Effects of alkaline treatment on the surface properties an 2027 Minerals Eng

Alkaline regulators can alter the surface properties of scheelite and thereby affect its interaction with collectors. This study compared the effects of NaOH and Na2CO3 on the surface properties and morphology of representative crystal surfaces using microflotation tests, contact-angle measurements, atomic force microscopy (AFM), N2 adsorption – desorption measurements, X-ray diffraction (XRD), and inductively coupled plasma atomic emission spectrometry (ICP-AES). At pH 11, the mean scheelite recoveries were 90.41 % in the NaOH system and 81.93 % in the Na2CO3 system. The XRD patterns showed no appreciable change in the bulk crystal structure after either treatment. NaOH induced pronounced surface modification and increased the BET specific surface area from 0.0778 to 0.1696 m2⋅g−1; these changes coincided with a stronger NaOL-induced hydrophobic response. By contrast, Na2CO3 treatment was associated with surface flattening, a decrease in BET specific surface area to 0.0599 m2⋅g−1, and weaker NaOL-induced hydrophobic response. The combined AFM, BET, XRD, and ICP-AES results were consistent with localized surface modification in the NaOH system and carbonate-associated surface modification or passivation in the Na2CO3 system. In single-run closed-circuit tests of the actual ore, the NaOH system produced a concentrate with a WO3 grade of 66.43 % and a WO3 recovery of 67.40 %, compared with 65.98 % and 64.89 %, respectively, in the Na2CO3 system. Under the investigated conditions, NaOH caused more pronounced surface modification and a stronger NaOL-induced hydrophobic response than Na2CO3.