Production and characterization of bioflocculants for mineral processing applications

• Higher yields of bioflocculants were obtained from Bacillus licheniformis and Bacillus firmus.
• Bioflocculants shows the presence of carbohydrate conjugated proteins.
• The bioflocculants promoted clay flocculation and decolorization of dyes.
• Bioflocculants can be used as potential absorbents for toxic Cr (VI) ions from aqueous solutions.

A comparative study of two bacterial strains namely, Bacillus licheniformis and Bacillus firmus in the production of bioflocculants was made. The highest bioflocculant yield of 16.55 g/L was obtained from B.licheniformis (L) and 10 g/L from B.firmus (F). The bioflocculants obtained from the bacterial species were water soluble and insoluble in organic solvents. FTIR spectral analysis revealed the presence of hydroxyl, carboxyl and sugar derivatives in the bioflocculants. Thermal characterization by differential scanning calorimetry (DSC) showed the crystalline transition and the melting point (Tm) at 90-100 °C. Effects of bioflocculant dosage and pH on the flocculation of clay fines were evaluated. Highest bioflocculation efficiency on kaolin clay suspensions was observed at an optimum bioflocculant dosage of 5 g/L. The optimum pH range for the maximum bioflocculation was at pH 7–9. Bioflocculants exhibited high efficiency in dye decolorization. The maximum Cr (VI) removal was found to be 85 % for L (bioflocculant dosage at 2 g/L). This study demonstrates that microbial bioflocculants find potential applications in mineral processing such as selective flocculation of mineral fines, decolorization of dye solutions and in the remediation of toxic metal solutions.

SEM micrographs of a) bioflocculant L (B. licheniformis) and b) bioflocculant F (B. firmus)Figure optionsDownload as PowerPoint slide