Biosorption Of Pb(Ⅱ)、Zn(Ⅱ)、Cd(Ⅱ) From Aqueous Solution By Waste Beer Yeast

In this work, we use waste beer yeast, a by-product of brewing industry, which is cheapas adsorbent for adsorbing lead, zinc and cadmium from wastewater. The surface morphologyand the structure features representation of the waste beer yeast were characterized. Effects ofdifferent parameter were also investigated, and then the dynamic model was studied. Finally,adsorption mechanism by waste beer yeast was discussed. Specific content and conclusion areas follows:Through various measurements such as scanning electronic microscopy, Fouriertransform-infrared absorption spectrum, BET surface area measurement, inert electrolytetitration, the surface morphology and the structure features representation of the waste beeryeast has been put forward. The aperture of waste beer yeast is mainly distributed between the0¹0nm. Its specific surface area is about1.976m²·g^-1; the surface of the waste beer yeast isrough and bumpy and has some of the groove and potholes. But there is less pore structure;Infrared spectra show that waste beer yeast mainly composed by protein and carbohydratessuch as cellulose, hemicelluloses and lignin.Functional groups such as Amino acid, hydroxylwhich can participate in the activity of adsorption is existing.The zero point of charge of thewaste beer yeast appeared in the pH6.8.Surface of adsorbent is positively charged when PHvalue of the solution is less than6.8, while the pH value is greater than6.8, it becomesnegatively charged.The experiment investigated effects of different parameter, such as pH value of initial,time of the adsorption, absorbent dose, initial concentration of heavy metal ion and theinteractions between ion of lead, zinc and cadmium. The experimental results indicated that,pH, time of the adsorption, absorbent dose are important factors on adsorption. Theadsorption of lead, zinc and cadmium by waste beer yeas all can achieve a high efficiencywhen pH value is3⁷.Adsorption at the beginning is very fast. The removal rate of lead,zinc and cadmium is respectively to98%,86%and90%of the maximum removal rate in15minutes and become equilibrium in90min. The co-existence of three metal ions hasinfluenced each other during the adsorption. The amount of zinc and cadmium absorbedincreased with increasing the absorbent dose, decreased with increasing the initialconcentration of ion. The increase of initial concentration did not generate a large fluctuationfor the removal rate of lead within the scope of the experiment. The removal rate of lead, zinc,cadmium were96.4%,68.1%and78.9%on optimized condition. Pseudo-second-order model was found to explain the kinetics of lead、zinc、cadmiumadsorption well. The process of adsorption controls by internal and liquid membrane diffusionmodel together.Research on the mechanism of waste beer yeast adsorption shows: The structure of wastebeer yeast remained relatively complete after the absorption. Compared with raw waste beeryeast, the removal of heavy metal ions decreased after chemical treatment, and combined withFTIR, indicates that amino and hydroxyl play important roles in the process of absorption. Inthe process of absorption, inorganic precipitation caused by the increase of pH value is alsoone of the adsorption mechanisms.