New insights into selective-depression mechanism of novel depressant EDTMPS on magnesite and quartz surfaces: Adsorption mechanism, DFT calculations, and adsorption model

In this study, to improve the separation efficiency of magnesite from quartz, ethylenediamine tetra(methylene phosphonic acid) sodium (EDTMPS) was first introduced as a chelation depressant for the selective depression of magnesite in magnesite-quartz flotation system when using dodecylamine (DDA) as the collector. The results of micro-flotation tests indicated that EDTMPS selectively depressed magnesite flotation and achieved the separation of magnesite from quartz via reverse flotation. Contact-angle and zeta-potential measurements demonstrated that EDTMPS interfered with the interaction of DDA with magnesite rather than quartz, resulting in the low hydrophobicity of magnesite in the presence of DDA. Fourier-transform infrared (FTIR) spectroscopy and Xray photoelectron spectroscopy (XPS) analysis showed that EDTMPS could prevent DDA adsorption onto a magnesite surface could be attributed to selective chelation on Mg, but had only a slight impact on a quartz surface. Density functional theory (DFT) calculations further revealed that the interaction between DDA and magnesite was weakened by the pre-adsorption of EDTMPS; this observation was supported by the enlarged distance between N atoms for DDA and magnesite surface (from 2.636 angstrom to 8.003 angstrom) in the presence of EDTMPS. Based on these results, a possible model for the flotation separation process was proposed.

Automated summary

In this study, EDTMPS was introduced as a chelation depressant to selectively depress magnesite in a magnesite-quartz flotation system using DDA as the collector. Results from micro-flotation tests showed that EDTMPS interfered with the interaction of DDA with magnesite, leading to the successful separation of magnesite from quartz. The study also utilized contact-angle and zeta-potential measurements, FTIR and XPS analysis, as well as DFT calculations to understand the mechanism behind the improved separation efficiency.