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The emerging technology of pressure retarded osmosis (PRO) has been intensely studied over the past decades due to its potential in harvesting salinity gradient energy, but membrane fouling can deteriorate the PRO performance. To mitigate membrane fouling, the outer surface of the inner-selective thin-film composite (TFC) polyetherimide (PEI) hollow fiber membrane was modified by depositing poly-(allylamine hydrochloride) (PAH) and poly acrylic acid (PAA) polyelectrolytes. The results show that the outer surface of the modified membrane had less pores exposed and was more negatively charged, which was beneficial for preventing the entrance and adsorption of the negatively charged foulants into the membrane substrate. It was further proved that the modified membrane was effective in reducing PRO fouling by organic macromolecules such as alginate and bovine serum albumin, while maintaining the mechanical properties and intrinsic separation properties well. Interestingly, after 200 ppm alginate was introduced to the feed water, the power density of the modified membrane could be maintained constant at 16.2 W·m − 2 at 15 bar while that of the non-modified membrane reduced around 17% at the end of a 300-min testing period. The results suggest that the polyelectrolytes deposition is a feasible strategy for adding anti-fouling property to PRO membranes. [ABSTRACT FROM AUTHOR]

Thin-film composite (TFC) membranes are generally preferred over integrally skinned asymmetric (ISA) membranes in pressure retarded osmosis (PRO) process due to their much higher water permeability, but they cannot operate in the active layer facing feed solution (AL-FS) orientation because of potential delamination of the rejection layer under the high applied pressure. However, operating under AL-FS orientation is preferred as a strategy for better fouling control. Hence, in this study, three ISA hollow fiber membranes were fabricated using a dry-jet wet-spinning method, followed by chemical cross-linking to obtain membranes for PRO application. The best-performing membrane was subjected to fouling test in two orientations. Our results demonstrate that the AL-FS orientation is better for a sustainable long-term PRO operation, given the stable performance throughout the two-day testing. Also, the current use of power density per membrane area as a performance benchmark may not be practical for large-scale PRO operation, and the volumetric power density per module is more relevant. In terms of volumetric power density for a hypothetical 5-in. module, our best-performing membrane is predicted to generate a 3.6 to 10 times better power density than commercial modules, rendering our ISA hollow fiber membranes promising for scaling-up to bigger modules. [Display omitted] • Operating under AL-FS orientation is preferred as a strategy for better fouling control. • Integrally skinned asymmetric hollow fiber membranes were developed for AL-FS orientation in PRO. • The membranes achieved sustainable power production when wastewater was employed. • The volumetric power density was predicted to yield promising solution for practical application. [ABSTRACT FROM AUTHOR]

Thin-film composite (TFC) membranes are generally preferred over integrally skinned asymmetric (ISA) membranes in pressure retarded osmosis (PRO) process due to their much higher water permeability, but they cannot operate in the active layer facing feed solution (AL-FS) orientation because of potential delamination of the rejection layer under the high applied pressure. However, operating under AL-FS orientation is preferred as a strategy for better fouling control. Hence, in this study, three ISA hollow fiber membranes were fabricated using a dry-jet wet-spinning method, followed by chemical cross-linking to obtain membranes for PRO application. The best-performing membrane was subjected to fouling test in two orientations. Our results demonstrate that the AL-FS orientation is better for a sustainable long-term PRO operation, given the stable performance throughout the two-day testing. Also, the current use of power density per membrane area as a performance benchmark may not be practical for large-scale PRO operation, and the volumetric power density per module is more relevant. In terms of volumetric power density for a hypothetical 5-in. module, our best-performing membrane is predicted to generate a 3.6 to 10 times better power density than commercial modules, rendering our ISA hollow fiber membranes promising for scaling-up to bigger modules. [Display omitted] • Operating under AL-FS orientation is preferred as a strategy for better fouling control. • Integrally skinned asymmetric hollow fiber membranes were developed for AL-FS orientation in PRO. • The membranes achieved sustainable power production when wastewater was employed. • The volumetric power density was predicted to yield promising solution for practical application. [ABSTRACT FROM AUTHOR]