Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, China; College of Environment and Resources, Guangxi Normal University, 541004 Guilin, China.
College of Environment and Resources, Guangxi Normal University, 541004 Guilin, China.
Colloids Surf B Biointerfaces. 2023 Jul;227:113348. doi: 10.1016/j.colsurfb.2023.113348. Epub 2023 May 13.
Extracellular polymeric substances (EPSs) are macromolecular polymers formed by metabolic secretion, and they have great potential for removing heavy metal (HM) ions from the aquatic phase. In this study, the contributions of soluble EPSs (S-EPSs), loosely bound EPSs (LB-EPSs) and tightly bound EPSs (TB-EPSs) secreted by Enterobacter sp. to Cd and Pb adsorption were analyzed. The results indicated that in a solution containing both Cd and Pb, pH= 6.0 was best suited for the adsorption process, and adsorption equilibrium was reached in approximately 120 min. Moreover, the mechanism for adsorption of Cd and Pb by the different layers of EPSs involved spontaneous chemical processes. However, Cd adsorption by the three layers of the EPSs was an exothermic process (∆H <0), but Pb adsorption by the three layers of the EPSs was an endothermic process (∆H >0). The variations in zeta potentials indicated that ion exchange occurred during Cd and Pb adsorption. FT-IR, XPS and 3D-EEM analyses indicated that the functional groups of the EPSs involved in adsorption were mainly the CO, C-O and C-O-C groups of the polysaccharides; furthermore, fulvic acid-like substances, humic-like substances and tyrosine-like proteins played important roles in the adsorption of Cd and Pb by the different EPS layers.
胞外聚合物（EPS）是由代谢分泌形成的高分子聚合物，具有从水相中去除重金属（HM）离子的巨大潜力。在这项研究中，分析了肠杆菌属分泌的可溶性 EPS（S-EPS）、松散结合 EPS（LB-EPS）和紧密结合 EPS（TB-EPS）对 Cd 和 Pb 吸附的贡献。结果表明，在含有 Cd 和 Pb 的溶液中，pH=6.0 最适合吸附过程，大约 120 分钟即可达到吸附平衡。此外，EPS 不同层吸附 Cd 和 Pb 的机制涉及自发的化学过程。然而，EPS 三层对 Cd 的吸附是一个放热过程（∆H <0），但 EPS 三层对 Pb 的吸附是一个吸热过程（∆H >0）。zeta 电位的变化表明，Cd 和 Pb 吸附过程中发生了离子交换。FT-IR、XPS 和 3D-EEM 分析表明，参与吸附的 EPS 官能团主要是多糖的 CO、C-O 和 C-O-C 基团；此外，富里酸类物质、腐殖酸类物质和酪氨酸类蛋白质在 EPS 不同层对 Cd 和 Pb 的吸附中发挥了重要作用。
