Simple Scalable Fabrication of Laser-Induced Graphene Composite Membranes for Water Treatment

Laser-induced graphene (LIG)-polymer composite materials might be potentially useful in many applications, including water purification technology. For example, water treatment membranes with antibacterial and antibiofouling surfaces that could utilize the electrically conductive property of the surface are envisioned. Polymer composites consisting of LIG fabricated on porous surfaces such as water treatment membranes are mechanically robust, and the solute rejection properties of the membrane can also be tailored. With a goal of assessing the future large-scale fabrication of this membrane configuration, here we established a simple method of coating and cross-linking poly(vinyl alcohol) (PVA) on LIG membrane supports. Ultrafiltration membranes with sizes of ≤20 cm × ≤30 cm were used as substrates to make conductive LIG porous surfaces using a 10.6 μm CO₂ pulsed laser, after which 2.5% PVA/glutaraldehyde was coated and immediately cross-linked at 175 °C using a heat gun. The 2.5% LIG-PVA composite membranes showed good surface conductivity, mechanical−thermal stability, and high permeability ranging from 900 to 1300 LMH bar⁻¹. Permeate water with 0.60 NTU was obtained using feedwater containing sludge from a membrane bioreactor, and 10- and 25-fold decreases in COD and BOD, respectively, were observed. An enhanced removal of bacteria was observed at 2.5 V during filtration. This work demonstrates a method to scale up LIG composite membranes, a crucial step that is necessary in determining their commercial potential in water technology applications.