沉镍残液处理研究

【作者】 杨群；

【导师】 宁平；

【作者基本信息】 昆明理工大学 ， 环境工程， 2009， 硕士

【摘要】 随着现代工业的高速发展、城市化的加速和人口急剧增长,各种废水给人类的生存环境带来了日益严重的危害,特别是重金属废水,对人类健康和环境的危害越来越严重,有效的去除废水中的多种重金属离子并不造成二次污染的任务已迫在眉睫。论文以云南元江镍业有限公司的沉镍残液作为研究对象,考察了铁氧体法和中和法处理模拟沉镍残液的工艺条件和处理效果。该残液呈酸性,含有大量镁离子和多种重金属离子,需要采用净化处理工艺中和酸性废液,同时去除重金属离子。确定了影响铁氧体法的工艺参数：pH值、温度、搅拌时间和投药比。试验结果表明,该法最佳操作条件为：pH值11左右,投料比10,温度50℃,搅拌时间25min。经铁氧铁法处理的沉镍残液,出水中重金属离子的浓度均达到了污水综合排放标准；处理后的铁氧体沉渣便于分离,沉渣化学性质稳定,粒度均匀,磁性强,可以通过处理回收利用。从沉渣中分离出来的磁性产物的X-射线衍射图谱及尖晶石型铁氧体Fe304的衍射图谱对比可以看出,运用该法所得的沉淀物中的磁性部分具有尖晶石型铁氧体的晶体结构。但铁氧体法处理大量废水,升温较为困难,消耗相当多的铁盐、一定数量的苛性钠及热能,且处理时间较长,使处理成本较高。中和法处理沉镍残液,对比研究了两种处理工艺。一种是用先用5%石灰乳调pH值到9.5左右,沉淀、过滤,再将上清液pH调到12.5左右；另一种是先用5%石灰调pH值到12.5左右,沉淀、过滤,再用聚合硫酸铁将上清液pH调到8.5左右。同时考察了污泥回流及污泥回流方式对以上两种处理工艺的影响。试验结果表明,经过这两种处理工艺处理的沉镍残液,出水中重金属离子浓度均达到了污水综合排放标准。对于第一种方法,先碱化污泥再中和的处理效果要比先酸化再中和好,最佳的污泥回流量分别为40%和50%,但出水pH值较高,无法直接排放。对于第二种方法,最佳的污泥回流量为30%～40%,出水pH值在8左右,可以直接排放,与同样条件下不采用污泥回流的处理工艺相比,其形成的污泥含水率从93.27%降到90.81%,生成的污泥量减少了1/4左右,沉降速率明显加快,同时也提高了处理效率,减少了药剂用量。论文通过对铁氧体法和中和法的比较认为,污泥回流-石灰中和-聚合硫酸铁回调法工艺合理、流程简单、操作方便、处理成本低,建议采用此法对该厂的沉镍残液进行处理。同时对试验中产生污泥提出了处理与处置建议。更多还原

【Abstract】 Nowadays wastewater from different industries has brought increasing damage to human society, especially heavy metal wastewater, which made the environment and human health greatly suffered. So it is urgent to find effective ways to reduce manifold heavy metals from wastewater before it is dischared into the nature in case it should cause secondary pollution.This paper chose nickel precipitation residue liquor(from Yuanjiang nickel Industry Company in Yunnan province)as object and focused on the operation conditions and effects of two treatment process, ie.ferrite process and neutralization process, to find out a simple but effective way for the removal of heavy metals in the residue.In ferrite process, four influencing process parameters were set, ie.pH, temperature, stirring time and reagents adding ratio. The results showed that the optimum operating conditions were pH value of 11, temperature of 50℃, stirring time of 25min and reagents adding ratio of about 10. After the treatment, heavy metals concentration of the treated residue liquor was lower than that of the national wastewater discharge standard. The sediment from ferrite process can be reused or recycled, which has stable chemical properties, uniform granularity and strong magnetism and is easy to be separated. By comparation the X-ray diffraction pattern and the spinel ferrite Fe3O4 diffraction pattern, it can be seen that the magnetic part of the sediments has crystal structure of the spinel ferrites. However, ferrite process has some deficiencies, such as warmming difficulties, comsumption of ferric salt, caustic soda and heat energy, long processing time and higher processing costs.In neutralization process, two processes were compared. In one process,5% lime was put into the residue liquor to regulate its pH value to about 9.5 firstly. Then after precipitation and filtration, put lime into the supernatant to regulate its pH value to be about 12.5. In the other process, put 5% lime into wastewater to regulate its pH value to be about 12.5. After precipitation and filtration, put polymeric ferric sulfate (PFS) into supernatant to regulate its pH value to be about 8.5. At the same time, the impact of refluent sludge and the refluent way were studied. The results showed that the concentration of the heavy metals of the treated residue liquor was lower than that of the national wastewater discharge standard. For the first process, firstly alkalizing the sludge and then neutralizing is better than firstly acidulating sludge and then neutralizing, and the optimum volume of refluent sludge is 40% and 50%. But the pH value of the treated residue liquor is higher, and it can not be discharged directly. For the second process, the optimum volume of refluent sludge is 30%-40%, and the pH value of the treated residue liquor is about 8. So it can be discharged directly. Compared with processes without sludge refluece, the sludge moisture of the sludge refluence process decreased from 93.27% to 90.81%, resulting that:the sludge volume was reduced by 1/4; the sedimentation rate was more efficient; the processes was more efficient and reduced the reagent consuming as well.Through the comparation of the ferrite process and the neutralization process, it’s concluded that sludge recycling-lime neutralization-PFS process is the optimum process for the nickel precipitation residue liquor. It’s simple, easy-operation, cheaper and adapt to the wastewater from nickel smelter. At the same time, some advices were gived for treating sludge.更多还原