Effects of reaction temperature and ageing time on aragonite formation using steamed ammonia liquid waste

Abstract

Aragonite is an important dimorph of calcium carbonate (CaCO₃), but only a few studies have reported its preparation and formation mechanism. This study presents a novel method for producing aragonite using steamed ammonia liquid waste as a calcium source and employing urea as both the carbon source and additive. X-ray diffraction and scanning electron microscopy were used to analyse various CaCO₃ polymorphs and their morphologies. The effects of the reaction temperature and reaction time on the formation of aragonite were studied systematically. The results indicate that the content and shape of the aragonite crystals were significantly influenced by the reaction temperature and reaction time. Single crystals of aragonite CaCO₃ were prepared at a reaction temperature of 140 °C and a reaction time of 120 min. An analysis of the formation mechanism showed that the reaction temperature and reaction time determine the thermal decomposition process of urea, thus controlling the nucleation and growth of aragonite CaCO₃.