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Photocatalytic membrane reactors (PMRs) have been widely used in wastewater treatment over the past few years. In this study, P-doped g-C 3 N 4 (PCN), a metal-free, visible light (Vis)-driven photocatalyst, was prepared and coated on an Al 2 O 3 substrate followed by integration with an inorganic Al 2 O 3 hollow fiber membrane module for use as a PMR. The 10 wt % of PCN exhibited the highest degradation activity for methyl blue (MB) removal under Vis irradiation because the C sites and vacancies within the heptazine rings of the CN units were substituted with P to improve charge separation and reduce the number of unpaired electrons. The PMR exhibits higher efficiency and stability in the removal of MB, methyl orange, phenol solution, and a mixture of the three organic compounds than do individual hollow fiber membranes or photocatalysis systems. The TOC (total organic carbon) analysis revealed that more than 92% of the phenol was decomposed and mineralized in the PMR, which also had a MB removal efficiency of greater than 90% when repeatedly used for four times. These results indicate that the PMR developed in this study is highly active and stable, and can serve as a promising system for effective removal of organic pollutants in wastewater. Photocatalytic membrane reactor integrated with P-doped g-C 3 N 4 with Al 2 O 3 hollow fiber membrane module exhibits excellent photocatalytic activity. Image 1 • P replaces C in g-C 3 N 4 structure to improve charge separation and photocatalysis. • P-doped g-C 3 N 4 was fabricated and integrated with photocatalytic membrane reactor. • PMR can be used for wastewater treatment under irradiation of simulated sunlight. • PMR degrades MB under irradiation with light of wavelength larger than 400 nm. [ABSTRACT FROM AUTHOR]

In this study, cobalt-doped MIL-88B(Fe) (x CoMIL-88B(Fe)) was successfully synthesized and grown on an Al 2 O 3 support. The cobalt doping of MIL-88(Fe) not only enhanced its visible-light absorption but also improved free electron–hole pair separation. On adding peroxymonosulfate (PMS), 5CoMIL-88B(Fe) powder demonstrated superior photocatalytic phenol removal than that without the PMS or catalyst. The reactive seeding growth of cobalt-doped MIL-88B(Fe) was employed to prepare a 5CoMIL-88B(Fe) membrane coupled with a filtration module to produce a photocatalytic membrane reactor (PMR). The permeate flux of the photocatalytic membrane reactor (PMR) was approximately 2900–4000 L m−2 h−1 bar−1 (LMH), which demonstrated over 90% phenol removal efficiency and exhibited high stability, reusability, recyclability, and high photocatalytic activity for phenol degradation over 10 cycles utilizing 5CoMIL-88B(Fe)@Al 2 O 3 membrane with PMS. This is the first study to demonstrate a cobalt-doped MIL-88B(Fe) membrane through the reactive seeding method for a PMR system, which is an effective and sustainable process for wastewater treatment. [Display omitted] • 5CoMIL-88B(Fe)@Al 2 O 3 was used for photocatalytic membrane reactors. • 90% phenol removal efficiency were acheived with 6 mM PMS in photocatalytic membrane reactors. • Stable permeance flux (2900–4000 LMH) can be achieved in the PMR system. [ABSTRACT FROM AUTHOR]

To date no information about the stability of the polymer membranes in photocatalytic membrane reactors (PMRs) has been published. In order to implement this technology into the full scale the lifespan of the membranes should be assessed. In this paper the investigations on the influence of membrane properties, type of a TiO 2 photocatalyst (P25, ST-01, A700, and A800), a presence of oxidative species and the process parameters such as feed cross flow velocity and transmembrane pressure (TMP) on the stability of commercial polyethersulfone ultrafiltration membranes with different cut-off in a PMR are presented. Under the conditions prevailing in the PMR all the tested membranes lost their separation properties towards dextrans. The membrane characterized by the finest pores and thus the most delicate skin layer was damaged to the highest extent. The small angular-shaped particles of ST-01 caused a more severe damage of the membrane surface than the large round-edge shaped particles of A800. The deterioration of the membrane separation properties was less severe at low (1 bar) TMP value compared to that at TMP of 3 bar. The loss of the separation properties of the membranes was caused to a greater extent by the abrasion of their surface by the photocatalyst particles than by the action of oxidative species. [ABSTRACT FROM AUTHOR]

