Chemical Engineering and Processing 56 (2012) 10–18 Contents lists available at SciVerse ScienceDirect Chemical Engineering and Processing: Process Intensification j ourna l h o me pa ge: www.elsevier.com/locate/cep Carbamazepine removal from water by dielectric barrier discharge: Comparison of ex situ and in situ discharge on water Yanan Liu a,∗ , Shufang Mei a , Djakaou Iya-Sou b , Simeon Cavadias b , Stéphanie Ognier b a School of Environmental Science and Engineering, Dong Hua University, C-201620, Shanghai, China b UPMC Univ Paris 06, EA 3492, Laboratoire de Génie des Procédés et Traitements de Surface, F-75005, Paris, France a r t i c l e i n f o Article history: Received 16 February 2011 Received in revised form 5 March 2012 Accepted 7 March 2012 Available online 23 March 2012 Keywords: Dielectric barrier discharge Carbamazepine Advanced oxidation processes Ozonation Plasma processes a b s t r a c t Dielectric barrier discharges (DBD) were used for the degradation of carbamazepine (CBZ) in aqueous solution. The electric discharge was generated either ex situ or in situ directly on the water surface. To maintain the same ozone concentration of 40 ppm in both instances, the power injected was 0.7 W in the ex situ discharge and 12 W in the in situ discharge. The results showed 100% CBZ removal after 3 min of treatment with the ex situ discharge, while the in situ discharge only removed 81% of the CBZ after 60 min. According to measurements of UV absorbance at 285 nm and 254 nm, and of total organic carbon, the ex situ discharge system also proved to be more effective than the in situ system. The measurement of nitrogen oxides in both gaseous and liquid phases indicated that high energy in situ discharges produced a large amount of NO x . These species contributed to decreased pH and significantly slowed the CBZ oxidation rate, due to their competition with ozone. Production of NO x should be avoided when using the DBD technique for wastewater treatment. © 2012 Elsevier B.V. All rights reserved. 1. Introduction With the development of analytical techniques and environ- mental concerns, more attention has been paid to micropollutants in the environment [1,2], including pharmaceutically active com- pounds (PACs), which have been detected in water bodies around the world [3]. Although no evidence of adverse human health effects from PACs in water has been found, some PACs have been proven to be potential endocrine-disrupting substances [4]. Poor removal of PACs in municipal wastewater treatment plants (WWTPs) allows their release in the environment [5]. Carba- mazepine (CBZ) (Fig. 1) has been proven to be one of the most difficult pharmaceuticals to biodegrade in WWTPs [6,7]. CBZ is an antiepileptic drug, and 1014 ton of the drug are consumed around the world yearly [8]. It can be found in most water bodies in rela- tively high concentrations (a range of 30–1100 ng/L) compared to other PACs [9]). Thus, new techniques are needed for the removal of this kind of pollutant to insure the safety of WWTP discharges.In this challenging context, the development of new advanced oxida- tion processes (AOPs) is the subject of intense scientific activity at national and international levels. Among the different tech- niques, the “non-thermal plasma techniques” are very promising ∗ Corresponding author. Tel.: +86 21 67792537; fax: +86 21 67792522. E-mail address: liuyanan@gmail.com (Y. Liu). because the resulting processes are simple, effective and easy for further technological transfer and do not require the use of other chemical agents [10,11]. These techniques involve generating non- thermal plasma in direct contact with the water to be treated. Although this is not a trivial task, the technique unequivocally possesses several advantages compared to the conventional ozone treatments, which are considered to be today’s “gold-standard” for water treatment. In fact, in all the ozone-based methods, ozone is first produced by a non-thermal plasma discharge and then injected into the liquid stream to ensure the treatment. However, the ozone yield is low because in the plasma environment, energy is dissi- pated among different dispersive mechanisms, such as radiation, and other highly energetic chemical reactions [12]. On the con- trary, if the plasma discharge is generated in direct contact with the water to be treated, all the involved energies (UV radiation, shock waves, radical species, ions, free electrons, and others) will converge to oxidize the pollutants. Therefore, the energetic effi- ciency could be increased when compared to the standard ozone methods. In non-thermal plasma reactors with direct electrical discharge on the surface of the water, the role of ozone still remains unclear [13]. The question remains: is ozone the main species responsible for the initiation of chain reactions leading to the degradation of organic pollutants? In fact, ozone, the most popular agent for AOP, is generated ex situ from electrical discharges in air or oxygen, and plays an important role in non-thermal plasma reactors [14,15]. 0255-2701/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.cep.2012.03.003