去除水中硝氮的絮凝剂制备及其脱氮机理研究

It is difficult to remove nitrate-nitrogen from water with poor carbon source. Without an ideal solution, the biological technology for nitrate-nitrogen removal is used frequently even though it costs high, occupies large area and operates unstably. Flocculation is a widely-used water treatment technology that is easy to use and upgrade, however, nitrate-nitrogen can not be removed by traditional flocculant. Covalently bound inorganic and organic composite flocculant, which was prepared by the applicant, enhances flocculation performance greatly and broadens the scope of flocculation application. Based on this achievement, in this project, the applicant proposes a new method to remove nitrate-nitrogen from water by using a novel flocculant. The “tailor-made” method will be used to control the species and structure of the flocculant. The flocculant structure for nitrate removal will be obtained by adjusting the type and content of organic functional groups in this flocculant. The influence of co-existing ions and organic matter on nitrate-nitrogen removal will be investigated. Low chloride component and “accelerant” will be introduced to enhance selectivity for nitrate removal. The optimum preparation parameters and nitrate removal condition for the flocculant will be also obtained. The mechanism of nitrate removal by flocculation will be elucidated in this project and it will provide a simple, efficient and low-cost method to remove nitrate-nitrogen from water. The development and application of this new flocculant will easily overcome some obstacles that are unconquerable for traditional flocculation and other water treatment technology. The research results on flocculation behavior and nitrate removal mechanism in this project will be an addition to the present theory of flocculation and water treatment.

碳源缺乏条件下去除水中硝氮一直是水处理的难点。常用的生物脱氮技术投资和运行成本高，占地多，不稳定。絮凝技术应用广泛且有简单易用易升级的特点，但传统絮凝剂不能去除硝氮。申请者研制了共价键无机－有机复合絮凝剂大幅提高了絮凝效果并拓宽了絮凝应用范围，在此基础上提出采用新型絮凝剂去除硝氮的方法。本项目将利用“量身定制”的形态结构调控方法，通过调整该絮凝剂有机官能团种类和含量，获得可去除硝氮的絮凝剂结构和形态。研究絮凝过程中硝氮的去除特征和效果影响因素，尤其是共存离子以及有机物等对脱氮效果的影响。通过使用低氯组分并引入“促进剂”，进一步提高絮凝脱氮的选择性。获得絮凝剂最佳制备参数和最佳脱氮条件，阐明絮凝脱氮机理，为简单、高效、低成本地去除水中硝氮提供一条新途径。脱氮絮凝剂的研制与应用将使传统絮凝以及目前水处理技术难以解决的问题简单化，其絮凝行为和脱氮机理的研究成果将是絮凝理论和水处理理论的重要补充。

碳源缺乏条件下去除水中硝氮一直是水处理的难点。常用的生物脱氮技术投资和运行成本高，占地多，不稳定。絮凝技术应用广泛且有简单易用易升级的特点，但传统絮凝剂不能去除硝氮。针对此问题，本项目研发出可去除硝氮的海葵式絮凝剂，研究了具有硝氮选择性且结构稳定的絮凝剂制备方法并优化制备参数，利用多种手段对絮凝剂的物化性质和结构进行详细表征。利用实际二级生物出水验证了海葵式絮凝剂的脱氮效果以及对其他污染物的去除效果，探究了海葵式絮凝剂的混凝行为，并利用分子模拟从分子层面详细阐释了硝氮去除机理。本研究结论归纳如下：.项目选用了具有季铵基团和长碳链3-（三甲氧基硅烷基）丙基二甲基十二烷基氯化铵（TPDDAC）的硅烷偶联剂和AlCl3作为原料制备了脱氮絮凝剂，季铵基团的引入可以赋予絮凝剂去除硝氮的能力，长烷基链可以提高对硝氮的选择性。通过酸碱控制-自组装的方法代替缓慢滴碱法能够显著提高絮凝剂的稳定性。.通过多种手段对海葵式絮凝剂的物化性质和结构进行了详细表征。海葵式絮凝剂通过Si-O-Al键将有机组分和无机铝组分通过共价键连接，其zeta电位比传统絮凝剂有显著提高，具有更强的电中和能力，粒径在50 nm左右并呈现均匀分散的球状核壳结构。该结构使絮凝剂具有极强的稳定性，几乎不会发生因无机和有机组分胶凝导致絮凝剂失稳的现象。.该类絮凝剂在二级生物出水深度处理和污泥处置中表现优异。对于二级生物出水深度处理，多项指标的去除率达到90%以上。这些指标不仅包括浊度、DOC以及总磷等常规指标，还包括目前广泛关注的有机微污染物、传统絮凝剂几乎不能去除的硝氮以及其他溶解性污染物。对于污泥脱水处置，利用该类絮凝剂对污泥高效脱水后，其浸出液中污染物含量显著降低，可以达到直接排放的要求，不会对周围水质造成污染。.项目组深入研究并阐释了海葵式絮凝剂的絮凝行为和脱氮机理。具有球状核壳胶束结构的海葵式絮凝剂在絮凝过程中会发生构型反转，类似海葵把收缩的触手由内向外张开。絮凝剂无机铝组分发挥水解聚合、析出凝聚核并形成沉淀絮体的功能，有机组分通过静电引力等 作用捕捉硝氮等小分子并携带其进入沉淀，从而实现了絮凝去除硝氮等小分子溶解物质。