Thermal decomposition of magnesium ammonium phosphate and adsorption properties of its pyrolysis products toward ammonia nitrogen

High-purity magnesium ammonium phosphate （MAP） was precipitated by controlling pH value of the reaction system of 9.0-9.5. The thermal decomposition behavior of MAP and the adsorption properties of its pyrolysis products toward ammonia-nitrogen were also studied by XRD, SEM, TGA-DTA and FT-IR methods. The results indicated that high-purity MAP was obtained at pH value of 9.0-9.5. Upon heating to 100-120℃ for 120 min, MAP was thermally decomposed, losing water and ammonia concomitantly with a reduction in grain size and crystallinity. The capacity of pyrolysis products for ammonia nitrogen adsorption reached 72.5 mg/g, with a removal rate of up to 95% from an 800 mg/L solution. The characteristic diffraction peaks corresponding to MAP mainly appeared in their XRD patterns after adsorption of ammonia nitrogen. The pyrolysis products of MAP at 100-120 ℃ could be recycling-used as the chemical treatment regents of ammonia nitrogen in the practical application.

Temperature-programmed pyrolysis of magnesium ammonium phosphate and removal of ammonia-nitrogen by its pyrolysate

In order to achieve the dual goals of complete deamination of magnesium ammonium phosphate（MAP） and ensure the pyrolysate＇s good removal properties towards ammonia-nitrogen, a temperature-programmed method for the pyrolysis of MAP was studied, as well as the thermodynamic and kinetic processes involved in the removal reaction system between MAP pyrolysate and aqueous ammonium. It was found that the pyrolysis method and pyrolysis final temperature had significant effects on the MAP pyrolysate＇s removal properties towards aqueous ammonium, and the following conditions were deemed to be more appropriate： pyrolysis final temperature and heating rate at 180 ℃ and 5 ℃/min, respectively, and a pH level of 9.5 for the removal reaction system. The resultant ammonium removal capacity by the MAP pyrolysate was 95.62 mg/g. After 120 min, the removal rate with an initial concentration of 1000 mg/L was 82%. The kinetic and thermodynamic results indicated that the removal of aqueous ammonium by MAP pyrolysate was the exchange process between H^＋ and NH4^＋ via MAP precipitation. The kinetics complied with the Lagergren quasi second-order model with an equilibrium time of 120 min, while the isothermal curves complied with the Freundlich model.

The development road of ammonium phosphate fertilizer in China

Ammonium phosphate fertilizer is the compounds containing nitrogen and phosphorus that are usually produced through the neutralization reaction of phosphoric acid and ammonia.At present,there are a variety of products,such as slurry monoammonium phosphate(MAP),diammonium phosphate(DAP),industrial grade MAP,water soluble MAP,water soluble ammonium polyphosphate(APP)and so on.After more than 60 years of development,China’s ammonium phosphate fertilizer industry has experienced the road of from scratch and from weak to strong.The successful development of the slurry MAP technology ended the history that the high concentration phosphate fertilizer cannot be produced by using the medium and low grade phosphate ore.The continuous,stable and large-scale production of DAP plant provides sufficient guarantee for DAP products in China.The development of new ammonium phosphate fertilizer products,such as industrial grade MAP,water soluble MAP,water soluble APP,provides technical support for the transformation and upgrading of phosphorus chemical enterprises.In this paper,the production methods,the development history and the latest research progress of ammonium phosphate fertilizers were reviewed.

Effects of Co-Existing Ions on the Phosphorus Potassium Ratio of the Precipitate Formed in the Potassium Phosphate Crystallization Process

Livestock wastewater is mainly treated with activated sludge, but ions such as phosphorus, potassium, ammonium, nitrate and sulfate remain in the effluent. In this study, the effects of residual ions on phosphorus recovery using the magnesium potassium phosphate crystallization method were investigated when magnesium was added to increase the pH. If co-existing ions affect the products, the phosphorus to potassium molar ratio (K/P ratio) of the precipitate will deviate from being equimolar. Artificial wastewater test solutions containing 5.6 - 20.3 mM ammonium, 25.6 mM potassium, 6.5 mM phosphorus, 0 - 7.35 mM nitrate, and 0 - 3.06 mM sulfate were used. First, the optimum operating pH and amount of magnesium added to give a high phosphorus removal rate and recovery rate were determined. The experimental setup was a 10 L aerated and stirred reactor, and a 5 L settling tank. The K/P ratio in precipitate was approximately 1 using the optimum conditions. Continuous 2 h treatment allowed a white precipitate containing about 30 g of needle-like crystals to be obtained. Next, the effects of varying the ammonium, nitrate, and sulfate ion concentrations in the artificial effluent were investigated. Ammonium and sulfate ion concentrations of 8 mM or more and 3 mM or more, respectively, caused the K/P ratio to decrease to about 0.7 and 0.5, respectively. Varying the nitrate concentration did not affect the K/P ratio, even at a nitrate concentration of 7.35 mM.

