Fabrication of Graphene Oxide/Polyacrylonitrile Electrospun Nanofiber Membrane with a Carbon Nanotube Photothermal Layer for Solar-Driven Interfacial Water Evaporation Kateryne Rocio Ccama Mamani School of Environment and Energy Engineering Gwangju Institute of Science and Technology

Abstract

Water scarcity is a global issue that has been worsening in recent years. Due to the limited access to and depletion of natural freshwater sources, such as rivers and groundwater, desalination processes have emerged a crucial solution to address the insufficient water supply problem. However, a major environmental impact of this technology is the production of brine, a highly concentrated salt solution with significant ecological risks. To mitigate the impact of brine disposal, the Zero-Liquid Discharge (ZLD) concept recovers water and valuable resources like salts, preventing harmful environmental discharges. To reduce reliance on energy-intensive processes, the combination of solar-driven interfacial evaporation technology, a technology that harnesses sunlight to generate heat promoting water evaporation, with ZLD system, offers a sustainable alternative, minimizing environmental impact and improving brine management. In this research, a polyacrylonitrile (PAN) solution is combined with graphene oxide (GO) particles to fabricate an electrospun nanofiber membrane using electrospinning technique. Carbon nanotube (CNT) particles were subsequently incorporated onto the membrane via spraying, forming a uniform photothermal layer. Membranes are prepared with various graphene oxide concentrations (0.5 - 4 % relative to PAN wt%) and CNT spraying durations (30 - 120 seconds). The performance of these membranes was then evaluated in a solar-driven interfacial water evaporation process. The optimal conditions for the CNT-GO/PAN (CGOP) membranes were a 2% GO concentration and a CNT spraying of 90 seconds. Under these conditions, the membrane achieved an evaporation rate of 1.53 kg m-2 h-1, compared to 1.22 kg m-2 h- for the GO/PAN (GOP) and 0.89 kg m-2 h-1 for the pure PAN membrane. Testing the optimal membrane with simulated saline water (3.5 wt% NaCl) and brine (7 wt% NaCl) revealed a ~33% performance reduction for both cases. Despite this, the membrane demonstrated the ability to work under high salinity conditions and tolerance to salt crystal accumulation, highlighting its photothermal conversion potential for solar-driven evaporation applications, such as Zero-Liquid Discharge.