Preparation And Flocculation Performance Of High Substitution Degree Cationic Starch And Cationic Guar Gum By Microwave Dry Process

The property of polysaccharide will be improved after modification,so that the polysaccharide derivatives are widely used in papermaking,oil drilling,textile printing,wastewater treatment,food,medicine and other industries.In this paper,corn starch and guar gum as raw materials,and small molecular etherifying agent of 2,3-epoxytrimethylammonium(GTA)was used as cationic group,were prepared cationic starch with a degree of substitution(DS)of 0.19-0.51 and cationic guar gum with a degree of substitution of 0.16-0.47 by microwave dry method.Through orthogonal experiment to optimize the process parameters,the influence order of each factors on the degree of substitution of cationic starch and cationic guar gum was obtained by the range analysis respectively: water content > microwave power > microwave temperature > microwave time;n(isopropyl):n(GTA)> water content > microwave power > microwave time.Besides,the structural accuracy of cationic starch and cationic guar gum was verified by Kjeldahl method and infrared spectroscopy(IR)and so on.This paper systematically investigated the influence of microwave parameters on the viscosity and molecular weight of cationic starch and cationic guar gum.The results showed that the viscosity of product and the molecular weight have the same trend,and related to microwave power,microwave temperature,microwave time and water content.In this paper,kaolin suspensions were used as simulated wastewater to study the flocculation properties of cationic starch with substitution degree of 0.19,0.28,0.37,0.43 and 0.5 and cationic guar gum at 0.2,0.3,0.38 and 0.47.With the increase of DS,the required dosage in the same concentration kaolin suspension was gradually reduced.In the optimum dosage of each DS,the turbidity of kaolin suspension is also gradually reduced,the turbidity removal rate could reach more than 99%.In addition,the time of cationic starch reached sedimentation equilibrium(30 min)was longer than cationic guar gum(15 min).And the flocculants prepared in this paper have a pH range of 3 to 9.Finally,cationic starch and cationic guar gum with a degree of substitution of 0.4 were flocculated into leather industrial wastewater,investigated its practical application performance.The flocculation performance was evaluated by comparing the turbidity,volume of flocs and Chemical Oxygen Demand(COD)after flocculation with cationic starch,cationic guar gum,and the mixture of cationic starch and cationic guar gum volume ratio is 1:1,at the condition of best dosage(1 mg/L),the charge neutralization ability and removing organic chemical ability of cationic starch was more than cationic guar gum,however,the bridge ability of cationic guar gum is more than cationic starch,so that using the mixture of cationic starch and cationic guar gum will have a better result effect.The results also showed that the turbidity removal rate can reach more than 89.4% and the COD descend rate can reach 81% after using the mixture.