Morpholine-based Gemini surfactant: synthesis and its application for reverse froth flotation of carnallite ore in potassium fertilizer production.

Potassium fertilizer plays a critical role in increasing the food production. Carnallite is concentrated by reverse froth flotation and used as a raw material to produce potassium fertilizer (KCl) in agriculture. However, all the surfactants used in the carnallite reverse flotation process are conventional monomeric surfactants contain a single similar hydrophobic group in the molecule, which results in a low production efficiency. In this work, a new morpholine-based Gemini surfactant, 1,4-bis (morpholinododecylammonio) butane dibromide (BMBD) was prepared, and originally recommended as a collector for reverse froth flotation separation of halite (NaCl) from carnallite ore. The flotation results indicated BMBD had higher flotation recovery and stronger affinity of halite against carnallite, compared with conventional monomeric surfactant N-(n-Dodecyl) morpholine (DDM). FTIR spectra suggested that BMBD molecules were adsorbed on halite surface rather than the carnallite surface. Additionally, BMBD molecules can strongly reduce the surface tension of NaCl saturated solution. Considering the BMBD's unique properties, such as double reactive centers to mineral surfaces, double hydrophobic groups, and stronger surface tension reducing ability, made it be a superior collector for reverse flotation desalination from carnallite ores than DDM.