The sulfonation of solid acrylonitrile-butadiene-styrene, a feedstock that is often used in the 3D printing process of fused filament fabrication, and its application in characterizing liquid-solid mass transfer is reported. The ion-exchange capacity was assessed experimentally, and intraparticle diffusion coupled with extraparticle liquid-solid mass transfer was simulated. Tubular reactors and spherical particles were fabricated by 3D printing, modified by sulfonation, and used to determine mass transfer coefficients for laminar flow in a tubular reactor and a fixed bed of spherical particles. The results show good agreement with published correlations and demonstrate the applicability of this cost-effective, accurate, and reliable method.