Removal of arsenic and methylene blue from water by granular activated carbon media impregnated with zirconium dioxide nanoparticles.

This study investigated the effects of in situ ZrO(2) nanoparticle formation on properties of granulated activated carbon (GAC) and their impacts on arsenic and organic co-contaminant removal. Bituminous and lignite based zirconium dioxide impregnated GAC (Zr-GAC) media were fabricated by hydrolysis of zirconium salt followed by annealing of the product at 400 °C in an inert environment. Media characterization suggested that GAC type does not affect the crystalline structure of the resulting ZrO(2) nanoparticles, but does affect zirconium content of the media, nanoparticle morphology, nanoparticle distribution, and surface area of Zr-GAC. The arsenic removal performance of both media was compared using 5mM NaHCO(3) buffered ultrapure water and model groundwater containing competing ions, both with an initial arsenic C(0) ≈ 120 µg/L. Experimental outcomes suggested favorable adsorption energies and higher or similar adsorption capacities than commercially available or experimental adsorbents when compared on the basis of metal content. Short bed adsorber column tests showed that arsenic adsorption capacity decreases as a result of kinetics of competing ions. Correlation between the properties of the media and arsenic and methylene blue removal suggested that surface area and GAC type may be the dominant factors controlling the arsenic and organic co-contaminant removal performance of the fabricated Zr-GAC media.

The effect of carbon type on arsenic and trichloroethylene removal capabilities of iron (hydr)oxide nanoparticle-impregnated granulated activated carbons.

This study investigates the impact of the type of virgin granular activated carbon (GAC) media used to synthesize iron (hydr)oxide nanoparticle-impregnated granular activated carbon (Fe-GAC) on its properties and its ability to remove arsenate and organic trichloroethylene (TCE) from water. Two Fe-GAC media were synthesized via a permanganate/ferrous ion synthesis method using bituminous and lignite-based virgin GAC. Data obtained from an array of characterization techniques (pore size distribution, surface charge, etc.) in correlation with batch equilibrium tests, and continuous flow modeling suggested that GAC type and pore size distribution control the iron (nanoparticle) contents, Fe-GAC synthesis mechanisms, and contaminant removal performances. Pore surface diffusion model calculations predicted that lignite Fe-GAC could remove ∼6.3 L g(-1) dry media and ∼4 L g(-1) dry media of water contaminated with 30 µg L(-1) TCE and arsenic, respectively. In contrast, the bituminous Fe-GAC could remove only ∼0.2 L/g dry media for TCE and ∼2.8 L/g dry media for As of the same contaminated water. The results show that arsenic removal capability is increased while TCE removal is decreased as a result of Fe nanoparticle impregnation. This tradeoff is related to several factors, of which changes in surface properties and pore size distributions appeared to be the most dominant.

Rural suicide--people or place effects?

OBJECTIVE: To examine factors that may contribute to elevated rates of suicide among rural communities in Australia. METHOD: A wide-ranging literature search reviewed possible factors that may contribute to the geographical variation in suicide. Literature was organized to enable examination of compositional and contextual explanations, as well as collective social functioning and social practices. RESULTS: A variety of factors may contribute to elevated rates of suicide in rural compared with urban areas. Collective and contextual (place) factors seem to be of particular importance as possible contributors to the elevated rate of suicide among rural males. These include rural socioeconomic decline; facilitators and barriers to service utilization such as service availability and accessibility, rural culture, community attitudes to mental illness and help seeking; and exposure to firearms. CONCLUSIONS: Compositional, contextual and collective factors are hypothesized to influence the elevated rate of suicide in rural compared with urban areas. These factors need to be tested in empirical studies that consider both individual and community-based risk factors, and are designed to enable exploration of likely within-rural differences.