Effect of Fe ² ⁺ , Zn ² ⁺ , and Ca ² ⁺ on the Solvent‐Mediated Phase Transformation of Glycine

ABSTRACT This study investigated the effects of iron, zinc, and calcium ions (Fe 2 + , Zn 2 + , and Ca 2 + , respectively) on the solvent‐mediated polymorphic transformation of glycine and subsequent crystal properties. The transformation from β‐ into α‐glycine was monitored in real time using ultrasonic velocity measurements and revealed that these metal ions delayed the transformation in a concentration‐dependent manner, with Fe 2 + showing the strongest delay. x‐ray diffraction and microscopy analyses confirmed the complete transformation into α‐glycine, with significant morphology changes induced by the additives. Scanning electron microscopy and image‐based analyses showed that Fe 2 + led to compact, agglomerated crystals with irregular shapes, while Zn 2 + and Ca 2 + caused moderate thickening of the rod‐like α‐glycine crystals. Zeta potential measurements demonstrated metal ion adsorption on crystal surfaces, reducing surface charge and promoting agglomeration, particularly in the Fe 2 + system. Filtration tests revealed a sharp increase in specific cake resistance with Fe 2 + , while Zn 2 + and Ca 2 + improved filtration performance. Thermogravimetric analysis and in‐situ Fourier transform infrared spectroscopy analyses confirmed a consistent two‐step thermal degradation pattern across all samples, with minor variations in decomposition temperatures and evolved gas profiles.