Froth flotation is an effective method of quartz and feldspar separation. The development of highly selective reagents for separating feldspar from quartz has thus emerged as a research hotspot. In this study, an eco-friendly tannic acid (TA) was employed as a depressant to delve into its selective depressive effect on feldspar via meticulously designed pure mineral flotation tests and artificially mixed ore separation experiments. Its underlying mechanisms were investigated using such characterization techniques as Zeta potential, contact angle analysis, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Results reveal that under weakly acidic conditions, mixed ore flotation concentrates exhibited a quartz recovery rate of 92.79 %, with a selectivity index (SI) of 7.20, indicating effective separation of feldspar and quartz. The hydrophilic —OH groups of TA form coordinate bonds with Al³⁺ sites on feldspar surfaces. This impedes the adsorption of polyether amine (PEA) collectors onto feldspar via steric hindrance effects, thereby achieving the selective depression of feldspar. Therefore, in a weakly acidic system using PEA as the collector, TA serves as an effective depressant for achieving the flotation separation of quartz and feldspar.

This paper takes the lignite coal sample from Baori Hiller of Inner Mongolia as the research object.Through the coal flotation reverse flotation test and orthogonal test, the surface characteristics and flotation characteristics of lignite were analyzed and studied, and the types, dosages and processes of the lignite flotation were investigated.The results showed that the de-flotation effect of dodecyl amine(DDA)on lignite was better than that of octadecyl amine(ODA)and cetyltrimethylammonium bromide(CTAB).When the DDA dosage is 1 400 g/t, the reverse flotation efficiency is 6.89 %, the floating tail minimum ash is 11.23 %, the floating tail yield is 84.46 %, and the maximum difference between the floating fine and floating tail ash is 5.25 %. When the dosage of DDA is fixed and the dosage of dextrin is 1 600 g/t, the floating ash is divided into 15.58 %, the floating ash is 10.77 %, and the difference is 4.81 %; The effect of the amount of DDA, dextrin and octanol on the yield of floating tail was not significant, while the effect of DDA on floating tail ash was significant, but the effect of dextrin and octanol on floating tail ash was not significant.For lignite, continuous low-floating(10.20 %)and high recovery(up to 70 %)of clean coal can be obtained by successive multiple reverse flotation processes.Amine collectors have a good collection effect on minerals such as quartz, silicate and carbonate in lignite due to their physical adsorption and complex adsorption.In the pulp, the hydrogen atoms in the dextrin interact with a large number of strongly electronegative atoms such as oxygen and nitrogen present on the surface of the lignite to form a strong hydrogen bond, thereby forming a hydrophilic film on the surface of the coal particles, so that the coal particles become hydrophilic and suppressed.