活性污泥胞外聚合物对Pb^(2+)和Cu^(2+)的吸附机理

Adsorption Mechanism of Extracellular Polymeric Substances in Activated Sludge on Pb^(2+) and Cu^(2+)

采用优化的热碱法提取活性污泥中的胞外聚合物(EPS),探究Pb^(2+)和Cu^(2+)在EPS上的吸附规律,并采用傅里叶红外光谱仪(FTIR)、透射电镜(TEM)及X射线衍射仪(XRD)探讨其吸附机理。结果表明:p H值显著影响吸附效果,最适p H值为5~6,EPS的最佳投量为m(M^(2+))∶m(EPS)=1∶2,Pb^(2+)在前10 min即可完成快速吸附,而Cu^(2+)需20 min左右,EPS对Pb^(2+)和Cu^(2+)的理论最大吸附量分别为697和590 mg/g。FTIR分析表明,两种离子的吸附均涉及到羧基、羟基和磷酸基团,而Cu^(2+)的吸附还与氨基、亚甲基等官能团有关;TEM和XRD分析表明,EPS在吸附金属离子的过程中会形成水合磷酸盐,EDX能谱揭示了吸附中存在离子交换作用。

Extracellular polymeric substances （EPS） in activated sludge were extracted with an optimize dalkali-heat method. The adsorption law of EPS on Pb2＋ and Cu2 ＋ was studied, and the adsorp- tion mechanism was investigated by using FTIR, TEM and XRD. The results showed that pH had a sig- nificant influence on adsorption efficiency, and the applicable pH range was 5 to 6. m （n2＋ ） ： m （EPS） = 1 ： 2 was suggested to be the best dosage. The adsorption of Pb2＋ was completed rapidly within 10 min, while that of Cu2＋ spent 20 min. The maximum adsorption capacities for Pb2＋ and Cu2＋ were 697 mg/g and 590 mg/g, respectively. FTIR spectrum showed that carboxyl, hydroxyl and phosphate groups played an important role in the adsorption of Pb2＋and Cu2＋ , and amino and methylene were also in- volved in Cu2＋ adsorption. TEM and XRD analysis showed that phosphate crystals were formed during the adsorption process; EDX analysis suggested the involvement of ion exchange mechanism in the adsorp- tion.