Experimental and modeling of tetracycline degradation in water in a flow-through enzymatic monolithic reactor

Abstract

In this work, the laccase from Trametes versicolor was immobilized in highly porous silica monoliths (0.6 cm diameter, 0.5 cm length). These monoliths feature a unique homogeneous network of interconnected macropores (20 μm) with mesopores (20 nm) in the skeleton and a high specific surface area (330 m 2 /g). The enzymatic monoliths were applied to degrade tetracycline (TC) in model aqueous solutions (20 ppm). For this purpose, a tubular Flow-Through-Reactor (FTR) configuration with recycling was built. The TC degradation was improved with oxygen saturation, presence of degradation products and recirculation rate.The TC depletion reachs 50% in the FTR and 90% in a stirred tank reactor (CSTR) using crushed monoliths.These results indicate the importance of maintaining a high co-substrate concentration near active sites. A model coupling mass transfers with a Michaelis-Menten kinetics was applied to simulate the TC degradation in real wastewaters at actual TC concentration (2.8 10 -4 ppm). Simulation results show that industrial scale FTR reactor should be suitable to degrade 90% of TC in 5 h at a flow rate of 1 mL/min in a single passage flow configuration. Nevertheless, the process could certainly be further optimized in terms of laccase activity, oxygen supply near active sites and contact time.

Immobilized‐laccase bioreactors for wastewater treatment

“…[14] In Figure 2 flow rate of 1 mL min −1 with continuous recycling. [15] They found that 40%-50% of tetracycline was degraded in 5 h. Additionally, the silica monolith immobilized laccase presented high operational stability during 75 h which, according to the authors, indicated the applicability of the developed reactors on a large scale. However, the scalability of such minireactors is a matter to be researched.…”