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This work presents a ceramic tubular membrane coated with a continuous graphene-TiO nanocomposite thin-film for contaminants of emerging concern (CECs) removal from synthetic and real matrices in single-pass flow-through operation. Microfiltration ceramic membranes were coated in situ with graphene (G)-TiO-P25 nano-composite using two different methods: Membrane type A - TiO-P25 incorporated in the G preparation stage (1% [MA-1], 2% [MA-2] and 3% [MA-3] [w/v]), and Membrane type B - TiO-P25 thin-film uniformly coated over the G film surface (coating layers: 3 [MB-1], 6 [MB-2], and 9 [MB-3]). After the catalyst deposition and before the pyrolysis step, air was forced to pass through the membranes pores (inside-outside mode), providing a porous film. The CECs solution (diclofenac-DCF, 17β-estradiol-E2, 17α-ethinylestradiol-EE2 and amoxicillin-AMX) was prepared using Ultrapure water (UPW) or an urban wastewater after secondary treatment (UWW) fortified with 500 µg L of each CEC. Membranes were characterized by the following techniques: Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier-Transform Infrared spectroscopy (FTIR), Diffuse Reflectance UV-Visible spectroscopy (DR UV-Vis) and Raman spectroscopy. The membranes coated with MA-3 and MB-2 catalyst films, irradiated by UVA light, showed the highest ability for CECs removal. Furthermore, the Relative flux reduction ratio (RFR) decreased around 45% in the absence of UVA light, owing to membrane fouling. The combination of filtration and oxidation (G-TiO-UVA) provided a permeate with higher quality and minimized membrane fouling. Although membrane type B allowed for a permeate with higher quality, membrane type A provided a higher permeate flux., This work was financially supported by: i) Project NOR-WATER funded by INTERREG VA Spain-Portugal cooperation programme, Cross-Border North Portugal/Galizia Spain Cooperation Program (POCTEP); ii) Project SERPIC funded by the European Uniońs Horizon 2020 research and innovation programme under grant agreement No. 869178-AquaticPollutants; and iii) Base-UIDB/50020/2020 and Programmatic-UIDP/50020/2020 Funding of LSRE-LCM, funded by national funds through FCT/MCTES (PIDDAC). P. H. Presumido acknowledges FCT for his scholarship (SFRH/BD/138756/2018). Vítor J.P. Vilar acknowledges the FCT Individual Call to Scientific Employment Stimulus 2017 (CEECIND/01317/2017). Maja Đolić acknowledges the grants issued from the Ministry of Education and Science of the Republic of Serbia (Contract No. 451-03-9/2021-14/200135). We also thank Amparo Forneli for assistance in characterizing G-TiO2 films. Financial support by the Spanish Ministry of Science and Innovation (Severo Ochoa and RTI2018-890237-CO2-R1) and Generalitat Valenciana (Prometeo 2017-83) is also gratefully acknowledged.

The objectives of the current study are to assess and compare the performance of a developed photocatalytic membrane reactor (PMR) in treating industrial waste (e.g., organic dye waste) against membrane distillation. The current PMR is composed of a feed tank, which is a continuous stirred photocatalytic reactor containing slurry Titanium dioxide (TiO2) particles that are activated by using ultraviolet lamp irradiation at a wavelength of 365 nm, and a poly-vinylidene flouride (PVDF) membrane cell. The experimental setup was designed in a flexible way to enable both separate and integrated investigations of the photocatalytic reactor and the membrane, separately and simultaneously. The experimental work was divided into two phases. Firstly, the PVDF membrane was fabricated and characterized to examine its morphology, surface charge, and hydrophobicity by using a scanning electron microscope, surface zeta potential, and contact angle tests, respectively. Secondly, the effects of using different concentrations of the TiO2 photocatalyst and feed (e.g., dye concentration) were examined. It is found that the PMR can achieve almost 100% dye removal and pure permeate is obtained at certain conditions. Additionally, a kinetic analysis was performed and revealed that the photocatalytic degradation of dye follows a pseudo-first-order reaction.

This review presents a survey of some heterogeneous photocatalytic processes for the synthesis of high-value added compounds carried out in photocatalytic membrane reactors (PMRs). The two technologies can be easily integrated due to the similar conditions at which they usually operate. Furthermore, significant advantages derive from the coupling and in some cases also synergistic effects can be observed. These features have been highlighted for the photocatalytic syntheses reviewed along with engineering and design aspects investigated for some industrially relevant high-value added compounds. Notably, photocatalytic syntheses carried out in PMRs are still rare mainly because interdisciplinary competences and collaborations are often required in this field. However, we hope that a survey of the recently reported examples may inspire researchers for future developments and new opportunities.

