Fouling control in reverse osmosis membranes through modification with conductive carbon nanostructures

Abstract

A conductive form of networked cellulose, prepared by incorporating carbon nanotubes, has been used in polyvinyl alcohol (PVA) membranes for reverse osmosis. The use of networked cellulose and carbon nanostructures (CNS) not only helps control the thermal, mechanical and electrical properties of the membrane, but also enhances RO performance and allows the membrane surface to be cleaned electrolytically. High surface area multiwalled CNTs become trapped in the structure of networked cellulose. The modified material has greater tensile strength and elastic modulus, indicating an improvement in the mechanical properties of the membrane. Membranes with CNS demonstrate enhanced electrocatalytic activity when tested for hydrogen evolution in an acidic medium. The membranes are successfully applied to reverse osmosis using a feed of 25000 ppm NaCl, where the membranes with 7 wt. % CNS exhibited a 93% increase in flux compared to PVA-NC with no CNS, due to the nanotubes disrupting the compression of polymer chains under pressure. The membrane surface was recovered after fouling via electrolytic cleaning where the membrane was used as the cathode and a potential of-5V was applied for 20 minutes. All membranes retained a high salt rejection above 99.8%.

Fouling investigation of a full-scale seawater reverse osmosis desalination (SWRO) plant on the Red Sea: Membrane autopsy and pretreatment efficiency

“…Membrane fouling is still considered one of the main drawbacks In SWRO desalination, affecting drastically the operation and maintenance costs [4]. Although several approaches and methods have been proposed in recent years to mitigate fouling, it continues to be a main challenge in operations [5]. Fouling is due to undesired deposition of materials on the membrane surface or inside the membrane pores.…”

Poly(vinyl alcohol)‐based membranes for fuel cell and water treatment applications: A review on recent advancements

“…This observed higher water flux was attributed to preferential transport of water molecules through zeolite molecular sieves; while, high salt retention was ascribed to the restriction towards sodium ion passage through zeolite pores (i.e., size exclusion and ion‐exchange in zeolite) 153 . Ahmed et al 155 studied the effect of addition of randomly oriented multi‐walled carbon nanotube (MWCNT) in PVA‐NC to prepare electrically conductive PVA/NC/MWCNT nanocomposite film membrane. MWCNT‐modified PVA‐NC membrane showed higher flux and salt rejection than bare PVA‐NC membrane.…”

Progress and Perspectives of Desalination in China

“…Membrane surface modification has been developed to improve the membrane antifouling properties, by physical or chemical methods like nanomaterial penetration, mixing, coating, grafting, self-assembly, chemical coupling, physical adsorption, and irradiation, etc. [ 32 , 34 , 35 , 36 , 37 ].…”