基于多孔载镁炭质粘土的污水碳氮磷共回收及其协同钝化土壤重金属研究

At present, in the face of climate change, energy resources shortage and environment bearing capacity limited, resource cycle has become one of the focuses of the sewage treatment technology innovation and development. Aimed at the main problems of struvite precipitation (MAP) technology for nitrogen and phosphorus recovery, such as the interference of macromolecular organic matter interference on the generation of MAP crystal, high production cost of MAP, difficult recycling and the products application value is not high, this project is going to optimize the preparation of magnesium loaded porous carbonaceous clay composites (PMRB) with magnesium salt immersion and roasting method and by using rice husk and sodium base bentonite as raw material, the characteristics of PMRB are mainly macromolecular humic acid selective removal, adsorption induced crystallization and alkaline self-adjusting, which is used for recyling of carbon (humic acid type of macromolecular organic matter), nitrogen and phosphorus together from urban sludge dewatering supernatant. As a result, the recycled product which integrated humic acid, MAP, biomass carbon and clay has a high added value, and it not only has the functions of slow release fertilizer in land use, but also coordinate to passivation of heavy metals in the soil. The collected mechanism of carbon and nitrogen and phosphorus from wastewater by PMRB, and the long-term stability mechanism of soil heavy metal by recycling product are studied through laboratory and field test. Relevant research achievements have great significance to our country sewage nitrogen and phosphorus resource and heavy metal contaminated soil repair, and has a wide application prospects.

当前，面对气候变化、能/资源短缺和环境承载力有限等问题，“资源循环”已成为污水处理技术创新和发展的重点之一。本项目针对鸟粪石沉淀法（MAP）氮磷回收存在的主要问题，如腐殖酸类大分子有机物干扰MAP结晶、MAP生产成本高、回收困及其应用价值不高等，拟以稻壳和膨润土为原料，采用镁盐浸渍-焙烧方法，制备集对大分子腐殖酸选择性去除、吸附诱导MAP结晶和碱性自调节等功能于一体的多孔载镁炭质膨润粘土材料（PMRB），用于对污水中碳（腐殖酸类大分子有机物）、氮、磷的高效和便捷回收，得到集腐殖酸、MAP、生物质炭和粘土于一体的高附加值产品（HMCC），其在土地利用时除具有缓释肥功能外，能协同钝化土壤中的重金属。项目通过实验室和现场试验，深入探讨PMRB对污水中碳氮磷的共回收机制，及HMCC对土壤中重金属的长效稳定机理。有关研究成果对污水氮磷资源化和重金属污染土壤的修复具有重要意义，有着广阔的应用前景。

针对现有鸟粪石法回收污水中氮磷存在的不足，采用镁盐浸渍-焙烧制备方法，优化制备了3种镁盐改性粘土复合材料，即高活性氧化镁改性硅藻土(MgO-D)、凹凸棒土负载氧化镁复合材料（MgO-PAL）和多孔载镁炭质膨润粘土复合材料（PMRB），利用其对水中氮磷的吸附和鸟粪石生成作用，实现对污水中氮磷（碳）的同步回收，得到富集有鸟粪石的复合粘土产品，并进一步将上述回收产物用于水体和土壤重金属污染的治理。.MgO-D最佳制备条件为：镁土比30%，OH-/Mg2+比1.8，煅烧温度450˚C，煅烧时间3 h，MgO-D对氮磷的固定化回收量分别达到166.3和77.1 mg/g。MAP-D对水中Pb2+和Zn2+的去除实验结果表明，其主要是通过Pb10(PO4)6(OH)2、Zn3(PO4)2·2H2O等磷酸盐形式沉淀完成的。MAP-D投加量分别为5%和10%时，稳定8周后，其对土壤中铅锌的有效态含量分别减少70.9%和65.4%，钝化稳定性能良好。.MgO-PAL最佳制备条件为：Mg负载量为30%、焙烧温度为400℃、焙烧时间为4h，其对污水中氮磷最大回收量分别达到42.6 mg/g和69.8 mg/g。氮磷回收产物S-PAL对水中Cd(II)、Pb(II)和Cu(II)的最大吸附去除能力分别达到121.14 mg Cd/g、478.47 mg Pb/g和106.27 mg Cu/g，吸附机理主要包括离子交换、表面络合及磷酸盐沉淀。S-PAL对土壤中Cu(II)、Pb(II)和Cd(II)污染具有良好的钝化稳定性能，其作用机制主要为生成Cu3.04(PO4)2OH0.08·2H2O、Pb5(PO4)3OH、Cd3(PO3)2及Cd1.5Ca1.5(PO4)2的难溶性磷酸盐沉淀。.PMRB的最佳制备条件为：焙烧温度为450℃、焙烧时间为4 h，Mg负载量为30%，OH-/Mg2+比为2.0。PMRB对碳氮磷的最大回收量分别达到34.57，58.20和125.36 mg/g。碳氮磷回收产物HMCC对水中Zn (II)、Cu (II) 和Cd (II)的吸附去除量分别为163、198 和270 mg/g。HMCC投加后，土壤中重金属离子的酸溶性态浓度明显降低，同时实现ARGs丰度水平的消减。.有关研究成果对污水氮磷资源化和重金属污染土壤的修复具有重要意义，有着广阔的应用前景。