【作者】 赵艳侠；

【导师】 高宝玉；

【作者基本信息】 山东大学 ， 环境工程， 2014， 博士

【摘要】 本论文基于钛盐混凝剂广阔的应用前景,系统研究了四氯化钛混凝剂处理不同水体的混凝效果和混凝行为,结合絮体电荷特性的变化,研究四氯化钛的混凝作用机理。另外,通过在线监测四氯化钛的混凝动态过程,从絮体生长速度,粒径,强度,破碎后恢复能力和絮体结构五个方面研究了四氯化钛所产生的絮体特性。实验同时制备出新型的可稳定贮存的聚合氯化钛混凝剂,确定了聚合氯化钛混凝剂的制备工艺和条件,探讨了聚合氯化钛对不同水质的净化效果,研究了聚合氯化钛的混凝行为和絮体特性。实验最后研究了混凝处理后污泥的回用,并对所得产物进行了物化性质和光催化活性的表征。论文的具体研究内容及研究结论如下：(1)采用TiCl4混凝剂分别混凝处理腐殖酸-高岭土模拟水样,黄腐酸-高岭土模拟水样,引黄水库水实际水样和小清河实际水样,通过出水剩余浊度,UV254或UV278去除率和DOC去除率等混凝指标评价TiCl4的混凝效果,实验同时研究了TiCl4投加量和水样初始pH值对混凝效果的影响。实验结果表明,TiCl4是一种有效的水处理用混凝剂,能够有效的去除水体颗粒物和有机物,且TiCl4对有机物去除率明显高于传统铝盐和铁盐混凝剂。TiCl4在较低的投加量条件下能够发挥吸附电中和作用,而在较高投加量条件下,混凝机理主要为卷扫网捕作用。在水样初始pH发生变化时,与传统混凝剂相比,TiCl4对有机物的去除率较稳定,在较高的水样pH条件下,TiCl4对水体的除浊效果较高,这表明,TiCl4具有较宽泛的pH适用范围。(2)采用激光粒度散射仪在线监测TiCl4处理不同水样的混凝动态过程,通过计算絮体生长速度,粒径,强度因子和恢复因子来表征TiCl4所形成的絮体特性。实验同时研究了混凝剂投加量,水样初始pH值,混凝过程中的破碎强度和破碎时间等不同混凝条件对TiCl4絮体特性的影响。实验结果表明,TiCl4投入水体后,迅速发挥混凝作用,絮体生长速度明显大于传统混凝剂,在较短的混凝时间内,絮体粒径迅速增大至稳定粒径,所需要的水利停留时间较短,且絮体路径明显大于传统混凝剂的絮体粒径。处理腐殖酸-高岭土模拟水样时,铝盐混凝剂具有较大的絮体强度因子,絮体强度较高,TiCl4与铁盐混凝剂的絮体强度相当。TiCl4所形成的絮体恢复因子最小,破碎后再生能力最弱。处理黄腐酸-高岭土模拟水样时,随着TiCl4投加量的增大,絮体恢复因子逐渐降低,而絮体强度因子较小的受到混凝剂投加量的影响。处理引黄水库水实际水样时,在pH为8时,TiCl4所生成絮体粒径最大(560.4μm),絮体强度因子顺序如下：pH5<pH6<pH8<pH10,絮体恢复因子均随着pH的增大而减小,即酸性条件下所形成的絮体在破碎后恢复能力较强。处理小清河实际水样时,絮体生长速度和粒径均随着TiCl4投加量的增大而增大,较高投加量条件下的絮体恢复因子小于低投加量条件下的絮体恢复因子。不论水样种类和混凝剂种类,随着破碎强度的增大,絮体强度均逐渐减小,絮体破碎后再生能力均逐渐增强,破碎时间的延长均会降低絮体的强度和恢复能力。(3)研究了TiCl4在单次投加工艺和二次投加工艺混凝体系中的混凝效果,通过监测颗粒物和有机物去除率及混凝过程中絮体zeta电位的变化,对比两种投加工艺的混凝效果,研究二次投加工艺混凝过程的混凝机理。实验同时研究了水质特性(水体硬度和离子强度)对TiCl4混凝效果和絮体特性的影响。实验结果表明,二次投加少量的TiCl4能够有效的提高除浊及HA和FA去除率,二次投加的TiCl4能够有效的发挥电中和,吸附和共沉淀作用,絮体再生粒径明显增大,絮体破碎后恢复能力明显提高,絮体结构的密实程度增大。在TiCl4总投加量相同的条件下,二次投加工艺在水体除浊方面具有明显优势,絮体粒径较大,破碎后再生能力较强,但是絮体结构的密实程度有所降低。水质特性的影响实验表明,适当的提高水体的硬度和离子强度能够有效的增大颗粒物和有机物去除率,改善絮体特性。(4)分别采用阳离子型聚丙烯酰胺(PAM),聚二甲基二烯丙基氯化铵(PDMDAAC),复合型生物絮凝剂(CBF)和海藻酸钠(SA)作为TiCl4混凝剂的助凝剂,研究助凝剂对TiCl4混凝效果,作用机制和絮体特性的影响。实验结果表明,四种助凝剂均能够有效的提高TiCl4的除浊效果和有机物去除率,尤其在较低的TiCl4投加量条件下,助凝剂的助凝效果更加明显。TiCl4与助凝剂的投加顺序及助凝剂种类是影响混凝效果和絮体特性的重要因素。PAM做助凝剂时,对黄腐酸的去除率TiCl4-PAM> PAM-TiCl4,絮体粒径和生长速度大小顺序为：TiCl4-PAM> TiCl4> PAM-TiCl4, PAM的加入使得絮体结构变得松散。PDMDAAC做助凝剂时,腐殖酸去除率PDMDAAC-TiCl4> TiCl4-PDMDAAC, PDMDAAC能够有效的改善絮体的恢复能力和结构特性。(5)采用微量滴碱法制备了一系列可稳定贮存的碱化度不同的聚合氯化钛混凝剂,采用电喷雾电离质谱法分析了聚合氯化钛溶液中钛的水解形态,实验将聚合氯化钛应用于模拟水样和实际水体的混凝处理,并对聚合氯化钛的混凝动态过程进行在线监测,研究了聚合氯化钛的絮体特性。实验结果表明,与四氯化钛相比,聚合氯化钛能够更有效的去除水体浊度和溶解性有机物,且混凝结束后出水pH值较高,一定程度上解决了四氯化钛混凝结束后出水pH值较低的问题,另外,聚合氯化钛能够有效的改善絮体特性,增大絮体粒径,提高絮体生长速度,所生成絮体的结构更加密实。因此,聚合氯化钛是一种高效水处理剂。(6)混凝过程结束后,实验回收所得污泥并高温煅烧,采用现代分析手段表征所得煅烧产物的物化特性及光催化活性。实验结果表明,TiCl4和聚合氯化钛(PTC)混凝结束后回收污泥经高温煅烧能够得到具有广泛应用价值的二氧化钛(TiO2),对Ti02晶体形态的表征发现,污泥回用所得的TiO2为锐钛型,光催化活性实验表明,Ti02具有较高的光催化活性,能够有效的降解水体中的污染物。更多还原

【Abstract】 Based on the wide application prospect of titanium based coagulants, the coagulation efficiency, coagulation behavior and coagulation mechanisms of titanium tetrachaloride (TiCl4) were systematically investigated. Additionally, floc characteristics of TiCl4were investigated in terms of floc growth rate, floc size, strength, recoverability and floc structure through on-line monitoring of kinetic coagulation process. New and stable polytitanium chloride (PTC) coagulants were also synthesized in this study and the preparation process and conditions of PTC were investigated. The coagulation performance, coagulation behavior and floc characterisitcs were also evaluated for different water treatment. Finally, sludge produced after coagulation process was calcined to produce titanium dioxide (TiO1). Physicochemical characteristics and photo catalytic activity of TiO2were investigated. The