Daniel Johnson

Membrane fouling by mixed organic foulants remains a major limitation in nanofiltration (NF) for wastewater and natural water treatment. However, the combined influence of foulant composition and operating pressure on fouling mechanisms is not fully understood. This study examines the effects of bovine serum albumin (BSA), sodium alginate (SA), and operating pressure on flux recovery ratio (FRR), reversible and irreversible fouling, and dominant fouling mechanisms during dead-end NF using a DURACID membrane. A Central Composite Design within a Response Surface Methodology framework quantified linear, nonlinear, and interaction effects.,Pressure, particularly its quadratic effect, was the most influential parameter governing FRR, exceeding the contributions of BSA and SA concentrations. FRR reached a minimum at an intermediate pressure (7.5 bar), where fouling mechanisms were more uniformly. Hermia model analysis across 20 experiments showed that intermediate pore blocking (INTB) and complete blocking (CB) predominated, while standard blocking (SB) and cake formation (CF) were more significant at early filtration stages. Mixed BSA–SA systems produced the most severe and least recoverable fouling at low concentrations, highlighting concentration-dependent synergistic interactions.,AFM and SEM analyses showed that higher surface roughness and localized deposition, associated with INTB, corresponded to improved FRR, whereas smoother, more compressed fouling layers corresponded to irreversible fouling. Overall, fouling severity was governed by nonlinear interactions between pressure and foulant composition, providing a predictive basis for optimizing NF operation under complex organic fouling conditions,K

The utilization of graphene oxide and other two-dimensional nanomaterials in membrane fabrication has promises enhanced performance in a wide range of separation processes. At the same time, the large diversity in 2D material chemistry, as well as in the microstructural parameters of the constituent nanoflakes and the resulting membranes, leads to substantial variability in the reported membrane permeance values for both gases and liquids. For example, the reported water permeance through graphene oxide membranes spans a broad range from 0.5 to 200 L/(m2·bar·h). Therefore, a systematic analysis of the performance of 2D-material-based membranes requires a parameter that is largely decoupled from membrane microstructural characteristics. In our view, the diffusion coefficient of the permeating species can serve as such a parameter. Accordingly, in this work, we reprocess previously published data on permeance of 2D-material-based membranes in gas separation, as well as water and ion transport, within the framework of the solution-diffusion model to estimate diffusion coefficients under two limiting transport scenarios: isotropic diffusion and labyrinthine permeation. For the proper application of the proposed model, the sorption properties of two-dimensional materials are critically analyzed. The extracted diffusion coefficients are subsequently employed to elucidate transport mechanisms and to examine correlations between permeance and membrane microstructural parameters. In addition, recommendations for the characterization of membrane properties, microstructure, and chemical composition of 2D materials are proposed to further strengthen the contribution of future studies.

The performance of graphene oxide (GO) based nanofiltration membranes is strongly influenced by their interlayer spacing, governed by two competing factors: GO swelling in the liquid phase and penetrant adsorption.

The fouling of protein on the surface of reverse osmosis (RO) membranes is a surface phenomenon strongly dependent on the physical and chemical characteristics of both the membrane surface and the foulant molecule. Much of the focus on fouling mitigation is on the synthesis of more hydrophilic membrane materials. However, hydrophilicity is only one of several factors affecting foulant attachment. A more systematic and rationalized methodology is needed to screen the membrane materials for the synthesis of fouling-resistant materials, which will ensure the prevention of the accumulation of foulants on the membrane surfaces, avoiding the trial and error methodology used in most membrane synthesis in the literature. If a clear correlation is found between various membrane surface properties, in combination or singly, and the amount of fouling, this will facilitate the establishment of a systematic strategy of screening materials and enhance the selection of membrane materials and therefore will reflect on the efficiency of the membrane process. In this work, eight commercial reverse osmosis membranes were tested for bovine serum albumin (BSA) protein fouling. The work here focused on three surface membrane properties: the surface roughness, the water contact angle (hydrophilicity), and finally the Hansen solubility parameter (HSP) distance between the foulant understudy (BSA protein) and the membrane surface. The HSP distance was investigated as it represented the affinities of materials to each other, and therefore, it was believed to have an important contribution to the tendency of foulant to stick to the surface of the membrane. The results showed that the surface roughness and the HSP distance contributed to membrane fouling more than the hydrophilicity. We recommend taking into account the HSP distance between the membrane material and foulants when selecting membrane materials.