Influence of internal structure on the adsorption performance of 3D-printed polylactic acid filters with graphene oxide for water treatment

Three-dimensional (3D) printing enables the fabrication of customizable adsorbent filters with complex geometries and tunable internal structures. In this study, polylactic acid (PLA) filters were fabricated using fused deposition modeling, followed by acetone-assisted surface modification and graphene oxide (GO) doping to prepare composite GO/PLA filters for methylene blue (MB) removal. Unlike previous studies limited to a single design, this work systematically investigates the influence of two key internal structural parameters, infill ratio (10–80 %) and rotation angle (10°, 30°, 90°), on adsorption performance. Batch experiments (50 mg/L MB, 50 mL, 1 filter at 20–25 °C) revealed that a 40 % infill ratio provided the highest adsorption capacity (2.35 mg/g). In continuous column tests (3 mg/L MB, 1 mL/min, 8 filters), a rotation angle of 90° showed the best performance, yielding the highest adsorption capacity (1.89 mg/g) and Thomas rate constant (4.42 × 10^-4 L·mg⁻¹·min⁻¹). Image-based structural analysis was employed to quantify cross-sectional geometries and correlate them with adsorption performances, highlighting a trade-off between surface area and fluid permeability. Overall, this study identifies the optimal structural design of GO/PLA filters and provides a generalized framework for correlating 3D-printed filter geometry with adsorption efficiency, offering valuable guidance for the rational design of practical water treatment systems.