Removal of Arsenic from Strongly Acidic Wastewater Using Phosphorus Pentasulfide As Precipitant: UV-Light Promoted Sulfuration Reaction and Particle Aggregation

Strongly acidic wastewater (H₂SO₄) with a high arsenic concentration is produced by many industries. The removal of arsenic by traditional sulfide (e.g., Na₂S, FeS) from strongly acidic wastewater introduces cations (Na⁺ and Fe²⁺) to the solution, which may prevent the recycle of acid. In this study, a new sulfuration agent, phosphorus pentasulfide (P₂S₅) was employed, and its feasibility in arsenic removal from strongly acidic wastewater was investigated. In the dark, As­(III) was efficiently removed, but the removal rate of As­(V) was rather slow, which was the crucial defect for this method. We found that this defect can be efficiently overcome by UV irradiation through accelerating the formation and transformation of an intermediate species, monothioarsenate (H₃AsO₃S) in the As­(V) removal process. In addition, the hydrolysis of P₂S₅ was enhanced under UV irradiation, which resulted in the increase of the arsenic removal efficiencies. Besides, the aggregation of the formed particles was also promoted. Different from FeS and Na₂S, P₂S₅ introduces H₃PO₄ instead of cations to the solution, which can facilitate the recycle and reuse of arsenic and acid in strongly acidic wastewater

Synthesis of Pd/Fe₃O₄ Hybrid Nanocatalysts with Controllable Interface and Enhanced Catalytic Activities for CO Oxidation

Palladium is an important catalyst for many industrial processes and chemical reactions. The conjunction of Pd and a metal oxide is of particular interest for improving catalytic performance in heterogeneous catalysis. Here we report the synthesis of Pd/Fe₃O₄ hybrid nanoparticles with controllable interface and the evaluation of their catalytic activities for CO oxidation. The synthesis involves a seed-mediated process in which Pd nanoparticles serve as seeds, followed by the deposition of the Fe₃O₄ layer in the solution phase. The adhesion of the oxide layer to the metal surface is through the reduced form of Fe. Upon thermal annealing, the Fe₃O₄ layer evolved from complete to partial coverage on the Pd core surface. This process is accompanied by increased crystallinity of Fe₃O₄. The resultant Pd–Fe₃O₄ nanoparticles with a partial Fe₃O₄ shell significantly lower the light-off temperature of CO oxidation

Anisotropic Seeded Growth of Cu–M (M = Au, Pt, or Pd) Bimetallic Nanorods with Tunable Optical and Catalytic Properties

A general strategy to synthesize Cu–M (M = Au, Pt, or Pd) bimetallic nanorods has been demonstrated based on a seeded co-reduction method. In this approach, noble metal nanoparticles serve as seeds, and newly reduced Cu atoms are subsequently nucleated on one side of the seeds, resulting in Janus nanoparticles with an M-rich and a Cu-rich portion. The elongation of the particles originates from the site-specific deposition of Cu clusters on the Cu-rich side of these Janus nanoparticles by retarding reduction kinetics of Cu through galvanic replacement. Using this approach, Cu–M alloyed nanorods can be conveniently synthesized with tunable composition, crystal structure, and aspect ratio. These nanorods have also been demonstrated as a unique system for investigation of the structural and compositional effects on their optical and catalytic properties

Hemodynamic responses to six reversal frequencies examined in an event-related experiment.

<p>The symbols and error bars in each panel (mean ± SEM) show the average of original time course obtained from eight subjects. The solid curve in each panel shows the estimated hemodynamic response averaged from eight subjects (for clarity, error bars of estimated hemodynamic response are not shown). To quantify hemodynamic responses to different reversal frequencies, four parameters were extracted and are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0099547#pone-0099547-t001" target="_blank">Table 1</a>.</p

Synthesis of Copper–Silica Core–Shell Nanostructures with Sharp and Stable Localized Surface Plasmon Resonance

Copper nanoparticles exhibit intense and sharp localized surface plasmon resonance (LSPR) in the visible region; however, the LSPR peaks become weak and broad when exposed to air due to the oxidation of Cu. In this work, the Cu nanoparticles are successfully encapsulated in SiO₂ by employing trioctyl-<i>n</i>-phosphine (TOP)-capped Cu nanoparticles for the sol–gel reaction, yielding an aqueous Cu–SiO₂ core–shell suspension with stable and well-preserved LSPR properties of the Cu cores. With the TOP capping, the oxidation of the Cu cores in the microemulsion was significantly reduced, thus allowing the Cu cores to sustain the sol–gel process used for coating the SiO₂ protection layer. It was found that the self-assembled TOP-capped Cu nanoparticles were spontaneously disassembled during the sol–gel reaction, thus recovering the LSPR of individual particles. During the disassembling progress, the extinction spectrum of the nanocube agglomerates evolved from a broad extinction profile to a narrow and sharp peak. For a mixture of nanocubes and nanorods, the spectra evolved to two distinct peaks during the dissembling process. The observed spectra match well with the numerical simulations. These Cu–SiO₂ core–shell nanoparticles with sharp and stable LSPR may greatly expand the utilization of Cu nanoparticles in aqueous environments

Differences in knowledge scores across disparate regions (n = 308) (From ANOVA and Chi-square test).

<p>Differences in knowledge scores across disparate regions (n = 308) (From ANOVA and Chi-square test).</p

Differences in knowledge scores among women who received advice from doctors or not (n = 308) (From <i>t</i>-test).

<p>Differences in knowledge scores among women who received advice from doctors or not (n = 308) (From <i>t</i>-test).</p

Quantifying the Coverage Density of Poly(ethylene glycol) Chains on the Surface of Gold Nanostructures

The coverage density of poly(ethylene glycol) (PEG) is a key parameter in determining the efficiency of PEGylation, a process pivotal to <i>in vivo</i> delivery and targeting of nanomaterials. Here we report four complementary methods for quantifying the coverage density of PEG chains on various types of Au nanostructures by using a model system based on HS–PEG–NH₂ with different molecular weights. Specifically, the methods involve reactions with fluorescamine and ninhydrin, as well as labeling with fluorescein isothiocyanate (FITC) and Cu²⁺ ions. The first two methods use conventional amine assays to measure the number of unreacted HS–PEG–NH₂ molecules left behind in the solution after incubation with the Au nanostructures. The other two methods involve coupling between the terminal −NH₂ groups of adsorbed −S–PEG–NH₂ chains and FITC or a ligand for Cu²⁺ ion, and thus pertain to the “active” −NH₂ groups on the surface of a Au nanostructure. We found that the coverage density decreased as the length of PEG chains increased. A stronger binding affinity of the initial capping ligand to the Au surface tended to reduce the PEGylation efficiency by slowing down the ligand exchange process. For the Au nanostructures and capping ligands we have tested, the PEGylation efficiency decreased in the order of citrate-capped nanoparticles > PVP-capped nanocages ≈ CTAC-capped nanoparticles ≫ CTAB-capped nanorods, where PVP, CTAC, and CTAB stand for poly(vinyl pyrrolidone), cetyltrimethylammonium chloride, and cetyltrimethylammonium bromide, respectively

Demographic characteristics of women among different regions (n = 308) (From Chi-square test).

<p>Demographic characteristics of women among different regions (n = 308) (From Chi-square test).</p

Differences in knowledge scores and rate among women with different educational levels (n = 308) (From ANOVA and Chi-square test).

<p>Differences in knowledge scores and rate among women with different educational levels (n = 308) (From ANOVA and Chi-square test).</p