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.

Environmental Potential of Carbonized MOF-5/PANI Composites for Pesticide, Dye, and Metal Cations-Can They Actually Retain Them All?

The environmental application of the carbonized composites of the Zn-containing metal-organic framework MOF-5 and polyaniline (PANI) in its emeraldine salt and base forms (C-(MOF-5/PANI)) was investigated for the first time. Textural properties and particle size distributions revealed that composites are dominantly mesoporous and nanoscale in nature, while Raman spectroscopy revealed the ZnO phase beneath the carbon matrix. Adsorption of pesticide, dye, and metal cation on C-(MOF-5/PANI) composites in aqueous solutions was evaluated and compared with the behavior of the precursor components, carbonized MOF-5 (cMOF), and carbonized PANIs. A lower MOF-5 content in the precursor, a higher specific surface area, and the pore volume of the composites led to improved adsorption performance for acetamiprid (124 mg/g) and Methylene Blue (135 mg/g). The presence of O/N functional groups in composites is essential for the adsorption of nitrogen-rich pollutants through hydrogen bonding with an estimated monolayer capacity twice as high as that of cMOF. The proton exchange accompanying Cd2+ retention was associated with the Zn/Cd ion exchange, and the highest capacity (9.8 mg/g) was observed for the composite synthesized from the precursor with a high MOF-5 content. The multifunctionality of composites was evidenced in mixtures of pollutants where noticeably better performance for Cd2+ removal was found for the composite compared to cMOF. Competitive binding between three pollutants favored the adsorption of pesticide and dye, thereby hindering to some extent the ion exchange necessary for the removal of metal cations. The results emphasize the importance of the PANI form and MOF-5/PANI weight ratio in precursors for the development of surface, porosity, and active sites in C-(MOF-5/PANI) composites, thus guiding their environmental efficiency. The study also demonstrated that C-(MOF-5/PANI) composites retained studied pollutants much better than carbonized precursor PANIs and showed comparable or better adsorption ability than cMOF.

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.

Carbonization of MOF-5/Polyaniline Composites to N,O-Doped Carbon/ZnO/ZnS and N,O-Doped Carbon/ZnO Composites with High Specific Capacitance, Specific Surface Area and Electrical Conductivity.

Composites of carbons with metal oxides and metal sulfides have attracted a lot of interest as materials for energy conversion and storage applications. Herein, we report on novel N,O-doped carbon/ZnO/ZnS and N,O-doped carbon/ZnO composites (generally named C-(MOF-5/PANI)), synthesized by the carbonization of metal-organic framework MOF-5/polyaniline (PANI) composites. The produced C-(MOF-5/PANI)s are comprehensively characterized in terms of composition, molecular and crystalline structure, morphology, electrical conductivity, surface area, and electrochemical behavior. The composition and properties of C-(MOF-5/PANI) composites are dictated by the composition of MOF-5/PANI precursors and the form of PANI (conducting emeraldine salt (ES) or nonconducting emeraldine base). The ZnS phase is formed only with the PANI-ES form due to S-containing counter-ions. XRPD revealed that ZnO and ZnS existed as pure wurtzite crystalline phases. PANI and MOF-5 acted synergistically to produce C-(MOF-5/PANI)s with high SBET (up to 609 m2 g-1), electrical conductivity (up to 0.24 S cm-1), and specific capacitance, Cspec, (up to 238.2 F g-1 at 10 mV s-1). Values of Cspec commensurated with N content in C-(MOF-5/PANI) composites (1-10 wt.%) and overcame Cspec of carbonized individual components PANI and MOF-5. By acid etching treatment of C-(MOF-5/PANI), SBET and Cspec increased to 1148 m2 g-1 and 341 F g-1, respectively. The developed composites represent promising electrode materials for supercapacitors.

Natural Cyanobacteria Removers Obtained from Bio-Waste Date-Palm Leaf Stalks and Black Alder Cone-Like Flowers.

