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RISS 인기검색어
- 검색키워드
- 저자 : Pedro J. Alvarez (검색결과 5 건)
- 무료
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Investigating the magnetic entropy change in single-phase Y2Fe17 melt-spun ribbons
J.L. S anchez Llamazares,Pablo Alvarez-Alonso,C.F. S anchez-Vald es,P.J. Ibarra-Gayt an,J.A. Blanco,Pedro Gorria 한국물리학회 2016 Current Applied Physics Vol.16 No.9
The inspection of simplified fabrication and/or processing routes in order to produce materials with attractive magnetocaloric properties is of paramount importance for the development of environmentally friendly magnetic cooling technology. In this work, we have made use of the melt-spinning technique to obtain directly single-phase Y2Fe17 polycrystalline ribbons avoiding any high-temperature annealing for phase consolidation and homogenization. The melt-spun ribbons, with hexagonal Th2Ni17-type crystal structure, exhibit a moderate maximum value of the magnetic entropy change, | DSM peak| ¼ 2.4(4.4) J kg1 K1 under an applied magnetic field change of 2(5) T. Although these values are similar to those for the bulk alloy, the DSM(T) curves are manifestly broader, thus giving rise to an expansion of the working temperature range and the enhancement of about 15% in the refrigerant capacity. We also show that the magnetic field dependence of |DSM peak| at T ¼ TC follows a H2/3 power-law.
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Phosphorous recovery from sewage sludge using calcium silicate hydrates
Lee, Chang-Gu,Alvarez, Pedro J.J.,Kim, Hee-Gon,Jeong, Seongpil,Lee, Seunghak,Lee, Ki Bong,Lee, Sang-Hyup,Choi, Jae-Woo Elsevier 2018 CHEMOSPHERE - Vol.193 No.-
<P><B>Abstract</B></P> <P>Phosphorous is an essential limiting nutrient for which there is no substitute. Its efficient recovery from sewage treatment plants is important to mitigate both dependence on limited reserves of exploitable phosphate rock and eutrophication of surface waters. Here, we evaluate the use of calcium silicate hydrates (CSH) to recover phosphorous eluted from sewage sludge. Phosphorous elution experiments were conducted with acid and base leaching solutions. The phosphorous recovery efficiency with CSH was compared to that with other calcium compounds, and the final product was analyzed to assess its potential value as fertilizer. Dried sewage sludge from the West Lake Ecological Water Resource Center, South Korea, having 123 g-P kg<SUP>−1</SUP>, was used for these tests. About 55% of the phosphorus in the sludge was released with an elution solution of 0.1 M H<SUB>2</SUB>SO<SUB>4</SUB>. A dose of 15 g L<SUP>−1</SUP> of CSH recovered 89.6% of the eluted phosphorous without the need for additional pre-treatment, and the resulting calcium phosphate product (in brushite form, based on XRD analysis) exhibited superior settleability than that resulting from Ca(OH)<SUB>2</SUB>- and CaCl<SUB>2</SUB>-induced precipitation. XRD peaks of the calcium sulfate hydrate (in gypsum form) and residual CSH were also observed. The final product contained a relatively high content of the total P<SUB>2</SUB>O<SUB>5</SUB> eluted in a 2% citric acid solution (43.1%), which suggests that it might be readily used to fertilize crops.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Phosphorous eluted from sewage sludge can be effectively recovered by CSH. </LI> <LI> 55% of the phosphorus in the sludge (123 g-P/kg) was released into 0.1 M H<SUB>2</SUB>SO<SUB>4</SUB>. </LI> <LI> 15 g/L of CSH recovered 89.6% of the eluted phosphorus without further treatment. </LI> <LI> The resulting calcium phosphate product from CSH exhibited superior settleability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Lee, Chang-Gu,Alvarez, Pedro J.J.,Nam, Aram,Park, Seong-Jik,Do, Taegu,Choi, Ung-Su,Lee, Sang-Hyup Elsevier 2017 Journal of hazardous materials Vol.325 No.-
