Titanium dioxide (TiO₂) nanoparticles have been applied in membrane antifouling performance modification for years. However, the influence of TiO₂ nanoparticle dispersion status during the blending process on membrane properties and the inner mechanism has seldom been focused on. Herein, we investigated the influence of the various dispersing statuses of TiO₂ nanoparticles on membrane properties and antifouling performance by exploring various blending processes without changing the original recipe. Polyethylene glycol (PEG) was employed as a pore-forming agent during the membrane preparation process, and also as a pre-dispersing agent for the TiO₂ nanoparticles via the steric hindrance effect. Compared to the original preparation process of the PVDF/TiO₂ composite membrane, the pre-dispersing of TiO₂ via PEG ensured a modified membrane with uniform surface pores and structures on cross-sectional morphologies, larger porosity and water permeability, and more negative zeta potential. The contact angle was decreased by 6.0%, implying better hydrophilicity. The improved antifouling performance was corroborated by the increasing free energy of cohesion and adhesion, the interaction energy barrier (0.43 KT) between the membrane surfaces and approaching foulants assessed by classic XDLVO theory and the low flux decline in the filtration experiment. A kinetics mechanism analysis of the casting solutions, which found a low TSI value (<1.0), substantiated that the pre-dispersion of TiO₂ with PEG contributed to the high stability and ultimately favorable antifouling behaviors. This study provides an optimized approach to the preparation of excellent nano-TiO₂/polymeric composite membranes applied in the municipal sewage treatment field.

Herein, the influence of various contents of polyethylene glycol (PEG) on the dispersion of TiO₂ nanoparticles and the comprehensive properties of PVDF/TiO₂ composite membranes via the steric hindrance interaction was systematically explored. Hydrophilic PEG was employed as a dispersing surfactant of TiO₂ nanoparticles in the pre-dispersion process and as a pore-forming additive in the following membrane preparation process. The slight overlap shown in the TEM image and low TSI value (<1) of the composite casting solution indicated the effective dispersion and stabilization under the steric interaction with a PEG content of 6 wt.%. Properties such as the surface pore size, the development of finger-like structures, permeability, hydrophilicity and Zeta potential were obviously enhanced. The improved antifouling performance between the membrane surface and foulants was corroborated by less negative free energy of adhesion (about −42.87 mJ/m²), a higher interaction energy barrier (0.65 KT) and low flux declination during the filtration process. The high critical flux and low fouling rate both in winter and summer as well as the long-term running operation in A/O-MBR firmly supported the elevated antifouling performance, which implies a promising application in the municipal sewage treatment field.

The back-diffusion of inactive gases severely inhibits the hydrogen (H₂) delivery rate of the close-end operated hydrogen-based membrane biofilm reactor (H₂-based MBfR). Nevertheless, less is known about the response of microbial communities in H₂-based MBfR to the impact of the gases’ back-diffusion. In this research, the denitrification performance and microbial dynamics were studied in a H₂-based MBfR operated at close-end mode with a fixed H₂ pressure of 0.04 MPa and fed with nitrate (NO₃⁻) containing influent. Results of single-factor and microsensor measurement experiments indicate that the H₂ availability was the decisive factor that limits NO₃⁻ removal at the influent NO₃⁻ concentration of 30 mg N/L. High-throughput sequencing results revealed that (1) the increase of NO₃⁻ loading from 10 to 20–30 mg N/L resulted in the shift of dominant functional bacteria from Dechloromonas to Hydrogenophaga in the biofilm; (2) excessive NO₃⁻ loading led to the declined relative abundance of Hydrogenophaga and basic metabolic pathways as well as counts of most denitrifying enzyme genes; and (3) in most cases, the decreased quantity of N metabolism-related functional bacteria and genes with increasing distance from the H₂ supply end corroborates that the microbial community structure in H₂-based MBfR was significantly impacted by the gases’ back-diffusion.

The ubiquitous presence of tetrabromobisphenol A (TBBPA) in aquatic environments has caused severe environmental and public health concerns; it is therefore of great significance to develop effective techniques to remove this compound from contaminated waters. Herein, a TBBPA imprinted membrane was successfully fabricated via incorporating imprinted silica nanoparticles (SiO₂ NPs). The TBBPA imprinted layer was synthesized on the 3-(methacryloyloxy) propyltrimethoxysilane (KH-570) modified SiO₂ NPs via surface imprinting. Eluted TBBPA molecularly imprinted nanoparticles (E-TBBPA-MINs) were incorporated onto a polyvinylidene difluoride (PVDF) microfiltration membrane via vacuum-assisted filtration. The obtained E-TBBPA-MINs embedded membrane (E-TBBPA-MIM) showed appreciable permeation selectivity toward the structurally analogous to TBBPA (i.e., 6.74, 5.24 and 6.31 of the permselectivity factors for p-tert-butylphenol (BP), bisphenol A (BPA) and 4,4′-dihydroxybiphenyl (DDBP), respectively), far superior to the non-imprinted membrane (i.e., 1.47, 1.17 and 1.56 for BP, BPA and DDBP, respectively). The permselectivity mechanism of E-TBBPA-MIM could be attributed to the specific chemical adsorption and spatial complementation of TBBPA molecules by the imprinted cavities. The resulting E-TBBPA-MIM exhibited good stability after five adsorption/desorption cycles. The findings of this study validated the feasibility of developing nanoparticles embedded molecularly imprinted membrane for efficient separation and removal of TBBPA from water.