络合—超滤—电沉积处理含镍废水的研究

发布时间：2018-05-19 07:45

本文选题：镍(Ⅱ) + 聚乙烯吡咯烷酮　；参考：《湖南科技大学》2017年硕士论文

【摘要】：本文研究络合-超滤-电沉积集成技术,以阴离子型水溶性聚合物聚乙烯吡咯烷酮(PVP)和羧甲基纤维素(CMC)为络合剂,考察了PVP和CMC的预处理过程、络合-超滤处理含镍废水的浓缩、解络合、聚合物回收利用等过程,并进一步研究了电沉积处理络合-超滤后的含镍浓缩液。探讨了络合-超滤过程中pH、负载比L、透膜压TMP、络合时间、体积浓缩因子VCF和外加盐等因素对Ni(Ⅱ)去除率和膜通量的影响,研究了电沉积回收含镍浓缩液过程中电流密度、初始pH、电解时间、温度、极距、搅拌等参数对电沉积镍过程中电流效率和镍回收率的影响。首先,对聚合物进行预处理,发现:预处理聚合物PVP过程中,当络合时间从5分钟增加到50分钟,瞬时通量Ji略微下降,之后基本保持稳定;预处理聚合物CMC过程中,当络合时间从5分钟增加到40分钟,瞬时通量Ji略微下降,之后基本保持稳定。而两者均随着压力的增加,膜通量也随之增大,因为压力增大而提高了驱动力,从而导致膜通量的增大。当透膜压TMP从0.5 bar增大到1.5bar,截留率Rp和Rc几乎没有变化,这可能是因为压强不改变PVP和CMC的结构以及膜表面结构尺寸,而只是影响溶液的渗透率。稳定通量Js不随pH的变化而改变,这是因为pH并不改变聚合物结构一致性,也不会增加膜污染。在相同的压强条件下,当pH从3增大到10,其截留率R基本保持不变,这说明截留率R不受pH的影响。然后进行络合-超滤实验,发现:在络合-超滤过程中,随着pH的增大,镍离子去除率逐渐增大,最高可达到97%,PVP络合时最佳pH选择为7,而CMC络合时最佳pH选择为8;随着负载比从1增大到4,镍离子去除率逐渐增大,最高可达到97%,之后不再发生变化,PVP络合时最佳负载比为4,而CMC络合时最佳负载比为2;在相同实验条件下,分别使用两种络合剂时,膜通量随着透膜压的增加几乎呈线性增长,而镍离子去除率不受其影响;在络合反应的前期,截留率增加迅速,之后保持稳定,PVP络合时选择30min作为最优络合时间,而CMC则选择20 min为最优络合时间;外加盐(NaCl)对镍离子截留率和膜通量的影响相似,截留率和膜通量均稍微下降,但是幅度较小。之后对络合-超滤后的溶液进行浓缩、解络合和聚合物回收利用处理,发现:PVP-Ni浓缩过程在pH=7、TMP=1.0 bar、L=4、VCF=10作为浓缩条件下,浓缩液中的镍离子浓度Cr=192.3 mg/L,然而渗透液中的镍离子浓度Cp基本保持在1.5mg/L,解络合后,PVP-Ni(Ⅱ)络合物的解离率达到了42%,而再生的PVP和初始PVP络合能力非常接近,说明聚合物可再生使用;CMC-Ni浓缩过程在pH=8、TMP=1.0 bar、L=2作为浓缩条件下,得到的截留液浓度Cr=196.6 mg/L,然而渗透液中的镍离子浓度Cp基本保持在0.6mg/L,均略高于PVP-Ni浓缩过程,解络合后,CMC-Ni(Ⅱ)络合物的解离率达到了56%,亦高于PVP-Ni解络合过程,再生的CMC和初始CMC络合能力也非常接近,说明聚合物可再生使用,且优于PVP。最后采用电沉积法处理得到的含镍浓缩液,发现:当电流密度、电解时间增加时,电流效率随之下降,而镍回收率增大;当pH、极距增大时,电流效率和镍回收率均先增大后减小;温度升高和低速搅拌均可提高电流密度与镍回收率。在电流密度为3.5mA/cm2,pH为4,电解时间130 min,温度为50℃,极距为10 cm,加入低速搅拌等最优条件下,电流效率可达42%,镍回收率最高可达52%。
[Abstract]:In this paper, the complex ultrafiltration and electrodeposition integrated technology was studied. The pretreatment process of PVP and CMC was investigated with anionic water-soluble polyvinylpyrrolidone (PVP) and carboxymethyl cellulose (CMC) as complexing agent. The process of concentration, complexation, recovery and utilization of the nickel containing wastewater by complex ultrafiltration was studied, and the electrodeposition was further studied. In the process of complexing and ultrafiltration, the nickel concentration solution was studied. The effects of pH, load ratio L, permeable pressure TMP, complexation time, volume concentration factor VCF and outer salt on the removal rate of Ni (II) and membrane flux were investigated. The current density, initial pH, electrolysis time, temperature, polar distance, agitation and so on were studied. The effects of parameters on the current efficiency and nickel recovery during electrodeposition of nickel. First, the polymer was pretreated. It was found that in the process of pretreated polymer PVP, when the complexing time increased from 5 minutes to 50 minutes, the instantaneous flux Ji decreased slightly, and then remained basically stable; the complexing time increased from 5 minutes in the predisposed polymer CMC process. At 40 minutes, the instantaneous flux Ji decreases slightly, and then basically remains stable, and the flux increases with the increase of pressure, which increases the driving force and increases the flux of the membrane. When the membrane pressure increases from 0.5 bar to 1.5bar, the interception rate Rp and Rc almost does not change, which may be because the pressure is not strong. Change the structure of PVP and CMC and the size of the surface structure of the membrane, but only affect the permeability of the solution. The stable flux Js does not change with the change of pH, which is because pH does not