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Creators/Authors contains: "Ali, Abdul-Mehdi"

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  1. Free, publicly-accessible full text available January 10, 2024
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  4. The objective of this study was to investigate the application of manganese oxide [MnO x(s) ] and granular activated carbon (GAC) media for the removal of caffeine and acetaminophen from water. Organic contaminants of emerging concern represent a developing issue due to their effects on human health and the environment. Manganese oxides are effective for water treatment because of their ability to mediate adsorption and oxidation–reduction reactions for many organic and inorganic constituents. Laboratory scale column experiments were performed using different combinations of commercial MnO x(s) and GAC for assessing the removal of caffeine and acetaminophen, and the subsequent release of soluble Mn due to the reductive dissolution of MnO x(s) . The removal of acetaminophen was detected for all media combinations investigated. However, the removal of caffeine by adsorption only occurred in columns containing GAC media. There was no removal of caffeine in columns containing only MnO x(s) media. Manganese release occurred in columns containing MnO x(s) media, but concentrations were below the secondary drinking water standard of 50 μg L −1 set by the US Environmental Protection Agency. Soluble Mn released from a first process by MnO x(s) media column was removed through adsorption into the GAC mediamore »used in a second process. The results of this investigation are relevant for implementation of MnO x(s) and GAC media combinations as an effective treatment process to remove organic contaminants from water.« less
  5. We investigated the mechanisms of uranium (U) uptake by Tamarix (salt cedars) growing along the Rio Paguate, which flows throughout the Jackpile mine near Pueblo de Laguna, New Mexico. Tamarix were selected for this study due to the detection of U in the roots and shoots of field collected plants (0.6–58.9 mg kg −1 ), presenting an average bioconcentration factor greater than 1. Synchrotron-based micro X-ray fluorescence analyses of plant roots collected from the field indicate that the accumulation of U occurs in the cortex of the root. The mechanisms for U accumulation in the roots of Tamarix were further investigated in controlled-laboratory experiments where living roots of field plants were macerated for 24 h or 2 weeks in a solution containing 100 μM U. The U concentration in the solution decreased 36–59% after 24 h, and 49–65% in two weeks. Microscopic and spectroscopic analyses detected U precipitation in the root cell walls near the xylems of the roots, confirming the initial results from the field samples. High-resolution TEM was used to study the U fate inside the root cells, and needle-like U–P nanocrystals, with diameter <7 nm, were found entrapped inside vacuoles in cells. EXAFS shell-by-shell fitting suggest thatmore »U is associated with carbon functional groups. The preferable binding of U to the root cell walls may explain the U retention in the roots of Tamarix , followed by U–P crystal precipitation, and pinocytotic active transport and cellular entrapment. This process resulted in a limited translocation of U to the shoots in Tamarix plants. This study contributes to better understanding of the physicochemical mechanisms affecting the U uptake and accumulation by plants growing near contaminated sites.« less