Double active BEA zeolite/silver tungstophosphates - Antimicrobial effects and pesticide removal

Acetamiprid's degradation products and mechanism: Part II - Inert atmosphere and charge storage

Reuse and/or recycling of spent adsorbents is taking a central role in modern thinking and catalyzed carbonization is the way forward. Herein we explore the carbonization of adsorbed acetamiprid, in an inert atmosphere, as a way of recycling and producing nitrogen-rich carbon material for potential use in supercapacitors. Added value material and the reuse of the adsorbent were achieved by carbonization at 700 °C under argon. The formation of a nitrogen-doped carbon layer as an active material on the adsorbent, bonded through a C-Si linkage, has been conclusively verified through elemental composition quantification using XPS and EDX measurements. Two-stage catalytic decomposition and condensation of the adsorbed pesticide is followed by TGA and TPD-MS. Attained carbon-based materials give stable Faradaic capacitance with a slight dependency on the number of adsorbing cycles. Capacitance calculated with respect to the adlayer carbon material reaches values as high as 610 F g-1. Galvanostatic Charge/Discharge measurement confirmed the stability of explored materials with a slight increase in capacitance over 1000 cycles. The presented results envisage electroactive materials preparation from environmental pollutants, adding value to spent adsorbents.

Strong H-bonding from Zeolite Bro̷nsted Acid Site to Water: Origin of the Broad IR Doublet

Hydrogen bonding between water molecules and zeolite Bro̷nsted acid sites (BAS) has received much attention due to the significant influence of water on the adsorption and catalytic properties of these widely used porous materials. When a single water molecule is adsorbed at the BAS, the zeolite O-H stretch vibration decreases in frequency and splits into two extraordinarily broad bands peaked near 2500 and 2900 cm-1 in the infrared (IR) spectrum. This broad doublet feature is the predominant IR signature used to identify and interpret water-BAS H-bonding at low hydration levels, but the origin of the band splitting is not well understood. In this study, we used broadband two-dimensional infrared (2D IR) spectroscopy to investigate zeolite HZSM-5 prepared with a single water molecule per BAS. We find that the 2D IR spectrum is not explained by the most common interpretation of Fermi resonance coupling between the stretch and the bend of the BAS OH group, which predicts intense excited-state transitions that are absent from the experimental results. We present an alternative model of a double-well proton stretch potential, where the band splitting is caused by excited-state tunneling through the proton-transfer barrier. This one-dimensional model reproduces the basic experimental pattern of transition frequencies and amplitudes, suggesting that the doublet bands may originate from a highly anharmonic potential in which the excited state proton wave functions are delocalized over the H-bond between zeolite BAS and adsorbed H2O. Additional details about molecular orientation and coordination of the adsorbed water molecule are also resolved in the 2D IR spectroscopy.

Spectral evidence of acetamiprid's thermal degradation products and mechanism

Herein we unequivocally identify the mechanism of zeolite-catalysed thermal degradation of pesticide, employing Fourier-transform infrared spectroscopy (FTIR), Raman and mass spectrometry following temperature decomposition (TPDe/MS). We demonstrate that Y zeolite can effectively adsorb a significant amount of acetamiprid both in a single trial (168 mg/g) and in 10 cycles (1249 mg/g) with intermittent thermal regeneration at 300 °C. Sectional vibrational analysis of acetamiprid two-stage thermal degradation is performed for pristine and supported pesticide. The acetamiprid Raman spectral changes appear at 200 °C, while partial carbonization occurs at 250 °C. The gradual disappearance of the FTIR bands of acetamiprid is seen up to 270 °C when two Raman signature bands for carbonised material emerged. The TPDe/MS profiles reveal the evolution of mass fragments - in the first step, cleavage of the CC bond occurs between the aromatic core of the molecule and its tail-end, followed by cleavage of the CN bond. The mechanism of adsorbed acetamiprid degradation follows the same step, at significantly lower temperatures, as the process is catalysed by the interaction of acetamiprid nitrogens and zeolite support. Reduced temperature degradation allows for a quick recovery process that leaves 65% efficacy after 10 cycles. After numerous cycles of recovery, a subsequent one-time heat treatment at 700 °C completely restores initial efficacy. The efficient adsorption, novel details on degradation mechanism and ease of regeneration procedure place the Y zeolite at the forefront of future all-encompassing environmental solutions.

