REMOVAL OF NITRATE FROM DRINKING WATER BY USING PdCu STRUCTURED CATALYSTS BASED ON CORDIERITE MONOLITHS

Abstract

Structured catalysts were prepared, characterized and evaluated in NO 3 removal from drinking water. Different suspensions containing a previously optimized PdCu/5wt% ZrO 2-Al 2 O 3 powder catalyst (hereinafter PdCu/5ZA p) were prepared and deposited on cordierite monoliths by washcoating. The effect of suspension concentration, the particle size, the immersion number, the use of suspension stabilizer agent, and an alumina precoating on the coating adherence and catalytic performance were studied. All the prepared structured catalysts were active for the elimination of NO 3 and presented good selectivity to N 2 (> 93%) in synthetic water samples. The catalyst performance was related to the amount of deposited catalyst. The highest activity and the best coating adherence were obtained with the structured catalyst prepared by a single immersion in a 14 wt% concentration suspension, which was obtained from the powder catalyst milled for 10 h and stabilized with colloidal alumina. This catalyst also showed good activity when it was reused for four cycles and when it was evaluated with real water samples.

Activity and Stability of Pd Bimetallic Catalysts for Catalytic Nitrate Reduction

“…Since the catalytic reduction of nitrate is based on the continuous redox reaction between NO 3 − and the promoter metal, the irreversible oxidation of the latter could limit the progression of the reaction, weakening the reactivity of the bimetallic catalyst and decreasing the NO 3 − removal efficiency [25]. On the other hand, the fouling of the catalyst surface by salt precipitation is the most common deactivation cause in NO 3 − removal treatments in water wherein other compounds are present [13,24,[26][27][28][29][30][31][32]. The loss of metal components is highly dependent on the reaction pH [33] and can be avoided by modifying the catalyst characteristics [34] or operating conditions [33,35].…”

Development of PdCu Structured Catalysts Based on ZrO2–CeO2 Materials Supported on Cordierite Monoliths for Water Remediation: Removal of Hazardous Oxyanions

“…Also, monoliths having a macroporous structure with numerous channels allow a better contact between the reactants (H 2 , NO 3 − , NO 2 − , or BrO 3 − ) and the active phase. 18 In addition, clogging, fluidization, and a great loss of pressure, caused by the use of powder catalysts, are avoided.…”

“…23 If the structured catalysts are prepared by the washcoating method, different factors influence this adherence, such as the characteristics of the washcoat containing the active phase, the particle size of the solid to be deposited, the nature of dispersive medium, the amount of solid, and the pH. 18 This work focuses on developing different formulations and procedures to reach a good adherence of the active phase on prepared structured supports. Moreover, the development of a fixed-bed reactor containing structured catalysts is addressed in the present work.…”

“…One of the ways to avoid the loss of catalytic material is to use pellets, foams, or monoliths to synthesize structured catalysts. , Monolith-based structured catalysts with different chemical compositions are widely used in environmental catalytic applications. , The use of monoliths has the advantage of immobilizing the active phase, thus avoiding contamination of the treated water with metal particles. Also, monoliths having a macroporous structure with numerous channels allow a better contact between the reactants (H 2 , NO 3 – , NO 2 – , or BrO 3 – ) and the active phase . In addition, clogging, fluidization, and a great loss of pressure, caused by the use of powder catalysts, are avoided.…”

“…The adherence of the PdCu active phase to the structured support is a critical factor that must be controlled . If the structured catalysts are prepared by the washcoating method, different factors influence this adherence, such as the characteristics of the washcoat containing the active phase, the particle size of the solid to be deposited, the nature of dispersive medium, the amount of solid, and the pH . This work focuses on developing different formulations and procedures to reach a good adherence of the active phase on prepared structured supports.…”