This paper examines the acid leaching efficiencies of Fe and P from vivianite slurry (VS, Fe3(PO4)2·8H2O), which is magnetically separated from anaerobic digested sludge, and elaborates on Fe and P reuse routes. The characteristics and dissolution behavior of raw VS in hydrochloric, sulfuric, phosphoric, oxalic, and citric acids are investigated. Results reveal that the primary impurities in VS are organic matter, other phosphate compounds, and Mg present in the vivianite crystal structure. Hydrochloric and sulfuric acids could effectively extract P (90%) from VS at an optimal hydrogen-to-phosphorus (H⁺/P) ratio of 2.5, compared with sewage sludge ash (SSA) that normally needs an H⁺/P ratio greater than 3. Hence, VS can be employed as an alternative P resource following a similar recovery route used with SSA. However, in comparison to SSA, VS use can decrease acid consumption in P extraction and the requirement for the extensive purification of cationic impurities. Furthermore, oxalic acid effectively facilitates the separation of P and Fe in VS by precipitating Fe as insoluble ferrous oxalate in acidic conditions, leading to a high Fe recovery rate of 95%. The recovery and reuse of Fe through the oxalic acid route further improves the feasibility of VS as an alternate resource.

中文翻译：

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从污水污泥中分离出的 vivianite 酸浸，用于回收磷和铁


本文研究了从厌氧消化污泥中磁分离的 vivianite 浆料 （VS， Fe3（PO4）2·8H2O） 中 Fe 和 P 的酸浸效率，并详细阐述了 Fe 和 P 的再利用路线。研究了生 VS 在盐酸、硫酸、磷酸、草酸和柠檬酸中的特性和溶解行为。结果表明，VS 中的主要杂质是有机物、其他磷酸盐化合物和 vivianite 晶体结构中存在的 Mg。盐酸和硫酸可以以 2.5 的最佳氢磷 （H⁺/P） 比从 VS 中有效提取 P （90%），而污水污泥灰分 （SSA） 通常需要大于 3 的 H⁺/P 比。因此，VS 可以用作替代 P 资源，遵循与 SSA 类似的恢复路线。然而，与 SSA 相比，使用 VS 可以减少 P 萃取中的酸消耗和对阳离子杂质的广泛纯化要求。此外，草酸通过在酸性条件下将 Fe 沉淀为不溶性草酸亚铁，有效地促进了 VS 中 P 和 Fe 的分离，从而实现了 95% 的高 Fe 回收率。通过草酸路线回收和再利用 Fe 进一步提高了 VS 作为替代资源的可行性。