【作者】 张鹏；

【导师】 黄海明；

【作者基本信息】 燕山大学 ， 环境科学与工程， 2018， 硕士

【摘要】 污水中氮磷的排放不仅会导致水体污染,还会造成磷资源的流失。磷酸铵镁沉淀法可以同时去除废水中的氮和磷,结晶产物还能回收作为农肥。但磷酸铵镁结晶过程容易受重金属离子的影响,降低磷酸铵镁回收产物的品质。为了提高回收产物的品质,该论文探讨了废水中金属阳离子、有毒重金属离子等对磷酸铵镁结晶过程的影响,并研究了常见有机物对磷酸铵镁结晶过程中重金属分布的影响,最后利用改性四氧化三铁深度处理磷酸铵镁结晶出水中低浓度的磷,以使出水满足国家二级排放标准。论文首先考察了Mn²⁺和Ca²⁺对磷酸铵镁结晶过程的影响,结果表明Mn²⁺和Ca²⁺对磷酸铵镁的结晶过程影响显著。Mn²⁺和Ca²⁺对磷酸铵镁结晶的影响程度与Mn²⁺/Ca²⁺:Mg²⁺摩尔比例成正相关,然而溶液pH的影响却可以忽略不计。在溶液pH为9.5时,以不同的Mg:P摩尔比例加入镁源,实验发现,大约97%的磷酸盐可以被去除。采用分步沉淀技术,可以预先去除溶液中85%的Mn²⁺,剩余的Mn²⁺浓度控制在1.2 mg/L左右,而磷酸盐的去除率可以达到95%。模拟养猪废水研究表明,重金属离子Cu²⁺、Zn²⁺、Cr³⁺对磷酸铵镁结晶有显著影响。实验发现,重金属离子不仅可以抑制磷酸铵镁的结晶,并且还会影响结晶产物的纯度;在最优实验条件下,经过测量沉淀物中重金属,发现重金属含量分别为Cr³⁺（6.99 mg/g）、Zn²⁺（3.18 mg/g）、Cu²⁺（0.71 mg/g）。有机物对溶液中重金属离子有很强的络合作用。在最优的实验条件下,当溶液中EDTA的浓度为100 mg/L时,溶液中Cu²⁺的去除率仅为5.2%,而Cr³⁺的去除率也降低到了55%,结果表明大部分重金属离子被有机物络合在溶液中。基于上述研究,采用镧基改性四氧化三铁吸附处理磷酸铵镁结晶出水中剩余的低浓度的磷酸盐。结果表明,镧基改性四氧化三铁对磷酸盐的吸附速率快,反应时间为120 min时即可达到吸附平衡,最大吸附量可达到65 mg/g。镧基改性四氧化三铁沉降性能好、易于分离。采用镧基改性四氧化三铁吸附磷酸盐,磷酸盐的去除率可达到95%以上,出水满足国家排放标准。更多还原

【Abstract】 The discharge of nitrogen and phosphorus in sewage not only leads to water pollution,but also causes the loss of phosphorus resources.The magnesium ammonium phosphate precipitation method can simultaneously remove nitrogen and phosphorus from the waste water,and the crystallized product can be recovered as agricultural fertilizer.However,the crystallization process of ammonium magnesium phosphate is easily affected by heavy metal ions and reduces the quality of ammonium magnesium phosphate recovered from waste water.In order to improve the quality of the ammonium magnesium phosphate,the paper discussed the influence of cations and toxic heavy metal ions in the wastewater on the crystallization process of magnesium ammonium phosphate,and studied the influence of common organic matters on the distribution of heavy metals during magnesium ammonium phosphate crystallization,and finally studied the use of the modified Fe₃O₄ for advanced treatment of the low concentration of phosphorus in the water so that the effluent meets the national emission standards.Firstly,the effect of Mn²⁺and Ca²⁺on the crystallization of ammonium magnesium phosphate was investigated.The results showed that the presence of Mn²⁺and Ca²⁺had a significant effect on the crystallization of ammonium magnesium phosphate.The influence of Mn²⁺and Ca²⁺on the crystallinity of magnesium ammonium phosphate is positively related to the molar ratio of Mn²⁺/Ca²⁺:Mg²⁺,however,the effect of solution pH is negligible.At a solution pH of 9.5,magnesium sources were added at different molar ratios of Mg:P.It was found that approximately 97%of the phosphate can be removed.Using the step by step precipitation technique,it was found that 85%of Mn²⁺can be effectively removed,the remaining Mn²⁺concentration is controlled at about 1.2 mg/L,and the removal rate of phosphate can reach 95%.The simulation of swine wastewater shows that the heavy metal ions Cu²⁺,Zn²⁺and Cr³⁺have a significant effect on the crystallization of magnesium ammonium phosphate.It was found that heavy metal ions can not only inhibit the crystallization of ammonium magnesium phosphate,but also affect the purity of the crystallized product.Under the optimal experimental conditions,the heavy metals in the precipitate were found to be Cr³⁺（6.99 mg/g）,Zn²⁺（3.18 mg/g）,Cu²⁺（0.71 mg/g）respectively.Organic compounds have a strong complexing effect on heavy metal ions in solution.Under the optimal experimental conditions,when the concentration of EDTA in the solution is 100 mg/L,the removal rate of Cu²⁺in the solution is only 5.2%,and the removal rate of Cr³⁺is also reduced to 55%,indicating that most of the heavy metal ions are trapped by organic matter in solution.Based on the above studies,the remaining low-concentration phosphates in the wastewater of ammonium magnesium phosphate crystallization were treated with lanthanum modified Fe₃O₄.The results showed that the adsorption rate of phosphate was fast.When the reaction time was 120 min,it could reach adsorption equilibrium,and the maximum adsorption capacity could reach 65 mg/g.The adsorbent has good sedimentation performance and is easy to separate.phosphate removal rate can reach 95%or more,the effluent meet the national emission standards.更多还原