Quinic acid as a novel depressant for efficient flotation separation of scheelite from calcite

There are difficulties to the conventional depressant for achieving separation of scheelite from calcite for the sake of their similar surface properties. The paper reported that a new depressant quinic acid (QA) was used for separating scheelite from calcite. The adsorption experiments, zeta potential experiment, contact angle, FTIR, XPS analysis and crystal chemistry analysis were utilized to known the depression mechanism of selectivity. The results showed that the recovery of calcite decreased drastically after QA added, whereas hardly influenced on scheelite. The tungsten concentrate could reach 66.24% WO3 grade and 89.46% recovery with 1.5×10-4 mol·L-1 QA at pH=9. The surface adsorption quantity of the QA on calcite was much greater than scheelite, which enhanced significantly the hydrophilicity of calcite surface. Due to its negative charge, QA could be adsorbed on the surface of calcite which had positive charge instead of that of scheelite with negative charge. Subsequently, free carboxyl groups of QA could chelated with Ca2+ species on the calcite surface to form stable chemical adsorption in order to prevent the Pb-BHA to form further adsorption on that, so there was no increase significantly on hydrophobicity. However, QA was obviously weak for adsorbing while Pb-BHA which could still be chemically adsorbed on scheelite surface of pre-treated with QA.