Synthesis of N-acyl sarcosine from vegetable fatty acid as a novel collector and its low-temperature flotation performance and mechanism for apatite

The flotation performance of traditional fatty acid collectors for apatite is significantly reduced under low-temperature conditions, limiting their industrial application. To overcome this limitation, a novel collector, N-fatty acyl sarcosine (N-FAS), was synthesized from vegetable fatty acid and evaluated for low-temperature flotation separation of fluorapatite from quartz and K-feldspar. Micro-flotation tests demonstrated that N-FAS exhibited superior selectivity, enhanced collecting power, and improved low-temperature tolerance compared to conventional sodium fatty acid (SFA). The adsorption mechanism was investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), revealing that N-FAS adsorbs onto the fluorapatite surface through synergistic coordination of both acyl and carboxyl groups with surface Ca²⁺ sites. In contrast, SFA adsorbs via a single carboxyl group interaction with Ca²⁺ sites. Total organic carbon (TOC) measurements confirmed that N-FAS adsorption on fluorapatite was approximately 40 % higher than SFA at low temperature. Molecular dynamics simulations (MDS) further demonstrated that at 10 ℃, N-acyl sarcosine exhibits lower interaction energy with water molecules and adopts a more compact spatial configuration in proximity to the fluorapatite surface compared to sodium fatty acid. These results indicate that N-FAS is a highly efficient low-temperature collector for apatite. In conclusion, this research provides a novel multidimensional interpretation of the N-FAS mechanism by bridging molecular-level MDS with macroscopic dynamic foam analysis, offering a scientific framework for the rational development of low-temperature collectors.