Abstract: A novel cationic decolorant was synthesized by using dicyandiamide and formaldehyde as the main raw material, modified by urea and melamine. The flocculation ability of the polycondensate was studied by the flocculating sedimentation experiment in the simulated dyestuff wastewater that used acid red 18. Effects of material molar ratio, reaction time and reaction temperature on the performance of decolorant were studied by the single factor experiments. Mixed usage with polymeric aluminium chloride was also investigated. The infrared spectrogram showed that the product is the modified compound. The results showed that the modified decolorant had a better performance than the unmodification decolorant. The optimum conditions are that reaction temperature is 80℃, reaction time is 3h and the molar ratio of dicyandiamide to formaldehyde to ammonium chloride to urea to melamine is 1:3.5:0.75:0.13:0.03. When the best dosage of modified decolorant is 120mg/L, the decolorization rate is 94.6%. PAC is used alone with the optimal dosage of 60mg/L, the decolorization rate is only 57.6%. When the modified decolorant mixed with PAC which dosage is unchanged, the dosage of the modified decolorant is 80mg/L the decoloring rate reached 94.8%. The mixed usage of the modified decolorant and PAC not only benefit the decoloration efficiency but also reduce the dosage of the modified decolorant that made the processing cost reduced.

Key words: dicyandiamide, modification, synthesis, sedimentation, coagulation

摘要： 以双氰胺、甲醛为主要原料,尿素、三聚氰胺为改性剂,合成双氰胺甲醛型改性脱色絮凝剂,并用于酸性红18模拟染料废水脱色絮凝沉降实验。实验采用单因素法研究了物料摩尔配比、反应温度、反应时间对改性脱色剂脱色性能的影响,探讨了与无机混凝剂聚合氯化铝(PAC)复配使用情况。通过红外光谱图发现产物为改性的脱色剂。研究结果表明:改性双氰胺甲醛脱色剂性能优于未改性产品,其最佳反应时间为3h,最佳反应温度为80℃,最佳的物料摩尔比为双氰胺:甲醛:氯化铵:尿素:三聚氰胺=1:3.5:0.75:0.13:0.03。改性脱色剂的最佳投加量为120mg/L,其脱色率达到94.6%;单独使用PAC时,最佳投加量为60mg/L,脱色率仅为57.6%;改性脱色剂与PAC复配之后,PAC用量不变时,改性脱色剂投加量为80mg/L时,脱色率就达到94.8%,脱色剂与PAC的复配,不仅提升了脱色性能,并可减少有机脱色剂使用量,降低处理成本。

关键词: 双氰胺, 改性, 合成, 沉降, 混凝