Electrochemical mineral scale prevention and removal on electrically conducting carbon nanotube – polyamide reverse osmosis membranes

Abstract

The electrochemical prevention and removal of CaSO4 and CaCO3 mineral scales on electrically conducting carbon nanotube - polyamide reverse osmosis membrane was investigated. Different electrical potentials were applied to the membrane surface while filtering model scaling solutions with high saturation indices. Scaling progression was monitored through flux measurements. CaCO3 scale was efficiently removed from the membrane surface through the intermittent application of a 2.5 V potential to the membrane surface, when the membrane acted as an anode. Water oxidation at the anode, which led to proton formation, resulted in the dissolution of deposited CaCO3 crystals. CaSO4 scale formation was significantly retarded through the continuous application of 1.5 V DC to the membrane surface, when the membrane was operated as an anode. The continuous application of a sufficient electrical potential to the membrane surface leads to the formation of a thick layer of counter-ions along the membrane surface that pushed CaSO4 crystal formation away from the membrane surface, allowing the formed crystals to be carried away by the cross-flow. We developed a simple model, based on a modified Poisson-Boltzmann equation, which qualitatively explained our observed experimental results.

Electrochemical removal of hexavalent chromium using electrically conducting carbon nanotube/polymer composite ultrafiltration membranes

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In-situ combined dual-layer CNT/PVDF membrane for electrically-enhanced fouling resistance

“…Carbon nanotubes (CNTs), owing to their superior electrical conductivity and physicochemical stability, have drawn much attention as an ideal conductive material [26][27][28][29][30][31][32]. Polyvinylidene fluoride (PVDF), as one of the most extensively used membrane materials, is well known for its outstanding mechanical strength, chemical resistance, and thermal stability [33][34][35].…”

Bacteria inactivation at a sub-stoichiometric titanium dioxide reactive electrochemical membrane

“…REMs have the potential to extend the traditional roles of membranes beyond separations to include electrochemical reduction and oxidation reactions, as well as enhanced electrostatic rejection of charged species. The majority of the current research in this area is focused on using either mats of carbon nanotubes (CNTs) physically deposited on a membrane surface or blending CNTs with polymeric materials to form composite membranes [1][2][3][4][5][6][7][8][9][10]. These techniques have shown exceptional promise towards developing novel multifunctional membranes that have utility in disinfection, organic compound oxidation, and fouling prevention at the bench-scale [1][2][3][4][5][6][7][8][9][10].…”

“…The majority of the current research in this area is focused on using either mats of carbon nanotubes (CNTs) physically deposited on a membrane surface or blending CNTs with polymeric materials to form composite membranes [1][2][3][4][5][6][7][8][9][10]. These techniques have shown exceptional promise towards developing novel multifunctional membranes that have utility in disinfection, organic compound oxidation, and fouling prevention at the bench-scale [1][2][3][4][5][6][7][8][9][10]. However, key limitations of CNT-based membrane materials still exist, including: 1) high anodic potentials can lead to corrosion of the CNT network or degradation of the polymeric membrane material [11]; 2) high cost of CNTs (~ $100 kg -1 ) [12]; and 3) cytotoxicity of CNTs could potentially pose health risks if they are ingested or released into the environment [13][14][15][16].…”