加气混凝土砌块吸附初期径流中磷的效果与机制

Effect and mechanism of phosphorus adsorption in initial rainfall runoff by autoclaved aerated concrete block

为发掘具有高效除磷性能的新型基质,提高人工湿地处理初期径流能力。选用废弃的加气混凝土砌块(加气块)作为实验材料,通过吸附动力学、吸附等温线实验及磷形态分析实验等探究其对磷的吸附机制,并将其作为基质应用于人工湿地中处理初期降雨径流,与传统基质砾石作对比,考察湿地除磷效果。结果表明:吸附过程随时间呈现快速吸附、缓慢平衡的特点,且可用准二级动力学方程拟合;吸附过程中溶液的pH、Ca^(2+)浓度均随时间增加而升高;Langmuir吸附等温方程相较于Freundlich可更好地描述加气块对磷的等温吸附过程,最大吸附容量(Q_m)为4 170.71 mg·kg^(-1);吸附主要是以Ca-P形式的化学吸附,且不易解吸。加气块湿地除磷效果明显优于砾石湿地。因此,将加气块应用于湿地处理初期经流,能有效提高湿地除磷能力。

To find a new substrate with highly effective performance of phosphorus removal, improving the ability of constructed wetland to deal with initial rainfall runoff. The waste aerated concrete block（AAC） was selected as test material to explore its phosphorus adsorption mechanism, based on adsorption kinetics, adsorption isotherm and phosphorus transformation analysis experiments. And the effect of phosphorus removal was investigated, when AAC was reused as substrate in the constructed wetlands for initial rainfall runoff treatment, compared with traditional substrate gravel. The results indicated the characteristics of adsorbing fast, balancing slowly during the adsorption process, which could be fit by pseudo-second order kinetic equation. In addition, pH and Ca^2＋concentration generally increased with the extension of phosphorus adsorption. Compared with Freundlich adsorption isotherm equation, Langmuir adsorption one was better to describe the isothermal adsorption process with the maximum adsorbing capacity（Qm） achieved at 4 170.71 mg·kg^-1. Moreover, the presence of Ca-P adsorption in AAC reflected the chemical adsorption mechanism by AAC, which was not easily desorbed. In addition, phosphorus removal efficiency of AAC wetland was obviously higher than that of gravel wetland. Therefore, the application of AAC in the constructed wetlands for initial rainfall runoff treatment will improve the phosphorus removal ability.