【作者】 许伟颖；

【导师】 高宝玉；

【作者基本信息】 山东大学 ， 环境工程， 2012， 博士

【摘要】 本论文在综合国内外大量相关文献的基础上,基于新型纳米Al13混凝研究的应用前景,对Al13的混凝行为和效果进行系统、深入的研究。同时,对纳米Al13形成的絮体特性,包括絮体粒径、强度、再生能力以及分形结构等进行了系统的研究。另外基于目前混凝/超滤联合工艺的发展现状和研究背景,将Al13应用于混凝/超滤工艺中,探索了其对出水水质和膜污染的影响。主要研究内容及结论如下：1、采用预水解Al13对模拟染料废水、腐植酸(HA)模拟水样和黄河实际水样进行混凝处理,并通过脱色率、浊度、UV254以及DOC等指标的测定来对Al13的混凝效果进行评价。实验结果表明：Al13形态具有稳定性及高正电荷性,在低投加量下能够有效发挥吸附电中和作用,混凝效果较A12(SO4)3或PAC1好；在高投加量下的混凝效果同其它铝盐混凝剂相似。在水样pH变化时,Al13的混凝行为和效果较其它铝盐混凝剂(A12(SO4)3或PAC1)稳定；Al13在处理黄河水样时对亲水性小分子有机物的去除效果较PAC1好。2、采用透光率脉动检测技术和激光粒度散射技术对混凝动态过程进行监测,并通过对絮体以0、强度因数、恢复因数等指标的计算来评价Al13形成的絮体特性。实验结果表明：与其它铝盐混凝剂相比,预水解Al13在投入水体后能迅速发挥作用,絮体生长速度快,且形成的絮体特性受pH的影响较小。处理直接紫模拟染料废水时,与PACl相比,在投加量相同的条件下,Al13形成的絮体颗粒较小,但密实性较高,沉降性能好。Al13处理分散黄棕时形成的絮体颗粒破碎后较易再生。处理HA模拟水样时,与PACl相比,Al13在低投加量时形成的絮体粒径较大,当投加量增大时,HA-Al13絮体的粒径小于HA-PAC1的粒径。处理黄河水样时,铝盐混凝剂形成的絮体大小顺序为：Al2(SO4)3>PAC1>Al13。处理HA和黄河水样时,在相同的投加量和剪切力下,Al13絮体均比其它铝盐混凝剂形成的絮体的抗剪切能力强,破碎后的恢复能力高。3、采用小角激光散射法测定了不同铝盐混凝剂在处理HA模拟水样和黄河水样时形成絮体的分形结构并进行比较。实验结果表明：铝盐混凝剂在酸性和弱酸性条件下形成的絮体较密实,在碱性条件下形成的絮体较松散。与PAC1相比,相同投加量下Al13形成的絮体分形维数较大。在混凝过程中,絮体分形维数随混凝时间先显著增加,然后逐渐趋于稳定。絮体破碎再生后,分形维数增大,结构更加密实,且在低投加量和低pH下絮体分形维数的增加更显著。与PAC1相比,Al13形成的絮体在破碎后分形维数的增长更明显。4、采用单次投加和分次投加两种投药方式对HA水样进行混凝,并通过对UV254和zeta电位的测定,比较两种投药方式的混凝效果并探讨二次投加混凝剂的混凝机理。实验结果表明：在总投药量相等的前提下,采用二次投加方式能够在一定程度上提高传统单次投加混凝工艺的出水水质。在絮体破碎后二次投入的Al13,既发挥电中和作用,又发挥吸附架桥和共沉淀作用；且二次投加的Al13混凝剂,能够更有效提高絮体破碎后的再生能力。当Al13的二次投加量在等电点附近时,絮体再生能力最强,出水效果最好。絮体破碎后,适当投加Al13混凝剂可以增加絮体的分形维数。由于PAC1的正电荷较Al13低,所以二次投加的PAC1电中和作用较弱,主要是通过吸附架桥和共沉淀发挥作用,对絮体分形结构的影响不明显。Al13和PAC1采用二次投加方式均能够减轻高速剪切力对絮体的破碎程度。5、将Al13应用于混凝(沉淀)/超滤和混凝/超滤工艺中对HA水样进行处理,并通过测定UV254的去除率及膜通量下降来评价Al13混凝出水对后续超滤工艺的影响。实验结果表明：Al13在混凝(沉淀)/超滤和混凝/超滤工艺中对HA的去除效率与PAC1相似,只在投加量很低时,对HA的去除率较PAC1高。在混凝(沉淀)/超滤工艺中,与PAC1相比,Al13混凝出水引起的过膜总阻力较小,膜通量较大；而在混凝—超滤工艺中,Al13混凝出水引起的吸附阻力和滤饼层阻力较大,膜通量小于A12(SO4)3和PAC1混凝出水的通量。混凝过程中絮体破碎再生后,Al13出水的过膜通量变化最小,而A12(SO4)3混凝出水受絮体破碎影响最大。絮体破碎程度越高,混凝出水引起的膜通量越低。长时间絮体破碎能够进一步增大滤饼层阻力,降低膜通量。采用A12(SO4)3为混凝剂时,混凝—超滤膜通量受剪切时间的影响最严重,而Al13混凝出水引起的膜通量几乎不受混凝过程中破碎时间的影响。6、将聚硅铝盐混凝剂应用于混凝*超滤工艺中,并将其对超滤工艺的影响与铝盐混凝剂对比,实验结果表明：与铝盐混凝剂相比,聚硅铝盐混凝剂形成的絮体粒径较大,强度较高,但是絮体破碎后的再生能力较弱,分形维数较低,结构较松散。所以采用聚硅铝盐混凝剂对水样进行预处理,能够显著降低吸附阻力和滤饼层阻力,提高膜通量。另外,聚硅酸的加入缩小了Al13和PAC1混凝形成的絮体特性之间的差异,包括絮体粒径、强度、再生能力、分形维数等,因此,聚硅氯化铝和聚硅Al13混凝出水的膜阻力和膜通量差异较小更多还原

【Abstract】 Based on the previous researches on Al13species, coagulation behavior and efficiency of Al13were investigated in this study. Meanwhile, the floc characteristics formed by Al13, including floc size, strength, re-growth ability and fractal dimension, were systemically studied. Additionally, on the basis of previous studies on ultrafiltration technology, Al13was applied in coagulation/ultrafiltration hybrid process, and its effects on water quality and membrane fouling were evaluated. The main research and conclusions are as follows:1. Simulated dye wastewater, humic acid (HA) solution and the Yellow River water were coagulated by Al13species. The decolorization efficiency as well as turbidity, UV254and DOC removal efficiencies were measured to evaluate the coagulation behaviors of Al13. The results showed that:at