The flotation of fine hematite by selective flocculation using sodium polyacrylate

Abstract

• Fine hematite was separated from fine quartz by PAAS flocculation flotation . • The hematite particle size increased by 52% due to PAAS selective flocculation. • The adsorption mechanism of PAAS on the hematite surface was discussed in detail. Fine hematite and quartz are particularly difficult to separate using classic flotation and magnetic separation methods because the particles were very small and readily reported to the wrong product. The effect of sodium polyacrylate (PAAS) on the flotation separation of fine hematite from quartz and its mechanism were investigated by micro-flotation experiments using NaOL as a collector, particle size analysis, zeta potential measurements, FT-IR, SEM analysis as well as XPS analyses. The flotation tests found that the flotation recovery of fine hematite increased observably to 94.51% from 68.69% by adding 4 mg/L PAAS before NaOL at pulp pH 7.3; in the separation of mixed hematite and quartz, the separation efficiencies of fine hematite with and without the addition of the PAAS are 85.71% and 68.84%, respectively. After treatment with the PAAS, the fine hematite was well flocculated so that the average hematite particle size increased to 26.73 μm from 17.69 μm, and the particle size distribution of hematite less than 17 μm decreased to 29.58% from 52.51%. Zeta potential variations indicate that the collector NaOL is able to adsorb on the hematite surface after flocculation by the flocculant PAAS whereas the adsorption of the PAAS on quartz plays an inhibitory role in the adsorption of collector NaOL on the quartz surface, considerably improving the floatability of fine hematite, and thus realizing the effective separation of fine hematite from fine quartz. Furthermore, FT-IR, SEM, and XPS analyses suggest that the flocculant PAAS adsorbs on the hematite surface in a scattered punctiform morphology via a chemical bond in which the Fe 3+ of the hematite surface reacts with the –COO – of PAAS to form dimers, including (RCOO) 2 2– or RCOOH-RCOO - .