main research contents and conclusions are as follows:(1) Coagulation efficiency of TiCl4were investigated in terms of residual turbidity, UV254or UV278removal and DOC removal etc. for the treatment of humic acid-kaolin sydnthetic water, fuvic acid-kaolin synthetic water, reservoir real warer and Xiaoqinghe real water. The effect of coagulant dose and initial solution pH on coagulation performance was investigated. Results showed that TiCl4is an efficient coagulant for water treatment, which can effectively remove the particulates and organic matter in water. The organic matter removal efficiency of TiCl4was obviously higher than that of the conventional aluminium (Al) and iron (Fe) coagulants. At low TiCl4doses, the main coagulation mechanism is adsorption and charge neutralization, while at high TiCl4doses, the main coagulation mechanism changes to sweep flocculation. The organic matter removal efficiency of TiCl4was more stable under various initial solution pH conditions than the conventional coagulants. Compared to the conventional coagulants, TiCl4is superior in terms of turbididy removal under high pH conditions and has wider pH application range.(2) Flocs formed by TiCl4were characterized in terms of floc growth rate, size, strength factor and recovery factor through on-line monitoring of kinetic coagulation process using laser light scattering technology Mastersizer2000(Malvern, UK). The influences of coagulant dose, initial solution pH, shear force and shear period on floc characterisitics were also inverstigated. Results showed that, compared with the conventional coagulants, TiCl4reacted more quickly with pollutants, resuting in larger floc size with higher floc growth rate. In case of humic acid-kaolin synthetic water treatment, the flocs formed by Al based coagulants had more enhanved strength, as refelected by higer strength factors, than the Fe based coagulant and TiCl4. The flocs formed by TiCl4showed the weakest recoverability after breakage, as reflected by the lowest recovery factor. In case of fulvic acid-kaolin synthetic water treatment, the floc recovery factor decreased with increasing TiCl4dose, while floc strength factor was barely affected by coagulant dose. In case of reservoir real water treatment, TiCl4achieved the largest floc size of560.4μm at initial solution pH of8. Floc strength factor follows the order of pH5<pH6<pH8<pH10, while floc recovery factor decreased with increasing pH. That is, the flocs formed in acidic conditions had strong recoverability. In case of Xiaoqinghe real water treatment, both floc growth rate and floc size increased with inceasing coagulant dose and the floc recovery factors under high coagulant dose conditions were lower than those under low coagulant dose conditions. Regardless of water properties and coagulant types, the increase in shear force resulted in the decrease in floc strength and increase in floc recoverability. The extension in breakage period decreased floc strength and recoverability.