Self-assembled membrane manufactured by metal–organic framework (UiO-66) coated γ-Al2O3 for cleaning oily seawater

In order to effectively clean oily seawater with anionic polyacrylamide (APAM), UiO-66 coated γ-Al₂O₃ (UA) composites were firstly synthesized using γ-Al₂O₃ as a template to induce the growth of high hydrophilic UiO-66 on its surface to form a uniform UA self-assembled membrane. The UA composites and self-assembled membrane were characterized and analyzed. Also, the membrane performance was investigated. The results show that the hydrophilicity of particles is enhanced with the water contact angle decreasing from 39.8° (γ-Al₂O₃ particles) to 26.2° (UA composites) by introducing the UiO-66 coating. Moreover, the UA self-assembled membrane performs attractive water yield and separation performance. The oil concentration in the permeate treated by the first class of UA self-assembled membrane declines apparently from 91.22 to 18.90 mg L⁻¹, while the water yield is as high as 657.89 L m⁻² h⁻¹. The reclaimed separation experiments show that the membrane materials could be recycled by calcination at 200 °C and hydraulic cleaning, which gives the material potential application in cleaning oily seawater.

The self-assembled membrane manufactured by UA composites exhibits excellent separation performance and water yield in the treatment of oily seawater.

New insight into the adsorption behaviour of effluent organic matter on organic-inorganic ultrafiltration membranes: a combined QCM-D and AFM study

Adsorption of organic matter on membranes plays a major role in determining the fouling behaviour of membranes. This study investigated effluent organic matter (EfOM) adsorption behaviour onto poly(vinylidene fluoride) (PVDF) membrane blended with SiO₂ nanoparticles using quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). The QCM-D results suggested that low adsorption of EfOM and an EfOM layer with a non-rigid and open structure was formed on SiO₂-terminated membrane surfaces. Conformational assessment showed that EfOM undergoes adsorption via two steps: (i) in the initial stage, a rapid adsorption of EfOM accumulated onto the membrane; (ii) the change in dissipation was still occurring when the adsorption frequency reached balance, and the layer tended towards a more rearranged or organized secondary structure upon adsorption onto the more hydrophilic surface. For the AFM force test, when a self-made EfOM-coated probe approached the membrane, a 'jump-in' was observed for the hydrophobic membrane after repulsion at a small distance, while only repulsive forces were observed for PVDF/SiO₂ membranes. This study demonstrated that the PVDF/SiO₂ membrane changed the entire filtration process, forming a 'soft' open conformation in the foulant layer.

New insights into the humic acid fouling mechanism of ultrafiltration membranes for different Ca2+ dosage ranges: results from micro- and macro-level analyses

To reveal the mechanisms of the influence of Ca²⁺ on membrane fouling with humic acid (HA), the adhesion forces of HA with both other HA molecules and the membrane, the HA fouling layer structure, HA fouling experiments, and the HA rejections at a wide range of Ca²⁺ dosages were investigated. The results indicated that the effect of Ca²⁺ on HA fouling can be divided into three stages. At lower ionic strength (IS) of CaCl₂, the change in electrostatic forces is the main factor in controlling HA fouling behavior; i.e., increasing Ca²⁺ dosages resulted in more serious membrane fouling. When the IS of CaCl₂ reached 10 mM, HA aggregates became the dominant factor in the fouling process, which could result in a porous fouling layer accompanied by less membrane fouling. Interestingly, much weaker membrane fouling was observed when the IS increased to 100 mM and the HA rejection began to decline. This was because a stronger hydration repulsion force was generated, which could weaken the compactness of the fouling layer and the adhesion forces of HA with both the membrane and HA, while enabling smaller-sized HA to pass more easily into the permeate, which led to less membrane fouling and a lower HA rejection.

Preparation and Anti-Fouling Property of Acryloylmorpholine-Grafted PVDF Membrane: The Effect of Cross-Linking Agent

Inspired by the hydration capability of hydrogel materials, cross-linked poly(N-acryloylmorpholine) (PACMO) chains were designed into poly(vinylidene fluoride) (PVDF) backbones to synthesize the copolymers (PVDF-g-PACMO) using the radical polymerization method. These copolymers were then cast into the porous membranes via immersion phase inversion. The effects of N,N′-methylenebisacrylamide (MBAA) in the reaction solution on the structure and performance of as-prepared copolymer membranes were evaluated by elemental analysis, X-ray photoelectronic spectroscopy, field emission scanning electron microscopy, water contact angle measurement, protein adsorption and filtration experiment. The grafting degree of PACMO increases with the increase of MBAA amount in the reaction solution, which endows the copolymer membrane with a good hydrophilicity. The protein adsorption and irreversible membrane fouling decrease and then further increase with the elevated grafting degree of PACMO. This result indicates that the anti-fouling property of membrane not only depends on the surface hydrophilicity and but also associates with the grafting structures of PACMO. This work provides a fundamental understanding of various grafting structures governing the performance of anti-fouling properties.

A PVDF/PVB composite UF membrane improved by F-127-wrapped fullerene for protein waste-water separation

F-127-wrapped fullerene was prepared successfully in a solvent before casting solution preparation, the composite membrane shows excellent hydrophilicity and capacity for protein waste-water separation.