pH值对磷酸铵镁(MAP)晶体生成的影响研究

在MAP生成过程中,溶液的pH的影响和变化都十分明显,重点研究了pH值对MAP生成过程、产量及晶型的影响。溶液的pH值在8~11范围内,随着MAP晶体的形成,溶液的pH值急剧下降,加药8 min后迅速降低至7左右。但是当溶液的pH值增加到12后,其变化变缓,但沉淀物中杂质成分明显增加,基本不再生成MAP晶体。MAP产量影响实验表明:pH值10为最佳MAP生成条件,此时晶体产量高达2.52 g,且沉淀物中杂质成分很少,主要为磷酸铵镁晶体。沉淀物的SEM和XRD谱图分析显示:pH值不同,沉淀物的成分是不一样的。pH值为8~10条件下,主要为磷酸铵镁。pH值为11~12时,沉淀物成分较为复杂,主要为磷酸镁、氢氧化镁、磷酸铵镁的混合物。研究结果表明:在磷酸铵镁晶体的形成过程中,溶液pH值的影响十分显著。

以轻烧镁粉为镁源的MAP沉淀法去除废水中氨氮研究

向氨氮废水中投加磷源和镁源可以形成磷酸铵镁(MAP)沉淀。本实验采用轻烧镁粉作为MAP法的镁源,考察了磷源与镁源配比、反应时间等因素对氨氮去除率的影响,确定了最佳反应条件。实验结果表明:当N、Mg、P物质的量比为1∶8∶1(将轻烧镁粉看作纯氧化镁计算)、反应时间为50 min时,氨氮去除率达到90%。

偏高岭土对MAPC基钢结构防火涂料性能的影响

为了研究偏高岭土(MK)对磷酸铵镁水泥(MAPC)基钢结构防火性能的影响,测试了其防火性能、正拉粘结强度以及吸水率,并将其与空白样进行对比。结果表明:MK的加入有助于提升MAPC涂层的防火性能,养护28 d后其防火性能相较于M0提升了61 s;MK的微集料效应,使得MAPC涂层的结构更加致密,从而减小MAPC涂层与钢基材粘结界面的缺陷,提升其粘结性能,使其28 d的正拉粘结强度达到0.169 MPa;MK的加入减少开口孔的生成,减小了MAPC涂层的吸水率;掺入MK的MAPC涂层中有磷酸铝类物质生成,新的水化产物包裹在MKP之间,改善MAPC涂层的微观结构。

Thermodynamic study on phosphorus removal from tungstate solution via magnesium salt precipitation method

The thermodynamic equilibrium diagrams of Mg2＋- 3-4PO - ＋4NH -H2O system at 298 K were established based on the thermodynamic calculation. From the diagram, the thermodynamic conditions for removing phosphorus from the tungstate solution by magnesium salt precipitation were obtained. The results show that when the concentration of total magnesium increases from 0.01 mol/L to 1.0 mol/L, the optimal pH for the phosphorus removal by magnesium phosphate decreases from 9.8 to 8.8. The residual concentration of total phosphorus almost keeps the level of 4.0×10-6 mol/L in the system. MgHPO4, Mg3（PO4）2 and the mixture of Mg3（PO4）2 and Mg（OH）2 are stabilized in these system, respectively. However, increasing the total concentration of magnesium has little effect on phosphorus removal by magnesium ammonium phosphate, while it is helpful for phosphorus removal by increasing the total ammonia concentration. The calculated results demonstrate that the residual concentration of total phosphorus can decrease to 5.0×10-7 mol/L as the total concentration of ammonia reaches 5.0 mol/L and the optimal pH value is 9-10. Finally, verification experiments were conducted with home-made ammonium tungstate solution containing 50 g/L WO3 and 13 g/L P. The results show that when the dosage of MgCl2 is 1.1 times of the theoretical amount, the optimum pH for removing phosphorus is 9.5, which matches with the results of the theoretical calculation exactly.

