【作者】 胡凯；

【导师】 赵庆良；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2007， 硕士

【摘要】 本文以火电厂排放的固体废弃物——粉煤灰为原料,利用酸溶和碱溶提取其中有用的Al、Fe、Si元素,并将得到的Al、Fe盐溶液通过慢速滴碱法研制出了聚合硫酸铝铁（PAFS）。在对原料粉煤灰特性进行分析的基础上,研究了以H₂SO₄为溶剂,常温常压下搅拌反应,考查了酸种类、酸浓度、酸灰比、搅拌时间等因素对Fe³⁺、Al³⁺溶出效果,但是酸的利用率不高,而且Fe³⁺、Al³⁺的溶出率有限（最大值为13.5%、5.0%）,需要通过高温焙烧活化粉煤灰,提高酸溶出率。详细讨论了影响焙烧反应和酸溶反应的各种因素,得到了提取粉煤灰中Al、Fe元素的最佳工艺为:33.333g粉煤灰与2g的Na₂CO₃在805℃下焙烧1h,产物冷却粉碎后在沸腾回流条件下与4mol/L的H₂SO₄反应0.5h、余温冷却0.5h,所得抽滤液中Al³⁺浓度为0.207mol/L,Fe³⁺浓度为0.040mol/L。酸溶法主要提取的是粉煤灰中的Al、Fe元素,Si的提取只有采用碱性溶液法。常温下NaOH溶解粉煤灰,碱浸液中的Si浓度普遍较小。提高反应温度会极大地增加Si溶出率,NaOH浓度和碱灰比越大、碱浸搅拌时间越长,Si的溶出率越高。4mol/L的NaOH、碱灰比20mL/g、沸腾反应0.5h、余温冷却0.5h下的Si溶出率达到32.83%,远远好于常温下的酸溶或碱溶效果。通过对热碱溶后粉煤灰残渣的XRD分析看出,粉煤灰的主要存在形式变为低品质石英、Al₂SiO₅结构和Na₂Al_2xO_3x+1结构。最佳溶出条件下的粉煤灰酸溶出液,可作为混凝剂直接投加,也可以进一步制备PAFS。直接投加时,对于大豆加工废水,混凝适宜的pH值为中性条件（6⁸）,投加量适用范围较宽（12⁶0mL/L）,最佳投药量为20mL/L,此时COD去除率28.04%。对于乳品废水的处理,适宜的混凝pH为4⁸之间,pH值继续增加,混凝效果直线下降,可能是混凝剂中的SO₄^2-阴离子影响所致。中性环境下,絮体10min即可沉降完全。混凝效果在投量大于1.2mL/L后趋于稳定,此时的COD去除率59.35%,SS去除率92.62%。对于PAFS的制备,考查了Al/Fe摩尔比、Na₂CO₃浓度、滴定终点的pH值、Al+Fe的总浓度、碱化剂种类等因素对产品混凝性能的影响,确定了最佳合成条件为100g/L的Na₂CO₃溶液慢速滴定溶出液至pH=1.1¹.2左右。利用Ferron逐时络合比色法研究了PAFS中Al、Fe的形态分布规律,利用pH滴定法研究了溶出液Al（Ⅲ）+Fe（Ⅲ）的水解-聚合反应过程,利用红外光谱分析法研究了铝铁水解产物间的相互作用。结果表明,样品制备时pH值越大,[Al,Fe]_a越少,[Al+Fe]_b和[Al+Fe]_c增加。最佳条件下获得的PAFS,其中[Al,Fe]_a占57.06%,[Al+Fe]_b占5.58%,[Al+Fe]_c占37.36%。随着时间的延长,样品的pH值有下降的趋势,结合Ferron比色法测定的形态变化结果,这是熟化过程中低聚物分子与游离OH^-络合生成较高聚合度分子所致。PAFS中既有以羟基桥联的铁的聚合物,也有以羟基桥联的铝的聚合物。PAFS的烧杯实验结果显示,处理乳品废水的效果优于PAC,并且用量较少。适宜pH值范围为6⁹,静沉15min即可达到COD去除率63.9%,SS去除率94.4%。更多还原

