Phosphorus (P) is one of the essential nutrients for all life but also is involved in the major factor of water eutrophication. This study aimed to investigate a low-cost approach for highly efficient P removal and recovery from wastewater with blast furnace slag (BFS) as the adsorbent. The adsorption characteristics were consistent with the Langmuir adsorption isotherm (q₀ 0.1370~0.3848 mg/g) and quasi-secondary kinetic model (R² = 0.9986~0.9997), suggesting monomolecular-layer chemical adsorption might be the dominant pathway. According to the determination of scanning electron microscope and energy dispersive spectroscopy, P was distributed uniformly with other elements in the surface of BFS and even formed needle-like crystals. This indicated that P might be also further deposited in the surface of BFS after the initially chemical adsorption via coordination with the active sites, which led to the slow accumulation of P along with the adsorption experiments. The binding energy and atomic composition analysis of X-ray photoelectron spectroscopy revealed that phosphate mainly existed as HPO₄²⁻ in the surface of BFS, especially for those non-magnetic particles with relative low Fe content (<30%), indicating the preference of P to the hydroxyl basic sites. Compared with those magnetic particles, the adsorption capacity of the non-magnetic particles was larger and could be restored more easily with the elution of sulfate acid, resulting in about two times the P recovery capability. Based on the P adsorption mechanism in the surface of BFS, the operation conditions of the BFS adsorption column for P recovery were optimized in an alkaline condition with a low phosphate concentration and long residual time. Therefore, non-magnetic BFS with small size could be used to recover P resources from rural wastewater with low P concentration and facilitated the on-site reuse of P resources in rural districts.

中文翻译：

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不同磁性高炉渣对磷的吸附及其回收磷的潜力

磷(P)是所有生命必需的营养物质之一，也是水体富营养化的主要因素。本研究旨在研究一种以高炉渣 (BFS) 作为吸附剂的废水中高效磷去除和回收的低成本方法。吸附特性与Langmuir吸附等温线(q ₀ 0.1370~0.3848 mg/g)和准二级动力学模型(R ²= 0.9986~0.9997），表明单分子层化学吸附可能是主要途径。根据扫描电镜和能量色散谱测定，P在BFS表面与其他元素均匀分布，甚至形成针状晶体。这表明在最初的化学吸附后，P 也可能通过与活性位点的配位进一步沉积在 BFS 表面，这导致 P 随着吸附实验的缓慢积累。X射线光电子能谱结合能和原子组成分析表明，磷酸盐主要以HPO ₄ ^{2−的形式存在。}在 BFS 的表面，特别是对于那些 Fe 含量相对较低（<30%）的非磁性颗粒，表明 P 对羟基碱性位点的偏好。与那些磁性颗粒相比，非磁性颗粒的吸附能力更大，更容易随着硫酸的洗脱而恢复，从而使P的回收能力提高了约2倍。基于BFS表面的P吸附机理，优化了BFS吸附柱在低磷酸盐浓度、长残留时间的碱性条件下进行P回收的操作条件。因此，小尺寸无磁BFS可用于从低P浓度的农村废水中回收P资源，促进农村地区P资源的现场回用。