Energy efficient BPA degradation through F-etched-Ni-Sn-C-N-TiO2 nano-layered thin film reactors

Abstract

Increasing wastewater generation rates and micro-pollutant levels in environmental matrices constrain energy-efficient and fast control technologies. In this study, different optical and geometrical photocatalytic reactor (PCR) design have been investigated experimentally using BPA molecule as a model pollutant. N-TiO2, Ni-N-TiO2, Sn-NTiO2, Ni-Sn-C-N-TiO2 and F-etched-Ni-Sn-C-N-TiO2 nano-layered thin films (TFs) have been produced and employed as immobilized nano-catalysts. An ultrasound-assisted fluorine (F) etching method was applied to Sn and Ni co-doped TFs. The synthesized TFs were characterized by SEM-EDX, AFM, XPS, FT-IR and UV-Vis spectroscopies. Three different types of PCRs with different geometrical and optical design were operated using different light sources, wavelengths and technologies. A box type photoreactor, vertical and horizontal coated quartz tubular reactors (CQTRs) were fabricated and their performances were evaluated considering BPA degradation kinetics and unit energy consumption figures (xi, kJ energy used mg(-1) BPA(removed)). Vis, UV A, UV C lamps and SMD 5050 blue (450 nm) and UV (365 nm) LEDs were employed as irradiation sources to initiate photocatalytic reactions. The highest pseudo first-order reaction rate (k) and the lowest xi value were obtained by F-etched-Sn-Ni-C-N-TiO2, positioned in vertical type reactor under UV LED irradiation as 20.5 min(-1) and 56 kJ mg(-1) BPA(removed) respectively. Whereas, the highest BPA degradation rate (k) and the lowest xi value for the box type reactor under 257 nm UV C irradiation were estimated as 20.3 min(-1) and 1581 kJ mg(-1) BPA(removed) respectively for F-etched-Sn-Ni-C-N-TiO2. Although similar reaction rates were obtained for both reactor types, energy consumption was lowered approximately 28-fold in the developed vertical positioned reactor system in addition to several other benefits. While UV LED based-PCR yielded elevated levels of BPA removal efficiency, 257 nm UV C irradiation did not contribute to BPA degradation when positioned vertically. Furthermore, obtained experimental results also revealed that F-etched-Sn-Ni-C-N-TiO2 has significant potential to function under solar irradiation. (C) 2020 Elsevier B.V. All rights reserved.