非固定化和固定化啤酒酵母对Cd^2＋和Cu^2＋的吸附特性研究

对比了不同吸附剂对重金属的吸附效果，同时研究了啤酒酵母的固定化方法、菌体用量对吸附效果的影响、非同定化和固定化啤酒酵母吸附热力学特性。研究结果表明，非固定化死啤酒酵母对Cd^2＋的单位菌体吸附量是常用吸附剂活性炭的3倍；由1：3的海藻酸钠与碱处理啤酒酵母（w／w）制得的固定化颗粒吸附效果最好；菌体用量的增加会降低单位菌体对重金属的吸附量；啤酒酵母对重金属的吸附位点有限，Cd^2＋的实际最大吸附量为13．95mg／g，Cu^2＋为7．67μg／g。非固定化和固定化啤酒酵母对Cu^2＋和Cd^2＋的等温吸附过程均可用Linear方程、Langmuir方程和Freundlich方程来进行拟合，但非同定化啤酒酵母以Langmuir方程最优，其拟合计算的最大吸附量qmzxCd和qmxxCu分别为13．96mg／g和8．01mg／g；固定化啤酒酵母以Freundlich方程最优，实际最大吸附量Cd为75．41mg／g，Cu为66．58mg／g。

Characteristics of biosorption of Cd^2＋ and Cu^2＋ by free and immobilized Saccharomyces cerevisiae

This paper compared the sorption performance of heavy metal by different sorbents. It also investigated the immobilization of Saccharomyces cerevisiae, effect of biomass on biosortion, and isotherm adsorption of Cd^2＋ and Cu^2＋ by free and immobilized Saccharomyces cerevisiae. The results indicated that the sorption capacity of free dead Saccharomyces cerevisiae for Cd^2＋ was three times of common activated carbon. The immobilization beads prepared by the ratio of 1：3 （w/w） of alginate to dead yeast treated by 0.5M NaOH got best biosorption performance. The increase of biomass could reduce the unit biosorption capacity of Saccharomyces cerevisiae for heavy metals. The adsorption sites on surface of Saccharomyces cerevisiae for heavy metals were limited and the maximum biosorption capacities were 13.95 mg/g for Cd^2＋ and 7.67 mg/g for Cu^2＋ , respectively. The isotherm adsorption process of Cd^2＋ and Cu^2＋ biosorption by free and immobilized Saccharomyces cerevisiae could be simulated by Linear equation, Laugmuir equation and Freundlich equation. The Langmuir equation was best for the isotherm adsorption process of free Saccharomyces cerevisiae. Contrast to the maximum biosorption capacity of Cd^2＋ and Cu^2＋ , the maximum biosorption capacity were respectively 13.96 mg/g and 8.01 mg/g for Cd^2＋ and Cu^2＋ , according to Langmuir equation. The Freundlich equation simulating the isotherm adsorption process of immobilized Saccharomyces cerevisiae was better than other equations, and correspondingly the maximum biomass capacity was 75.41 mg/g and 66.58 mg/g for Cd^2＋ and Cu^2＋, respectively.