Del Bubba M, Arias C A, Brix H
Department of Chemistry, University of Florence, Via della Lastruccia 5, Sesto Fiorentino, Florence 50019, Italy.
Water Res. 2003 Aug;37(14):3390-400. doi: 10.1016/S0043-1354(03)00231-8.
The P-adsorption capacities of 13 Danish sands were studied by short-term isotherm batch experiments and related to the physico-chemical characteristics of the sands. The maximum P-adsorption capacities (Q) and P-binding energy constants (b) were calculated using the Langmuir-isotherm model. The Freundlich model was also used, but it was not useful for the description of adsorption phenomena per se since it fitted well P-removal data even if precipitation of P-salts occurred simultaneously. The Langmuir model described the data well (R(2)=0.90-0.99) when precipitation of phosphates did not occur and seems therefore to be useful for describing the adsorption processes per se. The relationships between maximum sorption capacities and physico-chemical characteristics of the sands were investigated using classical univariate and partial least squares regression analyses. Among the physico-chemical properties of the sands, Ca and Mg content, grain size, porosity, bulk density and hydraulic conductivity were significantly related (P<0.1) to the maximum adsorption capacity as estimated by the Langmuir model. Using the maximum P-adsorption capacities, it was estimated how long the P-removal can be sustained with the different sands in subsurface flow constructed reed beds. If the most efficient sand for P-adsorption was used, the adsorption capacity would be used up after about 1 year, while, for the less efficient sands, the P-retention would go on for about 2 months. This suggests that, in order to sustain a long-term P-removal in subsurface flow constructed reed beds, precipitation reactions of insoluble P-salts should be promoted. P-binding energy constants were not significantly related to the physico-chemical properties of the sands, except the Ca content, which showed, however, a low correlation coefficient.
通过短期等温线批量实验研究了13种丹麦沙子对磷的吸附能力，并将其与沙子的物理化学特性相关联。使用朗缪尔等温线模型计算了最大磷吸附容量（Q）和磷结合能常数（b）。也使用了弗伦德利希模型，但它对吸附现象本身的描述并无用处，因为即使同时发生磷盐沉淀，它也能很好地拟合磷去除数据。当不发生磷酸盐沉淀时，朗缪尔模型能很好地描述数据（R² = 0.90 - 0.99），因此似乎可用于描述吸附过程本身。使用经典单变量和偏最小二乘回归分析研究了最大吸附容量与沙子物理化学特性之间的关系。在沙子的物理化学性质中，钙和镁含量、粒度、孔隙率、堆积密度和水力传导率与朗缪尔模型估计的最大吸附容量显著相关（P < 0.1）。利用最大磷吸附容量，估计了不同沙子在地下流人工芦苇床中可持续去除磷的时间。如果使用对磷吸附最有效的沙子，吸附容量将在约1年后耗尽，而对于效率较低的沙子，磷保留将持续约2个月。这表明，为了在地下流人工芦苇床中维持长期的磷去除，应促进不溶性磷盐的沉淀反应。除了钙含量（然而其相关系数较低）外，磷结合能常数与沙子的物理化学性质没有显著关系。
