重金属离子的生物吸附容量与离子性质之间的关系

Relationship of Biosorption Capacity of Heavy Metal Ions by Saccharomyces cerevisiae and Their Ionic Characteristics

利用金属离子毒性评价和预测领域中的QSAR方法,探讨了重金属离子性质对生物吸附容量的影响.选用啤酒工业废弃的酿酒酵母为生物吸附剂,进行了10种金属离子Ag+,Cs+,Zn2+,Pb2+,Ni2+,Cu2+,Co2+,Sr2+,Cd2+,Cr3+的生物吸附实验.选用22种参数来表征金属离子的物理化学性质,建立了金属的离子特性与生物吸附容量之间的关系.利用Langmuir方程计算得到酵母吸附金属离子的理论最大吸附量qmax,由大到小排序为Pb2+>Ag+>Cr3+>Cu2+>Zn2+>Cd2+>Co2+>Sr2+>Ni2+>Cs+.离子性质与吸附量之间的线性拟合分析结果表明,共价指数X2mr与qmax具有良好的线性关系,共价指数越高,离子吸附量越大,金属离子与吸附剂表面官能团共价结合所占比重越大,键结合越牢固.对金属离子进行分类(按价态或离子的软硬性质)可以改善拟合效果.极化力Z2/r、水解常数|lgKOH|、电离势IP等多种物化性质与不含软离子的离子之间的理论最大吸附量也表现出良好的线性关系.

Utilizing similar methods and ideas of QSAR in metal toxicity assessment, we tried to establish the relationship between the ion characteristics of heavy metals and the biosorption capacity by waste biomass of Saccharomyces cerevisiae, obtained from a local brewery. The biosorption experiment was carried out and the maximum biosorption capacity （ qmax ） was determined by the Langrnuir isotherm model. The values of qmax decreased in order on mole basis ： Pb^2＋ 〉 Ag^＋ 〉 Cr^3＋ 〉 Cu^2＋ 〉 Zn^2＋ 〉 Cd^2＋ 〉 Co^2＋ 〉 Sr^2＋ 〉 Ni^2＋ 〉Cs^＋ . Thebiomass prefer to bind class B ions （Pb2~ and Ag~ ）, then borderline ions, and last hard ions （Sr^2＋ and Cs^＋ ） based on the HASB principle. Twenty two parameters of physiochemical characteristics of ions were selected to correlate qmax. Linear regression analysis showed that only one parameter, i.e. , the covalent index Xm^2r was correlated well to qmax for all metal ions tested. The greater the covalent index value of metal ion was, the greater was potential to form covalent bonds with biological figands, and the larger was the metal ion biosorption. Classification of metal ions （for divalent ion or for soft-hard ion） improved the models. More properties such as polarizing power Z^2/r or the first hydrolysis constant ｜ lgKoH｜or ionization potential IP were statistically significant. Xm^2r seemed to be suitable to account for metal ions containing soft ions, whereas Z^2/r, ｜ lgKoH ｜ and IP suitable for only soft ions or metal ions without soft ions.