A reactor with a packed bed anode assembly for studying Electro-Oxidation processes

SILVA BARNI, M. F.; RODRIGUEZ, C; PROCACCINI, R.; AYUDE, A.

Buenos Aires

Congreso; WCCE11 - 11th World Congress of Chemical Engeneering; 2023

The commercially available ceramics based on a mixture of sub-stoichiometric titanium oxides (TinO2n-1, 4≤n≤10), known as Magnéli phases (Ebonex®) have gained interest as promising working electrodes for the electrochemical degradation of diverse organic pollutants mainly due to their high electrical conductivity (~1000 S.cm-1), chemical stability in a wide range of media, high oxygen evolution potential, and relatively low manufacturing costs. Despite these characteristics, some controversy had recently been raised regarding electronics and stability to corrosion during anodic oxidation [1]. In a previous study, laminar Ti4O7 porous platforms were evaluated as anodes in the Electro-Oxidation process (EO) [2]. Enhanced EO activity and lower specific energy consumption were attained when the liquid was recirculated through the lamellar structure of the electrodes.In this work, a reactor with a packed bed anode assembly was investigated in the EO of Orange G (OG) solutions (0.23 mM). The electrochemical behavior of the system was preliminarily evaluated by a cyclic voltammetry performed between -1.5 and 2.0 V at 20 mV s-1 of scan rate, in a tree-electrode cell setup, using a saturated calomel electrode (SCE) as reference, and two Pt foils as working and auxiliary electrodes. Voltammograms for OG at pH 2.8, 3.81 and 5 showed no Faradaic peaks below 1.8 V that may interfere with the EO process studied at the reactor. Experiments were conducted in a batch recycle up-flow tubular reactor using a power supply under galvanostatic conditions at room temperature. A Ti mesh and a Pt/Ti mesh (30 × 30 mm) were employed as cathode and anode collector, respectively with a distance of 8 mm in between. The electrical contact was attained by gluing each mesh to a Ti wire. Anode and cathode potential were measured against a SCE located at the reactor entrance. About 4g of Ebonex® powder, provided by QuanVerge Inc., were packed around the anode collector with the aid of two polypropylene cloths. The inlet liquid flow rate was set to 0.2 L·h−1. The discoloration and chemical oxygen demand removal rates were notoriously improved with the addition of powder. The system exhibited very good stability along 7 cycles of 5 h reaction. Results highlighted the need of monitoring and controlling the anodic potential in a two-electrode reactor supplied by a power system to maintain electrochemical activity in successive cycles of reaction. The influence of different packed bed weights on the system performance is currently being explored.