(3) A two-stage TiCl4dosing strategy is applied for investigating the coagulation effect of TiCl4on particulate and organic matter removal. Coagulation performance of one-shot dosing TiCl4was investigated for comparison. This study also investigated the coagulation mechanism of TiCl4during two-stage TiCl4dosing process. Additionally, this study evaluated the effect of water hardness and ionic strength on coagulation performance and floc characteristics of TiCl4. Resutls showed that a small second TiCl4dose essentially decreased the residual turbidity and improved the organic matter removal. Also, flocks with larger size and better recoverability result and having more compact structure than those obtained without the second TiCl4dose. The main coagulation mechanisms duting second coagulation process are charge neutralization, adsorption and coprecipitation. At the same total TiCl4coagulant concentrations, the two-stage dosing mode reveals significant advantage over the single coagulant dosing in terms of turbidity removal, flock size and recoverability although organic matter removal and flock compactness degree are more or less deteriorated during the two-stage dosing process. Based on the results of the influence of total hardness and ionic strength on coagulation performance, appropriate total hardness and ionic strength of raw water could effectively enhanced particulate and organic matter removal. Besides, the floc characteristics can be improved.(4) This study separately assessed the effect of coagulant aid cationic polyacrylamide (PAM), polydimethyldiallylammonium chloride (PDMDAAC), compound bioflocculant (CBF) and sodium alginate (SA) on coagulation performance, coagulation mechanism and floc characteristics of TiCl4. Results showed that the coagulation efficiency of TiCl4can be significantly improved by coagulant aid, especially under low TiCl4dose conditions. Dosing sequence of TiCl4and coagulant aid and type of coagulant aid are two main factors influencing coagulation efficiency and floc characteristics. For PAM as coagulant aid, the removal of fulvic acid followed the order of TiCl4-PAM> PAM-TiCl4and the floc growth rate and size followed the order of TiCl4-PAM> TiCl4PAM-TiCl4.Additionally, degree of floc compactness decreased due to PAM addition. For PDMDAAC as coagulant aid, the removal of humic acid followed the order of PDMDAAC-TiCl4>TiCl4-PDMDAAC. Both floc recoverability and compactness were significantly improved by PDMDAAC addition.(5) Novel and stable polytitanium chloride (PTC) with series of basicities were successfully synthesized using slow alkaline titration method. Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) was first utilized to identify various Ti species in both TiCl4and PTC solutions. Jar tests were conducted to assess coagulation performance of PTC using both synthetic and real raw water samples and the floc characteristics were monitored online using a laser diffraction particle size analyzer. Results showed that, compared to TiCl4, higher or comparable turbidity and organic matter removal efficiency could be achieved by PTC with improved floc characteristics in terms of size, growth rate and structure. Besides, the water pH after PTC coagulation was significantly improved towards neutral pH. This study indicates that PTC is an effective and promising coagulant for water purification.(6) Sludge produced after coagulation process was calcined to produce titanium dioxide (TiO2), which was characterized in terms of physicochemical properties and photocatalytic activity. Results showed that, the TiCl4and PTC flocculated sludge were able to recycle and produce functional TiO2photocatalyst. As-prepared TiO2exhibited only anatase structure, whereas P-25TiO2showed both anatase and rutile structures. Besides, the photocatalytic efficiency of as-prepared TiO2was comparable to P-25TiO2.更多还原