The impact of urbanization and modern agricultural practice has led to accelerated eutrophication of aquatic ecosystems, which has resulted in the massive development of cyanobacteria. Very often, in response to various environmental influences, cyanobacteria produce potentially carcinogenic cyanotoxins. Long-term human exposure to cyanotoxins, through drinking water as well as recreational water (i.e., rivers or lakes), can cause serious health consequences. In order to overcome this problem, this paper presents the synthesis of completely new activated carbons and their potential application in contaminated water treatment. The synthesis and characterization of new active carbon materials obtained from waste biomass, date-palm leaf stalks (P_AC) and black alder cone-like flowers (A_AC) of reliable physical and chemical characteristics were presented in this article. The commercial activated carbon (C_AC) was also examined for the purpose of comparisons with the obtained materials. The detailed characterization of materials was carried out by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), low-temperature N2 physisorption, and Field emission scanning electron microscopy (FESEM). Preliminary analyzes of the adsorption capacities of all activated carbon materials were conducted on water samples from Aleksandrovac Lake (Southern part of Serbia), as a eutrophic lake, in order to remove Cyanobacteria from water. The results after 24 h showed removal efficiencies for P_AC, A_AC, and C_AC of 99.99%, 99.99% and 89.79%, respectively.

Size-strain line-broadening analysis of anatase/brookite (TiO2)-based nanocomposites with carbon (C): XRPD and Raman spectroscopic analysis.

A size-strain line-broadening analysis of the XRPD patterns and Raman spectra for two anatase/brookite (TiO2)-based nanocomposites with carbon (C) was carried out and the results compared with those of a similar sample free of carbon. The crystal structures and microstructures of anatase and brookite, as well as their relative abundance ratio, have been refined from XRPD data by the Rietveld method (the low amount of carbon is neglected). The XRPD size-strain analysis resulted in reliable structure and microstructure results for both anatase and brookite. The experimental Raman spectra of all the samples in the region 100-200 cm-1 are dominated by a strong feature primarily composed of the most intense modes of anatase (Eg) and brookite (A1g). The anatase crystallite sizes of 14-17 nm, estimated by XRPD, suggest the application of the phonon confinement model (PCM) for the analysis of the anatase Eg mode, whereas the relatively large brookite crystallite size (27-29 nm) does not imply the use of the PCM for the brookite A1g mode. Superposition of the anatase Eg mode profile, calculated by the PCM, and the Lorentzian shape of the brookite A1g mode provide an appropriate simulation of the change in the dominant Raman feature in the spectra of TiO2-based nanocomposites with carbon. Raman spectra measured in the high-frequency range (1000-2000 cm-1) provide information on carbon in the investigated nanocomposite materials. The results from field-emission scanning electron microscope (SEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and nitrogen physisorption measurements support the XRPD and Raman results.

Removal of methyl orange using combined ZnO/Fe2O3/ZnO-Zn composite coated to the aluminium foil in the presence of simulated solar radiation.

In this paper, the optimal preparative conditions (current density, deposition temperature, calcination temperature) for the original electrochemical synthesis of ZnO-Zn coating on aluminum foil support (ZnAF) were examined and determined the application for the removal of methyl orange (MO). Optimal application conditions for removing MO (volume and concentration of a treated solution) were also determined. In the following, four immobilized ZnO/Fe2O3 photocatalysts with different molar ratios of Zn to Fe (0.42, 0.84, 1.68, and 3.36) were synthesized via the chemical precipitation method on optimized electrochemically synthesized ZnAF support. Characterization studies of synthesized materials included SEM-EDS and Raman scattering analyses. The efficiency of these catalysts for MO removal in the presence/absence of simulated solar radiation (SSR) was investigated. The adsorption isotherms were investigated, and the results show that the adsorption data were best fitted with the Freundlich adsorption isotherm model. Assessment of the thermodynamic parameters showed that although the adsorption process was weakly endothermic over the range of temperatures studied, the relatively high entropy change gave an overall negative change in Gibbs free energy making the processes spontaneous. In the presence of SSR, the optimal molar ratio of Zn to Fe was determined to be 1.68. The possibility of potential reusing the catalyst was examined six times in a row. The possibility for multiple uses of suspension, which is used for immobilization, was also examined. It was also determined that the application of the 1.68Zn/Fe/ZnAF/H2O2/SSR system after the dye removal generates hydrogen at a rate of 186.5 µmol g-1 after 6 h. Furthermore, in the presence of SSR and using a suspended form of catalyst, the removal efficiency was 1.6 times higher than the efficiency achieved with immobilized ZnO/Fe2O3 catalyst. Using the HPLC method for 1.68Zn/Fe/ZnAF/SSR system, five primary intermediates were found to be formed. The applicability of ZnO/Fe2O3/ZnAF for removal of other dyes was also examined.

