Interplay between the Transport of Solutes Across Nanofiltration Membranes and the Thermal Properties of the Thin Active Layer

Abstract

The thin active layer (TAL) of seven nanofiltration (NF) membranes was studied using differential scanning calorimetry, and the membranes were classified into two groups according to the polymer physical state (amorphous or semicrystalline). NF membrane performance in terms of permeate volume flux density and rejection of neutral solutes was investigated in temperature cycles. The modeling of rejection using a hindered transport theory showed irreversible and opposite pore size changes for the two groups of NF membranes when the maximum operating temperature of the cycle exceeded the glass-transition temperature of the TAL. A mechanism of pore deformation is proposed to explain the variation of the solute transport properties as a function of the temperature and the polymer physical state in the TAL.

Reverse osmosis performance of organosilica membranes and comparison with the pervaporation and gas permeation properties

“…When the feed temperature was decreased gradually back to the starting level, water permeability returned to approximately the initial value, and high salt rejection was maintained. Only a few polymeric NF membranes withstood a temperature cycle of up to 65°C without a significant change in filtration performance . The high reproducibility of the RO performance in temperature cycles indicated superior hydrothermal stability of the BTESE membranes, which would benefit applications of high‐temperature reverse osmosis.…”

“…Moreover, operation of RO at high temperatures is desired in many industrial applications, such as the food and textile industries . Unfortunately, the maximum operating temperature for most polyamide membranes is normally below 55°C . Hence, a major objective in new RO membrane development is the combination of high permeability and selectivity, along with durability in harsh environments.…”

Enhanced performance of inorganic-polyamide nanocomposite membranes prepared by metal-alkoxide-assisted interfacial polymerization

“…According to the Ferry equation [36], rejection by a sieving membrane with a uniform pore size (i.e., diameter) can be expressed simply as R = [1 − (1 − d s /d p ) 2 ] 2 × 100, where R is the percent rejection, d s is the solute diameter, and d p is the diameter pore size of the membrane. In the hindered diffusion model, which has been used for characterization of polyamide membranes, rejections are formulated in a more complicated manner [37][38][39][40]. In both models, Stokes radii were used for solute sizes, d s , which can be calculated from the diffusivities.…”

Factors contributing to the change in permeate quality upon temperature variation in nanofiltration

“…5) applicable to charged species is derived by Bandini et al [26]. Temperature dependence of solute diffusivity, 3,* , is accounted for by the Stokes-Einstein equation [18], [27] and values of the dynamic viscosity of water, 4 , are taken from reference [28]. Extent of ion partitioning by membrane between feed solution and poreentry…”