Photocatalysis combined with membrane technology could offer an enormous potential for power generation in a renewable and sustainable way. Herein, we describe the one-step hydrogen and oxygen evolution through a photocatalytic membrane reactor. Experimental tests were carried out by means of a two-compartment cell in which a modified Nafion membrane separated the oxygen and hydrogen evolution semi-cells, while iron ions permeating through the membrane acted as a redox mediator. Nanosized Au/TiO2 and Au/CeO2 were employed as suspended photocatalysts for hydrogen and oxygen generation, respectively. The influence of initial Fe3+ ion concentration, ranging from 5 to 20 mM, was investigated, and the best results in terms of hydrogen and oxygen evolution were registered by working with 5 mM Fe3+. The positive effect of gold on the overall water splitting was confirmed by comparing the photocatalytic results obtained with the modified/unmodified titania and ceria. Au-loading played a key role for controlling the photocatalytic activity, and the optimal percentage for hydrogen and oxygen generation was 0.25 wt%. Under irradiation with visible light, hydrogen and oxygen were produced in stoichiometric amounts. The crucial role of the couple Fe3+/Fe2+ and of the membrane on the performance of the overall photocatalytic system was found.

After the dyeing process, part of the dyes used to color textile materials are not fixed into the substrate and are discharged into wastewater as residual dyes. In this study, a heterogeneous photocatalytic process combined with microfiltration has been investigated for the removal of C.I. Disperse Red 73 from synthetic textile effluents. The titanium dioxide (TiO2) Aeroxide P25 was selected as photocatalyst. The photocatalytic treatment achieved between 60% and 90% of dye degradation and up to 98% chemical oxygen demand (COD) removal. The influence of different parameters on photocatalytic degradation was studied: pH, initial photocatalyst loading, and dye concentration. The best conditions for dye degradation were pH 4, an initial dye concentration of 50 mgL-1, and a TiO2 loading of 2 gL(-1). The photocatalytic membrane treatment provided a high quality permeate, which can be reused

Kinetic fitting of substrate disappearance and of total organic carbon (TOC) mineralization of organic micropollutants, in water and air, by photocatalytic membranes immobilizing titanium dioxide, was carried out. A model was used in which mineralization of substrate to CO2 is supposed to occur, with kinetic constant k1, through one single intermediate, mediating the behaviour of all the numerous real intermediates formed in the path to CO2, kinetic constant of formation of the latter being k2. A competitive Langmuirian-type adsorption of both substrate and ‘intermediate’ was also supposed to be operative, as expressed by pseudo-thermodynamic constants K1 and K2 respectively, these constants possessing a, partly at least, kinetic significance. Nonlinear models could be fitted to data by using the least-squares method. The very satisfactory matching is shown for the laboratory-scale mineralization kinetics of methane, as model molecule of aliphatic contaminants, both in the gas phase and in aqueous solution. Furthermore, in pilot plant experiments, using phenol, as model molecule of aromatics, modelling of quantum yields was carried out, as a function of concentration and of adsorbed radiant power. Kinetics of hydroxyl radicals reacting between themselves, leading to hydrogen peroxide, other than with substrate or intermediates leading to mineralization, was considered, paralleled by a second competition kinetics due to superoxide anion radical and its conjugate acid, equally leading to mineralization. In this model the contribution of hydroxyl radicals to mineralization decreases with irradiance, while the contribution of superoxide anion radical and its conjugate acid increases. If the regression equations of these two contributions are considered together, in a linear combination, the surface model perfectly fits the experimental data. Copyright © 2008 John Wiley & Sons, Ltd.

A photo-catalysis and dynamic membrane reactor system (PMR), with coated dynamic layer on polypropylene non- woven fabric material, was studied for continuous photocatalysis and retention of catalysts in a single device, in removing halogenated compound 2,4,6-Tribromophenol in water. Different dynamic layer materials such as graphite oxide, graphene oxide and nonoCaCO3 were applied to evaluate the efficiency in removing COD, 2,4,6- Tribromophenol and in debromination. The pre-coated dynamic membrane can significantly enhance the filtration performance and improve the debromination efficiency. The PMR system with dynamic layer and Fe-ZnIn2S4 photocatalyst completely removed 2,4,6-Tribromophenol when the retention time maintained 2.0 h in the continuous mode. The hybrid system achieved 58%, 74% and 85% debromination when the dynamic layer materials were graphite oxide, graphene oxide and nanoCaCO 3 , respectively. And, the COD removal efficiencies were in the order of nanoCaCO 3 (72%) > graphite oxide (51%) > graphene oxide (42%). NanoCaCO 3 was found able to assist and improve debromination efficiency during UV irradiated photolysis. The combination of dynamic membrane and photocatalysis provides a new alternative for practical application of photocatalysis.