Comparative analysis of uranium adsorption by Varion-AP and A500 resins in a CSTR cascade: Modeling, optimization, and mass transfer insights

Efficient uranium removal in continuous ion exchange cascades depends on understanding coupled mass transfer resistances. This study compares a gel-type (Varion-AP) and microporous (A500) resin in a seven-stage CSTR (Continuous Stirred-Tank Reactor). Modeling confirmed the clear superiority of Varion-AP, which showed faster kinetics k LDF,opt = 3.25 h −1 and a significantly better model fit ( SSE ≈ 0.0021) compared to A500. Analysis revealed a mixed-control mass transfer regime, while intraparticle diffusion is dominant ( Biot number > 100), a non-negligible external film resistance slows the overall rate, explaining the limitations of simple LDF and PSO models. Multi-objective optimization also favored Varion-AP for its superior operational trade-offs. This study provides a framework for resin evaluation and highlights the importance of mechanistic models that account for both resistances as essential for reliable process design. • CSTR cascade study of uranium adsorption from copper solution using Varion-AP & A500 • Varion-AP outperformed A500 in uranium removal from copper PLS in CSTR cascade. • Mixed film-intraparticle mass transfer governs uranium adsorption kinetics. • Multi-objective optimization showed Varion-AP needs less resin for same removal. • Monte Carlo shows Freundlich constant (K f ) had strongest impact on K LDF uncertainty.