Flotation Separation of Scheelite from Calcite Using Sulfonated Naphthalene–Formaldehyde Condensate as Depressant

Abstract

In this paper, the potential of sulfonated naphthalene formaldehyde (SNF) condensate as a depressant in the flotation separation of scheelite from calcite was verified and investigated. The results of microflotation experiments showed that SNF had a stronger depressant performance on calcite than a conventional depressant—water glass and had an excellent performance in fine-grained particles (−0.037 mm) treatment. Adsorption tests were conducted to quantitatively study the selective adsorption of SNF on the surface of scheelite and calcite. At 200 mg/L SNF, the adsorption density of SNF on the calcite surface reached 5.48 mg/g, which was more than four times than that of scheelite. In addition, compared with scheelite, the adsorption of SNF on the calcite surface had a more significant negative effect on the contact angle. Moreover, infrared (IR) measurements combined with X-ray photoelectron spectroscopy (XPS) analysis were performed to investigate the adsorption mechanisms of SNF on scheelite and calcite surfaces. The results showed that the adsorption of SNF on scheelite was more likely to be physical attraction, while the –SO3− group in SNF could chemically react with Ca species on the surface of calcite, resulting in a stronger adsorption than on scheelite.