| As a commonly used water treatment agent,water treatment flocculant plays an important role in water treatment due to its wide range of applications,good treatment effect,low use requirements,large consumption,and low price.Some disadvantages of traditional inorganic flocculants such as high dosage requirements,high terminal sludge output,and large metal ion residues do harm to the use of it;organic flocculants are also facing bottlenecks for the problem of residual toxic monomers and the difficulty of degradation;Biological flocculants are difficult to promote in depth under the constraints of high prices and difficulty in industrial production.In the context of increasing demands for environmental protection,saving and efficiency in the water treatment industry,natural organic polymer flocculants are entering people’s vision.This type of environmental friendly flocculants represented by starch-based flocculants is based on the type of materials,environmental friendliness,biodegradability,modification difficulty,etc.which is superior to other types of flocculants,becoming a popular polymer flocculant product.At present,the related research work based on natural starch flocculants mainly focuses on improving the solubility of starch flocculants,improving the flocculation performance of starch flocculants,and enhancing the removal performance of starch flocculants to specific pollutants.The purpose of this experience is to use corn starch as the backbone to make a low and medium tempreture soluble starch(referred to as LTS-CS).In the experiment,the starch material was pre-treated by ultrasound,with the etherification reaction conditions for preparing modified cationic starch(referred to as CS)optimizing,and then the process of ethanol-alkali treatment of CS was optimized to prepare LTS-CS.The main research contents include: With a single factor test,using CS cation degree and synthesis reaction efficiency as evaluation criteria,it determines the best parameters of ultrasonic time,ultrasonic power,dosage of CTA,Na OH of dosage,system water ratio and etherification temperature.Then optimum value in the process of synthesizing CS,and use response surface test to get the value of the main factors;After that,a other single factor test was gone,using LTS-CS solubility as the evaluation standard,to get the best parameters of Na OH concentration,ethanol volume fraction,and processing temperature during the ethanol-alkali process.Otherwise,a orthogonal test was used to analyze the significance of factors.Furthermore,a experiment about the effect of dissolution temperature on the dissolution performance was gone,revealing the synthesis mechanism.In addition,FTIR,NMR hydrogen spectroscopy(1HNMR),XRD spectroscopy,differentialthermogravimetric analysis(TG-DSC)and field emission scanning electron microscope(SEM)are used to analyze and compare the structure and morphology of LTS-CS,CS and ultrasonic-treated starch.Finally,the optimal flocculation conditions of LTS-CS flocculant were determined by the simulated kaolin water sample flocculation test,which mainly focused on the dosage,initial p H and settling time and other factors,and compared with the conventional organic flocculant PAM.Conclusions of thef study are following below:(1)Ultrasonic power,ultrasonic time,the dosage of CTA,dosage of Na OH,the proportion of water in the system,the etherification temperature all contribute to the improvement of the cationicity and reaction efficiency of the product.Among them,dosage of CTA and dosage of Na OH make more sense.The cation degree can reach 0.695,and the reaction efficiency can reach 80.1%,under a optimal test condition.(2)The single factor test and orthogonal test of ethanol-alkali treatment shows that the Na OH concentration has the greatest effect to the dissolution performance of LTS-CS,and the ethanol volume fraction has the smallest effect.4mol/L is the best concentration.(3)The dissolution test of LTS-CS at different dissolution temperatures shows that the solubility of the prepared product LTS-CS is significantly improved compared with CS and St,with the solubility up to 80.09%.Ultrasonic pretreatment has played an important role in the optimization of starch chain structure,and the preparation of CS and LTS-CS.(4)FTIR and 1H-NMR analysis showed that a new peak of CN bond absorption and a quaternary ammonium cationic hydrogen-containing group appeared on LTS-CS,which confirmed the successful compounding of cationic starch and produced a new product;XRD analysis showed that LTS-CS was intramolecular,and it has a V-shaped spiral structure.SEM analysis shows that LTS-CS has good potential on flocculation with adequate superficies.Finally,TG-DSC analysis shows that LTS-CS products are stable to temperature.(5)LTS-CS has a good flocculation effect on simulated kaolin suspension,and has a wide range of p H application.The best amount added to water is 10mg/L,and the turbidity removal rate can reach 95.97%. |
PDF Full Text Request