Zero-valent iron (Fe 0 ) is restricted in phosphate removal due to the formation of a passive P–Fe layer on its surface. A micro-electric field (0.20 mA cm −2 ) was employed in Fe 0 column to facilitate iron corrosion for enhanced phosphate removal with a Fe 0 column as the control. The performance of two columns was compared by batch experiment at a Fe 0 filling rate of 10 vol% with quartz sand as dispersing media. The stability and reusability of micro-electric field driven Fe 0 (MFD-Fe 0 ) column was estimated by cyclic test. Solid phase analysis showed promoted iron corrosion, iron ion generation, and secondary mineral production such as lepidocrocite and magnetite in the MFD-Fe 0 column. Since iron ions tended to precipitate with phosphate, and iron minerals provided reaction sites for phosphate adsorption, the MFD-Fe 0 column achieved an enhanced phosphate removal of 94.1%, 2.8 times higher than that of the Fe 0 column. The increase of current density from 0 to 0.20 mA cm −2 significantly improved phosphate removal from 24.5% to 94.1%, further demonstrating the promoting effect of micro-electric field on iron corrosion. The MFD-Fe 0 column also possessed excellent stability and reusability. It only showed a slight decrease of phosphate removal from 94.1% to 89.7% in eight cycles. It restored a phosphate removal capacity of 97.4% as compared to the initial MFD-Fe 0 column by eluting iron (hydro)oxides on Fe 0 and quartz sand surfaces with sulfuric acid . This study indicated that MFD-Fe 0 is a promising method to remove phosphate from water and an alternative strategy for overcoming Fe 0 passivation.
Yitong Yin,Shanshan Yang,Fei Liu,Xue Wang,Yue Chen,Ximing Luo
Sulfide induces the reductive dissolution of iron (oxyhydr) oxides, the primary host phases for arsenic (As), thereby triggering As release. We investigates the physicochemical mechanisms of three types of low molecular weight organic acids (LMWOAs) on sulfide-mediated reductive dissolution of As(V)-ferrihydrite and As release using batch experiments combined with hydro-chemical, spectroscopic, and microscopic analyses. Arsenate dominated the aqueous (97.2–100 %) and solid phases throughout the experiment. LMWOAs accelerated S(-II) consumption and As release by inhibiting FeS formation, with rates ordered as citric acid (CA) > oxalic acid (OA) > malic acid (MA) > control (Kb). At S(-II): Fe = 0.5, maximum As release was 11.78 % (Kb) and 14.60 % (CA); at S(-II): Fe = 1, it was 27.58 % (Kb) and 30.71 % (OA). LMWOAs enhanced As release via non-reductive ligand dissolution of As(V)-ferrihydrite. Secondary mineral formation in later stages re-immobilized As, with mineral layers ≥50 nm thick. LMWOAs interacted differently with secondary minerals: CA primarily adsorbed on surfaces, while MA integrated into the matrix. LMWOAs influenced As redistribution in secondary minerals, increasing contamination risks. Thus, the complex effects of organic matter (OM) on Fe, S, and As biogeochemistry must be considered in risk assessments and remediation strategies for As-contaminated sites in sulfidic environments.
危险品化学品经营许可证（带存储）