Highly efficient desorption and reuse of fatty acid collectors adsorbed on mineral surface: A case study of scheelite

Flotation is the most common method to recover valuable minerals by selective adsorption of collectors on target mineral surfaces. However, in subsequent hydrometallurgy of mineral flotation concentrates, the adsorbed collectors must be desorbed since it can adversely affect the efficiency of metallurgical process and produce wastewater. ZL, as a fatty acid mixture, is a typical industrially used collector for scheelite flotation in China. Sodium oleate (NaOL) has similar fatty acid group as ZL. In this study, the desorption behavior of NaOL/ZL from scheelite surface by a physical method of stirring at a low temperature was investigated. Single mineral desorption tests showed that a desorption rate of 77.75% for NaOL from scheelite surface into pulp was achieved in a stirring speed of 2500 r/min at 5°C in a neutral environment. Under the above desorption condition, in the pulp containing desorbed collector by adding extra 30% normal NaOL dosage, the scheelite recovery stayed above 95% in the single mineral flotation test. Desorption and reuse of ZL collector for the flotation of real scheelite ore showed only a 75% normal dosage of ZL could produce a qualified concentrate for hydrometallurgy. Molecular dynamics simulations (MDS) demonstrated that the adsorption energy between NaOL and scheelite surface was lower at 5 °C than at 25 °C in a neutral pH, indicating that a low temperature was beneficial for the desorption of collector from mineral surface proved by the measurement results of contact angle, zeta potential, fourier transform infrared spectroscopy (FTIR) and atomic force microscope (AFM). Due to its simplicity and economy, the method we proposed of desorption of collector from mineral surface and its reuse for flotation has a great potential for industrial application.