low dose, pre-hydrolyzed Al13with high positive charge could keep stable after addition into the coagulation system and contribute to effective charge neutralization and thus higher efficiencies compared with A12(SO4)3and PACl. At high doses, besides charge neutralization, bridging and sweep mechanisms caused by Al13aggregates and amorphous precipitates also played important roles in Al13coagulations and the coagulation efficiencies of Al13were similar with those of other Al-based coagulants, Al2(SO4)3and PACl. Al13presented more stable coagulation behaviors and efficiencies than Al2(SO4)3and PACl when pH of water sample varied. Al13could better remove the small hydrophilic natural organic matters than PACl in the Yellow River water treatment.2. Using light transmittance pulse testing technology and laser light scattering technology to monitor the dynamic flocs during coagulation. Floc properties were assessed by measuring floc d50and determining the strength factor, recovery factor of flocs. The results showed that:compared with other Al-based coagulants, Al13could react immediately after addition into the coagulation systems and the flocs grew fast. Additionally, the flocs formed by Al13had stable properties when exposed to various pHs. For simulated dye wastewater, Al13contributed to smaller and denser flocs with better settling than PACl at the same dose. Flocs formed by Al13had better recovery abilities than those formed by PACl due to the better charge neutralization of Al13. For HA samples, Al13contributed to larger flocs than PACl at lower doses; while PACl flocs were larger at higher doses. The sequence of floc size in the Yellow River water treatment by Al-based coagulants was as follows: Al2(SO4)3>PACl>Al13. Flocs formed by Al13were stronger and had better recovery abilities than those formed by other aluminum coagulants in both HA and the Yellow River water treatments.3. Floc fractal structures formed by various Al-based coagulants in HA water and the Yellow River water treatments were measured using small-angle laser light scattering (SALLS). The results showed that:at acidic ambience, aggregates formed by Al-based coagulants were compacter and denser than those formed at alkaline pH. Al13contributed to flocs with larger fractal dimension (Df) than PACl under the same coagulation conditions. The Df of flocs increased continuously during the whole coagulation process. Breakage of flocs could improve floc fractal structure at acidic pH while this effect was not so evident at alkaline pH. Compared with PACl coagulation, the increase of floc Df caused by floc breakage was more evident in Al13coagulation.4. HA solution was coagulated with two dosing methods:1-shot dosing and2-times dosing methods. The coagulation efficiencies and mechanisms by these two dosing methods were evaluated through the measurements of UV254and zeta potentials. The experimental results showed that:at the same total dose with1-shot dosing,2-times dosing could increase the