change the consistency of the polymer structure and does not increase the membrane fouling. In the same pressure condition, when pH increases from 3 to 10, the retention rate R remains unchanged basically, which indicates interception. The rate of R is not affected by pH. Then, the complexing ultrafiltration experiment shows that with the increase of pH, the removal rate of nickel ions increases gradually, the maximum can reach 97%, the best pH selection is 7 when PVP complexing, and the best pH selection is 8 when CMC complexing, and the nickel ion removal rate increases gradually with the load ratio from 1 to 4, and the maximum can reach 97%. After the PVP complexation, the optimum load ratio is 4 and the optimum load ratio of CMC complexing is 2. Under the same experimental conditions, the membrane flux is almost linearly increased with the increase of the permeable pressure, but the removal rate of nickel ions is not affected; the retention rate increases rapidly in the early stage of the complex reaction, after which the retention rate is guaranteed. When PVP is stable, 30min is selected as the optimal complexing time, while CMC chooses 20 min as the optimal complexing time. The effect of added salt (NaCl) on the retention rate of nickel ions and membrane flux is similar, the interception rate and membrane flux are slightly decreased, but the amplitude is small. Then the solution of complex and ultrafiltration is concentrated, complexing and polymer recovery. It is found that the concentration of nickel ions in the concentrated solution is Cr=192.3 mg/L under the concentration of pH=7, TMP=1.0 bar, L=4 and VCF=10, while the concentration Cp of nickel ions in the liquid is basically maintained at 1.5mg/L, and the dissociation rate of the PVP-Ni (II) complex is 42%, and the regeneration PVP and initial complexing ability is very connected with the concentration of the concentration of nickel ions in the concentration solution, while the concentration of nickel ions in the concentration solution is Cr=192.3 mg/L. It is close to explain the renewable use of polymers; the concentration of CMC-Ni concentration in pH=8, TMP=1.0 bar, L=2 as concentration conditions, the concentration of the retention solution is Cr=196.6 mg/L, but the nickel concentration Cp in the osmosis is basically maintained at 0.6mg/L, slightly higher than the PVP-Ni concentration process. After the solution, the dissociation rate of the CMC-Ni (II) complex is 56%, and is higher than that of PVP-. The complexing process of Ni solution, the regenerated CMC and the initial CMC complexing ability are also very close, indicating that the polymer is renewable and is better than the nickel concentration solution obtained by electrodeposition at the end of PVP.. It is found that the current efficiency decreases and the nickel recovery increases when the current density increases and the nickel recovery increases. When pH, the polar distance increases, the current efficiency and the current efficiency are increased. The recovery rate of nickel increases first and then decreases, and the current density and nickel recovery can be increased by the increase of temperature and low speed agitation. The current efficiency can reach 42% and the nickel recovery can reach to 52%. at the current density of 3.5mA/cm2, pH 4, 130 min, 50 C, 10 cm and low speed agitation.
【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703

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