MAP 结晶法回收和去除尿液中的磷

以分解后的尿液为研究对象,采用MgCl₂·6H₂Ｏ 溶液作为MAP结晶剂,对MAP结晶同步回收尿液中的磷和部分氮的影响因素Mg/PO^３－₄-P摩尔比、反应pH、反应时间、沉淀时间和搅拌速度等进行小试试验.结果表明,Mg/PO^３－₄-P摩尔比是重要的运行参数,当其摩尔比超过1.3∶1时,磷的回收率超过95%,上清液剩余PO^３－₄-P浓度小于10 mg/Ｌ,而提高反应pH不能明显增加磷的回收率.该工艺的最佳运行条件为反应时间20 min,沉淀时间2.0 h,搅拌速度120 r/min,不需要pH调节控制.选择Mg/PO^３－₄-P摩尔比分别为1∶1、1.3∶1和1.5∶1,对在最佳条件下反应获得的3种产物采用SEM、XRD和ICP分析表明,3种产物都为比较纯净的MAP产品,其主要元素P、N、Mg的含量接近于MAP的理论含量（P=12.62%, N = 5.71%, Mg= 9.91%）,分别为13.54%, 5.34%,9.01% (Mg/PO^３－₄-P =1∶1)、13.78%,5.23%,9.36% (Mg/PO^３－₄-P =1.3∶1)和13.34%,5.12%,9.15% (Mg/PO^３－₄-P=1.5∶1),具有较高的回收利用价值.

Phosphorus Removal and Recovery from Human Urine with MAP Crystallization

To realize the simultaneous removal and recovery of phosphate and partial nitrogen from stale human urine, a series of lab-scale jar tests, adopting MgCl2 x 6H2O as precipitant, were conducted to study the influence of the molar ratio of Mg/PO4(3-)-P, pH, mixing speed, reaction time and precipitation time on MAP precipitation. The experiment results showed that the molar ratio of Mg/PO4(3-)-P was found to be a very important operating parameter to affect phosphorus recovery efficiency. When the molar ratio of Mg/PO4(3-)-P was above 1.3:1, the phosphorus recovery efficiency was above 95% and the residual phosphorous was less than 10 mg/L in the solution. Increasing pH with 10 mol/L NaOH solution could not increase the recovery phosphorus efficiency obviously. Without pH control, the optimal parameters of reaction time, precipitation time and mixing speed could be set at 20 min, 2.0 h and 120 r/min, respectively. To reveal the chemical characteristics of MAP products from human urine, three MAP product samples, with no pH adjustment and under the above optimal operation condition, were obtained at different Mg/PO4(3-)-P molar ratios of 1:1, 1.3:1 and 1.5:1, respectively, and analyzed with SEM, XRD and ICP instrumentation. These precipitates were identified as nearly pure struvite (12.62% of P, 5.71% of N and 9.91% of Mg) with the presence of trace calcium, potassium and sodium. The contents of phosphorus, nitrogen and magnesium in the precipitates were 13.54%, 5.34% and 9.01% (Mg/PO4(3-)-P = 1:1), 13.78%, 5.23% and 9.36% (Mg/PO4(3-)-P = 1.3:1), as well as 13.34%, 5.12% and 9.15% (Mg/PO4(3-)-P = 1.5:1), respectively.