Montmorillonite functionalized with pralidoxime as a material for chemical protection against organophosphorous compounds

Ag(I) Pyridine-Amidoxime Complex as the Catalysis Activity Domain for the Rapid Hydrolysis of Organothiophosphate-Based Nerve Agents: Mechanistic Evaluation and Application

Two novel Ag(I) complexes containing synergistic pyridine and amidoxime ligands (Ag-DPAAO and Ag-PAAO) were first designed as complex monomers. Taking advantage of the molecular imprinting technique and solvothermal method, molecular imprinted porous cross-linked polymers (MIPCPs) were developed as a robust platform for the first time to incorporate Ag-PAAO into a polymer material as a recyclable catalyst. Advantageously, the observed pseudo first-order rate constant (k_obs) of MIPCP-Ag-PAAO-20% for ethyl-parathion (EP) hydrolysis is about 1.2 × 10⁴-fold higher than that of self-hydrolysis (30 °C, pH = 9). Furthermore, the reaction mechanism of the MIPCP-containing Ag-PAAO-catalyzed organothiophosphate was analyzed in detail using density functional theory and experimental spectra, indicating that the amidoxime can display dual roles for both the key coordination with the silver ion and nucleophilic attack to weaken the P-OAr bond in the catalytic active site.

Cu2O nanoparticles for the degradation of methyl parathion

Methyl parathion (MP) is one of the most neurotoxic pesticides. An inexpensive and reliable one-step degradation method of MP was achieved through an aqueous suspension of copper(I) oxide nanoparticles (NPs). Three different NPs sizes (16, 29 and 45 nm), determined with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM), were synthesized using a modified Benedict's reagent. 1H nuclear magnetic resonance (NMR) results show that the hydrolytic degradation of MP leads to the formation of 4-nitrophenol (4-NPh) as the main product. While the P=S bond of MP becomes P=O, confirmed by 31P NMR. Although Cu2O is a widely known photocatalyst, the degradation of methyl parathion was associated to the surface basicity of Cu2O NPs. Indirect evidence for the basicity of Cu2O NPs was achieved through UV-vis absorption of 4-NPh. Likewise, it was shown that the surface basicity increases with decreasing nanoparticle size. The presence of CuCO3 on the surface of Cu2O, identified using X-ray photoelectron spectroscopy (XPS), passivates its surface and consequently diminishes the degradation of MP.

Shielded α-Nucleophile Nanoreactor for Topical Decontamination of Reactive Organophosphate

Here, we describe a nanoscale reactor strategy with a topical application in the therapeutic decontamination of reactive organophosphates (OPs) as chemical threat agents. It involves functionalization of poly(amidoamine) dendrimer through a combination of its partial PEG shielding and exhaustive conjugation with an OP-reactive α-nucleophile moiety at its peripheral branches. We prepared a 16-member library composed of two α-nucleophile classes (oxime, hydroxamic acid), each varying in its reactor valency (43-176 reactive units per nanoparticle), and linker framework for α-nucleophile tethering. Their mechanism for OP inactivation occurred via nucleophilic catalysis as verified against P-O and P-S bonded OPs including paraoxon-ethyl (POX), malaoxon, and omethoate by ¹H NMR spectroscopy. Screening their reactivity for POX inactivation was performed under pH- and temperature-controlled conditions, which resulted in identifying 13 conjugates, each showing shorter POX half-life up to 2 times as compared to a reference Dekon 139 at pH 10.5, 37 °C. Of these, 10 conjugates were further confirmed for greater efficacy in POX decontamination experiments performed in two skin models, porcine skin and an artificial human microtissue. Finally, a few lead conjugates were selected and demonstrated for their biocompatibility in vitro as evident with lack of skin absorption, no inhibition of acetylcholinesterase (AChE), and no cytotoxicity in human neuroblastoma cells. In summary, this study presents a novel nanoreactor library, its screening methods, and identification of potent lead conjugates with potential for therapeutic OP decontamination.

Simultaneous Removal and Recovery of Metal Ions and Dyes from Wastewater through Montmorillonite Clay Mineral

The main objective of this work was to evaluate the potential of Montmorillonite nanoclay (Mt), readily and inexpensively available, for the simultaneous adsorption (and removal) of two classes of pollutants: metal ions and dyes. The attention was focused on two "model" pollutants: Ce(III) and crystal violet (CV). The choice is due to the fact that they are widespread in wastewaters of various origins. These characteristics, together with their effect on human health, make them ideal for studies on water remediation. Moreover, when separated from wastewater, they can be recycled individually in industrial production with no or simple treatment. Clay/pollutant hybrids were prepared under different pH conditions and characterized through the construction of the adsorption isotherms and powder X-ray diffraction. The adsorption behavior of the two contaminants was revealed to be significantly different: the Langmuir model reproduces the adsorption isotherm of Ce(III) better, thus indicating that the clay offers a unique adsorption site to the metal ions, while the Freundlich model proved to be the most reliable for the uptake of CV which implies heterogeneity of adsorption sites. Moreover, metal ions do not adsorb at all under acidic conditions, whereas the dye is able to adsorb under all the investigated conditions. The possibility to modulate the adsorption features by simply changing the pH conditions was successfully employed to develop an efficient protocol for the removal and separation of the different components from aqueous solutions mimicking wastewaters.

Iron-montmorillonite clays as active sorbents for the decontamination of hazardous chemical warfare agents

Montmorillonite clay was modified to introduce iron species and acid sites in the interlayer space, aiming to obtain a catalyst with oxidising and acid properties for the degradation of chemical warfare agents.