Electrospun Nickel Manganite (NiMn2O4) Nanocrystalline Fibers for Humidity and Temperature Sensing.

Nickel manganite nanocrystalline fibers were obtained by electrospinning and subsequent calcination at 400 °C. As-spun fibers were characterized by TG/DTA, Scanning Electron Microscopy and FT-IR spectroscopy analysis. X-ray diffraction and FT-IR spectroscopy analysis confirmed the formation of nickel manganite with a cubic spinel structure, while N2 physisorption at 77 K enabled determination of the BET specific surface area as 25.3 m2/g and (BJH) mesopore volume as 21.5 m2/g. The material constant (B) of the nanocrystalline nickel manganite fibers applied by drop-casting on test interdigitated electrodes on alumina substrate, dried at room temperature, was determined as 4379 K in the 20-50 °C temperature range and a temperature sensitivity of -4.95%/K at room temperature (25 °C). The change of impedance with relative humidity was monitored at 25 and 50 °C for a relative humidity (RH) change of 40 to 90% in the 42 Hzπ1 MHz frequency range. At 100 Hz and 25 °C, the sensitivity of 327.36 ± 80.12 kΩ/%RH was determined, showing that nickel manganite obtained by electrospinning has potential as a multifunctional material for combined humidity and temperature sensing.

Influence of selective acid-etching on functionality of halloysite-chitosan nanocontainers for sustained drug release.

The functionality of halloysite (Hal) nanotubes as drug carriers can be improved by lumen enlargement and polymer modification. This study investigates the influence of selective acid etching on Hal functionalization with cationic biopolymer chitosan. Hal was subjected to lumen etching under mild conditions, loaded under vacuum with nonsteroidal antiinflammatory drug aceclofenac, and incubated in an acidic solution of chitosan. The functionality of pristine and etched Hal before and upon polymer functionalization was assessed by ζ-potential measurements, structural characterization (FT-IR, DSC and XRPD analysis), cell viability assay, drug loading and drug release studies. Acid etching increased specific surface area, pore volume and pore size of Hal, decreased ζ-potential and facilitated binding of the cationic polymer. XRPD and DSC analysis revealed crystalline structure of etched Hal. Successful chitosan binding and drug entrapment were further confirmed by FT-IR and DSC studies. XRPD showed surface polymer binding. DSC and FT-IR analyses confirmed the presence of the entrapped drug in its crystalline form. Drug loading was increased for ≈81% by selective lumen etching. Slight decrease of drug content occurred during chitosan functionalization due to aceclofenac diffusion in the polymer solution. The drug release was more sustained from etched Hal nanocomposites (up to ≈87% for 12 h) than from pristine Hal (up to ≈97% for 12 h) due to more intensive chitosan binding. High human fibroblast survival rates upon exposure to pristine and etched Hal before and after chitosan functionalization (>90% in the concentration of 1000 µg/mL) confirmed that both lumen etching under mild conditions and polymer functionalization had no significant effect on cytocompatibility. Based on these findings, selective lumen etching in combination with polycation modification appears to be a promising approach for improvement of Hal nanotubes functionality by increasing payload, polymer binding capacity, and sustained release properties with no significant effect on their cytocompatibility.

Improved Water-Gas Shift Performance of Au/NiAl LDHs Nanostructured Catalysts via CeO2 Addition.

Supported gold on co-precipitated nanosized NiAl layered double hydroxides (LDHs) was studied as an effective catalyst for medium-temperature water-gas shift (WGS) reaction, an industrial catalytic process traditionally applied for the reduction in the amount of CO in the synthesis gas and production of pure hydrogen. The motivation of the present study was to improve the performance of the Au/NiAl catalyst via modification by CeO2. An innovative approach for the direct deposition of ceria (1, 3 or 5 wt.%) on NiAl-LDH, based on the precipitation of Ce3+ ions with 1M NaOH, was developed. The proposed method allows us to obtain the CeO2 phase and to preserve the NiAl layered structure by avoiding the calcination treatment. The synthesis of Au-containing samples was performed through the deposition-precipitation method. The as-prepared and WGS-tested samples were characterized by X-ray powder diffraction, N2-physisorption and X-ray photoelectron spectroscopy in order to clarify the effects of Au and CeO2 loading on the structure, phase composition, textural and electronic properties and activity of the catalysts. The reduction behavior of the studied samples was evaluated by temperature-programmed reduction. The WGS performance of Au/NiAl catalysts was significantly affected by the addition of CeO2. A favorable role of ceria was revealed by comparison of CO conversion degree at 220 °C reached by 3 wt.% CeO2-modified and ceria-free Au/NiAl samples (98.8 and 83.4%, respectively). It can be stated that tuning the properties of Au/NiAl LDH via CeO2 addition offers catalysts with possibilities for practical application owing to innovative synthesis and improved WGS performance.

