Research On Flocculation And Decolorization Of Printing And Dyeing Wastewater By Inorganic-organic Polymer Flocculants

With the development of the economy,the treatment of wastewater has become a serious environmental issue.Due to the characteristic of complex composition,high organic concentration,and difficult degragation,the treatment of dyeing wastewater has become one of the bottlenecks in industry.Flocculating is currently a common technology for dye wastewater treatment.However,using a single type flocculant is usually difficult to achieve ideal decolorization effeciency.To improve the decolorization property of the flocculant,several flocculants were prepared and the decolorization performance was investigated.The following results are obtained:1.Using inorganic flocculant（PFC）and organic flocculant（CGG）as the raw material,a new composite flocculant（PFC-CGG）was prepared.Under neutral conditions,the decolorization rate of Reactive Black 5 can reaches 95.26%at mass ratio of m_CGG:m_PFC=0.01;when the mass ratio m_CGG:m_PFC=0.04,the decolorization rate of Reactive Red 195 can reache 94.98%,which is significantly higher than the decolorization rate of PFC and CGG under the same conditions.2.The optimal synthesis conditions of dicyandiamide formaldehyde（DCDF）are:the molar ratio of n dicyandiamide:n formaldehyde:n ammonium chloride=1:1.75:0.9,the reaction temperature 80℃,and the synthesis time 3 h.The maximum decolorization rates for Reactive Black 5 and Reactive Red 195 treated with DCDF alone are 95.15%and 95.95%,respectively.3.With the composite use of DCDF,PFC and polyacrylamide（PAM）,when the mass ratio of m_DCDF:m_PFC=1:0.5 and the dosage of PAM is 24 mg/L,a maximum decolorization efficiency can be achieved.When pH=7,and the total dosage of flocculant is 366-720 mg/L,the decolorization rates are 99.78%and 99.85%,respectively for Reactive Black 5 and Reactive Red 195.The combination of organic and inorganic flocculants improves the decolorization effect greatly and reduces the amount of flocculants.4.Using ethylenediamine as the modifier,a new organic flocculant（EM-DCDF）was synthesized.At the molar ratio of ndicyandiamide:n formaldehyde:n ammonium chloride:n_{ethylenediamine}=1:2.25:0.8:0.1 and pH=7,the decolorization rate of Reactive Black 5and Reactive Red 195 are 98.73%and 98.68%,respectively.The decolorization performance of EM-DCDF is significantly higher than that of DCDF under different pH and electrical conductivity,indicationg that EM-DCDF is an excellent organic flocculant.