【作者】 张占梅；

【导师】 ?忱?；

【作者基本信息】 重庆大学 ， 分析化学， 2006， 硕士

【摘要】 随着科学技术的进步,已产生许多水处理方法,如吸附法、化学氧化法、离子交换法、生化法、电渗析及絮凝沉淀法等。而应用最广、适用性最强、成本最低廉的方法是絮凝沉淀法。絮凝沉淀法作为一种较为有效的预处理方法,其絮凝剂絮凝效果的好坏直接决定后续处理单元的运行工况、处理费用和最终出水水质,而目前应用最为广泛的絮凝剂就是无机高分子絮凝剂,无机高分子絮凝剂主要有聚合铝及聚合铁两大类。聚合铝盐类絮凝剂及其水解产物存在着沉降速度慢、污泥疏松量大、除色效果差、残余铝具有毒性等缺点;虽然聚合铁盐类絮凝剂及其水解产物形成的絮体强度大、沉降性好、脱水性能强、净水效果显著、受水质影响小、pH适用范围广、价格低廉,但铁盐具有很强的腐蚀性,残余铁通常会使处理后水体带黄色,影响出水效果。而聚合氯化铝铁絮凝剂(PAFC)是在铝盐和铁盐絮凝剂的基础上发展起来的一种无机高分子絮凝剂,它同时具有铝盐和铁盐絮凝剂的优点,又弥补了二者的不足,尤其是对低温低浊水,低温高浊水处理效果更佳,可广泛用于饮用水、市政用水及多种工业废水的处理。低品位铝矾土矿是指Al2O3含量在25%～4O%,全Fe含量大于2%的高铁矾土矿。我国有许多铝矾土矿都是这种低品位铝矾土。由于其含铁量较高,既不适合作工业铝的生产原料,又不适宜作耐火材料,而目前普遍采用的拜耳法和烧结法从铝土矿中提取氧化铝,由于该工艺对铝的含量要求极高,一般铝含量小于45%的铝土矿都被视为废渣而不能使用。而化工厂的废盐酸及氯化氢气体排放到环境中,不仅浪费大量的宝贵资源,也对环境造成巨大的压力。因此研究利用废弃的低品位铝矾土及回收化工厂废酸制备无机高分子絮凝剂,对于充分利用资源,保护环境都有良好的经济效益和社会效益。本文以低品位铝矾土、铝酸钙粉、废盐酸为主要原料采用两步法制备聚合氯化铝铁絮凝剂。首先将铝矾土在800℃高温下焙烧2h,粉碎过60目筛(颗粒直径为0.25mm)。在第一步反应中,在铝矾土中加入适量的混和酸加热搅拌反应一定的时间,使铝矾土中氧化铝和铁充分溶解出来,因为铝矾土本身含有大量的铁,所以在制备过程中不需要再另外加入高价格的含铁试剂,只需要在第二步反应中加入适量的铝酸钙粉调节氧化铝和铁的含量,同时提高产品的盐基度,继续加热搅拌,反应一定时间,冷却沉化即可制得聚合氯化铝铁絮凝剂。实验结果表明:在铝矾土的酸溶实验中,将300ml15%的混和盐酸和110mlH2O水加入带有回流冷凝管的四口烧瓶中,溶液加热至80℃,再加入150g铝矾土,加热搅拌反应3h,保持反应温度为105℃,铝矾土中氧化铝溶出率为80.84%,全铁的溶出率为92.15%。在第一步酸溶反应液中再加入142ml15%的混合盐酸和140ml水,60g铝酸钙粉,减缓搅拌速度,加热温度至105℃,继续聚合反应7h,同时在反应的过程中通入适量的水蒸汽,即可制得Al2O3含量为9.73%,,Fe含量为1.62%,盐基度B为79.4%的聚合氯化铝铁絮凝剂。经电镜扫描和红外光谱分析,制备的聚合氯化铝铁絮凝剂物貌结构既不同于聚铝,也不同于聚铁,是具有较大聚合度的一种新型无机高分子絮凝剂。将自制聚合氯化铝铁絮凝剂用于实际废水的处理时,形成的矾花大而密实,沉降速度快,适用水体的pH值范围宽,处理洗水、印染废水、造纸废水、棉纺废水都可达到理想的絮凝效果,色度、浊度、COD均能得到有效的去除。和其它絮凝剂相比,自制氯化铝铁絮凝效果优于市售同类产品。更多还原

