Zinc(II) Removal by Chemically Treated Dead Biomass of Yeast Species

In the present study, the dead biomass of the two yeast species viz., Candida rugosa and Cryptococcus laurentii were subjected to various chemical treatments to assess the effects of pretreatment on zinc(II) removal from aqueous solution. Yeast biomass was pretreated with anionic surfactants viz., sodium dodecyl sulphate (SDS), sodium dodecyl benzene sulphonate (SDBS) and dioctyl sulphosuccinate sodium (DSS), alkali (sodium hydroxide, sodium carbonate and sodium bicarbonate), acids (hydrochloric acid, sulphuric acid and acetic acid), and organic solvents viz., methanol, formaldehyde and gluteraldehyde. Pretreatment of dead yeast biomass with anionic surfactants was found to improve the zinc(II) removal remarkably compared to all other treatments. Acid treatments resulted in significant reduction in zinc(II) removal efficiency. The pattern of zinc(II) removal efficiency of both the yeast species was found to follow the order: SDS (3 mM) > SDBS (3 mM) > DSS (3mM) > Na₂CO₃ (9 mM) ≥ NaOH (9 mM) ≥ untreated biomass > C₂H₅O₈ (7 mM) ≥ NaHCO₃ (9 mM) > CH₃OH (7 mM) > HCHO (7 mM) > CH₃COOH (5 mM) > HCl (5mM) > H₂SO₄ (5 mM). Maximum zinc(II) removal was noted in case of SDS treated C. rugosa and C. laurentii which exhibited 84.7 % and 74.5 % zinc(II) removal compared to the removal efficiency of 65.4 % and 54.8 % obtained by untreated C. rugosa and C. laurentii.