【作者】 陈晓燕；

【导师】 张志剑；

【作者基本信息】 浙江大学 ， 环境工程， 2011， 硕士

【摘要】 粉煤灰是我国排放量最大的固体废弃物之一,其有效利用率低,大量的粉煤灰的堆放不仅污染环境而且对人体健康产生隐患,因此开展粉煤灰的综合利用是一项艰巨而重要的任务。粉煤灰合成沸石已经广泛应用于环境工程实例中解决环境污染等问题,是一种颇有前途的资源。而针对目前粉煤灰合成沸石的过程机理的不明确性以及合成沸石对高浓度氮磷废水处理能力有限的现状,本论文着重研究了粉煤灰纳米沸石复合颗粒的合成机理及其最优化的条件,尝试了掺杂法和阳离子置换法强化其同步去除沼液污水中氨氮和磷酸盐的技术途径,以期为粉煤灰的综合利用及粉煤灰纳米沸石复合材料的研究应用拓展新的领域。本研究所得结论总结如下：根据四种分别来源于浙江杭州、浙江北仑、浙江长兴和河南开封火电厂的粉煤灰其合成沸石的转化率、母液的Si和Al浓度、产物物相组成、产物的化学组成及其表面性状的动态变化的共性分析,可以将粉煤灰合成沸石的转化机理分为五个阶段：第一阶段,诱导期或初始期,即快速升温到设定温度的0.5h,粉煤灰微珠将均匀分散在氢氧化钠液相溶液中；第二阶段,加速期或溶解期,0.5～12h,粉煤灰中大量的Si和Al溶出,其表层活性SiO2及Al2O3与钠离子反应生成富硅的水化硅铝酸钠凝胶,并覆盖在粉煤灰微珠表面；第三阶段,伪平衡期或成核期,12～24h,随着硅铝酸盐凝胶中硅铝比的降低,其内部开始生成晶核,氢氧化钠的消耗速度降低,SiO2及Al2O3与氢氧化钠的反应平缓；第四阶段,快速生长期或结晶期,24～48h,24h后粉煤灰微珠表面呈现多通道的网络状结构,加快硅铝酸盐凝胶结晶,根据异相成核原理,纳米沸石生成物在粉煤灰微珠表面,晶粒快速生长；第五阶段,转化期或稳定期,48h以后粉煤灰表面的纳米沸石晶体粒子随着反应时间的延长,沸石内部的结构组成开始发生变化,由亚稳态的NaPl型沸石结构转化为相对稳态的羟基方钠石或方沸石等晶体结构。高温和延长反应时间能够促使沸石相转化为羟基方钠石,即二次结晶。粉煤灰合成沸石最优化条件为反应时间为48h,液固比为6ml/g、NaOH浓度为2mol/L以及反应温度为95℃,此时合成产物为粉煤灰纳米NaPl沸石复合颗粒,且阳离子交换容量(CEC)值最高为235.8cmol/kg。根据四种粉煤灰纳米沸石复合颗粒的理化性能比较分析,得出硅铝比比较高的北仑和长兴粉煤灰(硅铝比分别为1.82和1.52)较低硅铝比的杭州和开封粉煤灰(硅铝比分别为0.54和1.21)更适合作为合成沸石的原材料。浙江北仑和浙江长兴粉煤灰合成产物的CEC都分别比其原始粉煤灰提高了两个数量级,其比表面积(SBET)比其原始粉煤灰提高了1个数量级,因此具有较大的氨氮的离子交换与吸附潜能。针对合成的粉煤灰纳米沸石复合颗粒对磷吸附能力的不足,为了强化其对磷吸附容量,采用掺杂合成法和阳离子置换法这两种方法对粉煤灰纳米沸石复合颗粒进行功能强化设计。结果表明,钙镁盐掺杂合成法及钙镁阳离子置换法能够显著强化粉煤灰纳米沸石复合颗粒的磷素吸附容量与性能,其中钙镁阳离子置换所得产物的最大磷固定系数(PIC)比原始的合成粉煤灰纳米沸石复合产物增加了2.7～3.2倍。钙饱和置换产物能够增强粉煤灰合成沸石对氨的去除率；而镁饱和置换却有副作用；钙镁盐饱和以及钙掺杂强化处理能够显著提高粉煤灰纳米沸石复合颗粒对P的吸附去除率,且随着投加量的增加,其对P的吸附去除率显著增加,而镁掺杂强化处理对磷的去除率增加不明显。考虑氨氮的同步去除率,钙盐掺杂和饱和置换对粉煤灰纳米沸石复合产物的脱氮除磷强化效果显著,其中钙饱和置换后的合成产物最适合用于沼液废水的脱氮除磷,当投加量为0.25-8.00g/100ml时,其对氨氮和磷的去除率分别达到41.32%-95.00%和87.72%-98.59%。钙掺杂或阳离子置换处理的粉煤灰纳米沸石复合产物在投加量为8.00g/100ml时沼液的氨氮分别降为67.46mg/L和31.75mg/L、磷降为1.47mg/L和0.44mg/L,满足浙江省畜禽养殖业污染物排放标准对沼液废水的脱氮除磷的排放要求。更多还原