The evaluation of the influence of photocatalyst (TiO 2 P25) loading, feed cross-flow velocity ( v ), transmembrane pressure (TMP) and feed pH on the fouling phenomenon of polyethersulfone microfiltration (HFK618 – 0.1 μm) and ultrafiltration (UE10 – 10 kDa, UE50 – 100 kDa) membranes in a photocatalytic membrane reactor (PMR) is presented. Scanning electron microscopy, atomic force microscopy and laser scanning microscopy were applied for the observation of the fouling cake. The increase of the velocity v led to an increase of the permeate flux which was attributed to the formation of a thinner TiO 2 layer. The permeate flux, the thickness and the roughness of the fouling layer depended on the TiO 2 loading only at the first stage of the process. The increase of TMP resulted in a stronger flux decline caused by the increase of the fouling layer thickness. No permeate flux deterioration was observed in case of HFK618 and UE10 when TMP of 0.05-0.1 MPa was used. In case of UE50 exhibiting the highest pure water flux the fouling was the most severe. When the feed pH was changed to pH 3 or 9 the flux decline was much stronger than when no pH adjustment was done. [ABSTRACT FROM AUTHOR]

Abstract: The photocatalytic degradation of natural organic matter (NOM) would be an attractive option in the treatment of drinking water. The performance of a submerged photocatalytic membrane reactor (PMR) was investigated with regard to the removal of NOM and the control of membrane fouling. In particular, this work focused on the adsorption and desorption of humic acids (HA) and lake water NOM at the surface of TiO2 photocatalyts and ferrihydrite (FH) adsorbents in the PMR for water treatment. The addition of FH particles with a large sorption capacity helped remove the NOM released from TiO2 particles, but FH suspended in water affected the photocatalysis of lake water NOM with a low specific UV absorbance (SUVA) value. To prevent the UV light being scattered by FH without any photocatalytic activity, FH particles were attached to a submerged microfiltration (MF) membrane, which contributed to a greater removal of NOM during long-term PMR operation. The further removal of NOM from aqueous solution was achieved due to the synergistic effect of TiO2 photocatalysis and FH adsorption in PMR while minimizing the influence of photoinduced desorption of NOM. No significant membrane fouling occurred when the submerged PMR was operated even at high flux levels (>25L/m2 h), as long as photocatalytic decomposition took place. [Copyright &y& Elsevier]

Coupling UV photolysis, stable photoactive TiO 2 layers and water filtration in a single photocatalytic membrane reactor can be beneficial to achieve high quality drinking water since the membrane retains microorganisms and chemical pollutants whereas the photocatalytic treatment decreases fouling components and treats the concentrated retentate. In this work, a newly designed photocatalytic membrane reactor combining filtration with UV photolysis/photocatalysis under a low pressure mercury lamp (wavelength emission at 254 nm) using ceramic modified membranes was used to treat filtered surface water inoculated with Aspergillus fumigatus. The photocatalytic membranes used in this study were produced using an environmental friendly modification process. Results showed high percentages of adsorption and retention of the spores for both the unmodified and modified membrane. The lower pore size of the modified membrane has the advantage of retaining the spores at the surface instead of trapping the spores inside as observed for the unmodified membrane. Direct photolysis achieved retentate treatment percentages up to 99% after 60 min of treatment. The effect of the combined treatment showed that direct photolysis and photocatalysis were able to cause the deformation of spores and led to changes in membrane permeability and enzymatic activity. Image 1 • A new photocatalytic membrane reactor was used to treat surface water. • A. fumigatus was retained and inactivated using the hybrid treatment. • Scanning electron microscopy displayed morphology changes in the spores. • Flow cytometry showed effects on membrane permeability and enzymatic activity. [ABSTRACT FROM AUTHOR]