The Synthesis And Application Of Dicyandiamide- Formaldehyde-Al/Fe

Wastewater treatment turns into an environmental issue with the increasing concern of our country to water quality. The technology for the treatment of printing and dyeing wastewater, in large amount with complex composition including massive organic compounds mostly of which can’t be eliminated by biodegradation, has become one of the bottlenecks in wastewater treatment. Currently, integrated process combining enhanced anaerobic hydrolysis, biochemical treatment and coagulation-sedimentation-filtration is commonly adopted in domestic textile industry, by which COD and SS can be well controlled but the chromaticity color of the effluent rarely meet the requirement of the national standard.With the purpose of decreasing the chromaticity color of the printing and dyeing wastewater, a novel multianatomic organic-inorganic composite flocculant is developed in this dissertation on the basis of sufficient survey and analysis on corresponding literature. Firstly, flocculating agent A is synthesized with dicyandiamide(DCD) and formaldehyde(HCHO) as starting materials, and ammonia chloride(NH4Cl) as catalyst added in batches to confirm the optimal reaction time. Next, aluminum sulfate(saturated solution) and ferrous sulfate are introduced to determine the optimal synthesis technology to meet the quality specification of the effluent. Faint yellow, clear and viscous composite flocculant B is synthesized at 80?C by 2h when the mole ratio of DCD/HCHO/NH4Cl/Al2(SO4)3 is fixed as 1/1.5/0.57/0.2 and the mass fraction of FeSO4 is 1.5%. As for flocculant B, the removal rates of COD and pHospHorus are 65.5% and 82.6% respectively, and the decolourization ratios for acidic and alkaline wastewater catch up to 80.5% and 90.0% respectively.According to the IR data of flocculant B, typical absorbance can be assigned to amine salt, assumed to react with the sulfonic acid group of most pigments in wastewater which can occur more easily with the presence of Fe2+. Polymerized Al3+ is highly adsorptive with neutralization, and consequently, flocculant B with much lower molecular weight compared to traditional flocculants effectively degrade the pollution factor of printing and dyeing wastewater. This work focus on the synthesis and flocculating performance of composite flocculants, and the specific mechanism for flocculating remains to be further studied.