MAP法处理焦化废水中氨氮的pH值影响

采用化学药剂Na2HPO4·12H2O和MgCl2·6H2O与焦化废水中的高浓度氨氮反应生成磷酸铵镁(MAP),着重探讨了pH值对氨氮去除效果的影响。实验结果表明,在Mg2+,HN4+,PO43-物质的量比为1.3∶1∶0.9,得到最佳pH为8.5～10,原废水中的NH3-N可由2380mg/L降到100mg/L以下,生成的MAP晶体纯度较高,对废水中的有毒、有害物质无吸附,并具有良好的沉降性能。

MAP热分解产物的氨氮吸附性能研究

以TG-DTA、XRD、SEM等手段研究了MAP的热分解行为,并对热分解产物的氨氮吸附性能进行了研究。结果表明,热分解MAP可将水和氨释放出来,热分解产物粒径变小,结晶度降低,其XRD图谱主要出现MgHPO4.3H2O的特征衍射峰,但在吸附氨氮后,则主要出现MgNH4PO4.6H2O的特征衍射峰;控制MAP在100℃条件下热分解3 h再用于氨氮的处理药剂是合适的,氨氮吸附反应体系的pH值以10较为适宜,在此条件下反应40 min对氨氮的去除率即达90%。

磷酸铵镁(MAP)沉淀法处理低浓度氨氮污海水

大量氮磷营养物质排入海湾,引起了富营养化、赤潮等一系列海洋污染问题,污海水中氮磷处理技术研究已引起人们的重视。磷酸铵镁化学沉淀法具有可同时脱除氨氮和磷酸盐,但还未应用于低浓度氨氮废水的处理,尤其是污海水中氨氮的处理。本文采用磷酸铵镁（MAP）化学沉淀法对污海水中氨氮进行处理实验研究,利用污海水中大量存在的Mg2＋,以Na2HPO4作为沉淀剂,探讨了初始反应体系pH值、PO43/NH4＋投配比、反应时间等因素对氨氮脱除效果的影响。结合沉淀结晶物XRD和SEM分析,确定了MAP沉淀法处理污海水中氨氮的最佳反应条件：初始反应体系pH值为9.5~10.5,PO43/NH4＋投配比为1.1/1,反应时间为40 min。实验结果表明,在最佳反应条件下,随着氨氮初始浓度的增大,氨氮去除率逐渐增大,当进水氨氮浓度为12 mg/L时,氨氮去除率达到42.80%。

MAP法处理氨氮废水最佳条件的研究

MAP法是一种比较新颖有效的处理氨氮的方法,该方法是通过化学沉淀的方式使废水中的氨氮浓度降到很低。而且沉淀反应不受温度、水中毒素的限制。由单项试验以及正交实验的方法对MAP法处理氨氮废水的工艺进行优化研究,结果表明,在pH=8.5,反应时间为3h,Mg:N:P=1.3:1.0:1.1时为较佳反应条件;氨氮的去除率随着反应时间的增加而增加,随着Mg:N比值的增加而增加。

海水MAP法去除N、P废水实验研究

海水中富含大量的镁盐,利用镁盐和废水中的氮、磷生成白色的磷酸铵镁沉淀,可以实现废水中氮磷的脱除。本研究首先测出海水中镁的含量,然后根据镁含量设计正交试验开展研究。实验结果表明,对于废水中氮元素的去除,时间因素的影响程度较大,对于废水中磷元素的去除,pH值的影响程度较大;当pH=9.5,n(Mg2+):n(NH4+):n(PO34-)=1.3∶1∶1.08,反应时间为60 min时,氮磷的去除率可以达到63.01%和95.39%。因此,利用海水中的镁盐,去除废水中的氮磷元素,可以实现海水资源的有效利用,同时,可以提高去除氮磷的效率,降低废水处理的费用。本研究可实现氮磷废水处理的同时,实现海水资源化利用。

MAP化学沉淀法处理氨氮废水的工艺研究

以氯化镁和磷酸氢二钠为沉淀剂,研究了磷酸铵镁(MAP)化学沉淀法去除模拟废水中氨氮的工艺条件。结果表明:MAP化学沉淀法对初始质量浓度为500～10000mg/L的氨氮废水有很好的适应性,能达到去除水体中高浓度氨氮的目的。氨氮初始浓度、pH值、反应温度、反应时间、沉淀剂投加比例等操作条件,对氨氮的去除率有明显影响,在实际操作中,控制反应温度为25～35℃,pH值为10,镁、氮、磷的量比为1.2∶1∶1.2较适宜,在此条件下反应20min,对初始质量浓度为1000mg/L的氨氮废水的去除率达98.7%。

