Kaolin based 3D printed porous adsorbent structures for aqueous dye removal technologies

Abstract

Porous kaolin-based adsorbent structures were fabricated by direct ink writing (3D printing) and tested for methylene blue (MB) removal in a rotating contactor configuration. Two pastes were developed: kaolin-only (70 wt% kaolin/30 wt% water) and starch-modified (56 wt% kaolin/14 wt% starch/30 wt% water), both exhibiting shear-thinning viscoelastic behavior suitable for extrusion-based printing. Structures were calcined at 550°C, yielding BET surface areas of 45.25 and 52.57 m2/g for the kaolin-only and starch-modified samples, respectively. Starch incorporation increasedsurface area by 16% and pore volume by 24%, reducing equilibrium adsorption time by ~55% (from ~6200 to ~2800 min). The kaolin-only structure followed the Weber–Morris intraparticle diffusion model (R2 = 0.98), while the starch-modified sample obeyed pseudo-second-order kinetics (R2 = 0.98), confirming that starch addition eliminates intraparticle mass-transfer limitations. Both materials fitted the Langmuir isotherm (R2 ≥ 0.998), with maximum adsorption capacities of 38.6 and 45.7 mg/g, respectively.Preliminary desorption tests showed MB recovery under acidic conditions without structural damage. These results establish 3D-printed kaolin as a viable, low-cost platform for structured adsorption, with corn starch modification providing a simple route to enhanced water treatment performance.