【Abstract】 Fly ash (FA) is one of the largest emissions of solid waste in China, while its effective utilization rate is low and its disposal as landfill poses major challenges and serious economic and environmental problems. However, zeolite synthesis from FA (ZFA) has been receiving a lot of attention and the potential use of ZFAs in water decontamination has been evaluated by a number of research groups. Because the the transformation mechanism of ZFAs from FA is unclear and waste water with high concentrations of nitrogen and phosphorus can not be effectly treated by ZFAs. This paper focuses on the synthesis mechanism of fly ash/nano-zeolite composite material from fly ash and optimization of the synthesis program. Try the doping method and the cation exchange method to modify the synthesized product in order to simultaneous removal of ammonia nitrogen and phosphates in livestock waste water. Conclusions of this study were summarized as follows:Different FAs were collected from four thermal power plans in China (Hangzhou, Beilun, Changxing and Kaifeng). To clarify the mechanism of zeolite synthesis from fly ash, the hydrothermal reaction was carried out. The changes in various physical and chemical properties, such as crystal structure, chemical composition, surface structure of the obtained zeolites and the dissolved amount of Si and Al in alkali solution were investigated during the hydrothermal reaction. The zeolitisation mechanism mainly consists of five successive steps. The first step is the induction period or initial period in the first 0.5h with the fly ash and alkali solution mixed together and the temperature of the slurry reaches to the setted value. The second step is called accelerated phase or dissolution phase in the reaction time of 0.5-12h, the dissolution of the FA leads rapidly to the reprecipitation of a rather Si-rich aluminosilicate gel intermediate. The third stage is the pseudo-equilibrium phase or the nucleation phase in the reaction time of 12-24h with formation of nuclei in aluminosilicate gel. During the fourth stage of the arpid growing or crystalline in the reaction time of 24-48h, the rapid crystallisation of nano zeolite-NaPl begin. The last stage is called stable or transformation phase after 48h with partial transformation of Na-Pl zeolite into the more stable hydroxysodalite or analcime.The optimal conditions for synthesis of fly ash/nano-zeolite composite material composite particles with the hightest cation exchange value (CEC) were with the reaction time of 48h, the liquid to solid ratio of 6ml/g, the NaOH concentration of 2mol/L and the reaction temperature of 95℃.According to comparative analysis of the physical and chemical properties the products synthesized from four different fly ash samples, it was found that the fly ash from Beilun and Changxing with higher Si/Al ratio (Si/Al ratio of 1.82 and 1.52, respectively) were more suitable for synthesis of zeolite materials than that from Hangzhou and Kaifeng with lower Si/Al ratio (Si-Al ratio of 0.54 and 1.21, respectively). Besides, the CEC and the SBET values of the synthetic products from the fly ash of Changxing and Beilun increased by two orders of magnitude and one order of magnitude, respectively, compared to that of their original fly ash.In order to improve the adsorption capacity of P of the synthesized zeolite, doping method and the cation exchange method with CaCl2 and MgCl2were conducted. The results showed that the two methods effectively modified the synthesis products and significantly strengthen their phosphorus sorption property.Considering the simultaneous removal of ammonia and phosphate of, the products with cation exchange of Calcium salt treatment was the most suitable for the treatment of anaerobically digested livestock wastewater. The removal rates of ammonia nitrogen and phosphate reached 41.32%-95.00% and 87.72%-98.59% respectively with the dosage of aboved product of 0.25-8.OOg/100ml.When the dosage of fly ash/nano-zeolite composite products by calcium doping or cation exchange treatment reached 8.OOg/100ml, the concentration of ammonium and phosphate of livestock waste water after treatment decreased from 67.46 mg/L and 31.75mg/L to 1.47mg/L and 0.44mg/L respectively, reached the discharge standard of pollutants for livestock and poultry breeding of Zhejiang province.更多还原