Suppressing Salt Transport through Composite Pervaporation Membranes for Brine Desalination

Abstract

Featured Application: The pervaporation membranes fabricated in this study can be potentially used for brine treatment.Abstract: Pervaporation membranes have gained renewed interest in challenging feedwaters desalination, such as reverse osmosis (RO) concentrated brine wastewater. In this study, composite polyvinyl alcohol (PVA)/polyvinylidene fluoride (PVDF) pervaporation membranes were prepared for brine treatment. The composite membrane was firstly studied by adjusting the cross-linking density of PVA by glutaraldehyde: the membrane with higher cross-linking density exhibited much higher salt rejection efficiency for long-term operation. A trace of salt on the permeate side was found to diffuse through the membrane in the form of hydrated ions, following solution-diffusion mechanism. To further suppress the salt transport and achieve long-term stable operation, graphene oxide (GO) was incorporated into the PVA layer: the addition of GO had minor effects on water permeation but significantly suppressed the salt passage, compared to the pure PVA/PVDF membranes. In terms of brine wastewater containing organic/inorganic foulant, improved anti-fouling performance was also observed with GO-containing membranes. Furthermore, the highest flux of 28 L/m 2 h was obtained for the membrane with 0.1 wt. % of GO using 100 g/L NaCl as the feed at 65 • C by optimising the pervaporation rig, with permeate conductivity below 1.2 µS/cm over 24 h (equivalent to a salt rejection of >99.99%).

Preparation and characterization of PVA/GA/Laponite membranes to enhance pervaporation desalination performance

“…The reason is that at a higher temperature, the vapor pressure of water became more influenced by feed concentration. Therefore, increasing the feed concentration results in decreasing the water permeation flux [20]. For further understanding of the influence of temperature on water permeability through the PVA-Lap membrane, the relationship between water flux and feed temperature follows the Arrhenius equation [60]: (10) where, the is the component i flux of (kg /m 2 .h), is the pre-exponential factor (kg /m 2 .h), is the apparent activation energy for component i transport through the membrane (kJ/mol), R is the gas constant (kJ/ mol.K) and T is temperature (K).…”

“…Recently, mixed matrix membranes have attracted great interest for pervaporation process due to their remarkable advantages of both polymer and inorganic materials. After recognizing these combined advantages, different researchers developed MMMs for pervaporation desalination such as PVA/silica [14], GO/CS [19], and PVA/PVDF/GO [20].…”

Microstructure and Performance of a Porous Polymer Membrane with a Copper Nano-Layer Using Vapor-Induced Phase Separation Combined with Magnetron Sputtering

“…The maximum pore diameter and pore diameter distribution were observed by the gas permeation method. The maximum pore diameter ( r ) can be defined by the Laplace Equation (3) [18]:r=2σcosθΔP where σ is the coefficient of the surface tension of the wetting fluid, θ is the contact angle between the wetting fluid and the membrane, and Δ P is the operating pressure when the first normal bubble appears.…”

Pinning Down the Water Transport Mechanism in Graphene Oxide Pervaporation Desalination Membranes

“…Pervaporation desalination experiments were conducted with a laboratory built pervaporation testing unit (Scheme 1). 47 A membrane with an effective surface area of 14 cm 2 was placed in the module, where one thermocouple was installed close to the membrane surface to monitor the feed side temperature. During the pervaporation test, the feed solution was preheated in a water bath and recirculated through the membrane module at a flow rate of 100 mL/min with ambient pressure.…”