海带对镉、铅的吸附作用及其机理

利用大型海藻海带(Laminaria japonica)作为可降解性生物吸附材料,对有害重金属镉离子和铅离子的吸附作用和机理进行了研究.结果显示,通过电位差滴定法,得到海带的酸性基数量为1.25mmol.g-1,其解离常数为0.18 mmol.l-1.对平衡吸附量与pH的关系进行了模型模拟.海带对于金属离子的吸附为Bidentate型,吸附平衡常数分别为5.72×103L.mol-1,6.28×104L.mol-1.同时,采用拟二次速度模型对镉离子和铅离子的吸附速度进行了模拟,得到的吸附速度常数分别为0.010 min-1,0.014min-1.结论,海带对二价镉、铝离子的吸附量大于很多其它藻类吸附剂,对它的研究可为重金属化湖泊水质的改善和生态修复提供参考依据.

BIOSORPTION OF Cd~(2+) , Pb~(2+) ONTO LAMINARIA JAPONICA

It's very important to develop highly economical, effective and practical technologies for the removal of heavy metals in the environment Biosorption of Cd~(2+) and Pb~(2+) onto Laminaria japonica was studied by batch adsorption system to investigate the adsorption mechanism.Acid number and acid dissociation constant of car-boxylic functional groups (metal-binding site) for Laminaria japonica were determined by conductometric and potentiometric titration.The number and the acid dissociation constant were determined as 1.25 mmol · g~(-1) and 0.18 mmol · g~(-1).The Cd~(2+)and Pb~(2+) adsorption data were analyzed using two different binding models.The models were based on the monodentate or bidentate binding reactions of bivalent metal ions to acidic sites.The results showed that the biosorption of bivalent metal ions onto Laminaria japonica followed the bidentate adsorption model, and the bidentate binding constants were 5.72×10~3 and 6.28 × 10~4L · mol~(-1) for Cd~(2+) and Pb~(2+) respectively.It was also shown that the adsorption process of Laminaria japonica followed the pseudo-second-order kinetics.We concluded that the biosorption amounts of Cd~(2+) and Pb~(2+) were more than other seaweed biosorbents.