The Study On The Synthesis Of The Dicyandiamide-formaldehyde Flocculant And Its Application

Flocculating is one of the main methods in treating printing and dyeing wastewater(PDW), and the dicyandiamide-formaldehyde flocculants(DCD-HCHO) showed special performance in the decolorization of waster containing dissolved dyes. The paper based on summarizing the treatment technologies of PDW, especially in discussing the synthesis of DCD-HCHO. A highly efficient decolorizing flocculant nominated DCD-HCHO is synthesized by using different modifier. The paper also studied the performance in the PDW, works made in this paper were as follow:1. The rules of the factors were studied based on the main reaction between dicyandiamide and formaldehyde at hydroxymethylation period, such as material molar ratio,reaction time,reaction temperature. The results shows that the optimal temperature is80℃, the most suitable molar ratio of formaldehyde and dicyanodiamide is 2:1, the reaction time is probably in 1 hour.2. The product's performance were researched by using different acidity catalyzer like ammonium chloride,Aluminum chloride,Iron(Ⅲ) chloride at fascution period. The results showed that the suitable catalyzer is ammonium chloride and Aluminum chloride and the molar ratio of dicyanodiamide: ammonium chloride=1:0.5; dicyandiamide: Aluminum chloride=1:0.1, reaction time is 1hour, reaction temperature is 70℃. We synthesized 1# flocculants as these methods.3. In order to improve 1#'s performance, we using different modifier to synthesize 2# flocculants and the suitable modifier is dimethylenediamine. On the basis of selection of the range of experiment condition, and optimum symthetic condition was determined by the evaluation criterion of the removal of CODcr and decolourization.4. The pH,dissociative formaldehyde content,ion types of 1# and 2# flocculants were measured and the functions in IR spectrum were analysised.5. The performance of the removal of CODcr and decolourization of 2# flocculants perared in the optimum condition applying in reactive red X-3B,acid red FGS and disperse red SE/KB wastewater treatment was researched and application character was found out.