An inclusive outlook on the fate and persistence of pesticides in the environment and integrated eco-technologies for their degradation

Intensive and inefficient exploitation of pesticides through modernized agricultural practices has caused severe pesticide contamination problems to the environment and become a crucial problem over a few decades. Due to their highly toxic and persistent properties, they affect and get accumulated in non-target organisms, including microbes, algae, invertebrates, plants as well as humans, and cause severe issues. Considering pesticide problems as a significant issue, researchers have investigated several approaches to rectify the pesticide contamination problems. Several analyses have provided an extensive discussion on pesticide degradation but using specific technology for specific pesticides. However, in the middle of this time, cleaner techniques are essential for reducing pesticide contamination problems safely and environmentally friendly. As per the research findings, no single research finding provides concrete discussion on cleaner tactics for the remediation of contaminated sites. Therefore, in this review paper, we have critically discussed cleaner options for dealing with pesticide contamination problems as well as their advantages and disadvantages have also been reviewed. As evident from the literature, microbial remediation, phytoremediation, composting, and photocatalytic degradation methods are efficient and sustainable and can be used for treatment at a large scale in engineered systems and in situ. However, more study on the bio-integrated system is required which may be more effective than existing technologies.

Mitigating toxicity of acetamiprid removal techniques - Fe modified zeolites in focus

All remediation pathways in aqueous solutions come down to three dominant ones - physical, chemical, and combinations thereof. Materials proposed for adsorption and oxidative degradation can induce positive or negative effects on cells compared to the pollutants themselves. Present research deals with the effects different methods for pesticide remediation have and how they impact cytotoxicity. With this particular intention, Fe-modified zeolites (obtained via citrate/oxalate complexes) of three zeotypes (MFI, BEA and FAU) were prepared and tested as adsorbents and Fenton catalysts for the removal of the acetamiprid pesticide. The materials are characterized by AFM, FTIR spectroscopy and ICP-OES. A different effect of the zeolite framework and modification route was found among the samples, which leads to pronounced adsorption (FAU), efficient Fenton degradation (MFI) or synergistic effect of both mechanisms (BEA). The cytotoxic effects of acetamiprid in the presence of zeolites, in pristine and modified forms, were tested on the MRC-5 human fibroblast cell line. A complete survey of the toxicity effect behind different pesticide removal methods is presented. Since neither adsorption nor catalytic degradation is the best option for pesticide removal, the focus is shifted to a combination of these methods, which proved to be optimal for pesticide toxicity reduction.

Environmental and Pharmacokinetic Aspects of Zeolite/Pharmaceuticals Systems—Two Facets of Adsorption Ability

Zeolites belong to aluminosilicate microporous solids, with strong and diverse catalytic activity, which makes them applicable in almost every kind of industrial process, particularly thanks to their eco-friendly profile. Another crucial characteristic of zeolites is their tremendous adsorption capability. Therefore, it is self-evident that the widespread use of zeolites is in environmental protection, based primarily on the adsorption capacity of substances potentially harmful to the environment, such as pharmaceuticals, pesticides, or other industry pollutants. On the other hand, zeolites are also recognized as drug delivery systems (DDS) carriers for numerous pharmacologically active agents. The enhanced bioactive ability of DDS zeolite as a drug carrying nanoplatform is confirmed, making this system more specific and efficient, compared to the drug itself. These two applications of zeolite, in fact, illustrate the importance of (ir)reversibility of the adsorption process. This review gives deep insight into the balance and dynamics that are established during that process, i.e., the interaction between zeolites and pharmaceuticals, helping scientists to expand their knowledge necessarily for a more effective application of the adsorption phenomenon of zeolites.

