and dissociative adsorption of DMMP, Sarin and Soman on dry and wet TiO2(110) using density functional theory

Titania, among the metal oxides, has shown promising characteristics for the adsorption and decontamination of chemical warfare nerve agents, due to its high stability and rapid decomposition rates. In this study, the adsorption energy and geometry of the nerve agents Sarin and Soman, and their simulant dimethyl methyl phosphonate (DMMP) on TiO2 rutile (110) surface were calculated using density functional theory. The molecular and dissociative adsorption of the agents and simulant on dry as well as wet metal oxide surfaces were considered. For the wet system, computations were done for the cases of both molecularly adsorbed water (hydrated conformation) and dissociatively adsorbed water (hydroxylated conformation). DFT calculations show that dissociative adsorption of the agents and simulant is preferred over molecular adsorption for both dry and wet TiO2. The dissociative adsorption on hydrated TiO2 shows higher stability among the different configurations considered. The dissociative structure of DMMP on hydrated TiO2 (the most stable one) was identified as the dissociation of a methyl group and its adsorption on the TiO2 surface. For the nerve agents Sarin and Soman on hydrated TiO2 the dissociative structure was by the dissociation of the F atom from the molecule and its interaction with a Ti atom from the surface, which could indicate a reduction in the toxicity of the products. This study shows the relevance of water adsorption on the metal oxide surface for the stability and dissociation of the simulant DMMP and the nerve agents Sarin and Soman on TiO2.

Adsorption and decomposition of dimethyl methylphosphonate (DMMP) on expanded graphite/metal oxides

Composites based on expanded graphite (EG) and metal oxides (MOs) were prepared by an explosive combustion and blending method. A metal oxide (Ag2O, CuO or ZnO)-containing phase was employed as a component with reactive functionality, which was supported on EG as a component with adsorptive functionality. The physical properties of the EG/MO composites were examined using SEM and FTIR spectroscopy, the results of which indicated that the MOs were incorporated in the EG matrix after impregnation. Solid state magic angle spinning (MAS) 1H, 31P and cross polarization (CP) MAS 13C NMR studies of the EG/MO composites were performed after adsorption of dimethyl methylphosphonate (DMMP). The FTIR and NMR data showed that the initial uptake occurred through both molecular and reactive adsorption. Molecular adsorption occurred by van der Waals interaction of M(Zn, Cu, Ag)⋯OP and hydrogen-bond formation to isolated hydroxyl groups. Reactive chemisorption appeared to occur through interaction with both Lewis acid sites and active oxygen species present on the MO surface. The FTIR and NMR results exhibited a trend of reactivity towards DMMP in the order Ag2O > ZnO > CuO, which indicated stronger interaction between the Lewis acid sites and the phosphoryl O atom of DMMP for Ag2O as compared with ZnO and CuO, with concomitant formation of surface-coordinated DMMP and bridge-bonded OPO phosphorus oxide species.

Dimethyl methylphosphonate adsorption and decomposition on MoO2 as studied by ambient pressure x-ray photoelectron spectroscopy and DFT calculations

Organophosphonates range in their toxicity and are used as pesticides, herbicides, and chemical warfare agents (CWAs). Few laboratories are equipped to handle the most toxic molecules, thus simulants such as dimethyl methylphosphonate (DMMP), are used as a first step in studying adsorption and reactivity on materials. Benchmarked by combined experimental and theoretical studies of simulants, calculations offer an opportunity to understand how molecular interactions with a surface changes upon using a CWA. However, most calculations of DMMP and CWAs on surfaces are limited to adsorption studies on clusters of atoms, which may differ markedly from the behavior on bulk solid-state materials with extended surfaces. We have benchmarked our solid-state periodic calculations of DMMP adsorption and reactivity on MoO2 with ambient pressure x-ray photoelectron spectroscopy studies (APXPS). DMMP is found to interact strongly with a MoO2 film, a model system for the MoOx component in the ASZM-TEDA© gas filtration material. Density functional theory modeling of several adsorption and decomposition mechanisms assist the assignment of APXPS peaks. Our results show that some of the adsorbed DMMP decomposes, with all the products remaining on the surface. The rigorous calculations benchmarked with experiments pave a path to reliable and predictive theoretical studies of CWA interactions with surfaces.

Structural Effect of Thioureas on the Detection of Chemical Warfare Agent Simulants.

The ability to rapidly detect, identify, and monitor chemical warfare agents (CWAs) is imperative for both military and civilian defense. Since most CWAs and their simulants have an organophosphonate group, which is a hydrogen (H)-bond acceptor, many H-bond donors have been developed to effectively bind to the organophosphonate group. Although thioureas have been actively studied as an organocatalyst, they are relatively less investigated in CWA detection. In addition, there is a lack of studies on the structure-property relationship for gas phase detection. In this study, we synthesized various thioureas of different chemical structures, and tested them for sensing dimethylmethylphosphonate (DMMP), a CWA simulant. Molecular interaction between DMMP and thiourea was measured by 1H NMR titration and supported by density functional theory (DFT) calculations. Strong H-bond donor ability of thiourea may cause self-aggregation, and CH-π interaction can play an important role in the DMMP detection. Gas-phase adsorption of DMMP was also measured using a quartz crystal microbalance (QCM) and analyzed using the simple Langmuir isotherm, showing the importance of structure-induced morphology of thioureas on the surface.

