Preparation Of Insoluble Canna Edulis Ker Starch Xanthate And Its Effect On Wastewater Treatment

At present,the heavy metal water pollution and the random discharge of printing and dyeing wastewater have brought serious burden on the ecological environment and seriously affected human health.Natural polymer flocculant has become a research hotspot for the adsorption of heavy metal ions and printing and dyeing wastewater because of its environmental protection and no secondary pollution.Among them,modified starch flocculants are favored by researchers because of their advantages such as wide sources of starch,low cost,and biodegradability.At present,starch is mainly derived from corn,potatoes and cassava.The purpose of this study was to replace the commonly used food crops such as corn and potatoes with high-yield,high-starch,and non-food Canna edulis Ker.Compared to other modified starch flocculants,xanthate has the advantages of simple operation,flocculation and sedimentation without residual sulfides,and it can exhibit good flocculation effect.In this paper,the cross linking reaction of Canna edulis Ker starch was first used in the two step method.With the sedimentation product as the index,the cross-linked starch with high cross-linking degree was optimized by the response surface method.The optimal preparation conditions were:Canna edulis Ker starch 10 g,the dosage of ECH0.90 mL,the dosage of 10%NaOH 4.40 mL,temperature 39?,time 4 h,and the minimum sedimentation rate was 1.43 mL,corresponding to the cross-linking degree of cross-linked starch was the largest.The xanthogenation reaction was then carried out with the cross-linked starch,and the insoluble Canna edulis Ker starch Xanthate?IKX?was optimized by response surface methodology using Cu²⁺removal rate as the index.The optimal preparation conditions were:the cross-linked starch 5 g,the dosage of CS₂1.1 mL,the dosage of 20%NaOH 13.4 mL,temperature 35.4?,time 2.1 h,at this time,the Cu²⁺maximum removal rate of 99.5%.The IKX was characterized by infrared spectroscopy and scanning electron microscopy.The characteristic peaks of the infrared spectrum showed the formation of ether bonds,indicating the success of the crosslinking.Scanning electron microscopy showed that the surface of IKX was wrinkled and the voids were easy to attached to the heavy metal ions and cationic dyes.IKX was used to flocculate the simulated heavy metal ions(Cu²⁺,Cd²⁺)solution,the optimum flocculation conditions were obtained.The maximum removal rate of Cu²⁺was99.8%and the maximum removal rate of Cd²⁺was 99.8%.For the static adsorption studies,the adsorption of Cu²⁺and Cd²⁺on IKX satisfies the pseudo-second-order kinetics and adsorption isotherm fits the monolayer adsorption of Langmuir model.The adsorption process of IKX on Cu²⁺and Cd²⁺is mainly affected by chemical adsorption and both are favorable adsorption.For the first time,the flocculation test of simulated cationic dyeing wastewater cationic red X-GRL?cationic red X-GRL as azo dye?and cationic violet 3R was performed using IKX,both of which achieved good decolorization effect,and the maximum decolorization rate of cationic red X-GRL was 93.5%,the maximum decolorization rate of cationic violet 3R was 88.7%,and the decolorization of cationic red X-GRL was better than that of cationic violet 3R.Then static adsorption studies show that the adsorption of cationic red X-GRL and cationic violet 3R on IKX meets quasi-second order kinetics,and the adsorption isotherm of cationic red X-GRL conforms to Langmuir model monolayer adsorption,and to cationic violet 3R.The adsorption isotherm was in accordance with the Freundlich model of multi-layer adsorption,and the adsorption process of IKX on the cationic red X-GRL and cationic violet 3R was mainly controlled by chemical adsorption and both were favorable for adsorption.