复杂离子共存下含磷废水结晶介稳区差异化调控原理和资源化方法

Due to generate large volumes of sludge and low efficiency resource for phosphorus in the process of treatment wastewater with phosphorus, metastable zone as one of the controlling key factors of solution crystallization system, regulation principle of differentiation metastable zone of crystallization and resource approach by induced crystallization for wastewater with phosphorus and coexisting complex ions will be studied in this project from the point of crystal transformation of magnesium ammonium phosphate (MAP). The main contents include: the kinds of the crystalline compounds formed by phosphorus and coexisting complex ions will be analysed, and change rule of metastable zone of MAP under induction by coupling interaction of fluidized bed reactor and ultrasonic will be studied, while the influence of crystallization thermodynamics MAP and the effect of phosphorus removal will also be studied; regulation principle of differentiation metastable zone of MAP crystallization from wastewater with phosphorus will be explored, and the special precipitation rule of MAP in the process of phosphorus removal and chemical reaction kinetics will be revealed under induction by coupling interaction of fluidized bed reactor and ultrasonic; and then, high-efficiency crystallization installation of MAP for potential treatment actual wastewater with phosphorus will be built under induction by coupling interaction of fluidized bed reactor and ultrasonic, and the relationship between condition control and crystallization selection will be illustrated, and morphological transformation of phosphorus and regulation principle of MAP growth will be established. These research can supply available data and approach for high-efficiency crystallization from wastewater with phosphorus, and realize phosphate removal and resource, and reduce environment pollution.

针对含磷废水处理渣量大、未能有效实现磷资源化等难题，以溶液结晶体系关键控制因子介稳区为基础，围绕复杂离子共存时含磷废水磷酸铵镁(MAP)结晶形态转化过程，进行诱导沉淀结晶体系介稳区差异化调控原理和资源化方法研究。主要内容包括：系统分析磷与共存离子形成晶体化合物的类型，研究流化床/超声场诱导作用时复杂离子共存时含磷废水MAP介稳区变化规律，并考察对其它结晶热力学性质、除磷效果的影响；探明在流化床/超声场耦合诱导结晶作用下沉淀结晶介稳区差异化调控原理，明晰废水溶液MAP析出的特殊规律及除磷化学反应动力学过程；建立流化床/超声场作用下实际含磷废水溶液可能实施大规模的MAP高效结晶生长系统，阐明条件控制与选择结晶的相关关系，构建磷形态转化和MAP生成调控方法。上述研究能为含磷废水中磷的高效结晶提供有效的基础数据和技术方法，从而实现磷的去除和资源化，减少环境污染。

我国是一个贫磷大国,也是个需磷大国。几乎排放的所有生活污水和许多工业废水均存在含磷量过高问题, 很容易造成严重环境污染和巨大资源浪费。目前含磷废水普遍存在组成成分复杂, 难以有效达标处理和资源化困难等难题, 这为含磷废水磷资源的回收带来挑战。与其他回收磷的技术相比, 磷酸铵镁结晶技术因可以将磷转为磷酸铵镁, 使其作为缓释肥运用于农业生产当中而受到广泛关注。本研究从晶体化学角度出发, 通过研究磷酸铵镁结晶的超溶解度、介稳区等热力学参数和典型共存离子对磷酸铵镁结晶过程的影响, 发现磷酸铵镁的介稳区会随着超溶解度降低而降低, 且共存离子的存在会使废水组成更加复杂进而影响磷酸铵镁的介稳区。此外, 晶种和超声场的存在也都会改变磷酸铵镁的介稳区而促进结晶过程; 通过超声场作用调控磷酸铵镁的介稳区以获得相关动力学数据, 结果显示超声的空化作用能够改变磷酸铵镁的介稳区进而促进结晶过程, 同时磷酸铵镁的原子核密度、成核及生长速率也随着超声功率的增大先增大后减小。晶种的加入也能促进磷酸铵镁的结晶过程的进行, 主要是晶种通过使细小的鸟粪石颗粒在其自身上结晶来促进晶体生长, 从而帮助克服成核的初始能量障碍, 充当二次成核和后续结晶的中心; 最后, 通过自主搭建的流化床诱导结晶装置并对尿液废水进行了处理, 通过优化反应参数以维持其高效稳定运行, 结果显示在pH 9.5、P:Mg:N摩尔比1:1.4:1.2、回流速率12 L min-1的最佳条件下, 磷酸根的去除效率为96.57%, 钾离子的去除率为68.40%, 获得沉淀产品的纯度高达98.84%, 平均粒径为27.2 μm, 产品中含有较少的沉淀离子, 明显优于其他传统技术。研究结果为复杂含磷废水磷的回收利用提供新的思路和技术参考。