Preparing Potassium Dihydrogen Phosphate Using Waste Phosphoric Acid: A Green Chemistry Experiment

A green chemistry experiment was designed to produce potassium dihydrogen phosphate from the phosphoric acid waste generated by the classic organic chemistry experiment “Preparation of Cyclohexene.” The waste was treated with concentrated phosphoric acid at high temperatures to promote the polymerization and carbonization of organic matter, followed by filtration and activated carbon adsorption to remove impurities. The concentration of the resulting phosphoric acid solution was determined by titration, and K2CO3 was added to convert the phosphoric acid to potassium dihydrogen phosphate. Finally, potassium dihydrogen phosphate crystals were obtained by crystallization, filtration, and drying. Green chemistry injects the concept of sustainable development into experiments, transforming originally wasted concentrated phosphoric acid into potassium dihydrogen phosphate, which can be used as a fertilizer for plants. This not only cultivates students’ environmental awareness and innovative spirit but also achieves positive teaching outcomes.