Simultaneous adsorption of Cd2+ and methylene blue from aqueous solution using xanthate-modified baker's yeast

Xanthate-modified baker's yeast (XMBY) was successfully synthesized by grafting xanthate groups onto the surface of baker's yeast and was used for the simultaneous adsorption of cadmium (Cd2+) and methylene blue (MB) from aqueous solution. Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the synthesized adsorbent. The results indicated that the sulfur groups were successfully introduced onto the surface of the baker's yeast and participated in the adsorption processes. The kinetic and isotherm data showed good correlations with the pseudo-second-order model and the Langmuir model, respectively. The equilibrium time and the maximum values obtained from the two models were 40 min, 239.8 mg/g for Cd2+ and 300 min, 64.45 mg/g for MB, respectively. The thermodynamic analysis (G<0, H>0, S>0) demonstrated that the adsorption processes of Cd2+ and MB onto the XMBY were endothermic and spontaneous. In the binary-component solution (Cd2+ and MB), the adsorption capacity for MB was almost unaffected by the presence of Cd2+ and interestingly, the adsorption capacity for Cd2+ increased in the presence of MB. Overall, these results indicated that XMBY could be a promising adsorbent for the treatment of wastewater containing both Cd2+ and MB.