铝炭微电解处理刚果红废水的效果及脱色机理研究

采用铝炭微电解法处理刚果红废水,通过批式实验和正交试验考察了主要因素对刚果红脱色及COD去除效果的影响,并采用紫外扫描、离子色谱及LC-MS分析了脱色产物.结果表明,在铝粉投加量为8～24 g·L-1范围内,刚果红脱色率及COD去除率均随铝粉投加量的增加而提高,合适的铝粉投加量为16 ～24 g·L-1；刚果红脱色率和COD去除率随着铝炭质量比的减小呈现先增加后降低的趋势,适宜的铝炭质量比为1∶3～1∶1；初始pH对处理效果影响最大,在pH为10～12.5时,刚果红脱色率及COD去除率随着pH升高而急剧增加；在溶解氧为1.25 ～7.59 mg·L-1的范围内,刚果红脱色率及COD去除率随着溶解氧的升高而降低.最佳条件(铝粉投加量24 g·L-1、铝炭质量比1:2、pH=12、反应时间90 min)下,刚果红脱色率及COD去除率分别为90.4％和78.6％刚果红脱色历程为:刚果红分子中的N=N双键在新生态H]的攻击下断裂,生成3,4-二氨基萘-1-磺酸盐和4-氨基3-((4’-氨基-1,1'-联苯]-4-基)偶氮基)萘-1磺酸盐；后者在H]的进一步作用下,发生N=N双键的断裂,转化为3,4-二.氨基萘-1-磺酸盐和联苯胺,萘环开环和C-S键断键,分别生成4-氨基-3-((4’-氨基-1,1’-联苯]-4-基)偶氮基)-1-磺酸盐和2-((4'-氨基-1,1’-联苯]-4-基)偶氮基)-1-萘胺.研究表明,铝炭微电解法不能将刚果红完全矿化.

Treatment effect and decolorization mechanism of Congo red wastewater by aluminum-carbon microelectrolysis

Congo red wastewater was treated by aluminum-carbon microelectrolysis, and key factors affecting the decolorization and COD removal were investigated by batch and orthogonal experiments.Decolorization products were determined by UV spectrum, ion chromatography and LC-MS.The results showed that the decolorization and COD removal of Congo red increased with the dosage of aluminum powder in the range of 8~24 g·L^-1, and the appropriate dosages were determined in the range of 16~24 g·L^-1.The decolorization and COD removal of Congo red first increased and then decreased with increase of the Al/C mass ratio and the appropriate ratio was determined as 1:3~1:1.Initial pH was the key factor affecting the treatment process.The decolorization of Congo red was significantly enhanced with increasing pH in the range of 10~12.5.An increase in DO in the range of 1.25~7.59 mg·L^-1 led to decreased decolorization and COD removal of Congo red.Under the optimum conditions (aluminum powder 24 g·L^-1, Al/C mass ratio 1:2, pH=12 and reaction time 90 min), the decoloration and COD removal of Congo red rose up to 90.4% and 78.6%, respectively.The decolorization pathways of Congo red are proposed as follows: the azo linkage within Congo red molecule is firstly broken down by H] and two intermediates, 3,4-diaminonaphthalene-1-sulfonate and 4-amino-3-((4'-amino-1,1'-biphenyl]-4-yl)diazenyl) naphthalene-1-sulfonate, are formed; the latter is further transformed to 3,4-diaminonaphthalene-1-sulfonate and benzidine, 4-amino-3-((4'-amino-1,1'-biphenyl]-4-yl)diazenyl)-1-sulfonate and 2-((4'-amino-1,1'-biphenyl]-4-yl)diazenyl)naphthalen-1-amine are formed due to ring opening of naphthalene and breakdown of C-S linkage.Congo red cannot be mineralized by aluminum-carbon microelectrolysis.