【作者】 彭云辉；

【导师】 张一敏； 曹波；

【作者基本信息】 武汉科技大学 ， 矿物加工工程， 2002， 硕士

【摘要】 随着环保要求的日益严格，硫酸生产废水引起的环境污染愈来愈引起人们的重视。由于硫铁矿原料品种杂、品位低，硫酸生产过程中排放的废水通常具有色度大、酸度高、含有多种有害物质的特点。如果该类废水不经过处理而直接排放到环境中，不仅会使水体或土壤酸化，对生态环境造成危害，而且浪费大量的资源。因此，处理时不仅要改善其外观和去除其强腐蚀性，更重要的是去除其中的舯、氟等有害物质。在进行该类废水处理时，吸附法、浮选法、离子交换法、膜分离法等方法有良好的应用前景，但是与实际应用仍有较大的距离。目前常用的处理方法是石灰—铁盐法，该法处理中小型硫酸厂废水具有工艺流程比较简单，投资少，占地少等优点，仍是今后广泛应用的方法，只是在工艺技术研究方面，仍需进一步挖掘潜力。 在前人研究工作的基础上，本文以湖北金山店硫酸厂的生产废水作为研究对象，考察了石灰中和沉淀法、石灰中和—鼓风氧化法、石灰中和—铁盐共沉淀法、石灰中和—鼓风氧化—铁盐共沉淀法、石灰中和—鼓风氧化—铁盐共沉淀—品种循环法以及铁氧体法处理该厂废水的工艺条件和处理效果，主要目的是找出一种简单有效的处理该厂废水的工艺流程并考察其运行条件。试验结果表明，采用前三种方法处理该厂废水，出水中砷的浓度均大于0.5mg／l；采用后三种方法处理该厂废水，砷的去除率均大于99％，出水中砷的浓度小于0.5mg／l，出水浊度小于6度，能够达到废水排放标准。通过对这几种方法的比较，结合金山店硫酸厂原有的处理设施，建议采用石灰中和—鼓风氧化—铁盐共沉淀—晶种循环法对该厂的废水进行处理。 笔者分析了曝气氧化和添加铁盐使砷去除率提高的原因，及pH值在去除砷过程中的重要作用。根据电离平衡理论和溶度积理论及试验研究结果表明，利用曝气氧化将废水中的三价砷氧化为五价砷可生成溶度积更小的砷酸盐沉淀，有利于提高砷的去除率。经理论分析，在低pH值氧化铁砷体系除砷过程中，废水中的砷酸根离子与铁离子形成溶度积很小的砷酸铁，当加入石灰乳后，能生成粒径较大的氢氧化铁沉淀，絮凝过程加速，从而提高了去除砷离子和其它重金属离子 的效果。且研究了用溶液中砷的总浓度表示的砷酸钙的溶解度随pH值变化的规 律，得出随着溶液pH值的增加，溶液中砷的总浓度降低，但当pH值大于一定值 后溶液中砷的总浓度开始升高，说明了在含砷废水处理过程中控制pH值的必要 性和重要性。此外大气中二氧化碳对砷酸钙的溶解度有一定的影响，对于长期露 天堆放的砷渣来说，砷可能在大气中二氧化碳的作用下重新进入溶液而造成污染。更多还原

【Abstract】 With the higher demand of environmental protection, more and more attention is being paid to the pollution brought by wastewater of sulphuric acid production. Effluent from sulphuric acid production is characterized by deep chromaticity color, high acidity and many harmful substances because the raw material of the plant is usually low in grade and its variety is complicated. If this type of wastewater is discharged into natural environment without being treated, it will make the water body and soil acidified, the ecological environment damaged and a great number of resources wasted. So the treatment of wastewater from sulphuric acid plants includes not only improving its appearance characteristics and removing its strong corrosivity but also removing the harmful substances such as arsenic and fluorine. Many treating methods such as adsorptive process, floatation process, ion-exchange technique and membrane separation technique etc. have promising future in the application of the sulphuric acid plant wastewater treatment. But there is still a long way to go to the practical operation. At present Lime-Ferric Salt Process (LFSP) is the common way to treat the sulphuric acid plant wastewater. It has many advantages such as a simple process, lower operating cost and less ground occupation when it is applied in the wastewater treatment of small or middling plants. It will also be used widely in the future, but more research is needed to improve related technology thus to fully make use of it.On the basis of forerunner’s work, by taking the production wastewater from Jin Shan Dian Sulphuric Acid Plant in Hubei province as the research object, the research was done on the process conditions and treatment effects of Lime Neutralization and Precipitation Process (LNPP), Lime Neutralization-Air Oxidation Process (LNAP), Lime Neutralization-Ferric Salt Coprecipitation Process (LNFC), Lime Neutralization-Air Oxidation-Ferric Salt Coprecipitation Process (LNAFC), Lime Neutralization-Air Oxidation-Ferric Salt Coprecipitation-Crystal Seed Recycling (LNAFCC) and Ferrite Process (FP), which were used to treat the production wastewater from the said sulphuric acid plant. The main aim was to find out a simple but effective process and the correlative operating conditions. The experimental results showed that the arsenic concentration of the effluent was above 0.5mg/l when using the former three processes. And when using the latter three processes the effluent quality can meet the demand of the effluent-quality standard. The arsenic concentration of theeffluent was lower than 0.5mg/l and the arsenic removal efficiency was above 99%, and the turbidity of the effluent was lower than 6 degree. By comparing these processes and combining with the intrinsic treating establishments of the said plant, the Lime Neutralization-Air Oxidation-Ferric Salt Coprecipitation-Crystal Seed Recycling Process (LNAFCC) is proposed to treat its wastewater.As stated above, when air oxidation and ferric salt were applied in experiments, the arsenic removal efficiency was improved and pH played an important role, the reasons of which were further analyzed. According to the theory of ionization equilibrium, solubility product theory and the experimental results, it was helpful to the arsenic removal that As(III) in the wastewater was oxidized to As( V) because arsenate with lower solubility can be formed through air oxidation. It was demonstrated by theoretical analysis that under low pH condition AsO43" reacted with Fe3+ and formed FeAsO4, whose solubility is very low. When lime milk was mixed with wastewater, coarser Fe(OH)3 granules can be formed and the flocculation was accelerated, thus the removal efficiencies of arsenic and other heavy metal ions were improved. The regulation that the Ca3(AsO4)2 solubility (expressed by the total concentration of arsenic in the solution) changed with the pH of solution was established. It was concluded that the concentration of total arsenic fell with the increase of the pH. But it rose when the p更多还原