植物多酚吸持-硫酸铁沉淀法去除水中氨氮的效果及影响因素研究

[目的]吸附法去除水中氨氮通常是采用固体吸附剂吸附后采用固液分离法去除。本文采用具有一定可溶性的天然高分子物质与水中氨氮结合，形成可溶的结合物，然后采用沉淀剂一步沉淀去除的新方法，探索其影响因素。[方法]以天然植物多酚类物质Y（以下简称"植物多酚Y"）为吸持剂，以硫酸铁为沉淀剂，研究了模拟的氨氮废水的pH值、初始氨氮浓度、温度、植物多酚投加量和共存阳离子等因素对吸持沉淀法去除氨氮的影响。[结果]在含单一氨氮的模拟废水中植物多酚Y对氨氮吸持量在本试验条件下可高达到31.9 mg？g-1，模拟计算最大吸持量可达到46.5 mg？g-1。仅25 mg？L-1的共存阳离子K+、Na+、Mg2+、Ca2+的存在对植物多酚Y络合氨氮就有明显竞争作用，导致氨氮吸持量减少约15%~32%，当共存阳离子浓度提高到250 mg？L-1时，其中Ca2+可使植物多酚Y对氨氮吸持量降低54%。影响程度从大到小依次为Ca2+、Mg2+、K+、Na+。等质量浓度Ca2+的影响程度分别是Mg2+、K+、和Na+的1.4、1.7和2.1倍。Freundlich方程（R2=0.983 4）能很好地描述氨氮在植物多酚上的络合行为；吉布斯自由能变化（ΔG）、焓变（ΔH）和熵变（ΔS）的计算结果表明：植物多酚对氨氮的络合是自发的放热过程。[结论]天然植物多酚物质对氨氮具有较大吸持量，形成分散均匀且稳定的胶体体系，易于被少量的金属盐脱稳而沉淀，这使其作为一种新方法用于含氨氮废水的快速处理成为可能，但共存阳离子对其吸持有明显抑制作用。
[Objectives]Solid adsorbent is usually used to remove NH4+-N from wastewater since it could be easily drawn out. In this paper,a soluble natural plant polyphenols Y was used to remove NH4+-N from simulated water by combining with ammonia to form a soluble conjugate which could be precipitated by a precipitant. Natural plant polyphenols Y shows tremendous potential in the adsorption of NH4+ in aqueous solution. [Methods]The effects of pH,initial concentration,temperature,adsorbent dosage and coexisting cations on the adsorption of NH4+-N were investigated. [Results]The adsorption capacity of plant polyphenols Y to ammonia nitrogen in simulated wastewater only containing ammonium nitrogen reached as high as 31.9 mg？g-1,and the maximum adsorption capacity reached 46.5 mg？g-1 in simulation. The removal rate of NH4+-N was enhanced with the increasing dosage of Y and the coexistence of K+,Na+,Mg2+ or Ca2+ inhibited the adsorption of NH4+-N on plant polyphenols Y,which followed the order of Ca2+,Mg2+,K+,Na+. Moreover,the presence of only 25 mg？L-1 of coexisting cations K+,Na+,Mg2+ and Ca2+ significantly competed with plant polyphenols Y combining with ammonium nitrogen,resulting in a reduction of ammonia nitrogen uptake of about 15%-32%. The effects of Ca2+ of equal mass concentration were 1.4,1.7 and 2.1 times that of Mg2+,K+ and Na+,respectively. The complexation data showed that the complexation isotherms fitted well to the Freundlich model(R2=0.983 4). It was also demonstrated that the adsorption of NH4+-N is a spontaneous exothermic process based on the Gibbs free energy(ΔG<0),enthalpy change(ΔH<0) and entropy change(ΔS<0). [Conclusions]The natural plant polyphenols Y shows a large adsorption capacity for NH4+-N and is able to get good settlement with the addition of polymeric ferric sulfate,which makes it a novel potential adsorbent for the adsorption of NH4+-N. However,coexisting cations