MFI, BEA and FAU zeolite scavenging role in neonicotinoids and radical species elimination

Ecotoxicity caused by neonicotinoid pesticides is largely due to oxidative stress on non-target species. Due to the fact that reactive radical species reach the environment, materials intended for pesticide removal should be applicable for the simultaneous removal of reactive radicals, as well. This work uses the spectroscopic, adsorptive and antioxidant responses from MFI, FAU and BEA zeolites as descriptors of their potential environmental importance. Different network structures and Si/Al ratios were correlated with excellent zeolite adsorption properties, as over 200 mg g^-1 of investigated neonicotinoids, acetamiprid and imidacloprid, was achieved in one cycle. Additionally, after two regeneration steps, over 450 mg g^-1 adsorbed pesticides were retained, in three adsorption cycles. Overall the best results were detected for the FAU zeotype in both tested applications, insecticide adsorption and radical-scavenging performance, with and without insecticides present. The proposed mechanism for adsorption relies on kinetic investigation, isotherm modelling and spectroscopic post-adsorption analysis and targets zeolite hydroxyl/siloxane groups as active sites for insecticide adsorption via hydrogen bonding. Neat, well-defined zeolite structures enable their prospective application in ecotoxic species removal.

Structural Characterization of Protonated Water Clusters Confined in HZSM-5 Zeolites

A molecular description of the structure and behavior of water confined in aluminosilicate zeolite pores is a crucial component for understanding zeolite acid chemistry under hydrous conditions. In this study, we use a combination of ultrafast two-dimensional infrared (2D IR) spectroscopy and ab initio molecular dynamics (AIMD) to study H₂O confined in the pores of highly hydrated zeolite HZSM-5 (∼13 and ∼6 equivalents of H₂O per Al atom). The 2D IR spectrum reveals correlations between the vibrations of both terminal and H-bonded O-H groups and the continuum absorption of the excess proton. These data are used to characterize the hydrogen-bonding network within the cluster by quantifying single-, double-, and non-hydrogen-bond donor water molecules. These results are found to be in good agreement with the statistics calculated from an AIMD simulation of an H⁺(H₂O)₈ cluster in HZSM-5. Furthermore, IR spectral assignments to local O-H environments are validated with DFT calculations on clusters drawn from AIMD simulations. The simulations reveal that the excess charge is detached from the zeolite and resides near the more highly coordinated water molecules in the cluster. When they are taken together, these results unambiguously assign the complex IR spectrum of highly hydrated HZSM-5, providing quantitative information on the molecular environments and hydrogen-bonding topology of protonated water clusters under extreme confinement.

Uptake and release characteristics of serotonin hydrochloride by natural Cuban zeolite containing clinoptilolite and mordenite

Serotonin (5-HT) plays an important role in human physiology. An excess of this native regulator within the human gut can be partially controlled by orally consuming zeolite. Therefore, this study focuses on the kinetics of the uptake and release of serotonin hydrochloride (5-HT-hc) by natural Cuban zeolite containing clinoptilolite and mordenite at different pH levels using UV–Vis spectroscopy. 5-HT-hc is stable under the following investigated experimental conditions: incubation temperature of 36 °C; and at a pH of 5, 7, and 9. Independent of the zeolite framework, the 5-HT-hc is adsorbed without changing its molecular structure. The uptake and release of 5-HT-hc were not correlated to the textural properties of these aluminosilicates. The investigated zeolites adsorbed 5-HT-hc at about 14 mg per gram zeolite with no large differences observed between different samples. Release studies of 5-HT-hc-loaded zeolite revealed that the 5-HT-hc is strongly bound to the zeolite, and independent of the pH value and zeolite framework only up to 12.7% was released into the water.

