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In this work, a fast and low-cost method for the highly selective determination of ultratrace Hg(II) ions by total-reflection X-ray fluorescence spectrometry (TXRF) is presented. The procedure is based on dispersive micro-solid phase extraction (DMSPE) using thiosemicarbazide-functionalized carbon nanotubes (CNT-TSC). The experiment shows that Hg(II) ions are affectively adsorbed on CNT-TSC at pH 2 within 10 min using an extremely low adsorbent dosage of 1 μg mL−1. Moreover, CNT-TSC is characterized by excellent selectivity toward Hg(II) ions, which can be quantitatively adsorbed from the solution of very high ionic strength (5 mol L−1) and in the presence of the coexisting ions at extremely high concentrations (100 000-fold excess). After the preconcentration/separation step, the suspension of CNT-TSC with adsorbed Hg(II) ions is pipetted onto a quartz reflector and dried. This article shows that the procedure allows overcoming the problems with the volatilization losses of mercury and eliminating the matrix effects in high salinity water. The quantitative DMSPE/TXRF analysis can be performed using the classical calibration curve and simplified approach using only an internal standard. The method is characterized by a very low detection limit of 2.6 pg mL−1 and uses minimal amounts of chemical reagents and a low-power TXRF instrument. The method was applied to analyze water samples, including seawater, and biological samples: lobster hepatopancreas, herring, cormorant, and cod tissues. The excellent selectivity and high adsorption capacity of CNT-TSC toward Hg(II) ions (188 mg g−1) also open the path for the effective removal of Hg(II) ions from aqueous solutions. [ABSTRACT FROM AUTHOR]

Graphene oxide decorated with cerium(IV) oxide (GO/ CeO2) was synthesized and applied in adsorption of several metal ions such as As(III), As(V), Se(IV), Cu(II), and Pb(II) from aqueous samples. The important feature of GO/CeO2 nanocomposite is also its selectivity toward selenite in the presence of selenate. The structure of GO/CeO2 has been proven by microscopic and spectroscopic techniques. The maximum adsorption capacities of GO/CeO2 calculated by Langmuir model toward arsenic, selenium, copper, and lead ions are between 6 and 30 mg g-1. An interesting feature of this adsorbent is its excellent dispersibility in water. Thus, GO/CeO2 nanocomposite is ideal for fast and simple determination of heavy metal ions using dispersive microsolid phase extraction (DMSPE). Moreover, coupling DMSPE with energy-dispersive X-ray fluorescence spectrometry (EDXRF) is extremely beneficial because it allows direct analysis of adsorbent. Thus, the analyte elution step, as needed in many analytical techniques, was obviated. The influence of sample volume and the sorption time as well as the influence of foreign ions and humic acid on the recovery of determined elements are discussed in the paper. The results showed that developed methodology provided low limits of detection (0.07- 0.17 μg/L) and good precision (RSD < 4%). The GO/CeO2 nanocomposite was applied to analysis of real water samples and certified reference materials (CRM) groundwater (BCR-610) and pig kidney (ERM-BB186). [ABSTRACT FROM AUTHOR]

In this study, we investigated different metal pairings of Au nanoparticles (NPs) as potential catalysts for glycerol dehydration for the first time. All of the systems preferred the formation of hydroxyacetone (HYNE). Although the bimetallics that were tested, i.e., Au NPs supported on Ni, Fe and Cu appeared to be more active than the Au/SiO2 system, only Cu supported Au NPs gave high conversion (ca. 63%) and selectivity (ca. 70%) to HYNE. [ABSTRACT FROM AUTHOR]

In this paper we report a new nanometallic, self-activating catalyst, namely, Ni-supported Pd nanoparticles (PdNPs/Ni) for low temperature ammonia cracking, which was prepared using a novel approach involving the transfer of nanoparticles from the intermediate carrier, i.e. nano-spherical SiO2, to the target carrier technical grade Ni (t-Ni) or high purity Ni (p-Ni) grains. The method that was developed allows a uniform nanoparticle size distribution (4,4±0.8 nm) to be obtained. Unexpectedly, the t-Ni-supported Pd NPs, which seemed to have a surface Ca impurity, appeared to be more active than the Ca-free (p-Ni) system. A comparison of the novel PdNPs/Ni catalyst with these reported in the literature clearly indicates the much better hydrogen productivity of the new system, which seems to be a highly efficient, flexible and durable catalyst for gas-phase heterogeneous ammonia cracking in which the TOF reaches a value of 2615 mmolH2/gPd min (10,570 molNH3/molPd(NP) h) at 600°C under a flow of 12 dm3/h (t-Ni). [ABSTRACT FROM AUTHOR]

Energy consumption steadily increases and energy production is associated with many environmental risks, e.g., generating the largest share of greenhouse gas emissions. The primary gas pollution concern is CO2, CH4, and nitrogen oxides (NOx). Environmental catalysis plays a pivotal role in NOx mitigation (DeNOx). This study investigated, for the first time, a collection of ceramic foams as potential catalyst support for selective catalytic NOx reduction (SCR). Ceramic foams could be an attractive support option for NOx removal. However, we should functionalize the surface of raw foams for such applications. A library of ceramic SiC, Al2O3, and ZrO2 foams ornamented with nanorod ZnO and TiO2 as W and V oxide support was obtained for the first time. We characterized the surface layer coating structure using the XPS, XRF and SEM, and TEM microscopy to optimize the W to V molar ratio and examine NO2 mitigation as the SCR model, which was tested only very rarely. Comparing TiO2 and ZnO systems reveals that the SCR conversion on ZnO appeared superior vs. the conversion on TiO2, while the SiC-supported catalysts were less efficient than Al2O3 and ZrO2-supported catalysts. The energy bands in optical spectra correlate with the observed activity rank. [ABSTRACT FROM AUTHOR]