【作者】 杨兴涛；

【导师】 王志；

【作者基本信息】 天津大学 ， 化学工程， 2006， 硕士

【摘要】 传统的电镀废水治理方法多为氧化-还原法和(或)沉淀法,虽然处理后的废水能够达到排放标准,但是许多有价值的重金属离子不能回用,而且污泥还会造成新的污染。若能采用物理法把重金属离子与废水分离,那么二者都可以回用,意义重大。本文利用自制的实验装置,开展了纳滤膜技术处理电镀废水的研究,系统地考察了纳滤过程中的各种影响因素。实验选用了三种不同渗透系数的亲水性纳滤膜:DL、DK、NTR-7450以筛选出适合处理电镀废水的膜。首先对某厂的电镀漂洗废水进行纳滤实验。该废水所含重金属离子主要为Cr和Cu。实验结果表明,重金属离子的去除受压力、流速、温度、pH和料液浓度等因素的影响。随压力的增加,膜通量逐渐增大,由于浓差极化和膜污染的影响,通量上升到一定值后开始下降,而膜对重金属离子的截留率比较稳定。预压会对纳滤膜结构产生影响,既可能使纳滤膜截留率增大,也可能使纳滤膜截留率降低;预压压力越高,纳滤膜渗透系数越低。膜面流速增大、料液温度升高会使通量增大,而流速和温度对截留率影响较小。由于随pH的变化,膜表面荷电和料液物性改变,pH值对离子的截留率影响较大,但pH值对膜通量影响较小。对于本实验体系,适宜的操作压力为0.6-1.2 MPa,温度为30-45℃,pH为中性或碱性。实验发现,DL和DK膜有较高的通量和截留率,适合处理电镀废水。DL膜渗透液中Cr平均浓度为0.52 mg/L,Cu平均浓度为0.95 mg/L;DK膜渗透液中Cr平均浓度0.80 mg/L,Cu平均浓度为1.63 mg/L,调节pH后可直接排放或返回电镀槽作漂洗水。电镀废水纳滤浓缩实验表明,随浓缩过程的进行,通量呈下降趋势。浓缩过程中DL和DK膜对Cr和Cu的截留率都在90%以上,分别把Cr和Cu由15.55和16.54 mg/L浓缩至107.75和129.45 mg/L,两种离子的浓缩倍数分别为6.93和7.83倍。DL膜在酸性电镀废水中耐受性较差,浸泡70天后,对Cr离子平均截留率由原来的96.6%降到60%以下,而DK膜则有较好的耐受性,对Cr离子的截留率始终保持在92%以上。DL和DK膜在中性电镀废水中都有较好的耐受性,浸泡70天后,两膜对Cr离子截留率都在90%以上。由于纳滤膜在溶剂中长时间浸泡可能发生溶涨,使得膜孔径增大,因此两膜的通量随浸泡时间延长而增大。更多还原

【Abstract】 The electroplating waste water is generally treated by conventional techniques such as oxidation-reduction and/or precipitation to make the effluents meet the standards for discharge to the sewage systems. However, many valuable heavy metals will be lost and new contaminants may be produced. If the heavy metals in the waste water can be separated by physical methods, both the water and collected heavy metals can be reused.In this work, the nanofiltration of electroplating waste water was investigated. Some key parameters which may influence the process were studied systematically. Three NF membranes—DL, DK and NTR-7450, which have different hydraulic permeabilities—were selected for the experiments.Experiments on the treatment of a real electroplating waste water containing Cr and Cu were carried out. The results indicate that the removal of heavy metals is influenced by pressure, crossflow velocity, pH, concentration and temperature of the feed solution. Cr rejection is higher than Cu rejection. As the operating pressure increases, Cr and Cu rejections keep steady. Permeate flux increases with increasing pressure, but declines at higher pressure due to concentration polarization and membrane fouling. The performance of NF membrane will change after precompaction, this may be due to the variation of the membrane structure. Increasing crossflow velocity and temperature will increase the permeate flux, and not affect the heavy metal rejections obviously. The varying of pH value will cause the great varying of heavy metal rejections, but small varying of permeate flux. The suitable operating pressure range is 0.6-1.2 MPa, temperature range is 30-45℃, pH range is 6-9. DL and DK membranes have high heavy metal rejections and high permeate flux, thus these two membranes can be selected as the suitable membranes for the treatment of electroplating waste water.The average permeate concentration of Cr and Cu is 0.52 and 0.95 mg/L respectively for DL membrane, and 0.80 and 1.63 mg/L respectively for DK membrane. The permeate water can be discharged or reused as rinse water after adjusting the pH.The nanofiltration concentration of electroplating waste water by DL and DK更多还原