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This manuscript describes the application of a novel sorbent, sodium titanate nanotube (STN) on partitioning of various divalent cations. Seven divalent cations, from alkaline earth, transition and post-transition groups, were used to determine the capacity and selectivity of STN. At pH 3 ± 0.02 and 0.1M ionic strength, STN displayed high capacity for Pb and Cd (1.27 and 0.39 mmol/g, correspondingly). The affinity of divalent cations was in the order Pb ≫ Cd>Cu>Zn>Ca>Sr>Ni. For six of the tested cations, their sorption capacity can be linearly correlated to its hydrolysis constant and electronegativity. STN has unusually low affinity for Ni and correlations of sorption capacity of Ni falls outside the 95% confidence intervals. Furthermore, it exhibited sorption behavior similar to alkaline earth cations, significant uptakes occurred only when pH>point of zero charge. In competitive sorption tests, STN preferentially sorb Cd over other metals (Zn, Ni, Ca and Sr) which coexist in industrial wastewater. As such STN is a potential novel sorbent useful for partitioning Cd from other metals in industrial wastewater., (Copyright © 2011 Elsevier B.V. All rights reserved.)

In this manuscript, titanate (Na(2)Ti(3)O(7)) nanotubes synthesized from alkali hydrothermal route, with high BET surface area (206 m(2)/g), were used as an effective sorbent to remove cadmium ions from water. Sorption capacity (q(m,Langmuir) = 1.1 mmol/g at pH 7) was higher than other sorbents. X-ray photoelectron spectroscopy (XPS) analyses performed on fresh and cadmium-sorbed samples reveal intensities of Na 1s peak decreased after sorption indicating ion-exchanging between cadmium and sodium ions occurred at interlayer of nanotubes. However kinetic study did not show a stoichiometrically equivalent amount of Na(+) being released suggesting Cd uptake was not due solely to ion-exchange mechanism. Batch tests also showed that cadmium uptake was not significantly affected by variation in ionic strength, signifying cadmium ions form an inner-sphere complexation with surface hydroxyl groups. Finally, surface complexation modeling was performed based on charge distribution multisite ion complexation (CDMUSIC) model. It was found that CDMUSIC was able to fit the experimental data best when inner-sphere complexation and ion-exchange were applied together., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The study reported herein indicated the stabilization mechanisms at work when copper-laden sludge is thermally treated with gamma-alumina and kaolinite precursors, and evaluated the prolonged leachability of their product phases. Four copper-containing phases - copper oxide (CuO), cuprous oxide (Cu(2)O), copper aluminate spinel (CuAl(2)O(4)), and cuprous aluminate delafossite (CuAlO(2)) - were found in the thermal reactions of the investigated systems. These phases were independently synthesized for leaching by 0.1M HCl aqueous solution, and the relative leachabilities were found to be CuAl(2)O(4)

Information on the fraction of total hand surface area touching a contaminated object is necessary in accurately estimating contaminant (e.g., pesticides, pathogens) loadings onto the hands during hand-to-object contacts. While several existing physical-stochastic human exposure models require such surface area data to estimate dermal and non-dietary ingestion exposure, there are very limited data sets. This paper provides statistical distributions of fractional surface areas (FSAs) for children's outdoor hand contacts. These distributions were constructed by combining information collected from two distinct studies exploring children's activity patterns and quantifying hand contact surface area. Results show that for outdoor contacts with "All Objects", a range of 0.13-0.27 captured median FSAs, while a range of 0.12-0.24 captured time-weighted FSAs. Overall, an FSA of 0.31 captured 80-100% of FSAs involved in each child's outdoor hand contacts, depending upon the object of interest. These values are much lower than the often conservative assumptions of up to 1 (i.e., the entire hand) that researchers currently make regarding FSAs involved in indoor and outdoor contacts [USEPA, 1997. Standard operating procedures (SOPs) for residential exposure assessments. Contract no. 68-W6-0030. http://www.epa.gov/pesticides/trac/science/trac6a05.pdf].

This study was conducted to describe exposure prone behaviors of infants and toddlers in the farmworker community. Analysis of hand and mouth contact frequencies and durations aids understanding of how children interact with their environment and are exposed via contact with surfaces. All 23 participating children (8 female infants, 5 male infants, 5 female toddlers and 5 male toddlers) lived with at least one farmworker. Children were videotaped at home for 2-6 h. Video footage was translated into micro-level activity time series (MLATS) for both hands and the mouth. MLATS were processed to calculate hourly duration in microenvironments, contact frequency, hourly contact duration and median contact duration. The median hourly duration spent indoors was 53 min/h. The median hand-to-mouth frequency was 15.2 events/h and the median object-to-mouth frequency was 27.2 events/h. The hourly mouthing duration was 1.2 and 2.2 min/h with the hands and objects, respectively. The median mouthing duration with hands and objects was 2 s. The median contact frequency for both hands combined was 689.4 events/h with an hourly contact duration of 100.5 min/h and a median contact duration of 3s. Infants had higher mouthing frequencies with non-dietary objects while toddlers had higher mouthing frequencies with objects associated with pica (i.e., paper). Boys had higher contact frequencies while girls had longer contact durations. These sub-group differences indicate factors such as age and gender should be accounted for when conducting exposure assessments. Contact frequencies in this study are higher than current US EPA recommendations, questioning their protective value for infants and toddlers.