Removal of Pesticides from Waters by Adsorption: Comparison between Synthetic Zeolites and Mesoporous Silica Materials. A Review

Pesticides are pollutants found in wastewater due to increasing agricultural activities over the years. Inappropriate dosing of pesticides results in the dispersal of active ingredients in the environment. The complete removal of pesticides from wastewater is an immediate concern due to their high toxicity and mobility. At present, adsorption is one of the most widely used methods for pesticide removal, in which synthetic zeolites and mesoporous silica materials are extensively applied. This article presents a systematic and comparative review of the applications and comparison of these adsorbents, based on the data reported in the literature. The paper summarizes the information collected from various studies, including the type of adsorbents and pesticides used, experimental conditions, and results of each work. The studies analyzed were laboratory-based and show potential advantages for the treatment of pesticide-bearing waters using functionalized and unfunctionalized synthetic zeolites and mesoporous silica materials. As a whole, functionalized materials are reported to exhibit better removal performance for different pesticides than conventional materials. It is expected that the results of this review will help researchers to establish a powerful strategy for the abatement of pesticides in wastewater.

New frontiers and prospects of metal-organic frameworks for removal, determination, and sensing of pesticides

Pesticides have been widely used in agriculture to control, reduce, and kill insects. Humans are also being using pesticides to control insidious animals in daily life. By these practices, a huge volume of pesticides is introduced to the environment. Despite broad-spectrum applicability, pesticides also have hazardous effects on both humans and animals at high and low concentrations. Long-term exposure to pesticides can cause different diseases, like leukemia, lymphoma, and cancers of the brain, breasts, prostate, testis, and ovaries. Reproductive disorders from pesticides include birth defects, stillbirth, spontaneous abortion, sterility, and infertility. Therefore, the application of determination and treatment methods for pre-concentration and removal of these toxic materials from the environment appears a vital concern. To date, different materials and approaches have been employed for these purposes. Among these approaches, multifunctional metal-organic frameworks (MOFs)-assisted adsorption and determination processes have always been in the spotlight. These facts are due to exclusive properties of MOFs in terms of the crystallinity, large surface area, high chemical, and physical stability, and controllable structure as well as unique features of adsorption and determination process in terms of simple, easy, cheap, available method and ability to use in large and industrial scales. In the present work, we illustrate the exceptional features of MOFs as well as the possible mechanism for the adsorption of pesticides by MOFs. The use of these fantastic materials for pre-concentration and removal of pesticides are extensively explored. In addition, the performance of MOFs was compared with other adsorbents. Finally, the new frontiers and prospects of MOFs for the determination, sensing, and removal of pesticides are presented.

Facile synthesis, characterization, mechanism and enhanced visible-light photocatalytic activity of SiW12/α-Fe2O3 nanocomposites

The photocatalytic mechanism of the SiW12/α-Fe2O3 nanohybrid.

Modulation of cytotoxicity by consecutive adsorption of tannic acid and pesticides on surfactant functionalized zeolites

This study investigated the environmental application of FAU type zeolites modified with cationic surfactants (cetylpyridinium chloride, tetrapropylammonium chloride and benzalkonium chloride). Adsorbent characterization was conducted using Fourier-transform infrared and Raman spectroscopy, thermogravimetry and differential thermal analysis, atomic force microscopy and X-ray powder diffraction. The efficiency for tannic acid adsorption from aqueous solution on the surface of prepared composites is studied and the adsorption process was modelled with different isotherm equations. Surfactant modifications of zeolites led to improved adsorption properties compared to FAU zeolites alone. The proposed mechanism controlling the adsorption of tannic acid onto surfactant modified zeolites mainly relies on π-π and hydrophobic interactions. The investigated materials are promising adsorbents for tannic acid and similar phenolics and may be important for environmental and dietary aspects of polyphenol persistence and usage. Further on, functionalized zeolites were studied for insecticide acetamiprid removal, prior to and after tannic acid retention. Promising findings of insecticide co-adsorption with tannic acid led to cytotoxicity evaluation. The cytotoxicity modulation effect of zeolites and tannic acid on acetamiprid points to the essential role of both components in insecticide toxicity reduction.