• 关键词：胞外聚合物  含镉聚合硫酸铁絮体  异化铁还原  次生矿物形成  镉再分配

• 基金项目：国家自然科学基金项目（No.41673090）；广州市科技计划项目（No.201904010101）

• 唐婕
• 华南理工大学环境与能源学院, 广州 510006

• 郝鑫瑞
• 华南理工大学环境与能源学院, 广州 510006

• 易筱筠
• 1. 华南理工大学环境与能源学院, 广州 510006;2. 工业聚集区污染控制与生态修复教育部重点实验室, 广州 510006

• 冯春华
• 1. 华南理工大学环境与能源学院, 广州 510006;2. 工业聚集区污染控制与生态修复教育部重点实验室, 广州 510006

• 党志
• 1. 华南理工大学环境与能源学院, 广州 510006;2. 工业聚集区污染控制与生态修复教育部重点实验室, 广州 510006

• 摘要：异化铁还原菌（Dissimilatory Iron Reducing Bacteria，DIRB）能够还原铁矿物，并对矿物中所含重金属的再分配产生深远影响.胞外聚合物（Extracellular Polymeric Substances，EPSs）是决定细胞体表微环境理化性质的关键组分，对金属迁移转化及矿物形成具有重要影响.本文探究EPSs对微生物还原含镉聚合硫酸铁絮体（Cd-loaded polyferric sulfate，Cd-PFS）过程的影响，该絮体通常在河流镉污染应急处理中形成.通过序批实验和矿化模拟实验，结合X射线衍射、扫描电镜、傅里叶红外光谱、X射线光电子能谱等分析方法，发现EPSs促进了微生物还原絮体中的Fe（Ⅲ），导致絮体解构，Fe³⁺、Fe²⁺及Cd²⁺释放进入溶液中.EPSs中磷酸化蛋白质和核酸中的磷酸基可作为成核位点，与铁原子形成P—O—Fe键，固定和聚集溶液中的Fe³⁺、Fe²⁺，加速铁的沉淀，促进纤铁矿、磁铁矿等铁矿物形成，而这些铁矿物含有丰富的羟基官能团，通过内层络合增强了对溶液中Cd²⁺的吸附，降低了Cd²⁺的可迁移性及可生化性.

• Abstract：It is well known that iron minerals can be reduced by dissimilatory iron reducing bacteria (DIRB), which will have a profound influence on the redistribution of heavy metals loaded in minerals. Extracellular polymeric substances (EPSs) connecting microorganisms and minerals are considered as the key components that determine the physicochemical and biological properties of cell surface microenvironment. EPSs play important roles in the metal migration and mineral formation. Our study aims to investigate the effect of EPSs on microbial-driven reduction of Cd-loaded polyferric sulfate flocs (Cd-PFS), which is commonly formed in the emergent treatment of Cd leakage in rivers. The results of the batch incubation and biomimetic mineralization tests, combined with the X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy characterizations indicated that EPSs promoted the microbial-mediated reduction of Fe(Ⅲ) in Cd-PFS, resulting in the release of Fe³⁺, Fe²⁺, and Cd²⁺ into the solution. Phosphate functional groups derived from nucleic acid or phosphorylated proteins of EPSs acted as nucleation sites to form P—O—Fe bonds, anchoring and accumulating the aqueous Fe³⁺ and Fe²⁺, and facilitating the formation of lepidocrocite and magnetite. EPSs induced the formation of large amounts of minerals rich in hydroxyl functional groups that enhance the chemical adsorption of Cd²⁺ through inner-sphere complexation, and help to reduce the migration and biodegradability of Cd²⁺.

• Key words：extracellular polymeric substances  Cd-loaded polyferric sulfate flocs  dissimilatory iron reduction  secondary minerals formation  Cd redistribution

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