Denitrification of natural water on supported Pd/Cu catalysts

Palomares, Emilio; Prato, José G.; Márquez, Francisco; Corma, Avelino

doi:10.1016/s0926-3373(02)00203-5

Cited by 80 publications

(42 citation statements)

References 26 publications

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“…6(c)). After 180 min reaction, the NO 2 − -N and NH 4 + -N concentrations were 1.86 and 0.55 mg/L respectively, which were lower than the result reported by Palomares et al [17] who used the hydrotalcite-supported catalyst (5 wt%Pd-1.5 wt%Cu). Consequently, in our study, the catalytic reduction of nitrate on the hydrotalcite-supported Pd-Cu catalyst exhibited higher selectivity, reaching 78.5%.…”

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confidence: 66%

Hydrotalcite-supported Pd-Cu catalyst for nitrate adsorption and reduction from water

Wang

Liu

et al. 2006

Sci. Bull.

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Hydrotalcite-supported Pd-Cu catalyst for nitrate adsorption and catalytic reduction from water is prepared by co-impregnation method and characterized by surface area (BET), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectrum (XPS). The performance of adsorption and hydrogenation of nitrate was evaluated and compared with Al 2 O 3 , TiO 2 , and HZSM-supported Pd-Cu catalysts. The experimental results demonstrated that hydrotalcite-supported Pd-Cu catalyst exhibited a high surface area (185.3 m 2 /g) and mesopore structure (average pore diameter of 52.2 Å). The active metal clusters were homogeneously dispersed on the support, and the size of the most was less than 10 nm. Excellent adsorption for nitrate resulted from that nitrate ions were forced to enter the interlayer space when the calcined hydrotalcite regenerated layer structure in nitrate solution. The adsorption isotherm could be well described by the Langmuir model. The comparison between the adsorption and catalytic hydrogenation for nitrate using hydrogen indicated that nitrate reduction on hydrotalcite-supported Pd-Cu catalysts was a consecutive and dynamic adsorption and catalytic hydrogenation process. Compared with the Al 2 O 3 , TiO 2 , and HZSMsupported catalysts, hydrotalcite-supported Pd-Cu catalyst possessed higher catalytic activity and selectivity. The analysis on the dissolving of metals in the solution demonstrated that there was hydrolyzation on the surface of the hydrotalcite-supported Pd-Cu catalyst. However, the concentrations of dissolved metals in the solution were lower than the standard executed in China. The activity of the hydrotalcite-supported Pd-Cu catalyst for nitrate reduction kept steady after repeated use.

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confidence: 66%

Hydrotalcite-supported Pd-Cu catalyst for nitrate adsorption and reduction from water

Wang

Liu

et al. 2006

Sci. Bull.

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“…A new technique that is actually under research is the catalytic reduction of nitrates to nitrogen, using hydrogen as reductant [2][3][4][5][6][7][8][9]. The catalysts used are based in a combination of a noble metal, such as Pd, Pt, Rh or Ir and a no noble metal, such as Cu, Sn, Ag or In [5][6][7][8][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

A study of different supports for the catalytic reduction of nitrates from natural water with a continuous reactor

2011

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The aim of this work is to study the activity for the nitrate catalytic reduction in natural water, using a continuous stirred tank reactor, of Pd/Cu and Pd/Sn catalysts supported on different materials. The studied supports are: -Al 2 O 3 (commercial), active carbon, graphite, hydrotalcite and alumina synthesized in our laboratory with a high surface area. The activity and selectivity of the catalysts supported on these materials have been compared. The best results have been obtained with the Pd/Sn catalysts supported on alumina. These results show that the surface area of the support is not the only important characteristic for an active catalyst in this reaction, being also very significant its acid-base properties, its electrical conductivity and its interaction with the metallic active sites. The adequate combination of these characteristics is necessary to obtain an active catalyst. The influence of the Pd/Sn content on the activity of the alumina supported catalysts was studied, observing that the best activity was obtained when the Pd/Sn ratio was higher than 1. This result clearly indicates that it is necessary to have both Pd and Pd-Sn centers in order to obtain an active catalyst.

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“…The reaction obeys a consecutive reaction scheme in which nitrite appears as an intermediate, while nitrogen and ammonia are the final products. Recently, developing a catalyst possessed higher activity and selectivity for nitrate reduction [9][10][11] and studying the influence of liquid properties [12][13][14], such as temperature, pH, co-existed ions, etc., have received many researchers' attention.…”

Section: Introductionmentioning

confidence: 99%

Effect of liquid property on adsorption and catalytic reduction of nitrate over hydrotalcite-supported Pd-Cu catalyst

Wang

Liu

2007

Journal of Molecular Catalysis A: Chemical

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This study focused on investigating the effect of liquid property on adsorption and catalytic reduction of nitrate over hydrotalcite-supported Pd-Cu catalyst. Batch experiments were conducted under specific operating conditions. It was found that nitrate ions were adsorbed apparently by hydrotalcite-supported Pd-Cu catalyst at different reaction temperature (10, 25 and 35• C). Adsorption isotherms for NO 3 − were described by Langmuir's equation. Higher reaction temperature accelerated nitrate adsorption and reduction, and simultaneously decreased the accumulation of NO 2 − and NH 4 + . Nitrate adsorption and reduction were independent of the initial pH because of the high buffering capacity of hydrotalcite when the initial pH of solution was from 5.25 to 7.4. However, the dissolve of hydrotalcite-supported Pd-Cu catalyst at low initial pH (3.77) and higher concentration of OH − ions at high initial pH (10.74) decreased nitrate adsorption and reduction. When using various nitrate salts as a source of nitrate ions, nitrate adsorption and reduction removal efficiency decreased in the order: Fe 3+ > Mn 2+ > Mg 2+ > Ca 2+ > Na + , which was attributed to different affinity toward OH − . Co-existed cations in water with higher valence and lower crystal ionic radius and solubility constant of hydroxide showed stronger affinity toward OH − and consequently increased the concentration of active sites accessible to NO 3 − and NO 2 − . The competitive adsorption of Cl − , SO 4 2− and HCO 3 − with nitrate on the catalyst surface suppressed the adsorption and reduction of NO 3 − . Besides, few metals dissolved in neutral and alkaline solution. The activity of the hydrotalcite-supported Pd-Cu catalyst for nitrate reduction kept steady after repeated use.

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Denitrification of natural water on supported Pd/Cu catalysts

Cited by 80 publications

References 26 publications

Hydrotalcite-supported Pd-Cu catalyst for nitrate adsorption and reduction from water

Hydrotalcite-supported Pd-Cu catalyst for nitrate adsorption and reduction from water

A study of different supports for the catalytic reduction of nitrates from natural water with a continuous reactor

Effect of liquid property on adsorption and catalytic reduction of nitrate over hydrotalcite-supported Pd-Cu catalyst

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