Applied Catalysis B: Environmental 41 (2003) 3–13 Denitrification of natural water on supported Pd/Cu catalysts A.E. Palomares a , J.G. Prato b , F. Márquez b , A. Corma b,∗ a Department of Chemical and Nuclear Engineering, Universidad Politécnica de Valencia, Avenida de los Naranjos s/n, 46022 Valencia, Spain b Instituto de Tecnolog´ ıa Qu´ ımica, Universidad Politécnica de Valencia, UPV-CSIC, Avenida de los Naranjos s/n, 46022 Valencia, Spain Received 10 December 2001; received in revised form 31 March 2002; accepted 1 April 2002 Abstract The influence of the support on the catalytic hydrogenation of nitrates in liquid phase was investigated. Pd/Cu supported on hydrotalcite and Pd/Cu supported on alumina catalysts were tested for this reaction and its activity and selectivity were compared. It has been observed a higher activity and a lower production of ammonium when the metals are supported on hydro- talcite than when they are supported on alumina. When rehydrated after calcination hydrotalcite recovers its layered structure. Nitrates can be located in the interlayer space diminishing the problems associated to mass transfer limitations and increasing the activity of the material. In addition, copper can be incorporated in the hydrotalcite structure by an isomorphical replace- ment of magnesium, obtaining thus a high dispersion of the copper centres, that is reflected in a higher activity if compared with copper impregnated samples. A XPS study was made in order to characterise the metals supported on the hydrotalcite. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Denitrification; Pd/Cu catalyst; Water; Pollution; Hydrotalcite 1. Introduction The increasing rigorousity of the drinking water quality standards and the toxicity of the nitrates, has generated the urgent need to develop a new technol- ogy for its removal from aqueous solutions [1]. Nowa- days, the main technologies used for nitrate removal from water are: (i) physicochemical processes such as electrodyalisis, ion exchange or reversed osmo- sis; and (ii) biological processes based on the nitrate reduction by micro-organisms into gaseous nitrogen [2]. The main disadvantage of the physicochemical processes is the fact that nitrates are not converted into harmless compounds but are concentrated in a secondary waste which has to be treated or disposed ∗ Corresponding author. Tel.: +34-6-3877800; fax: +34-6-3877809. E-mail address: acorma@itq.upv.es (A. Corma). off. Biological denitrification is a well known treat- ment for wastewater but its use for denitrification of ground water presents multiple difficulties. Therefore, the development of an environmental friendly and highly efficient technology is becoming a necessity. The most favourable way to remove nitrates from the environmental point of view is to convert them into N 2 . In order to do this, one of the most promising processes is the liquid phase nitrate hydrogenation over noble metal catalysts [3–7]. This reaction was first described by Vorlop and Tacke [8]. In this pro- cess nitrate reacts with hydrogen and it is converted into nitrogen and water using a solid catalyst. It is necessary a high selectivity of the catalyst to avoid the production of nitrite and ammonium ions. Typically, metal oxide supported bimetallic catalysts, consisting of a combination between a noble and a non-noble metal, were applied for this reaction. In these cat- alysts the bimetallic combination has a substantial 0926-3373/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0926-3373(02)00203-5