Abstract: As a kind of new biosorbent, aerobic granular sludge which has the advantages of strong adsorption capacity and easily-desorbing property, was paid great attention in the area of heavy metal waste water treatment. In this research, the adsorption behaviors of Pb²⁺ and Cd²⁺ by extracellular polymeric substances (EPS) which extracted from aerobic granular sludge using improved centrifugation methods were studied. The results showed that the adsorption capacity of Pb²⁺ and Cd²⁺ on EPS was considerably large. The experimental results were fit well with the Langmuir iostherms model. The maximum adsorption capacity for Pb²⁺ and Cd²⁺ by EPS was up to 534.76 mg/g and 478.47 mg/g, respectively. Furthermore, the competitive adsorption experiments presented that EPS exhibited a selective adsorption for Pb²⁺. Specially, there was a minor inhibition for Pb²⁺ adsorption in presences of Cd²⁺, while the adsorption capacity of Cd²⁺ was greatly decreased when Pb²⁺ co-existed in solutions. FT-IR and EEM analysis revealed that EPS was rich in hydrophilic groups and hydrophobic groups, which was benefit to combine heavy metals by complexation, ions exchange and chelation. The adsorption of Pb²⁺ and Cd²⁺ by EPS was mainly attributed to the ?COOH, ?NH2, ?CH, ?OH and ?C=O groups from protein fractions of them. The main adsorption mechanism of Pb²⁺ by EPS was ion exchange and complexation, while for Cd²⁺ was mainly took effect by complexation.

Key words: extracellular polymeric substances, Pb²⁺, Cd²⁺, adsorption mechanism

摘要： 利用改良离心法从好氧颗粒污泥中提取胞外聚合物(EPS), 并研究其对重金属废水中Pb²⁺和Cd²⁺的吸附行为。结果表明, EPS对Pb²⁺和Cd²⁺具有很强的吸附能力, 吸附行为符合Langmuir等温式, 拟合得到的最大吸附量分别可达534.76 和478.47 mg/g。Pb²⁺和Cd²⁺在EPS上存在竞争吸附, EPS对Pb²⁺的吸附选择性更强。Cd²⁺对EPS吸附Pb²⁺有一定的抑制作用, 但Pb²⁺的存在对EPS吸附Cd²⁺具有显著的抑制作用。傅立叶红外光谱(FT-IR)和三维荧光光谱(EEM)测定表明, 实验提取的EPS含有大量疏水和亲水性基团, 因此可通过络合作用、离子交换、螯合等多种作用与重金属发生强结合。对重金属起主要吸附作用的是存在于EPS蛋白质组分中的?COOH, ?NH2, ?CH2?, ?OH及?C=O官能团。研究表明, EPS吸附Pb²⁺的主要机理为离子交换和络合作用, 而对Cd²⁺的吸附则主要通过络合作用完成。

关键词: 胞外聚合物, Pb²⁺, Cd²⁺, 吸附机理