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由于产生的废水量大且成分复杂,纺织行业被普遍认为是污染最严重的行业之一。据不完全统计,纺织行业每年生产超过
$ 1\times {10}^{6} $ t染料,其中60%~70%是偶氮化合物,其特点是含有一种或多种偶氮键(—N=N—)及各种衍生物[1]。由于其毒性、致癌性和致突变性,偶氮染料及其降解中间产物对水生生物的生长具有较强的抑制作用,排放到自然环境中,会导致水体植物和动物大量死亡。此外,硫化物通常存在于染料废水中,一方面是添加硫化钠还原偶氮化合物而形成,另一方面可能是其他广泛存在于纺织染色工艺中的硫物质转化而来,如硫酸盐、亚硫酸盐和硫代硫酸盐[2]。有研究[3]表明,大量的硫化钠用于硫化染料的染色过程(>90%),产生含由15%~20%硫化物的废水。由于其毒性、风化性和腐蚀性强,硫化物(水性硫化物和气体硫化物)会对人体健康产生严重危害。因此,在含硫化物的偶氮染料废水最终排入天然水体之前,必须对其进行有效的处理。微生物燃料电池(microbial fuel cells, MFC)是一种在微生物的催化代谢作用下,使有机/无机污染物发生氧化反应,释放质子和电子,从而产生电流、并降解污染物的装置[4]。在MFC的运行中,阳极液pH能影响底物的代谢活性,进而影响质子和电子的生成和转移机制,对MFC的整体性能有着重要作用。外部pH的变化可导致几种主要生理参数的变化,包括内部pH、离子浓度、膜电位和质子动力[5]。一般来说,细菌的最佳生长需要接近中性的pH,而阴极电极上的氧还原反应会导致pH呈碱性[6]。传统的双室MFC可以保持2种不同的pH环境,以优化阳极反应和阴极反应。然而,空气阴极MFC中,在只有一种电解质存在的条件下不能做到这一点。在现有的研究中,电解质pH对空气阴极MFC产电性能和污染物降解的相关研究较少,因此,研究空气阴极MFC的最佳pH以及电解质pH对产电性能的影响是必要的。
本研究构建了单室空气阴极MFC,且将其用于处理含硫偶氮染料废水,以乙酸钠为底物,碳刷和碳布分别作为反应器的阳极和阴极材料。探究了阳极液在不同初始pH条件下单室微生物燃料电池的产电性能及其对硫化物和偶氮染料的降解效果,确定了该反应器运行的最佳pH,同时探究了硫和染料的协同降解机理。鉴于染料出水中含有大量的硫化物,MFC中硫化物作为本体还原剂和电子供体,可以加速偶氮染料的降解。本研究为印染厂染料废水的降解提供了一个新的思路。
不同pH下微生物燃料电池降解含硫偶氮染料废水的效能及其机理
Degradation efficiency and mechanism of sulfur-containing azo dye wastewater by microbial fuel cell under different pH conditions
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摘要: 构建单室空气阴极微生物燃料电池反应器(MFC)并用于处理含硫偶氮染料有机废水,研究初始pH对单室MFC的产电性能和对偶氮染料及硫化物的去除效果以及阳极生物膜电化学行为的影响。利用紫外可见光谱全波长扫描(UV-vis), 高效液相(HPLC)和液相色谱-质谱联用(LC-MS)分析偶氮染料还原反应过程的中间产物。结果表明,以乙酸盐为底物,单室MFC的阳极液在中性条件下有利于系统性能的提高。pH由5.0增加到9.0过程中,单室MFC的产电性能先增加后减小,中性条件下产电性能和目标物降解率最佳,其次为偏酸和偏碱条件,过酸或过碱最差。当pH=7.0时,电池的最大功率密度为24.5 mW·m−2,内阻最小为154.1 Ω;微生物的活性最高,硫化物和偶氮染料的降解率最大,硫化物去除率为98.40%,染料的脱色率达到84.60%,COD的降解率为49.56%。另外,通过CV扫描可知,pH对阳极产电菌的氧化还原能力有显著影响,中性条件下阳极产电菌的氧化能力最强。联苯胺和3,4-二氨基萘-1-磺酸被证实为刚果红降解反应典型的中间产物,而硫化物氧化的主要产物是硫单质,硫代硫酸盐和硫酸盐。以上研究结果可为处理实际的含硫偶氮染料废水提供一定的参考。Abstract: Single-chamber air cathode microbial fuel cells (MFC) were constructed to treat the sulfur-containing azo dye wastewater in this study. The effects of initial pH on the MFC performances of electricity production, the removal of azo dyes and sulfide, and electrochemical behavior by anode biofilm were investigated. Moreover, the intermediate products from azo dyes reduction were analyzed by UV-vis, HPLC and LC-MS. The results showed that the anolyte in single-chamber air cathode MFC with acetate as substrate was beneficial for the improvement of power output under neutral conditions. When the pH increased from 5.0 to 9.0, the power generation performance of MFC increased first and then decreased. At neutral pHs, the best power generation performance and target pollutants degradation occurred, followed by weak acidic and alkaline pHs, then over acidic and alkaline pHs. At pH=7.0, the maximum power density of MFC was 24.5 mW·m−2 and the minimum internal resistance was 154.1 Ω. Besides, the highest microbe activity occurred, as well as the highest degradation efficiency of sulfide, azo dyes and COD. The corresponding removal efficiencies of sulfide, azo dyes and COD were 98.40%, 84.60% and 49.56%, respectively. In addition, the CV curves showed that pH played an important role on the redox ability of the anodic bacteria, and the exoelectrogens had the strongest oxidation ability under neutral conditions. 4,4'-diamine biphenyl and 3,4-diaminonaphthalene-1-sulfonic acid were confirmed to be the typical intermediates of congo red degradation, and elemental sulfur, thiosulfate and sulfate were the main products of sulfide oxidation. This study provided a certain technical and theoretical support for the treatment of actual sulfur-containing azo dye wastewater.
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Key words:
- microbial fuel cells /
- azo dyes /
- power generation /
- pH /
- cyclic voltammetry
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表 1 刚果红降解的可能中间产物
Table 1. Possible degradation intermediates of Congo red
分子式 名称 质荷比m/z C10H10N2O3S 3,4-二氨基萘-1-磺酸 239 C12H12N2 联苯胺 184 C22H17N4SO3Na 4-氨基-3-[(4′-氨基[1,1′-联苯]-
4-基)二氮基]萘-1-磺酸钠441 C10H8NNaO3S 4-氨基-1-萘磺酸钠 245 C22H18N4 4′-[(1-氨基萘-2-基)二氮基]
[1,1′-联苯]-4-胺338 C10H10N2 萘-1,2-二胺 158 -
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