A Continuous Sono-Photochemical Reactor To Remove Pharmaceuticals In Wastewaters

The concentration of pharmaceuticals and veterinary drugs has dramatically increased in wastewaters (ng to µg per L range)[1]. Among seven water treatments, none of these removed ibuprofen and anticonvulsants effectively[2]. Photocatalysis by titanium dioxide is one of the most promising AOP to treat wastewaters[3]. Even though photocatalysts are effective, often they lead to incomplete degradation[4] and most of the research studied nano-material which poses health concerns[5]. To avoid the formation of byproduct, the coupling of diverse AOPs is necessary to balance the costs, which are higher compared to typical water treatment technologies[6]. Ultrasound creates micro-jets of fluid that induces high local temperature and pressure (> 2000 K and > 50 bar). These conditions induce water splitting and create hydroxy radicals, which assist titania photocatalyst in a coupled AOP. Here, we built a lab scale continuous reactor to treat solution of ibuprofen and paracetamol, which are ubiquitous wastewaters (Figure 1). We doped titanium Figure 1. Ractor picture dioxide with silver to improve its activity and give him antibacterical properties[7] also in dark. We deposited the photocatalyst on glass Rashig packaging (8x8 mm) and inserted them in the photocatalytic reactor (volume = 0.5 L). A Jelosil model GL8 germicide UV medium pressure Hg lamp LAMPNAME emitting in the UV-C range inserted in the reactor irradiated the catalyst with 55 W m-2. The stream exiting the photocatalytic reactor entered in the ultrasound reactor, with a volume of 0.5 L. A 20 kHz ultrasonic horn delivered 16,6 WL-1 to the solution, which was then recycled to a tap water-cooled tank. Ultrasound only does not mineralize Ibuprufen, while UV light (photolysis) degrades 15 % of the molecule after 6 h. TiO2 (either doped with Ag or not) reached full conversion of Ibuprufen after 6 h. Doping TiO2 with silver increases the mineralization from 25 % to 28 % after the same time. Coupling ultrasound and TiO2 photocatalysis reached the best result, with a mineralization of 31 % of ibuprofen. The results are encouraging and demonstrates that coupling AOP processes is advantageous.