Capstone lab project on crystallization of struvite

Abstract

Crystallization was carried out as one of the undergraduate chemical engineering lab projects. The crystallization lab conveyed concepts of crystallization fundamentals, i.e. crystallization rates, crystal growth and morphology. Specifically, it was designed to develop insights on how to relate the crystallization rates with the change in pH level. The experiment was environmentally safe, done at ambient temperatures and thus energy-efficient, and that the experimental data collection was easy. The experiment was actively guided by lecturers in a way to encourage meaningful lab experience. Analysis of the data involved straightforward mathematical expressions and graph plotting using familiar software. A typical of the lab projects, namely crystallization of magnesium ammonium phosphate hexahydrate (MgNH4PO4·6H2O), commonly known as struvite, is presented in this paper, of which the experimental results agreed with most published literature. The project was implemented in accordance with aspects of good laboratory practice, i.e. in alignment with content, assessment, and pedagogy. To assess learning outcomes, pre- and post-evaluation instruments were employed. The post-test scores were significantly higher than those of the pre-test indicating that the learning outcomes were achieved. Students’ overall feedback was positive, implying that the lab projects have been successfully implemented. In addition, the lab projects were found to increase students’ writing and presentation skills.