pH对MAP沉淀法去除尿液中氮磷的影响

目的研究不同pH值对MAP沉淀法处理预反应尿液中氮磷污染物的影响,并得出反应过程最佳pH值.方法以MgCl2.6H2O为投加镁盐,Na2HPO4.12H2O为外加磷源,在最佳反应条件下,即n(Mg)∶n(P)∶n(N)=1.4∶1∶0.9,搅拌速度100 r/min,反应时间15 min,沉降时间30 min,温度20～25℃,调节pH值,考察氮磷去除效果以及反应过程的变化.结果 pH=10时氨氮去除率最高,达到92.5%;pH>10时,氨氮去除率降低.pH=10时,PO34-的去除率最高,在90%以上,pH大于10以后将不再是磷酸铵镁结晶反应,而副反应使PO34-消耗,导致去除率增加.综上所述,最佳pH值仍取10.结论 pH为MAP沉淀法处理尿液中氨氮的重要影响因素,随着pH值的增加,氨氮的去除率先增大后减小,PO34-去除率随pH的上升而增加,过高的pH会有副产物产生,pH还对反应中沉淀快慢,沉淀颗粒大小和沉淀量都有一定影响.

铁炭微电解-MAP沉淀法联合预处理垃圾渗滤液

采用铁炭微电解-磷酸氨镁(MAP)沉淀法对垃圾渗滤液进行预处理,实验结果表明,铁炭比为5∶1,pH值为3,反应时间为3 h时,铁炭微电解的COD的去除率为47.5%;在投加药剂n(Mg2+)∶n(PO43-)∶n(NH4+)为1.4∶1∶1,pH值为9,反应时间为1 h的条件下,垃圾渗滤液氨氮去除率达到79.7%。

改进MAP沉淀法处理氨氮废水的研究

为了降低磷酸铵镁(MAP)化学沉淀法处理氨氮废水的药剂使用成本,探索了MAP的热分解及热解产物循环用于氨氮废水处理药剂的可行性。结果表明,控制反应体系的pH为9.5时,可得到纯度高的MAP沉淀物;将MAP沉淀物直接热分解,可将氨脱除,热解固体产物能吸附氨氮,循环用于氨氮废水处理药剂是可行的;实际操作时,控制热解温度为130℃、热解产物与氨氮的摩尔比为1:1、氨氮吸附体系的pH为9.5是合适的,对起始浓度为1 000 mg/L的氨氮废水的去除率达80%。

EDTA对剩余污泥磷释放及MAP法磷回收影响

探究乙二胺四乙酸(EDTA)的添加对剩余污泥厌氧过程中磷释放及后续鸟粪石(MAP)法磷回收的影响.根据EDTA添加量对污泥上清液中总磷(TP)、蛋白质、多糖、DNA和SCOD的影响确定了最优释磷条件,采用响应曲面法(RSM)构建MAP磷回收的二次多项式模型并验证了模型的有效性.结果表明:EDTA添加量为5mmol/L,厌氧5d时预处理效果最佳.污泥SCOD破解度(DD)和TP、DNA、蛋白质及多糖均有显著相关,其中TP相关性最强,皮尔逊相关系数为0.866.MAP磷回收的最佳工艺参数是:pH=9.5,n(Mg):n(P)=1.6,搅拌时间22min,此时磷回收率可达95.68%,形成晶体的主要成分为磷酸铵镁(MgNH_4PO_4×6H_2O),纯度为79.19%.

MAP法预处理高氨氮垃圾渗滤液的试验研究

采用磷酸铵镁沉淀法(MAP法)去除老龄垃圾渗滤液中的氨氮。试验结果表明,在pH值为8.25,Mg、N、P的量比为1.3∶1∶0.8,反应时间为2h,搅拌速度为200r/min,沉淀时间为30min的条件下,对氨氮、COD的质量浓度分别为1515、3295mg/L的垃圾渗滤液,氨氮的去除率达到91.2%,COD的去除率为26%,为后续生化处理创造了条件。

MAP法沉淀回收装置的运行条件优化研究

采用一种简易的MAP回收装置,研究了间歇运行条件下反应时间和曝气量对MAP法除磷效果的影响,确定出最佳反应时间为90 min,最佳曝气量为1.2 L/min,相应的除磷率可达98.26%,沉淀回收率为74.54%。当增加一个漏斗形隔板分离反应区和沉淀区并连续运行时,除磷率和沉淀回收率分别为92.11%和63.66%。当不投加镁盐和铵盐而仅调控实际污泥脱水滤液的pH值为9.8时,其连续运行的平均除磷率和MAP回收率分别可达95.16%和70%,运行性能比较稳定。