Potentiality of PLA 3D printed macro-structured feed spacers with a rational and facile layout for improved MD desalination performance

Abstract

Membrane performance, regarding water flux and water recovery during membrane distillation (MD), is crucial during desalination. In this study, the membrane performance was improved using 3D-printed macro-structured feed spacers. Typically, 3D-printed feed spacers offer maximum flexibility for designing favorable geometrical transformations. The role of 3D-printed spacers in enhancing the permeate flux and recovery in direct contact membrane distillation (DCMD) has been thoroughly investigated. A comparative assessment was performed for various designs of 3D printed feed spacers with varying hydraulic diameters and filament thicknesses. An economical, biocompatible, and highly robust 3D-printed membrane spacer was developed using polylactic acid (PLA), which has a high elastic modulus. PLA is a biodegradable and environmentally friendly material. The thermal stability of PLA materials is advantageous for temperature-driven MD processes. PLA filaments were subjected to thermogravimetric analysis (TGA) for evaluating thermal stability. It provides structural support for the membranes and enhances mass movement through the membrane surface. In addition, these 3D-printed membrane spacers employing PLA have proven superior to conventional layouts in performance. These 3D-printed feed spacers were rationally designed to create a high flow disruption, which can lead to increased turbulence, thereby increasing the permeate flux. The overall results suggest that the 3D printed spacers can be ranked like TR˃DI ≈ SQ ˃ CR in terms of water flux. Eventually, the presence of 3D-printed spacers may prevent the external foulant layer onto the surface of membrane. Thus, the 3D printed spacers were ranked as TR˃DI ≈ CR≈ SQ for fouling mitigation ability. Furthermore, the used PVDF membrane with 3D printed spacers indicates lower hydrophobicity reduction, 11–14%. Therefore, this paper illustrates a facile approach to designing 3D-printed feed spacers that exhibit increased membrane performance in MD operation.