Fe-Sensitized Zeolite Supported TiO2 for the Degradation of Tetracycline Using Blue LED Irradiation

Abstract

In this study, we investigated the photocatalytic degradation as a potential treatment of tetracycline (TC) antibiotic contaminated water using TiO2 semiconductor. To expand the activity of TiO2 into the visible light region and to enhance its adsorption capacity for TC, we explored its modification via sensitization with Fe ions and via immobilization on beta (BEA) zeolite support. The nano-sized beta zeolite, synthesized using the seed-assisted procedure, was used to immobilize TiO2 initially prepared by the sol-gel method. The immobilized TiO2/BEA catalyst was further ion exchanged with Fe3+ ions using FeCl3 precursor. Fe3+ modified TiO2/BEA (Fe-TiO2/BEA) catalyst was characterized using SEM, XRD, BET, UV-VIS DRS, and FTIR. After the immobilization of TiO2 over BEA, the surface area of TiO2 increased from 90 to 530 m2/g and similarly its TC adsorption efficiency increased from 10% to 33%. The photocatalytic performance of the Fe-TiO2/BEA was evaluated under blue LED light for TC degradation. Fe-TiO2/BEA exhibited higher TC removal efficiency (100%) compared to TiO2 (80%) after 90 min of irradiation using 50 W blue LED light for a 250 mg/L initial catalyst concentration and 20 mg/L TC concentration. The enhanced performance of the final catalyst was a result of the expanded surface area due to the immobilization of the TiO2 on the BEA zeolite, which resulted in an improved TC adsorption. Moreover, the presence of Fe3+ ions reduced the band gap energy of the TiO2, hence led to a red shift in its absorption spectrum to the visible light region and minimized the extent of the recombination of the charge carriers.

Titania-zeolite composite for tetracycline photocatalytic degradation under visible light: A comparison between doping and ion exchange

“…Fig. 3 , b, shows the structure of TiO 2 having a smooth surface and composed of aggregates with sharp edges in a similar finding by other studies [ 10 , 28 ]. The SEM images of the ion exchanged and the unmodified TiO 2 /BEA in Fig.…”

“…Similarly, the same H2 hysteresis loop type was recorded for the BEA zeolite and the prepared photocatalysts as a result of zeolite particles agglomerates that led to the formation of those meso-pores. This suggest that the meso-pores structure of BEA zeolite was conserved after Titania immobilization and iron ion exchange [ 10 ].…”

“…TiO 2 was prepared using the sol-gel method as described previously [ 10 ]. Two mixtures A and B were separately prepared before being mixed.…”

“…This improvement in the performance due to the doping was attributed to the lower band gap energy and suppressed charge carrier recombination effect. To increase the surface area and adsorption efficiency of TiO 2 , it is widely immobilized over inert porous non-organic substrates to help enhance the interactions between its active sites and the target molecules [ [10] , [11] , [12] , [13] ]. Zeolite is a porous material consisting mainly of aluminum and silica with a tetrahedron three-dimensional morphology, high surface area and pore volume, inertness, excellent stability, and transparency to light [ 7 , [14] , [15] , [16] , [17] , [18] ].…”

“…This excellent efficiency of the photocatalyst was attributed to minimized charge carrier recombination effect and enhanced visible light activity. In our previous work [ 10 ], we prepared highly crystalline embryonic Beta zeolite (BEA) to be used as a support for TiO 2 for the photocatalysis of antibiotics. However, the preparation of this meso-porous zeolite via a seed-assisted approach required a 3-day duration for the seed preparation followed by a 5-day thermal treatment for the BEA zeolite preparation.…”