Performance Analysis of Electrothermal Membrane Distillation with Carbon Nanotube-based Composite Spacers for Hypersaline Water Treatment

Abstract

Membrane distillation (MD) is a thermally driven separation process operating at moderate temperatures and near-atmospheric pressures, offering advantages such as low fouling and scaling tendencies. Despite its potential for hypersaline water treatment, the industrial application of MD remains limited by low energy efficiency. Recent efforts have therefore focused on improving thermal utilization and energy recovery. In this thesis, electrothermal membrane distillation (ETMD) is investigated in two sections of experimental and numerical using carbon nanotube (CNTs) composite spacers as electrically conductive layers to improve thermal efficiency. A comprehensive computational fluid dynamics (CFD)–based sensitivity analysis was performed to optimize both operating and material parameters, identifying conductive-layer characteristics and design guidelines that advance ETMD toward practical, energy-efficient desalination. At optimal operating conditions, with a power density of up to 60 kW/m², feed flow rate of 2 mL/ min, and feed salinity as high as 100 g/ L NaCl, the ETMD configuration exhibits stable performance and excellent heat-utilization efficiency. The carbonized CNT composite exhibits high electrical conductivity, corrosion resistance, and mechanical stability, significantly enhancing interfacial heat transfer through localized Joule heating. Large-scale modeling further revealed that employing a CNT layer with an electrical conductivity of 360,000 S/m enables a membrane length of 1.4 m, achieving permeate fluxes of approximately 35 kg/m².h. These findings demonstrate the strong potential of CNT-based ETMD systems for scalable, energy-efficient desalination of hypersaline water, paving the way for industrial deployment and zero-liquid-discharge (ZLD) applications.