Apatite–Calcite Flotation Separation Using Sodium N-Lauroylsarcosinate as a Selective Collector

Froth flotation is a commonly utilized beneficiation technique for effectively separating apatite from other gangue minerals, such as calcite. It is difficult to achieve good separation with fatty acid collectors due to their similar interactions with apatite and calcite. In this work, sodium N-lauroyl sarcosinate (SNLS) was used as the collector for the selective separation of calcite from apatite without a depressant. The experiments revealed that SNLS had a much better selectivity and a stronger affinity with calcite compared to apatite, with little effect on the flotation of apatite observed at a pH of 10. Fourier transform infrared (FTIR) analyses were conducted to explain the selective collector process of SNLS. The mechanism experiments demonstrate that SNLS can chemically bond to apatite and calcite minerals to produce Ca-NLS chelates. The active O atoms of the amide and carboxyl groups of SNLS accomplish this. Calcite has a greater Ca-reactivity than apatite, and as a result, the adsorption quantity on the calcite surface is greater than that on the apatite surface. FTIR analyses indicate that SNLS exhibits a greater affinity for the calcite surface than for apatite, a finding that is supported by first-principle density functional theory (DFT) calculations showing a higher adsorption energy of SNLS on the calcite surface. DFT calculations showed that SNLS forms stronger O-Ca bonds on the calcite surface and is less hindered by H₂O. This work shows that the surfactant sodium N-lauroylsarcosinate (SNLS) can be an ideal collector for the flotation of phosphate minerals.