Synthesis and antibacterial activity of iron manganite (FeMnO3) particles against the environmental bacterium Bacillus subtilis.

Nanocrystalline iron manganite powder was synthesized using the sol-gel combustion process, with glycine as fuel. It was further calcined at 900 °C for 8 h, resulting in the formation of a loose cubic FeMnO3 powder with a small specific surface area, net-like structure and plate-like particles as confirmed by XRD, N2 physisorption, FESEM and TEM analyses. The metal ion release was studied by ICP-OES and showed that less than 10 ppb of Fe or Mn ions were released by leaching in water, but 0.36 ppm Fe and 3.69 ppm Mn was found in LB (Luria-Bertani) bacterial medium. The generation of reactive oxygen species (ROS) was monitored in distilled water and bacterial medium and showed that FeMnO3 particles do not generate O2˙- ions with or without UV irradiation, but synthesize H2O2 and show an antioxidative effect. Besides the higher stability of FeMnO3 particles in aqueous solution they showed an inhibitory effect on Bacillus subtilis growth in LB medium even at low concentrations (0.01 mg ml-1), but not in BHI medium even at 1 mg ml-1. This study points out that the mechanism of antibacterial action of engineered metal oxides needs continued investigation and specific experimental controls.

Inorganically modified diatomite as a potential prolonged-release drug carrier.

Inorganic modification of diatomite was performed with the precipitation product of partially neutralized aluminum sulfate solution at three different mass ratios. The starting and the modified diatomites were characterized by SEM-EDS, FTIR, thermal analysis and zeta potential measurements and evaluated for drug loading capacity in adsorption batch experiments using diclofenac sodium (DS) as a model drug. In vitro drug release studies were performed in phosphate buffer pH6.8 from comprimates containing: the drug adsorbed onto the selected modified diatomite sample (DAMD), physical mixture of the drug with the selected modified diatomite sample (PMDMD) and physical mixture of the drug with the starting diatomite (PMDD). In vivo acute toxicity testing of the modified diatomite samples was performed on mice. High adsorbent loading of the selected modified diatomite sample (~250mg/g in 2h) enabled the preparation of comprimates containing adsorbed DS in the amount near to its therapeutic dose. Drug release studies demonstrated prolonged release of DS over a period of 8h from both DAMD comprimates (18% after 8h) and PMDMD comprimates (45% after 8h). The release kinetics for DAMD and PMDMD comprimates fitted well with Korsmeyer-Peppas and Bhaskar models, indicating that the release mechanism was a combination of non-Fickian diffusion and ion exchange process.

Study on fisetin-aluminium(III) interaction in aqueous buffered solutions by spectroscopy and molecular modeling.

Spectroscopic (UV/visible and IR) and theoretical studies were used to assess relevant interaction of fisetin, a tetrahydroxylated flavone molecule, and trivalent aluminium in a wide range of buffered aqueous solutions. The chelation sites, stoichiometry, stability and the dependence of the complexes structures on pH and aluminium/fisetin mole ratios were defined. Obtained results implicated successive formation of two complexes with aluminium(III)-fisetin stoichiometries of 1:1 and 2:1. Considering the fisetin molecular structure, results of vibrational analysis and theoretical calculations, it is possible to implicate 3-hydroxyl-4-carbonyl and 3'4'-dihydroxyl groups as those with the possible chelating power. The equilibrium geometries were optimized in vacuum at the B3LYP/6-31G(d) level of theory, which predict structural modifications between the ligand molecule in free state and in the complex structure. The theoretical model has been validated by both vibrational and electronic spectroscopies.