In this work, the mechanism of Pb(II)-mediated precipitation transformation to improve the removal of Cr(VI)-oxyanion on biogenic hydroxyapatite (BHAp) were investigated. The Pb(II)-preloading formed pyromorphite [Pb₅(PO₄)₃Cl] precipitate on the BHAp surface (Pb@BHAp), thus causing an increase of 2.2 times in the uptake of Cr(VI) by Pb@BHAp at pH of 2.4. It was primarily due to the dissolution of Pb₅(PO₄)₃Cl accompanied with the release of Pb(II), resulting in the rapid formation of crocoite (PbCrO₄). Although the K_sp of Pb₅(PO₄)₃Cl was approximately 23 orders of magnitude lower than that of PbCrO₄, Pb(II)-mediated precipitation transformation could still occur. XRD and SEM-EDX analyses demonstrated that the process was a time-dependent that included rapid crystal precipitation in the initial 10 min and subsequent precipitate accumulation for several hours. The Pb(II) released from the dissolution of Pb₅(PO₄)₃Cl was immediately immobilized by Cr(VI); therefore, it did not cause any retention risk of Pb(II) in the solution. Furthermore, a small quantity of Cr(VI) could be reduced to Cr(III) by BHAp, and Cr(III) could enter into the BHAp lattice for the exchange of Ca(II). This study provides a new insight into the resource utilization of Pb-bearing BHAp and a potential method for the successive removal of Pb(II) and Cr(VI).

在这项工作中，研究了 Pb(II) 介导的沉淀转化改善生物羟基磷灰石 (BHAp) 上 Cr(VI)-氧阴离子去除的机制。Pb(II)-预加载在 BHAp 表面形成焦极铁矿 [Pb ₅ (PO ₄ ) ₃ Cl] (Pb@BHAp)，从而导致 Pb@BHAp 对 Cr(VI) 的吸收增加了 2.2 倍pH 值为 2.4。这主要是由于Pb ₅ (PO ₄ ) ₃ Cl 的溶解伴随着Pb(II)的释放，导致铬铅矿(PbCrO ₄ )的快速形成。虽然Pb ₅ (PO ₄ ) _3的K _spCl比PbCrO ₄低约23个数量级，Pb(II)介导的沉淀转变仍可能发生。XRD 和 SEM-EDX 分析表明，该过程是时间依赖性的，包括最初 10 分钟内的快速晶体沉淀和随后几个小时的沉淀物积累。_{Pb 5} (PO ₄ ) ₃溶解释放的Pb(II)Cl 立即被 Cr(VI) 固定；因此，它不会导致溶液中 Pb(II) 的任何保留风险。此外，少量的Cr(VI)可以被BHAp还原为Cr(III)，Cr(III)可以进入BHAp晶格进行Ca(II)的交换。该研究为含铅 BHAp 的资源利用提供了新的见解，并为连续去除 Pb(II) 和 Cr(VI) 提供了一种潜在的方法。