【Abstract】 With the development of science and technology, there are many wastewater treatment methods available, such as adsorption, chemical oxidation, ion exchange, biochemical treatment, electro-dialysis and flocculation sedimentation and so on. As an effective pre-treatment method, Flocculation sedimentation has the widest applicable range、the lowest treatment cost and the best flocculation efficiency. Flocculation effect of flocculant directly determines the regular working of operational unit, treatment cost and the effluent water quality. At present, the widest application is inorganic polymeric flocculant, which mainly includes two kinds: polyaluminum salt flocculant and polyferric salt flocculant.Polyaluminum salt flocculant and its hydrolysate have the following disadvantages: its flocs sedimentation is slow、sludge produced is loose and large amount、its decolourity effect is not good and residual alum is harmful to human body; polyferric salt flocculant and its hydrolysate are used to treat wastewater with the following flocculation phenomena: forming compact and strong flocs、good precipitation and dewatering effect、wide applicable range of pH value、low treatment cost. In addition, wastewater quality influence on its flocculation efficiency is slim, but ferric salt flocculant haas strong erosion action to treatment equipment and residual ferric will make Wastewater to be treated yellow to affect the effluent quality. However, polyaluminum ferric chloride (PAFC) is a new kind of high-effective inorganic polymeric flocculant developed on basis of polyaluminum and polyferric flocculants. It has the advantages of polyaluminum and polyferric, at the same time, it can make up their weak points, particularly, it is used to dispose low temperature and low turbidity、low temperature and high turbidity wastewater, better flocculation efficiency can be achieved. It can be widely used to treat drinking water、urban water and industrial wastewater.Low concentration bauxite means the mineral its Al2O3 concentration ranges from 25% to 40% and total Fe concentration is over 2%. There are many these kinds of low concentration bauxites in China. It can be neither used as raw materials of industrial alum production nor used as refractory. However, the conventional extraction method, such as baler method and agglomeration method, their requirements to alum concentration are strict and high, in general, bauxite is regarded as waste solid and can’t be used if its Al2O3 concentration is below 45%; The main constituent of waste gas discharging from electrochemical factory is HCl, if the low concentration bauxite and waste gas were released into environment, it not only brings huge pressure to environment but also wastes lots of valuable resources, therefore, it is demonstrated to be necessary to carry out study on preparation of PAFC by using the bauxite and recycled waste gas, which has important society and economy profit.This research adopts two-step method to prepare PAFC by using bauxite、calcium aluminate and waste acid recycled from waste gas as main raw materials. At first, bauxite should be calcined at muffle stove at temperature of 800℃for 2 hours, and then cooling and comminuting to 0.25mm. In the first step, adding right amount of mixed hydrochloric acid, bauxite and water to vessel reacting some time in order to extract fully Al2O3 and Fe from bauxite. In the process of PAFC preparation, without adding additional ferric to mixed solution because bauxite itself contains amounts of ferric, what needs to do is to add calcium aluminate in the second step. Addition of calcium aluminate can both adjust Al2O3/Fe concentration ratio and enhances basicity of PAFC product. Stirring and heating for 7 hours, the product PAFC can be achieved after another 24 hours sedimentation. Experiment results show that:In the acid dissolution experiment of bauxite, adding 300ml 15% mixed hydrochloric acid and 110ml H2O into four outlet flask, then heating up to 80℃and putting 150g bauxite into the mixed solution react 3 hours under stirring condition, the reaction temperature was controlled at 105℃, after the end of reaction, Al2O3 and Fe concentration were investigated in order to calculate their dissolution rate. Experiment result showed that dissolution rate of Al2O3 and Fe can be up to 80.84% and 92.15% respectively. In the second step, 142ml 15% mixed hydrochloride acid、140ml H2O and 60g calcium aluminate were put into the acid dissolution solution reacting for 7 hours at 105℃, In the process of polymerization reaction,vapor was inpoured into the reaction solution to increase reaction temperature and to accelerate proceeding of polymerization reaction。The factors which affect the flocculation efficiency of PAFC product and the optimum conditions were investigated, such as dosage and concentration of mixed acid, reaction temperature, reaction time and dosage of calcium aluminate. After the end of polymerization reaction,cooling reaction solution and sedimentation for 24 hours in the air, the product PAFC was prepared. Its parameters are listed below: concentration of Al2O3 and Fe is 9.73% and 1.62% respectively, basicity is 79.4%.The self-prepared PAFC flocculant was analyzed by infrared spectrum and scanning electrode microscope and result showed that its micro-structure is alike to neither that of polyaluminum chloride nor that of polyferric. It has large molecular structure to form net so that its flocculation efficiency is better than that of other flocculants.The self-prepared polyaluminum ferric chloride flocculant (PAFC) was used to treat practical wastewater with large and compact flocs formed, fast sedimentation and wide range of applicable pH value. colourity、turbidity、chemical oxygen demand can be removed effectively. Good flocculation effect can be achieved to treat washing wastewater、printing and dyeing wastewater、paper making wastewater and cotton spinning wastewater. In comparison with other flocculations, its flocculation efficiency is superior to that of similar product in the current market.更多还原