Experimental Research On Removing Cadmium From Electroplating Wastewater By Waste Saccharomyces Cerevisiae

The technology of biosorption means to adsorb heavy metal ions from industrial wastewater, which is potential. In this paper, waste Saccharomyces Cerevisiae of wide source, low cost and no cultivating was chosen for adsorbent, and cadmium ion from electroplating wastewater was chosen for adsorate. Adsorption-sedimentation was used to remove cadmium ion from electroplating wastewater. The relationship was studied between experiment conditions, such as adsorption time, pH value of wastewater, adsorption temperature, adsorbent dosage, mixing speed and adsorption efficacy. The experiment about washed waste Saccharomyces Cerevisiae as adsorbent was tested compared with the experiment about waste Saccharomyces Cerevisiae. The SEM graph, microstructure, zeta potential under different pH value, IR spectrums before and after biosorption, variety of K+,Na+,Ca2+,Mg2+ in solution before and after biosorption were tested, and the mechanisms of adsorbent adsorbing cadmium from electroplating wastewater were discussed.The results showed that the adsorbing capability of washed waste Saccharomyces Cerevisiae is better than that of waste Saccharomyces Cerevisiae. The biosorption is a fast process, and equilibriums were reached within 10 minutes. The optimal pH values for waste Saccharomyces Cerevisiae and washed waste Saccharomyces Cerevisiae were 6.0,7.0, respectively; the optimal adsorbent dosage for waste Saccharomyces Cerevisiae and washed waste Saccharomyces Cerevisiae were 16.25g/L,40g/L(wet weight), respectively; temperature had little effect on biosorption, and room temperature would realize effective adsorption. The optimal mixing speed for adsorbent adsorbing cadmium ion both were 800r/min. With the concentration of cadmium ion in wastewater being 26mg/L, washed waste Saccharomyces Cerevisiae had better adsorption effect, reaching to 97.21%. After the second and the third adsorption, the cadmium concentration in wastewater was reduced to 0.24mg/L, 0.08mg/L, respectively, and the wastewater was let out because of reaching standard. After the sixth and seventh repetitive biosorption with washed waste Saccharomyce Cerevisiae, the adsorbing rates were more than 60% all the time. In the experiment of solid-liquid separation by precipitation, the wshed waste Saccharomyce Cerevisiae had better removal effect than waste Saccharomyces Cerevisiae, while getting 2.5h, removal rate reached 94.63%.The results of SEM graph and IR spectrums analysis showed that the surface of adsorbent is the important biosorption part; the functional organic groups on the surface of the cell, such as -OH,N-H,C=O,C-N,P-S could chelated with heavy metal ion-cadmium ion, which was the main form of adsorption. During the process of adsorption, ion-exchange and electrostatic adsorption also existed.