removal efficiency of HA. The additional Al13dosed at the end of breakage phases displayed charge neutralization, adsorption, bridging and sweep mechanisms, which could apparently improve the recovery abilities of broken flocs. The additional Al13dose near the isoelectric point contributed to the flocs with best recovery abilities and highest HA removal efficiency. Proper additional dose of Al13could improve the floc fractal structure. Compared with Al13, PACl had less positive charge and thus the charger neutralization of additional PACl was weaker and the main coagulation mechanisms of additional PACl were adsorption, bridging and co-sedimentation, which had negative effect on floc fractal structures. For both Al13and PACl, the2-times dosing could alleviate the damage of high shear on flocs.5. Al13was applied in the coagulation/ultrafiltration hybrid processes to treat HA solution, and its effects on HA removal and membrane fouling were evaluated by measuring UV254removal and flux declines, respectively. The results indicated that:HA removal efficiency treated by coagulation (sedimentation)-ultrafiltration and coagulation-ultrafiltration hybrid processes with PACl and Al13were similar. Al13contributed to higher HA removal efficiency at low doses. In coagulation (sedimentation)/ultrafiltration process, feed water pre-coagulatd by Al13caused smaller total resistance and thus less flux decline than that coagulated by PACl; while in coagulation/ultrafiltration process, the feed water treated by Al13caused larger adsorption and cake layer resistances when compared with those coagulated by Al2(SO4)3and PACl, and thus Al13coagulation effluent caused the least ultrafiltration flux. The flux changed least when pre-generated flocs by Al13were exposed to higher shears; while the flux of Al2(SO4)3effluents fluctuated most with the increased shears during coagulation unit. The membrane flux decreased with the increasing of breaking shear. Long breaking time could lead to larger cake layer resistance and smaller membrane flux. The flux caused by Al2(SO4)3effluents decreased most evidently by the prelonged breaking time during coagulation; while that caused by Al13was almost unaffected by the breaking time.6. PACl-Si and Al13-Si were applied in the coagulation/ultrafiltration process, and their effects on ultrafiltration were compared with those by PACl and Al13. The results proved that:compared with PACl and Al13, PACl-Si and Al13-Si contributed to flocs with larger sizes and strength but weaker recovery abilities and fractal dimensions. As a consequence, the feed water pre-coagulated by PACl-Si and Al13-Si could decrease the adsorption and cake layer resistances and thus higher membrane fluxes. Additionally, the addition of pSi reduced the differences bewteen floc properties generated by Al13and PAC1in terms of floc sizes, strength, recovery abilities and fractal structures. The gap between fluxes caused by PACl-Si and Al13-Si coagulation effluents was rather limited.更多还原