Catalytic ozonation of pharmaceutical wastewater over 3D printed Mn/α-Al2O3 monoliths

INCHAURRONDO, N.S.; FAGES, F.; HUNG HUNG, Y.M.X. ; FASCE, L. A.; TALOU, M.; DI LUCA, C.

Congreso; 11th World Congress of Chemical Engineering, WCCE 11; 2023

Water pollution by pharmaceuticals (PhACs) represents an emerging environmental problem. Whileconventional water treatment technologies were not originally designed to remove these types of compounds, oxidation technologies, such as Advanced Oxidation Processes (AOPs) and ozonation, can provide promising treatment alternatives for the removal of PhACs in water. Ozone is a powerful oxidizing agent, but only achieves limited mineralization of organic compounds. So as to intensify the oxidation process and promote less selective removal pathways, ozone has been combined with heterogeneous catalysts. Among active phases, Mn oxides are reported to be one of the most efficient catalysts [1]. Moreover, the screening of solid catalysts is typically performed with powders which difficult its application on a larger scale. To solve this, monolithic catalysts are an attractive alternative to conventional multi-phase reactors due to the high void fraction, high surface area, low pressure drop and because there is no need of catalyst separation. In this work, we aimed to explore the catalytic performance of 3D printed α-Al2O3 monoliths doped with Mn and tested for the catalytic ozonation of diclofenac (DCF), ciprofloxacin (CIP) and sulfamethoxazole (SMX). The α-Al2O3 monoliths were developed by indirect selective laser sintering (i-SLS) 3D printing employingalumina/polyamide 612/micron-sized graphite composite granules as feedstock. The 3D printed composites arts were burned out in air at 450 °C (1 h) and 800 °C (1 h, 1 °C/min), presintered in air at 1400 °C (1 h, 2°C/min) and finally sintered in air at 1580 °C (2 h, 3 °C/min). Afterwards, Mn species (1 wt%) were added by incipient wetness impregnation of monolithic α-Al2O3 using Mn nitrate as precursor, dried and calcined at 500 ºC (3 h). Ozonation of Phac’s (20 mg/L) was performed in a semi-batch stirred-tank reactor (1 L). Gas flow rate and ozone inlet concentration were kept constant at 40 L/h NTP and 10 mg/L NTP, respectively. The experiments were performed at 22 ºC, for 180 min. Ozone was produced from dry pure oxygen by an Enaly KNT24 generator. One monolith of Mn/α-Al2O3 ( m = 0.5 g, D = 16 mm, e = 5 mm) was directly added to the reactor and used in all the ozonation tests. The reaction progress was monitored in terms of [Phac’s] (HPLCor UV-Vis), Total Organic Carbon (TOC), ozone consumption, pH evolution and Mn leaching.From our preliminary ozonation results, it can be stated that: i) Mn/α-Al2O3 did not adsorb Phac’s; ii) Single ozonation was efficient for the complete abatement of Phac’s in 30 min, but achieved poorer mineralization levels (up to 52% for DCF) than catalytic ozonation; iii) In relation to ozonation alone, the presence of Mn species did not affect the removal rate of DCF, CIP and SMX, but did achieve a remarkable TOC removal up to 82, 59 and 44%, respectively, at acid pH; iv) In all cases, the Mn leaching was low and ranged between 0.048 – 0.2 mg/L Mn; v) Catalytic activity was mainly attribute to heterogeneous contribution for DCF (0.048 mg/L Mn leached), but the leaching of 0.2 mg/L Mn did contribute to the mineralization of SMX and vi). Catalytic activity was retained in successive reuses with the same piece of monolith. Further research is being performed in order to characterize surface properties of the monolithic catalyst.