赤泥诱导磷酸钙结晶法回收废水中的磷

Phosphorus Recovery from Wastewater by Red Mud-seeded Crystallization of Calcium Phosphate

  • 摘要: 为获取适用的废水磷回收工艺,以赤泥为晶种,诱导磷酸钙(HAP)结晶法回收模拟废水中的磷,研究工艺条件对回收效果的影响;运用扫描电子显微镜(SEM)、X-射线能谱仪(EDS)和X-射线衍射仪(XRD)对最优工艺条件下的结晶产物进行了表征。结果表明,当搅拌速度为180 r/min,搅拌时间为30 min,沉淀30 min后,在赤泥投加量为8 g/L,赤泥粒径为40~60目(250~380 μm),初始磷酸盐浓度为60 mg/L时,磷的回收率可达74.1%。不同初始磷酸盐浓度下,随pH升高,磷酸根离子、钙离子的回收率均增大,但增大速率随初始磷酸盐浓度的提高而减缓。磷酸根离子的回收率随着C与P物质的量比的增大而增大;而钙离子的回收率随C与P物质的量比的增大达到一个最大值,但随初始磷酸根浓度不同,出现最大值的C与P物质的量比也不同。赤泥晶种重复使用不宜超过3次。废水中的磷主要以磷酸钙形态被回收。

     

    Abstract: To obtain a practical process for phosphorus (P) recovery from wastewater, taking red mud as a seed crystal, the effects of process conditions on the crystallization of calcium phosphate for P recovery from synthetic wastewater were investigated. The scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and powder X-ray diffraction (XRD) were employed for the characterization of the recovered products. The results showed that with red mud mesh of 40-60, a seed concentration of 8 g/L and an initial phosphate concentration of 60mg/L, and under the conditions of stirring speed of 180rpm, stirring time of 30min and precipitation time of 30min, the phosphorous recovery efficiency could reach 74.1%. With different initial phosphate concentrations, the recovery of PO43- and Ca2+ increased with the increase of the pH, but the increase rate decreased with the increase of initial phosphate concentration. The recovery rate of PO43- increased with Ca:P molar ratio, and the recovery rate of Ca2+ had a peak with Ca:P molar ratio increasing. With different Ca:P molar ratio, there has different peaks under different initial phosphate concentrations. The repeated reuse times of seed crystal should not be more than 3 times. The results showed that the main recovered product of P from the wastewater was hydroxyapatite (HAP).

     

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