Electrohydrodynamic atomization of CNT on PTFE membrane for scaling resistant membranes in membrane distillation

Abstract

In this study, an electrohydrodynamic atomization or electrospraying technique is used for the uniform deposition of carbon nanotubes (CNT) on a commercially available PTFE membrane and employed for Membrane Distillation (MD) process. Modified PTFE-CNT membrane was characterized for water contact angle, liquid entry pressure (LEP), pore size distribution, and surface morphology. The electrospray coating of CNT on the PTFE membrane enhances the turbulence and thereby the temperature polarization coefficient (TPC). The pore size of the micropatterned PTFE-CNT membrane has been reduced and pore size distribution has been narrowed compared to the PTFE membrane. Field-effect scanning electron microscopy images of the membranes were observed before and after the MD process. Functionally graded PTFE-CNT membrane showed superior desalination performance compared to the PTFE membrane with less amount of cake layer formation on the membrane surface. Water vapor flux remained constant during 24-h continuous MD process operation with 99.99% rejection of inorganic salts.

Omniphobic, Bilayer Carbon Nanotube-Immobilized Fluorinated (FAS) Membranes for Bioethanol Recovery at High Concentrations via Membrane Distillation

“…74,75 CNTs are particularly well-suited for creating a micro/nanometer-level rough hierarchical surface 42,65 and the fluorination on the CNT-coated surface strengthened the re-entrant structures. 45,46,51 Due to the formation of these multiscale textures in FAS-CNIM, high surface roughness and contact angles were also observed which contributes a stable omniphobicity and antiwetting resistance. 51…”

“…The wetting property of membranes when exposed to increasing ethanol concentrations is an important consideration. 50,51 The contact angle at higher ethanol concentrations is an important parameter. This was performed using liquid droplets (4 μL) which were dropped on the membrane surface using a Hamilton microsyringe (0−10 μL), and a stagemounted video camera was used to record its picture.…”

“…The combination of increased surface roughness due to the CNTs and superior ominphobicity of the FAS showed the best results. 51,52 In order to enhance the omniphobicity via FAS coating, the dip-coating conditions were carefully optimized, considering factors such as the dip-coating time, number of cycles, and FAS concentration. Figure 5b illustrates the impact of dip-coating time on improving the surface oleophobicity of the modified membranes.…”

“…The lower membrane porosity is often associated with smaller pore sizes and higher LEPs to provide higher wetting resistance. 51 The ATR-FTIR spectra of the modified and unmodified samples were acquired using an Agilent Cary 610/620 FTIR instrument spanning the 400−4000 cm −1 range. The molecular bonding of the fluorinated alkyl silane (FAS) compound as well as the silica bonds on the membrane surface coated with FAS and unmodified surfaces were investigated.…”

Modified Electrospun Membranes Using Different Nanomaterials for Membrane Distillation

“…Advanced MD configurations also need to be explored with novel pristine ENMs and blended composite and modified MD membranes prepared via an electrospinning process [ 61 ]. Electrohydrodynamic atomization of nanomaterials to coat membrane surfaces to tune the surface characteristics is rarely explored [ 160 ]. So far, the application of ENMs in the MD process has been limited to lab-scale investigations.…”