Copper-pillared clays (Cu-PILC) for agro-food wastewater purification with H 2 O 2 Simona Caudo, Chiara Genovese, Siglinda Perathoner * , Gabriele Centi Dipartimento di Chimica Industriale ed Ingegneria dei Materiali, Universita ` di Messina, Salita Sperone 31, 98166 Messina, Italy Received 13 March 2007; received in revised form 30 April 2007; accepted 7 May 2007 Available online 18 May 2007 Abstract Copper-pillared clays (Cu-PILC) are effective and stable catalysts for the wet hydrogen peroxide catalytic oxidation (WHPCO) of waste in water. They are studied both in the conversion of model molecules (p-coumaric acid, p-hydroxybenzoic acid) and in the treat- ment of various real wastewaters from agro-food production: (i) deriving from citrus juice production, (ii) extracted concentrated poly- phenolics fraction from olive oil milling (OMW) and (iii) OMW derived from three different sources. In the latter cases, tests were made both in a lab-scale reactor and in a larger volume (about 10 l) reactor. The results showed that Cu-PILC layered materials might be used to treat real wastewater from agro-food production, and not only simple model chemicals as typically made in the literature. In all cases, using a semi-batch slurry-type reactor with a continuous feed of H 2 O 2 , the behaviour both in TOC (total organic carbon) and in poly- phenols abatement may be described using pseudo-first-order reaction rates. Using real wastewater the rate constants are one–two-orders of magnitude lower than using model molecules, and a decrease in the ratio between rate constant of phenols conversion and rate con- stant of TOC abatement is observed. However, this ratio maintains over one in all cases. A typical value is around two, but the com- position of wastewater and reaction conditions influences this ratio. Scaling-up to a larger volume semi-continuous slurry-type reactor causes a further lowering of one-order of magnitude in the rate constants of TOC and polyphenols depletion, due to fouling of the cat- alyst related to the preferential coupling of the organic radicals and deposition over the catalyst with respect to their further degradation by hydroxyl radicals generated from H 2 O 2 activation on the copper ions of the catalyst. The use of a different reactor to overcome this problem is suggested. Ó 2007 Elsevier Inc. All rights reserved. Keywords: Copper-pillared clay; Layered materials; Wastewater; H 2 O 2 ; PILC 1. Introduction The impact on the environment of agro-food production (particularly of water emissions) is an issue that was often underestimated, but which is receiving an increasing atten- tion in recent years [1]. In addition to great organic content and high nutrient levels, wastewater from agro-food pro- duction often contains a relevant concentration of hardly biodegradable compounds and/or bio- and/or phyto-toxic chemicals. The introduction of the latter in the environ- ment greatly reduces the effectiveness of the natural atten- uation processes in the soil and water systems. Therefore, in addition to a direct impact, these substances have a sec- ondary negative impact, because they reduce the self-depu- ration capacity of the environment. There is also an amplification of these effects in regions suffering of scarce water resources. An example of this issue is the impact on soil and water quality in the Mediterranean area given by the presence of polyphenolic compounds in olive oil milling wastewater (OMW) or in other water emissions from the agro-food sector, such as those deriving from the production of orange, lemon and other citrus juices (citrus juice produc- tion wastewater – CPW). Olive oil mills produce around 1387-1811/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2007.05.011 * Corresponding author. Tel.: +39 090 6765609; fax: +39 090 391518. E-mail address: perathon@unime.it (S. Perathoner). www.elsevier.com/locate/micromeso Available online at www.sciencedirect.com Microporous and Mesoporous Materials 107 (2008) 46–57