【Abstract】 A widely generated byproduct of coal-fired power plants, fly ash was explored as raw material to extract the aluminum and iron components into a solution by acid soaking and silicon component by base soaking. Then a Na₂CO₃ solution was slowly added to the acid solution to prepare the poly aluminum ferric sulfate（PAFS）.On the basis of characterization of fly ash, types of acid solution, H₂SO₄ concentration, ratio of H₂SO₄ to fly ash and stirring time were respectively examined as factors that influenced the converting efficiencies of iron and aluminum when soaking fly ash with acid solution at atmosphere and room temperature. However, due to the limitation of utilization of acid solution and low converting efficiencies, pretreatment of fly ash to increase the acid lixiviate property was needed. The method was as follows: fly ash of 33.333g was baked with Na₂CO₃ of 2g in the muffle furnace at 805℃for 1h, and then the sinter was soaked by H₂SO₄ of 4M at boiling point in a glass reactor with the water vapor condensed. The reaction was conducted for 0.5h, then the mixture was cooled for 0.5h before filtrated. The filtrated sample contained Al of 0.207M and Fe of 0.040M.Acid soaking didn’t give high conversion efficiency of silicon of fly ash while base did. The conversion efficiency for silicon compound increased with an increase in either NaOH concentration or ratio of NaOH to fly ash. A similar trend is shown with an increase in either stirring time or reaction temperature. A silicate solution was attained at the condition of NaOH-fly ash ratio of 20mL/g, NaOH of 4mol/L, reaction time of 0.5h and cooling time of 0.5h with conversion efficiency of 32.83%, a higher value than at the condition of acid soaking or room temperature. The XRD pattern of NaOH treated fly ash suggested that major phases were quartz, Al₂SiO₅ and Na₂Al_2XO_3x+1.The acid solution could be used as coagulant. When treating soybean wastewater, the optimum pH range of coagulation was 6⁸ with a wide coagulation dosage range. The COD reduction was 28.04% when the coagulant dosage of 12mL/L was employed. When treating dairy wastewater, the optimum pH range of coagulation was 4⁸. Out of the optimum coagulation pH range, the acid solution achieved worse coagulation performance at higher pH side because of SO₄^2-. The formed floc could settle in 10min in neutral medium. Removal efficiencies of COD and SS reached 59.35% and 92.62%, respectively when the coagulant dosage of 1.2mL/L was employed. Through researches done on affection to coagulation performance of PAFS by checking various Al/Fe mol ratios, Na₂CO₃ concentration, pH of PAFS, Al+Fe concentration and types of base solution, it was proved a successful condition when Na₂CO₃ of 100g/L was slowly added to the acid solution until the pH of the acid solution raised to 1.1¹.2.A ferron timed complexation colorimetric method was employed to classify the hydrolysis-polymerization law of Al（Ⅲ） and Fe（Ⅲ）. The hydrolysis- polymerization process of aluminum ions and ferric ions in acid solution was investigated by pH titration. Interaction between Al（Ⅲ） and Fe（Ⅲ） was studied by using Near-infrared Spectroscopy. The result showed that [Al,Fe]_a decreased as pH of PAFS was raised while [Al+Fe]_b and [Al+Fe]_c increased. For PAFS with pH of 1.1¹.2, the [Al,Fe]_a species was the main component, 57.06%, with 5.58% of [Al+Fe]_b and 37.36% of [Al+Fe]_c. The change of pH of PAFS with aging time to a lower value was in agreement with the transformation of Al and Fe species of oligomers to high polymers. PAFS was composed of OH-Al complexes and OH-Fe complexes.PAFS had shown a high coagulation effect, superior to that of PAC for dairy wastewater treatment at the same dosage. The optimum coagulation pH range of PAFS is 6⁹. After sedimentation period of 15min, removal efficiencies of COD and SS by this type of coagulant reached 63.9% and 94.4%, respectively.更多还原