Apatite flotation using saponified baker's yeast cells (Saccharomyces cerevisiae) as a bioreagent

Brazil has many mineral resources, one of them being phosphate rocks. Established in 1978, the current main mineral-processing route for the Brazilian phosphate rock igneous deposits consists in a direct flotation using alkaline-saponified fatty acids as collector. Looking for new sources of reactants to be used in mineral processing, commercial baker's yeast cells (BYC) from Fleishmann were tested. Saccharomyces cerevisiae was chosen because it is relatively easy to grow industrially, has no biological risk, and can be found worldwide. Microflotation experiments were conducted in a modified Hallimond's tube with high-purity apatite samples in order to investigate the influence of the pH and the biocollector dosage on the apatite recovery. High saponification levels for the BYC occurred many hours after its saponification and an optimal 96 h aging was established. The industrially adopted collector (Flotigam 5806 from Clariant) was used as collector benchmark. Apatite recoveries with the 96 h-aged saponified BYC were higher than with Flotigam 5806 (above 95% in all tested pH for dosages of saponified BYC ≥200 mg/L). Good results were found also at pH 7, which could lead to a reduction in the phosphate rock flotation pH in the future. No major differences were visually found between the 96h-aged saponified BYC and the Flotigam 5806 regarding the froth aspect and stability, suggesting that the biocollector possibly acted as a frother. Keywords: Bioflotation, Saccharomyces cerevisiae, Apatite, Hallimond tube