Selective flotation separation of spodumene from feldspar using sodium alginate as an organic depressant

Sodium alginate (SA) was investigated for use as a depressant in the spodumene-feldspar system. In this flotation system, the SA is added before the cation collector, dodecylamine (DDA). The effects of SA on mineral floatability were systematically investigated by flotation experiments, X-ray photoelectron spectroscopy (XPS), Fourier transform IR spectroscopy (FTIR), zeta potential measurements, and speciation analysis. Single-mineral flotation results showed that using 30 mg/L SA allowed the separation of spodumene from feldspar at pH 6, although there was a strong pH dependence. Zeta potential measurements and FTIR analysis showed that SA and DDA can adsorb onto both minerals. XPS analysis revealed the adsorption mechanism: the strong affinity of SA for the mineral surface arose from the complexation of SA and Al sites. Analysis of the surface and solution chemistry revealed that SA chelated Al3+ or its hydroxides and hindered the subsequent adsorption of DDA, resulting in a hydrophilic feldspar surface. In addition, there were more aluminium hydroxides and unsaturated O atoms on the spodumene surface than on that of feldspar, and these provided available sites for the adsorption of DDA to form a stable reticular structure with SA, thus improving the floatability of the spodumene at certain pH values. Lastly, a model for SA and DDA adsorption at the water-solid interface is proposed.