Determining the Mechanism and Efficiency of Industrial Dye Adsorption through Facile Structural Control of Organo-montmorillonite Adsorbents

The structural evolution of cost-effective organo-clays (montmorillonite modified with different loadings of CTAB (cetyltrimethylammonium bromide)) is investigated and linked to the adsorption uptake and mechanism of an important industrial dye (hydrolyzed Remazol Black B). Key organo-clay characteristics, such as the intergallery spacing and the average number of well-stacked layers per clay stack, are determined by low-angle X-ray diffraction, while differential thermogravimetric analysis is used to differentiate between surface-bound and intercalated CTAB. Insights into the dye adsorption mechanism are gained through the study of the adsorption kinetics and through the characterization of the organo-clay structure and surface charge after dye adsorption. It is shown that efficient adsorption of anionic industrial dyes is driven by three key parameters: (i) sufficiently large intergallery spacing to enable accommodation of the relatively large dye molecules, (ii) crystalline disorder in the stacking direction of the clay platelets to facilitate dye access, (iii) and positive surface charge to promote interaction with the anionic dyes. Specifically, it is shown that, at low modifier loadings (0.5 cation exchange capacity (0.5CEC)), CTAB molecules exclusively intercalate as a monolayer into the clay intergallery spaces, while, with increasing modifier loadings, the CTAB molecules adopt a bilayer arrangement and adsorb onto the exterior clay surface. Bilayer intercalation results in sufficiently large expansion of the intergallery spaces and significant disordering along the (001) stacking direction to enable high and relatively fast dye uptake via intraparticle diffusion. Poor and slow dye uptake is observed for the organo-clays with a monolayer structure, suggesting relatively inefficient dye adsorption at the clay edges. The optimized bilayer organo-clays (montmorillonite modified with 3CEC of CTAB) also show enhanced adsorption efficiencies for other important industrial dyes, highlighting the importance of structural control in organo-clays while also showing the adsorbents' great potential for use in industry where dye mixtures are encountered.

Effects of Modifier Type on Properties of in Situ Organo-Montmorillonite Modified Wood Flour/Poly(lactic acid) Composites

Wood flour (WF) was modified with sodium-montmorillonite (Na-MMT) and two types of surfactant modifiers, namely, didecyl dimethylammonium chloride (DDAC) and sodium dodecyl sulfonate (SDS) though a two-step process inside WF. The thus-modified WFs were characterized, and the effects of MMT type on physical, mechanical, and thermal properties of their composites with poly(lactic acid) (PLA) were investigated. The results showed: (1) either DDAC or SDS could modified Na-MMT into OMMT, and then uniformly distributed in WF cell walls; (2) OMMT improved the physical properties, most mechanical properties, and thermal properties of the composites except for the impact strength; and (3) compared with SDS, DDAC seemed to perform better in properties of composites. However, DDAC showed some negative effect on the early stage of composite thermal decomposition.

Transforming inorganic layered montmorillonite into inorganic–organic hybrid materials for various applications: a brief overview

The effects of various reaction parameters on the synthesis of silylated montmorillonites and several applications of these inorganic–organic layered materials are briefly overviewed in this review.

Characterization and properties of organo-montmorillonite modified lignocellulosic fibers and their interaction mechanisms

In this study, cellulose fiber/flour (CF) and lignin flour (LF) separated from poplar wood flour (WF) as well as xylan as a representative of hemicellulose flour (HF), were modified with organo-montmorillonite (OMMT) through a two-step method.

Montmorillonite nanodevices for the colon metronidazole delivery

The adsorption profiles of the antibiotic metronidazole (MNE) into the K10-montmorillonite (MMT-K10) clay and the subsequent release have been investigated as a function of pH and MNE/MMT-K10 ratio, in order to evaluate the potential of the MNE/MMT-K10 hybrids as controlled drug delivery system. The adsorption mechanism has been first elucidated by performing complementary equilibrium and kinetic studies and through the X-ray diffractometry (XRD) characterization of the obtained composite materials. The gathered results allowed us to propose a mechanism consisting of a multi-step pathway involving the neutral and the cationic form of the drug, which interact with different sites of the clay surfaces, i.e. the interlayer region and the faces of the lamella. In a second step the drug release kinetics has been studied under physiological pH mimicking conditions simulating the oral drug administration and delivery. For the sake of comparison the commercial formulation has also been employed for the release studies. The investigation of the release profiles and the comparison with the commercial formulation of the drug reveal that the new-tailor made formulation could be fruitful exploited for successfully prolonged the action of drug in the desired site.

Alkylaminopyridine-modified aluminum aminoterephthalate metal-organic frameworks as components of reactive self-detoxifying materials

Aluminum aminoterephthalate MOF particulate materials (NH(2)-MIL-101(Al) and NH(2)-MIL-53(Al)), studied here as components of self-detoxifying surfaces, retained their reactivity following their covalent attachment to protective surfaces utilizing a newly developed strategy in which the MOF particles were deposited on a reactive adhesive composed of polyisobutylene/toluene diisocyanate (PIB/TDI) blends. Following MOF attachment and curing, the MOF primary amino groups were functionalized with highly nucleophilic 4-methylaminopyridine (4-MAP) by disuccinimidyl suberate-activated conjugation. The resulting MOF-4-MAP modified PIB/TDI elastomeric films were mechanically flexible and capable of degrading diisopropyl fluorophosphate (DFP), a chemical threat simulant.