Crystallization in the presence of impurities: mechanisms, models and controls

Abstract

Industrial crystallization often follows synthesis steps, leaving the starting solution enriched with impurities such as unreacted materials, side products, degradants, and other residual contaminants. Although considerable progress has been made, developing effective impurity control strategies remains a key challenge in industrial crystallization. This review explores the thermodynamic and kinetic mechanisms through which impurities disrupt crystallization processes, particularly their effects on crystal growth and final product purity. Experimental strategies for diagnosing and controlling impurity retention are assessed, together with mechanistic models that elucidate incorporation pathways and support process design. By bridging fundamental insights with practical applications, this review aims to support enhanced impurity control in crystallization processes, offering a roadmap for improving product quality in impurity-laden systems.