Steven M. Kuznicki

Nanocomposites of graphene oxide, Ag nanoparticles, and magnetic ferrite nanoparticles for elemental mercury (Hg0) removal

Mercury emission from combustion flue gas causes considerable environmental challenges and serious adverse health threats, and elemental mercury (Hg0) is the most challenging chemical form for removal. In this work, four types of graphene oxide (GO) based composite adsorbents were successfully synthesized by depositing Ag nanoparticles (NPs) and/or magnetic ferrite NPs on GO sheets (denoted as GO, GO–Ag, MGO and MGO–Ag), characterized and applied for the removal of Hg0 for the first time. The presence of Ag NPs on GO greatly enhances the Hg0 removal capability of GO–Ag and MGO–Ag as compared to that of pure GO, which is mainly attributed to the amalgamation of Hg0 on Ag NPs. MGO–Ag shows the best Hg0 removal performance and thermal tolerance among the four types of adsorbents developed, which can effectively capture Hg0 up to 150–200 °C in a simulated flue gas environment and can be also effectively recycled and reused. Our results indicate that the graphene oxide based composites (i.e. MGO–Ag) have significant potential applications for mercury emission control in coal-fired power plants.

Natural clinoptilolite composite membranes on tubular stainless steel supports for water softening.

Disk membranes generated from high-purity natural clinoptilolite mineral rock have shown promising water desalination and de-oiling performance. In order to scale up production of these types of membranes for industrial wastewater treatment applications, a coating strategy was devised. A composite mixture of natural clinoptilolite from St. Cloud (Winston, NM, USA) and aluminum phosphate was deposited on the inner surface of porous stainless steel tubes by the slip casting technique. The commercial porous stainless steel tubes were pre-coated with a TiO2 layer of about 10 μm. Phase composition and morphology of the coating materials were investigated using X-ray diffraction and scanning electron microscopy. Water softening performance of the fabricated membranes was evaluated using Edmonton (Alberta, Canada) municipal tap water as feed source. Preliminary experimental results show a high water flux of 7.7 kg/(m(2) h) and 75% reduction of hardness and conductivity in a once-through membrane process at 95 °C and feed pressure of 780 kPa. These results show that natural zeolite coated, stainless steel tubular membranes have high potential for large-scale purification of oil sands steam-assisted gravity drainage water at high temperature and pressure requirements.

Separation of Argon and Oxygen by Adsorption on a Titanosilicate Molecular Sieve

Abstract A titanosilicate molecular sieve adsorbent, Ba-RPZ-3, was synthesized and tested for its use in the separation of O2+Ar mixtures at room temperature. A clean resolution of both gases was achieved in pulse chromatographic experiments using a standard column (0.25″ OD, 3.5 grams of adsorbent). In another experiment, using a column containing 30 grams of adsorbent and a continuous O2+Ar feed at 10 cm3/min, argon breakthrough was detected more than 5 minutes before the oxygen breakthrough, and the separation was sufficiently sensitive to achieve quantitative separation of mixtures with low argon content (5% Ar). Equilibrium adsorption isotherms and isosteric heats of adsorption for oxygen and argon were found to be almost identical at room temperature. The thermodynamic selectivity was found to be mildly in favor of oxygen (∼1.1–1.2). However, the adsorption of oxygen was observed to be much faster than argon, indicating that the separation of the O2+Ar mixtures was based on the sieving properties of the adsorbent and the difference in sizes of O2 molecules and Ar atoms. This indicates that a suitably-oriented oxygen is physically smaller than argon, despite the fact that many references assume that oxygen is larger than argon.

CHEMICAL UPGRADING OF SEDIMENTARY Na-CHABAZITE FROM BOWIE, ARIZONA

Natural zeolites may represent one of the greatest under-utilized resources of the mineral world. Even with their unique character and properties, issues of consistency, homogeneity and purity preclude them from many premium applications. We report a simple method to upgrade mineral sedimentary Na-chabazite from the well known Bowie, Arizona, deposit to near synthetic purity and consistency. During this alkaline-silicate digestion process, initially soft chabazite ore granules gain substantial mechanical strength. This may allow direct employment in adsorption and purification processes without the need for binding and forming. These granules manifest significantly improved adsorption properties, including enhanced water and CO2 adsorptivity.

THE SYNTHESIS OF A PLATY CHABAZITE ANALOG FROM DELAMINATED METAKAOLIN WITH THE ABILITY TO SURFACE TEMPLATE NANOSILVER PARTICULATES

Mineral chabazite has shown the unusual ability to surface template nanometal particles, especially Ag. A chabazite analog was synthesized from delaminated metakaolin. The chabazite formed retained the platy morphology of the base clay. This morphology is ideal for displaying surface-supported nanometal particles. The synthetic chabazite analog demonstrated the ability to form and support large concentrations of Ag nanoparticles, as observed in the related natural mineral. Due to greater Al content, the synthetic chabazite manifests significantly improved capacity for the formation of such Ag nanoparticles. As in the case of the mineral chabazite, surface Ag nanoparticles of high uniformity were observed in the range of 5–6 nm.

Chabazite-Clay Composite for Bitumen Upgrading

Abstract The Alberta oilsands resource is increasingly recognized as a strategic source for North American energy supply. We synthesized a novel chabazite-clay composite for improved oilsand bitumen upgrading by growing chabazite on kaolin under alkaline conditions. XRD, SEM, TEM, N 2 physical adsorption, and XPS surface elemental analysis confirmed that the chabazite-clay composite has a unique exterior surface, accessible to large hydrocarbon molecules, that could moderate bitumen upgrading reaction with high performance contaminant (sulfur, nitrogen, nickel, and vanadium) removal.

A clinoptilolite-PDMS mixed-matrix membrane for high temperature water softening.

A mixed-matrix membrane composed of polydimethylsiloxane (PDMS) as the continuous phase and clinoptilolite, a naturally occurring zeolite, as the active phase has been used to decrease the conductivity of water by more than 80% across the membrane. Testing was carried out using a cross-flow configuration at temperatures as high as 160 °C using a constant transmembrane pressure of 8 bar. The simple fabrication method for the membrane, the durability of the system under the test conditions, and a suitable flux rate make such membranes promising candidates for industrial wastewater treatment.