<P><B>Abstract</B></P> <P>This study investigates As(V) removal from aqueous solutions using a novel amine-doped acrylic ion exchange fiber. The amine doping reaction was confirmed using FT-IR, and the surface of the fiber was characterized using FEG-SEM. The synthesis process was completed within 60min using an AlCl<SUB>3</SUB>·6H<SUB>2</SUB>O catalyst at 100°C, and the resulting in a fiber with an ion exchange capacity of 7.5meq/g. The removal efficiency of the A-60 fiber was affected by the solution pH, and the efficiency was optimum at pH 3.04. As(V) adsorption on the fiber was rapid in the first 20min and reached equilibrium in 60min. As(V) removal followed pseudo-first-order kinetics, and the Redlich-Peterson adsorption isotherm model provided the best fit of the equilibrium data. The fiber has an As(V) adsorption capacity (<I>q<SUB>e</SUB> </I>) of 205.32±3.57mg/g, which is considerably higher than literature values and commercial adsorbents. The removal efficiency of the fiber was above 83% of the initial value after nine regeneration cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel amine-doped acrylic fiber was suitable for the removal of As(V) from water. </LI> <LI> The amine doping reaction was complete within 60min under catalysis at 100°C. </LI> <LI> The maximum adsorption capacity (<I>q<SUB>e</SUB>)</I> for As(V) was 205.3±3.6mg/g. </LI> <LI> This fiber can be an affordable and reusable ion exchange medium. </LI> </UL> </P>
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Kim, Heechan,Kim, Wooyul,Mackeyev, Yuri,Lee, Gi-Seon,Kim, Hee-Joon,Tachikawa, Takashi,Hong, Seokwon,Lee, Sanghyup,Kim, Jungbae,Wilson, Lon J.,Majima, Tetsuro,Alvarez, Pedro J. J.,Choi, Wonyong,Lee, Ja American Chemical Society 2012 Environmental science & technology Vol.46 No.17
<P>This study evaluates the potential application of tin porphyrin- and C<SUB>60</SUB> aminofullerene-derivatized silica (SnP/silica and aminoC<SUB>60</SUB>/silica) as <SUP>1</SUP>O<SUB>2</SUB> generating systems for photochemical degradation of organic pollutants. Photosensitized <SUP>1</SUP>O<SUB>2</SUB> production with SnP/silica, which was faster than with aminoC<SUB>60</SUB>/silica, effectively oxidized a variety of pharmaceuticals. Significant degradation of pharmaceuticals in the presence of the 400-nm UV cutoff filter corroborated visible light activation of both photosensitizers. Whereas the efficacy of aminoC<SUB>60</SUB>/silica for <SUP>1</SUP>O<SUB>2</SUB> production drastically decreased under irradiation with λ > 550 nm, Q-band absorption caused negligible loss of the photosensitizing activity of SnP/silica in the long wavelength region. Faster destruction of phenolates by SnP/silica and aminoC<SUB>60</SUB>/silica under alkaline pH conditions further implicated <SUP>1</SUP>O<SUB>2</SUB> involvement in the oxidative degradation. Direct charge transfer mediated by SnP, which was inferred from nanosecond laser flash photolysis, induced significant degradation of neutral phenols under high power light irradiation. Self-sensitized destruction caused gradual activity loss of SnP/silica in reuse tests unlike aminoC<SUB>60</SUB>/silica. The kinetic comparison of SnP/silica and TiO<SUB>2</SUB> photocatalyst in real wastewater effluents showed that photosensitized singlet oxygenation of pharmaceuticals was still efficiently achieved in the presence of background organic matters, while significant interference was observed for photocatalyzed oxidation involving non-selective OH radical.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2012/esthag.2012.46.issue-17/es301775k/production/images/medium/es-2012-01775k_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es301775k'>ACS Electronic Supporting Info</A></P>
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