Surface Decomposition of Dimethyl Methylphosphonate on SnO2 Nanoparticles: Role of Nanoparticle Size

We report the effect of SnO2 particle size on the adsorption behaviour of dimethyl methylphosphonate (DMMP). SnO2 nanoparticles with different particle sizes have been successfully synthesised by the reverse microemulsion method. Transmission electron microscopy and X-ray diffraction results were used to evaluate size distribution, shape and structure of the prepared SnO2 nanoparticles. The infrared spectra of adsorbed DMMP on SnO2 show that the adsorption is dissociative. In addition, it is shown that the size of SnO2 nanoparticles does not affect the reaction mechanism. Adsorption isotherms of DMMP show that by decreasing the size of SnO2 nanoparticles, the amount of DMMP adsorbed is increased. In addition, the calculated heats of adsorption of DMMP are increased as the SnO2 nanoparticle size decreases.

Thermal desorption of dimethyl methylphosphonate from MoO3

AbstractOrganophosphonates are used as chemical warfare agents, pesticides, and corrosion inhibitors. New materials for the sorption, detection, and decomposition of these compounds are urgently needed. To facilitate materials and application innovation, a better understanding of the interactions between organophosphonates and surfaces is required. To this end, we have used diffuse reflectance infrared Fourier transform spectroscopy to investigate the adsorption geometry of dimethyl methylphosphonate (DMMP) on MoO3, a material used in chemical warfare agent filtration devices. We further applied ambient pressure X-ray photoelectron spectroscopy and temperature programmed desorption to study the adsorption and desorption of DMMP. While DMMP adsorbs intact on MoO3, desorption depends on coverage and partial pressure. At low coverages under UHV conditions, the intact adsorption is reversible. Decomposition occurs with higher coverages, as evidenced by PCHx and POx decomposition products on the MoO3 surface. ...

Adsorption of Dimethyl Methylphosphonate on MoO3: The Role of Oxygen Vacancies

Dimethyl methylphosphonate (DMMP) is a common chemical warfare agent simulant and is widely used in adsorption studies. To further increase the understanding of DMMP interactions with metal oxides, ambient pressure X-ray photoelectron spectroscopy was used to study the adsorption of DMMP on MoO3, including the effects of oxygen vacancies, surface hydroxyl groups, and adsorbed molecular water. Density functional theory calculations were used to aid in the interpretation of the APXPS results. An inherent lack of Lewis acid metal sites results in weak interactions of DMMP with MoO3. Adsorption is enhanced by the presence of oxygen vacancies, hydroxyl groups, and molecular water on the MoO3 surface, as measured by photoelectron spectroscopy. Computational results agree with these findings and suggest the formation of methanol through several possible pathways, but all require a proton transferred from a hydroxyl group on the surface.

Reactive adsorption of toxic organophosphates parathion methyl and DMMP on nanostructured Ti/Ce oxides and their composites

Pure titanium and cerium oxides and their composites were prepared by the modified method of homogeneous hydrolysis with urea as the precipitating agent. The as-synthesized nanostructured oxides were examined by XRD, XPS, microscopic techniques (SEM, HRTEM), nitrogen physisorption, and vibrational spectroscopies (FTIR, Raman). Decontamination ability of the samples towards the toxic organophosphorus compounds was determined by two methods. The reactive adsorption of the warfare agent simulant Dimethyl methylphosphonate (DMMP) was observed by in situ FTIR spectroscopy. The degradation of the pesticide parathion methyl in a liquid medium was investigated by liquid chromatography (HPLC). Nano-ceria exhibited substantially higher degradation ability compared to nano-titania. The highest degradation efficiency was achieved with the composites with Ti:Ce 2:8 and 1:1 molar ratio. The strong interaction of Ti with Ce led to an increase of Ce3+ and formation of Ti<4+ states and changed surface area and porosity which may cause improved degradation efficacy for both DMMP and parathion methyl.

A DFT study of associative and dissociative chemical adsorption of DMMP onto SnO2(110) surface nano-cluster

Density functional theory has been applied to a computational study of associative and dissociative adsorption of dimethyl methylphosphonate (DMMP) on SnO2 (cassiterite). Rutile SnO2(110) surface, free of defects and of OH, has been modeled using free-standing nano-cluster with unsaturated edge atoms terminated with hydrogen. Associative (molecular) adsorption occurs via the formation of a Sn5c···O=P dative bond along with a very strong interaction between the adjacent Sn5c site and the methoxy O atom of the adsorbate. C–H···O hydrogen bonds between CH3 groups and surface O atoms also contribute. Associative adsorption of DMMP on SnO2(110) has been compared to TiO2(110). Two hypothetically possible products have been considered for the first step in dissociative adsorption of DMMP on the adsorbent. Dissociative adsorption of DMMP on the SnO2(110) surface shows formation of two dative bonds via O atoms of the O–P=O (bridge) and formation of a bidentate structure. The key requirement for the dissociative adsorption is the availability of pairs of under-coordinated metal cations and surface base sites (oxygen). Thus, the coordination environment of the surface cations and anions is the critical surface characteristics for describing surface reactions of Lewis and Bronsted acids.

Evaluation of activated carbon respirator filter effectiveness by concentration mapping of dimethyl methylphosphonate

Activated carbon (AC) has been used extensively in personal protective equipment (PPE) to adsorb toxic substances for the purpose of protecting the user from exposure. The ability to evaluate localized carbon utilization in multiple PPE designs would help engineers develop more effective PPE. Therefore, a method to map dimethyl methylphosphonate (DMMP), a common PPE testing agent, concentrations throughout AC filters was developed and tested on DMMP-exposed filters, some purposefully occluded to simulate defective filters. DMMP concentrations were highest at the point of entry and dispersed outward in a radial pattern from that site, decreasing with distance from the point of exposure. Occluded filters were detected by observing DMMP adsorption inconsistent with unblocked filters and showed high concentrations of DMMP localized in unblocked areas of the filter. The DMMP mapping technique detailed in this study provides a tool for testing AC utilization inside DMMP-exposed PPE.